Photocatalytic degradation of persistent organic pollutants by Co-Cl bond reinforced CoAl-LDH/Bi12O17Cl2 photocatalyst: mechanism and application prospect evaluation

Lewis acid sites-regulated microscopic interface on graphite felt surface for enhanced heterogeneous electro-Fenton process: Formation of confinement effect and generation of singlet oxygen

The short lifetime and limited diffusion capability of hydroxyl radicals (•OH) restrict the further development of heterogeneous electro-Fenton (Hetero-EF) technology. In contrast, singlet oxygen (1O2) demonstrates many advantages over •OH. In the present work, a porous confined graphite felt (PCGF) was prepared through in-situ etching of nickel oxide (NiOx) and used as the cathode for Hetero-EF, aiming at constructing a 1O2-dominated Hetero-EF system to enhance its degradation performance for various antibiotic pollutants in wastewater. The in-situ etching of NiOx introduced abundant Lewis acid sites within the porous architecture of PCGF, enabling the modulation of electrode's interfacial properties and selective adsorption of Lewis basic substances, thereby generating a characteristic "confinement effect". This enhanced interfacial interaction achieved 50.23 % adsorptive removal of oxytetracycline within 30 min without external power supply, facilitating the enrichment of pollutants at the cathode interface. Meanwhile, the "confinement effect" significantly enhanced the utilization efficiency of reactive oxygen species and the selectivity of 1O2. The PCGF electrode demonstrated excellent degradation performance across a wide range of pH and exhibited strong anti-interference capability. The results from radical quenching experiments and density functional theory calculations revealed that the generation of 1O2 proceeded through multiple routes involving hydrogen peroxide, •OH, and superoxide anions. The present study presents a novel strategy for advancing the development of 1O2-dominated Hetero-EF systems for treating antibiotic-containing wastewaters.

Fluid-induced piezoelectric field enhanced photocatalytic antibiotic removal over nitrogen-doped carbon quantum dots/Bi2WO6@polyvinylidene fluoride-co-hexafluoropropylene membrane in aqueous environments

Enhancing the charge separation efficiency of photocatalysts is crucial to their catalytic activity, which is still challenging. Herein, nitrogen-doped carbon quantum dots (N-CQDs) were combined with Bi2WO6 to construct an N-CQDs/Bi2WO6 heterocomposite, which was loaded onto the surface of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membrane to design a flexible, porous and hydrophilic N-CQDs/Bi2WO6@PVDF-HFP photocatalytic membrane. Piezo-response force microscopy (PFM) and the maximum effective piezoelectric coefficient (d33) measurements demonstrate that the PVDF-HFP membrane has favorable piezoelectric properties. Besides, fluid-induced mechanical energy can generate a piezoelectric field within the PVDF-HFP membrane. Theoretical calculations indicate that the difference in work function at the N-CQDs/Bi2WO6 heterocomposite interface creates an inherent electric field. Therefore, the synergistic effect of the two electric fields improves the separation and migration efficiency of photogenerated carriers in N-CQDs/Bi2WO6 heterocomposite. The membrane effectively removed 85.3 % of oxytetracycline (OTC) under the synergistic driving of water flow (900 r/min) and visible light, surpassing the results of only water flow (34.4 %) and visible light (63.1 %). Furthermore, the degradation performance of the membrane towards OTC remains almost unchanged after multiple recycles, highlighting its favorable reusability. This work addresses the issue of powdery catalysts in recovering for practical applications and underlines the potential of integrating with natural low-frequency water flows to purify organic-contaminated wastewater.

Efficient antibiotic tetracycline degradation and toxicity abatement via the perovskite-type CaFexNi1-xO3 assisted heterogeneous electro-Fenton system

As one of the emerging contaminants, antibiotics are posing a great threat to the human health and environment, which requires effective treatment methods. Heterogeneous electro-Fenton is a promising technique for organic contaminant elimination, but preparation of an appropriate heterogeneous electro-Fenton catalyst still remains challenging. In this work, the feasibility of perovskite-type CaFexNi1-xO3 as heterogeneous electro-Fenton catalyst for tetracycline (TC) removal and toxicity abatement has been explored. It was found that, among the examined CaFexNi1-xO3 catalysts with different Ni doping amount, CaFe3/4Ni1/4O3 exhibited the best performance, achieving 92.1 % TC removal within 30 min without pH adjustment in the presence of 0.05 M Na2SO4 electrolyte. Choosing Cl--containing electrolyte enabled further improvement towards TC elimination. In addition, the CaFe3/4Ni1/4O3 based heterogeneous electro-Fenton system presented other advantages including good recyclability and universal applicability, and significant toxicity reduction (verified via both ECOSAR simulation and soybean germination test). The TC degradation pathways were elucidated through identification of intermediate products and DFT calculations. Mechanism investigations revealed that there existed a strong synergy between Fe and Ni, and ·OH and ·O2- played the primary roles in the system while 1O2 played an auxiliary role. This study presented a promising heterogeneous electro-Fenton catalyst for degradation of antibiotics such as tetracycline.

Performance enhancement and mechanism of tetracycline removal by visible light-driven photo bio-electro-fenton system with CoFe-LDH/g-C3N4 cathode

Bio-electro-Fenton (BEF) technology has shown significant advantages in the treatment of antibiotic wastewater. However, the strict pH application range (2-3) still limits the practical application of BEF. To overcome the limitation of pH on traditional BEF, CoFe-LDH/g-C3N4 composite catalyst was synthesized by hydrothermal method and applied to the BEF cathode to construct a photo-BEF (PBEF) system. The performance of the PBEF system under visible light was investigated with tetracycline hydrochloride (TC) as the target pollutant. The results showed that the PBEF system could extend the pH application range to 3-11 and could maintain more than 80 % of TC removal. The highest removal efficiency of TC by PBEF reached 94.98 % at pH 5, and the highest TOC removal could achieve 70.09 %, indicating that the PBEF can effectively remove TC. Meanwhile, PBEF also showed good universality, anti-interference and stability. In addition, to explore the mechanism of TC degradation by PBEF, the quenching experiments and electron spin resonance (ESR) tests were used to identify and evaluate the contribution of the reactive oxygen species in TC removal. And the results showed that e- and •OH played the major role in TC removal. Density functional theory (DFT) calculations were used to analyze the active sites of TC molecules, and three possible degradation pathways of TC were proposed. Moreover, the toxicity of TC degradation by PBEF was effectively reduced. This study proposes a new way to broaden the application range of pH by PBEF and provides a novel alternative for antibiotics removal from wastewater.

Real "zero energy consumption" for efficient antibiotics degradation by floating photocatalysis: modeling, degradation pathway and toxicity assessment

Floating photocatalysis is a real "zero energy consumption" and practicable green water treatment technology because of no need for reactor and pump, and direct contact with sunlight to produce more free radicals compared to traditional immersion photocatalysts. To realize "green" and "safe" practical application, efficiency for different water quality bodies and toxicity assessment of degradation products are key factors. In this work, an economic and efficient floating photocatalyst Bi doped P25-TiO2 (Bi@P25)/expanded perlite (EP), named BTEP was successfully constructed, exhibiting stronger visible light absorption and faster photogenerated carriers separation ability due to Bi doping and formation of Bi-O-Si bond. Ciprofloxacin (CIP) degradation efficiency (10 mg/L) in deionized water and three types of ambient water reached 97.8 % and 52.9 %-75.2 %, respectively, based on the major active species (h+ and •O2-). Three degradation pathways were determined and the reduced toxicity of most intermediates proved the process is green and safe. BTEP had strong adaptability over a wide pH range (3-9). The degradation efficiency is promoted by higher temperatures, while depressed by humic acid (HA) (still maintain over 65.3 % at 15 mg/L of HA). Moreover, the Random Forest model is the most suitable to achieve degradation efficiency prediction of different water parameters duo to the lowest root mean square error (RMSE) value (9.52) and the highest R2 value (0.9045). The BTEP based floating photocatalysis promotes the practical application of solar photocatalytic technology and realizes zero energy consumption to remove pollutants.

Highly efficient degradation of perfluoroalkyl substances (PFAS) by a novel polytetrafluoroetylene piezocatalyst

Perfluoroalkyl substances (PFAS) are environmentally persistent, bioaccumulative and toxic pollutants. However, thorough degradation of PFAS remains exceptionally difficult due to the high dissociation energy of the C-F bond. Here, we report a viable strategy to markedly degrade PFAS completely by capitalizing on a harmless polytetrafluoroetylene (PTFE) as a piezocatalyst. Remarkably, perfluorooctanoic acid (PFOA), as one of the widely used PFAS, was almost completely removed with a degradation rate of 93.4 % and a defluorination rate of 91.5 % by the ultrasound excitation of PTFE for 1 h. On the basis of the intermediate analysis, we proposed an oxidation mechanism for the piezocatalytic PFOA degradation. Furthermore, this strategy was also efficient for the degradation of perfluoroheptanoic acid (PFNA), perfluorooctane sulfonate (PFOS) and hexafluoropropylene oxide dimer acid (Gen-X), implying its effectiveness to remediate water containing multiple PFAS. Impressively, due to the diverse energy gap between HOMO and LUMO energy of various PFAS, the degradation reaction kinetics of different PFAS are of significant difference. This study provides the deep insight into the piezocatalytic technique for the remediation of persistent and disparate PFAS.

Sustainability-Inspired Upcycling of Organophosphorus Pollutants into Phosphatic Fertilizer in a Continuous-Flow Reactor

With the increasing requirement for phosphorus resources and their shortage in nature, cyclic utilization of organophosphorus pollutants into phosphatic fertilizer might offer a sustainable approach to achieve the recycling of phosphorus. Herein, we first report the selective degradation of organophosphorus pollutants, via the synergistic effect of peroxymonosulfate (PMS) and sodium percarbonate (SPC), into phosphates (o-PO4 3-), which are continually converted into phosphatic fertilizer by struvite precipitation on the continuous-flow reactor. Quenching experiments, electron paramagnetic resonance (EPR) results, electrochemical analysis, and density functional theory (DFT) calculation suggest that the transfer of electrons from SPC to PMS results in the synthesis of catalytically active species (i.e., ·OH, ·O2 -, 1O2, and CO3·-) for hydroxyethylidene-1,1-diphosphonicacid (HEDP) degradation. For the real glyphosate wastewater, the PMS/SPC system exhibits excellent catalytic activity with 69.20% decrease in chemical oxygen demand (COD) and 37.80% decrease in the total organic carbon (TOC) after 90 min. Indeed, high performance liquid chromatography (HPLC) confirms that glyphosate is completely degraded in 90 min with the formation of 271.93 µmol/L of o-PO4 3-, which is further converted into phosphatic fertilizer by the precipitation of struvite with 87.20% yield on continuous-flow reactor. Finally, biotoxicity of glyphosate to zebrafish and wheat seeds are significantly deceased after treatment of PMS/SPC system by zebrafish toxicology assays and germination tests of wheat seeds.

Operando Exploration of CoAl-LDH: Transformations Driving Alkaline Oxygen Evolution Reaction

This work reports a comprehensive study on the morphology, composition, and electronic structure of CoAl layered double hydroxide (CoAl-LDH) during the oxygen evolution reaction (OER). To capture electrochemically induced transformations, operando spectroscopic and microscopic methods are combined. The complementary data provided by operando near-edge X-ray absorption fine structure (NEXAFS), supported by density functional theory (DFT) calculations, and electrochemical atomic force microscopy (AFM), reveal that under OER conditions, CoAl-LDH is fragmented into smaller particles due to Al leaching. This process forms a "resting" phase with an average Co oxidation state of 2.5+, which readily transforms into the OER-active β-CoOOH phase upon further potential increase. This work exemplifies how operando methods enable precise tracking of oxidation state changes, element dissolution, and structural transformations at the nanoscale while the electrocatalyst is active. This approach contrasts with conventional pre- and post-mortem characterization, which would instead suggest Co3O4 formation. These findings extend beyond the specific example of CoAl-LDH, emphasizing the crucial importance of selective cation leaching, recrystallization, and morphological restructuring, since these processes play a key role not only in designing advanced multi-element materials but also in understanding the complex nanoscale mechanisms that govern the activation and durability of practical electrocatalysts.

Enhanced peroxone reaction with amphoteric oxide modulation for efficient decontamination of challenging wastewaters: Comparative performance, economic evaluation, and pilot-scale implementation

The peroxone reaction, a promising alternative technology for water treatment, is traditionally hampered by its restricted pH operational range and suboptimal oxidant utilization. In this study, we introduced a novel amphoteric metal oxide (ZnO)-regulated peroxone system that transcended the pH limitations of conventional peroxone processes. Our innovative approach exploited the unique properties of ZnO to regulate the reaction pathway of the traditional O3/H2O2 (or peroxymonosulfate, PMS) processes, resulting in a 52.4 % (64.9 %) increase in the removal efficiency of electron-deficient pollutant atrazine under acidic conditions (pH=5.8). This was achieved through the facilitated generation of hydroxyl radicals (•OH) and sulfate radicals (SO4•-), alongside a marked increase in the utilization efficiency of O3, thus reducing the requisite amount of oxidant. The primary active sites within this system were identified as zinc-oxidant sites, with the critical interfacial interactions between ZnO and oxidants elucidated through comprehensive analytical techniques. These studies reveal that ZnO acted as an electron acceptor, with H2O2 (or PMS) serving as the electron donor, leading to the formation of a reactive intermediate. This intermediate subsequently engaged with O3, producing secondary radicals such as HO2• (SO5•-) and O3•-, which were instrumental in generating the final radical species, •OH and SO4•-. The efficacy of this ZnO-regulated peroxone process was validated through resistance to interference tests, treatment of pilot-scale coking wastewater (mineralization rate of over 70 %), and extensive biological toxicity evaluations, all of which validated the system's robust degradation capability, stability, and significant detoxification potential. A detailed comparison of reaction systems with conventional technologies using Electrical Energy per Order (EE/O) and Life Cycle Assessment (LCA) further highlighted the advantages. This investigation offers a groundbreaking solution for the treatment of complex wastewater, showcasing the substantial promise of ZnO-catalyzed peroxone for practical wastewater treatment applications.

Enhanced visible light photocatalytic degradation of oxytetracycline through sugarcane bagasse biochar supported layered WS2 type-II staggered heterojunction: Towards performance, degradation pathway, toxicity, and life cycle assessment

This research presents the synthesis of sugarcane bagasse biochar (SCB) integrated with WS2 nanosheets via one step facile solid-phase reaction. The as-prepared SCBW composites were then evaluated for their photocatalytic efficacy in degrading the antibiotic oxytetracycline (OTC) from water. Among the tested conditions using a Taguchi L9 orthogonal array, SCBW-10 achieved a maximum OTC degradation efficiency of 92.7% under optimal conditions (pH = 7, dose = 0.5 g L⁻1, initial concentration = 5 mg L⁻1, reaction time = 180 min). The study also examined the impact of other environmental factors, identified the predominant reactive oxygen species (•O2⁻ and •OH) responsible for OTC degradation, and conducted toxicity assessment and prediction of degradation products using Vigna radiata seed germination and T.E.S.T. software, respectively. Further, the SCBW-10 nanocomposite demonstrated reusability over four cycles with minimal loss in efficiency. Lastly, a life cycle assessment was performed to evaluate the environmental impact of the proposed remediation system from gate to gate viewpoint.

Mechanism of oxygen vacancy engineering CoOX/Fe3O4 regulated electrocatalytic reduction of nitrate to ammonia

To enhance the activity of the nitrate reduction reaction (NO3-RR), the development of oxygen vacancies electrocatalysts is a promising approach for improving the efficiency of ammonia synthesis. However, the mechanism by which oxygen vacancies regulate NO3-RR to ammonia remains poorly understood. In this study, a series of CoOX/Fe3O4 composite catalysts derived from ZIF-67 containing oxygen vacancies (OVs) were synthesized to elucidate the role of OVs on the activity and selectivity of ammonia synthesis. Structural characterization revealed that the concentration of OVs in the catalysts increased with the addition of iron ions. Electrochemical experiments and theoretical calculations demonstrated that OVs promote interfacial electron transfer, alter the adsorption conformation of NO3* on the catalyst surface, and reduce the activation energy barrier of NO3*. Nonetheless, we observed that high concentrations of OVs exhibited a preference for the product NO2- at high potentials, which we attribute to the strong adsorption of NO* by the OVs, impeding the subsequent hydrogenation process. Additionally, electron paramagnetic resonance (EPR) and activated hydrogen (H*) quenching experiments indicated that the catalyst was unable to deliver substantial amounts of H* in the buffered electrolyte, resulting in low ammonia productivity. The ammonia Faraday current efficiency (FE) of CoOX/Fe3O4-90 in 0.1 M KOH and 0.1 M NO3- was 82.22 %, with an ammonia production rate of 1.09 mmol h-1 cm-2.

Distinct pathways for superoxide radical generation induced by Mn and Cu-based catalysts in electro-Fenton like process

Superoxide radicals (·O2-) has been regarded as one of the reactive oxygen species (ROS) for the elimination of complex contaminants via electro-Fenton like (EF-like) technology. However, the generation path of ·O2- is diverse, and the influence of the physicochemical properties of metals on the mechanism of ·O2- conversion is significant in the EF-like treatment of wastewater. Herein, metals (M = Mn, Cu) loaded zeolitic imidazolate frameworks catalytic materials (M-NC) were prepared for sulfamethoxazole (SMX) removal to analyze the effect of metals on the pathways of ·O2- generation. The removal kinetic rate of SMX by Cu-NC was 1.32 times higher than that of Mn-NC. Quenching experiments demonstrated that ·O2- is the most important oxidizing species to achieve SMX removal. The RRDE measurements and quantitative experiment on the concentration of H2O2 experiments indicated that Mn-NC was more inclined to generate ROS through activation of H2O2 and Cu-NC through other ways. Therefore, the transformation pathways of ·O2- in different catalytic systems were thoroughly analyzed. Electron paramagnetic resonance test and reactive oxygen species quenching experiments indicated that the pathway for ·O2- production of Mn-NC was O2 → H2O2 → ·O2-, and that of Cu-NC was O2 → ·O2-. The strategy of using Mn and Cu-based catalysts to investigate the mechanism of the ·O2- generation pathway provided a way to efficiently utilize the conversion of ·O2-.

Nanocarriers for the delivery of plant-extracted camptothecin derivatives and hepatocellular carcinoma treatment

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide and a major cause of death in cirrhosis. The prognosis of HCC is poor, with a mortality rate close to the morbidity rate. Once HCC develops distant metastasis, the area affected by the cancer cells is significantly enlarged, and there is still no effective treatment for HCC. Therefore, the development of effective drugs is essential to improve the survival rate of HCC patients. We designed and optimised a delivery system for compound 1, derived from camptothecin extract, by developing a multifunctional fluorescent drug delivery platform composed of polylactic acid (PLA), chitosan (CS), and fluorescein isothiocyanate (FITC) (PLA-CS-FITC). This system successfully encapsulated CP1 and compound 1, forming a PLA-CS-FITC@CP1@1 composite nanocarrier with dual functions for drug delivery and real-time fluorescence monitoring. The effects of the system on HCC proliferation and its regulation were evaluated by treating HCC cells in vitro, which provided an experimental basis for the development of drugs for HCC.

Efficient degradation of ciprofloxacin in water using nZVI/g-C3N4 enhanced dielectric barrier discharge plasma process

Residual antibiotics in aquatic environments pose health and ecological risks due to their persistence and resistance to biodegradation. Thus, it is crucial to develop efficient technologies for the degradation of such antibiotics. This study presents a novel approach using a nano zero-valent iron/graphitic carbon nitride (nZVI/g-C3N4)-enhanced dielectric barrier discharge (DBD) plasma process for the degradation of ciprofloxacin (CIP). The combination of nZVI and g-C3N4 with DBD plasma significantly enhances CIP degradation efficiency, achieving an apparent first-order kinetic constant of 0.2849 min⁻1 at an input voltage of 12 kV, which is 5.22 times higher than standalone DBD treatment and 10.59 times higher than the ozonation treatment. The morphology, elemental valence states, and other properties of nZVI/g-C3N4 have been thoroughly characterized and demonstrate good reusability. Reactive species such as ·OH dominates CIP degradation. The Fe atoms in nZVI/g-C3N4 exhibit a strong tendency to donate electrons, generating reactive oxygen through the dissociation of adsorbed water. The cleavage of C-F bonds, hydroxylation and ring-opening oxidation of the piperazine group are the main pathways for CIP degradation, which helps to reduce biotoxicity after treatment. Overall, this study provides insights into the mechanism of reactive species in a DBD-nZVI/g-C3N4 system, a system that has the potential to become an efficient and environmentally friendly solution for the treatment of antibiotic wastewater.

Revealing multi-level shortrange migration of electrons on full-spectrum response e-LDH/t-BiOCl/Bi2S3 and their essential role in the detoxification of Cr(VI) and refractory organic pollutants

The toxic dyeing wastewater containing both carcinogenic Cr(VI) and refractory dyes poses serious threats to ecological safety and human health. Herein, a novel composite photocatalytic material e-LDH/t-BiOCl/Bi2S3 with an ultrathin sandwich structure constructed achieves removal rate constants of 0.044 and 0.019 min-1 for Cr(VI) and reactive red 2 by adsorption-photocatalysis synergistic mechanism in full-spectrum illumination. This structure employs the interface conditions and built-in electric field to form multilevel short-range charge migration channel, achieving the targeted reduction and oxidation of Cr(VI) and azoxy dyes by electrons (e-) and holes (h+). Besides facilitating the reduction of Cr(VI), e- can also enhance the effective utilization of h+ and mediate the formation of other reactive oxygen species that target RR2 degradation. The degradation mechanism, pathway, and biological toxicity of RR2 single and Cr(VI)/RR2 coexistence reaction system were discussed by DFT calculation, LC-MS characterization, and T.E.S.T. evaluation. Moreover, we further investigated the photocatalytic activity and cost-effectiveness of the e-LDH/t-BiOCl/Bi2S3 system under continuous flow and real water settings, and determined the primary water quality parameters that influence photocatalytic performance. This work establishes a new concept for the rational design of robust ternary heterostructure photocatalysts with desirable morphology and competitive performance for photocatalytic applications.

A novel Ag/Bi/Bi2O2CO3 photocatalyst effectively removes antibiotic-resistant bacteria and tetracycline from water under visible light irradiation

Currently, achieving dual applications of Bi2O2CO3-based photocatalysts in photocatalytic degradation and sterilization under visible-light conditions is challenging. In this study, a novel Ag/Bi/Bi2O2CO3 visible-light photocatalyst with bimetallic doping and rich oxygen vacancies was successfully synthesized using a one-pot hydrothermal crystallization method. The existence of oxygen vacancies was verified by X-ray photoelectron spectroscopy (XPS) and Electron spin resonance (ESR) analysis. The experimental results showed that Ag/Bi/Bi2O2CO3 killed ∼100% (log 7) of antibiotic-resistant Escherichia coli (AR-E. coli) within 60 min and degraded 83.81% of tetracycline (TC) within 180 min under visible light irradiation. Moreover, Ag/Bi/Bi2O2CO3 can still remove 61.07% of TC in water after 5 cycles, showing excellent photocatalytic cycle stability and reusability. The possible degradation pathway of TC was determined by liquid chromatography-mass spectrometry. It was found that the main active substances in the photocatalytic disinfection of AR-E. coli were 1O2, h+, and ·OH, while 1O2 was the dominant active species in the photocatalytic degradation of TC. This study presents a promising Bi2O2CO3-based visible light photocatalyst for treating both antibiotics (TC) and antibiotic-resistant bacteria (AR-E. coli) in water.

Fast Solid-Phase Exfoliation of Layered Double Hydroxides with Tunable Functionalization

Two-dimensional (2D) layered double hydroxides (LDHs) with adjustable compositions and structure have been promising candidates for various domains, including catalysis, water treatment, and energy storage. To unlock their full potential, there is a strong demand for versatile and effective exfoliation techniques capable of generating diverse types of 2D LDHs. However, the conventional liquid-phase exfoliation methods typically rely on toxic solvents and face challenges with agglomeration and restacking. Herein, a series of LDHs, including CoAl-LDH, MgAl-LDH, ZnAl-LDH, and NiFe-LDH, have been successfully exfoliated into nanosheets using a solid-phase exfoliation technique. Meanwhile, surface functional groups and defects are introduced into the exfoliated LDHs. The incorporation of surface functional groups improves the homogeneity and aqueous dispersion stability of LDH nanosheets, enabling them to be stably stored for over six months while remaining redispersible and processable even after freeze-drying. Furthermore, the induced defects alter the electronic structure of the LDH nanosheets, generating more active sites that enhance their electrocatalytic performance. These advantages contribute to the superior OER activity of the exfoliated NiFe-LDH nanosheets with an ultralow overpotential of 258 mV at 10 mA cm-2. This work highlights the potential of solid-phase exfoliation as an efficient, environmentally friendly, and scalable method for the preparation and functionalization of 2D LDHs.

Tubular nanofiber membranes combined with Z-scheme CuS@Co3S4 heterojunction catalyst for high-efficient removal of polyvinyl alcohol from waste water with high COD

Polyvinyl alcohol (PVA), a typical water-soluble polymer with huge global production, is becoming one of the most ubiquitous pollutants and indeed the villain of the piece contributing high chemical oxygen demand (COD) in wastewater. Membrane technology is an effective method for wastewater purification, in particular, with the combination of peroxymonosulfate (PMS)-assisted advanced oxidation or photocatalytic process, is capable of maintaining high water flux and anti-fouling. Herein, a ZIF-67 derived Z-scheme CuS@Co3S4 heterojunction catalyst immobilized by poly (m-phenylene isophthalamide) (PMIA) tubular nanofiber membrane (CuS@Co3S4/PMIA-TNM) is designed using a polyester braided tube as interior reinforcement. The resultant membrane features with outstanding superhydrophilicity and commendable porosity (82.1 %), leading to a significantly enhanced permeability (water flux > 82.3 L·m-2·h-1). Meanwhile, the membrane shows promising PVA removal efficiency (> 99.9 %) with a high COD removal efficiency (∼ 83.4 %) and enhanced antifouling capacity (flux recovery ratio > 99.7 %) with the assistance of PMS driven by an ultra low-power LED lamp. The universal applicability and environmental adaptability are also verified in various reaction conditions. In terms of ecotoxicological impacts of the PVA wastewater before and after treatment on aquatic organisms, Zebrafish embryonic development dynamically demonstrated that the treated PVA waste water by the developed hybrid membrane is healthy for fish to grow. Our study definitely opens up a new avenue to develop high-performance catalytic membranes for PVA-based wastewater treatment.

Vinylene-Linked Donor-π-Acceptor Metal-Covalent Organic Framework for Enhanced Photocatalytic CO2 Reduction

Intramolecular charge separation driving force and linkage chemistry between building blocks are critical factors for enhancing the photocatalytic performance of metal-covalent organic framework (MCOF) based photocatalyst. However, robust achieving both simultaneously has yet to be challenging despite ongoing efforts. Here we develop a fully π-conjugated vinylene-linked multivariate donor-π-acceptor MCOF (D-π-A, termed UJN-1) by integrating benzyl cyanides linker with multiple functional building blocks of electron-rich triphenylamine and electron-deficient copper-cyclic trinuclear units (Cu-CTUs) moieties, featuring with strong intramolecular charge separation driving force, extended conjugation degree of skeleton, and abundant active sites. The incorporation of Cu-CTUs acceptor with electron-withdrawing ability and concomitantly giant charge separation driving force can efficiently accelerate the photogenerated electrons transfer from triphenylamine to Cu-CTUs, revealing by experiments and theoretical calculations. Benefiting from the synergistically effect of D-π-A configuration and vinylene linkage, the highly-efficient charge spatial separation is achieved. Consequently, UJN-1 exhibits an excellent CO formation rate of 114.8 μmol g-1 in 4 h without any co-catalysts or sacrificial reagents under visible light, outperforming those analogous MCOFs with imine-linked (UJN-2, 28.9 μmol g-1) and vinylene-linked COF without Cu-CTU active sites (UJN-3, 50.0 μmol g-1), emphasizing the role of charge separation driving force and linkage chemistry in designing novel COFs-based photocatalyst.

Bimetallic Au/Ag coated on In2O3 for the effective removal of emerging organic contaminants under natural sunlight irradiation

Antibiotics-polluted wastewater, likely causing the spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), can be effectively remediated by photocatalytic degradation driven by endless solar energy. Herein, bimetallic Au/Ag is deposited on In2O3 surface via a one-step sintering process followed by a controllable chemical reduction approach. Under natural sunlight irradiation, the optimal Au/Ag/In2O3 (UGI-1.0) photocatalyst possesses a considerable norfloxacin (NOR) degradation rate constant of 0.013 min-1, which is 3.25, 1.63, and 1.86 times higher than that of In2O3, Ag/In2O3, and Au/In2O3 respectively. The effect of many water characteristics (e.g., humic acid, water bodies, pH values, and coexisting anions) on the photodegradation performance of NOR over UGI-1.0 is investigated. Moreover, other persistent organic pollutants (ofloxacin, phenol, 2,4-dichlorophenol, and rhodamine B) can also be degraded over UGI-1.0, suggesting its universal oxidation capacity. To settle the challenge of powder photocatalyst recovery, the UGI-1.0 photocatalyst is coated on a frosted glass sheet, which exhibits outstanding activity and stability for degrading NOR. The bimetallic Au/Ag deposited on In2O3 promote its photo-absorption, and enhance its photoinduced charge separation and transfer efficiency by serving as electron accepter, leading to the boosted activity of Au/Ag/In2O3 catalysts. Particularly, the cultivation of staphylococcus aureus (S. aureus) and cabbage seeds reveals the efficient toxicity reduction of NOR by photocatalytic degradation and the nontoxic characteristic of UGI-1.0 catalyst. This work unveils the feasibility of UGI-1.0 to remediate real wastewater with the assistance of solar energy.

Rational design of waste anode graphite-derived carbon catalyst to activate peroxymonosulfate for atrazine degradation

As the rapidly growing number of waste lithium-ion batteries (LIBs), the recycling and reutilization of anode graphite is of increasing interest. Converting waste anode graphite into functional materials may be a sensible option. Herein, a series of carbonaceous catalysts (TG) were successfully prepared using spent anode graphite calcined at various temperatures and applied for activating peroxymonosulfate (PMS) to degrade atrazine (ATZ). The catalyst obtained at 800 °C (TG-800) showed the optimum performance for ATZ removal (99.2% in 6 min). Various experimental conditions were explored to achieve the optimum efficiency of the system. In the TG-800/PMS system, free radicals (e.g., SO4·-, HO·), singlet oxygen (1O2), together with a direct electron transfer pathway all participated in ATZ degradation, and the ketonic (CO) group was proved as the leading catalytic site for PMS activation. The potential degradation routes of ATZ have also been presented. According to the toxicity assessment experiments, the toxicity of the intermediate products decreased. The reusability and universal applicability of the TG-800 were also confirmed. This research not only provides an efficient PMS activator for pollutant degradation, but also offers a meaningful reference for the recovery of waste anode graphite to develop environmentally functional materials.

Boosting the photocatalytic decontamination efficiency using a supramolecular photoenzyme ensemble

Continuous industrialization has raised daunting environmental concerns, and there is an urgent need to develop a sustainable strategy to tackle the contamination issues. Here, we report a supramolecular photoenzyme ensemble enabling the harvest of solar energy to remove contaminations in water. The well-sourced oxidoreductase, laccase, is confined into a photoactive hydrogen-bonded organic framework (PHOF) through an in situ encapsulation method. The direct electron migration between the oxidation center in a PHOF and the reduction center in laccase facilitates synergistic photoenzyme-coupled catalysis, showing two orders of magnitude higher activity than free laccase for pollutant degradation under visible light, without the need for sacrificial agents or costly co-mediators. Such high decontamination efficiency also surpasses the reported catalysts. The structure and decontamination function of this supramolecular photoenzyme ensemble remain highly stable in complex environment matrices, presenting desirable reusability and almost 100% conversion efficiency of pollutants for real sewage samples. Our conceptual photoenzyme hybrid catalyst offers important insights into green and sustainable water decontamination.

Insights on the efficiency and contribution of single active species in photocatalytic degradation of tetracycline: Priority attack active sites, intermediate products and their toxicity evaluation

Photocatalysis has been proven to be an excellent technology for treating antibiotic wastewater, but the impact of each active species involved in the process on antibiotic degradation is still unclear. Therefore, the S-scheme heterojunction photocatalyst Ti3C2/g-C3N4/TiO2 was successfully synthesized using melamine and Ti3C2 as precursors by a one-step calcination method using mechanical stirring and ultrasound assistance. Its formation mechanism was studied in detail through multiple characterizations and work function calculations. The heterojunction photocatalyst not only enabled it to retain active species with strong oxidation and reduction abilities, but also significantly promoted the separation and transfer of photo-generated carriers, exhibiting an excellent degradation efficiency of 94.19 % for tetracycline (TC) within 120 min. Importantly, the priority attack sites, degradation pathways, degradation intermediates and their ecological toxicity of TC under the action of each single active species (·O2-, h+, ·OH) were first positively explored and evaluated through design experiments, Fukui function theory calculations, HPLC-MS, Escherichia coli toxicity experiments, and ECOSAR program. The results indicated that the preferred attack sites of ·O2- on TC were O20, C7, C11, O21, and N25 atoms with high f+ value. The toxicity of intermediates produced by ·O2- was also lower than those produced by h+ and ·OH.

Ternary heterojunction of cross-linked benzene Polymer/Bi2MoO6-Graphene oxide catalysts promote efficient adsorption and photocatalytic removal of oxytetracycline

Antibiotics are refractory degradable organic pollutants that present a significant hazard to water environments. In this work, a ternary composite (KB/BMO-GO) comprising of graphene oxide (GO), Bi2MoO6 (BMO), and a cross-linked benzene polymer (KB) was synthesized and applied to promote the synergistic adsorption-photocatalytic degradation of the refractory pollutant, oxytetracycline (OTC). The inclusion of GO and KB in the composite enhanced the OTC adsorption performance of the catalysts, and the construction of Z-scheme heterojunction promoted the photogenerated charge separation efficiency and broadened the range of light absorption, thereby enhancing the photocatalytic performance. Moreover, we compared the performance of catalysts loaded with different mass ratios of KB (x% KB/BMO-GO). Among them, the 15 % KB/BMO-GO catalyst sample had the best OTC degradation performance. Specifically, 15 % KB/BMO-GO could adsorb 69.7 % of OTC in 30 min, reaching an OTC degradation rate of 93.3 % under visible light irradiation. h+ and 1O2 are the main active substances in the photocatalytic process. In addition, the catalysts are acid-alkali and salt-resistant, as well as good reusability. This study provides a valuable reference for the preparation of highly efficient photocatalysts for synergistic adsorption-photodegradation processes.

Vacancy Engineering in 2D Transition Metal Chalcogenide Photocatalyst: Structure Modulation, Function and Synergy Application

Transition metal chalcogenides (TMCs) are widely used in photocatalytic fields such as hydrogen evolution, nitrogen fixation, and pollutant degradation due to their suitable bandgaps, tunable electronic and optical properties, and strong reducing ability. The unique 2D malleability structure provides a pre-designed platform for customizable structures. The introduction of vacancy engineering makes up for the shortcomings of photocorrosion and limited light response and provides the greatest support for TMCs in terms of kinetics and thermodynamics in photocatalysis. This work reviews the effect of vacancy engineering on photocatalytic performance based on 2D semiconductor TMCs. The characteristics of vacancy introduction strategies are summarized, and the development of photocatalysis of vacancy engineering TMCs materials in energy conversion, degradation, and biological applications is reviewed. The contribution of vacancies in the optical range and charge transfer kinetics is also discussed from the perspective of structure manipulation. Vacancy engineering not only controls and optimizes the structure of the TMCs, but also improves the optical properties, charge transfer, and surface properties. The synergies between TMCs vacancy engineering and atomic doping, other vacancies, and heterojunction composite techniques are discussed in detail, followed by a summary of current trends and potential for expansion.

Unique effect of bromide ion on intensification of advanced oxidation processes for pollutants removal: A systematic review

Advanced oxidation processes (AOPs) have been developed to decompose toxic pollutants to protect the aquatic environment. AOP has been considered an alternative treatment method for wastewater treatment. Bromine is present in natural waters posing toxic effects on human health and hence, its removal from drinking water sources is necessary. Of the many techniques advanced oxidation is covered in this review. This review systematically examines literature published from 1997 to April 2024, sourced from Scopus, PubMed, Science Direct, and Web of Science databases, focusing on the efficacy of AOPs for pollutant removal from aqueous solutions containing bromide ions to investigate the impact of bromide ions on AOPs. Data and information extracted from each article eligible for inclusion in the review include the type of AOP, type of pollutants, and removal efficiency of AOP under the presence and absence of bromide ion. Of the 1784 documents screened, 90 studies met inclusion criteria, providing insights into various AOPs, including UV/chlorine, UV/PS, UV/H2O2, UV/catalyst, and visible light/catalyst processes. The observed impact of bromide ion presence on the efficacy of AOP processes, alongside the AOP method under scrutiny, is contingent upon various factors such as the nature of the target pollutant, catalyst type, and bromide ion concentration. These considerations are crucial in selecting the best method for removing specific pollutants under defined conditions. Challenges were encountered during result analysis included variations in experimental setups, disparities in pollutant types and concentrations, and inconsistencies in reporting AOP performance metrics. Addressing these parameters in research reports will enhance the coherence and utility of subsequent systematic reviews.

Ultrathin BiOCl-OV/CoAl-LDH S-scheme heterojunction for efficient photocatalytic peroxymonosulfate activation to boost Co (IV)=O generation

Sustainable and rapid production of high-valent cobalt-oxo (Co(IV)=O) species for efficiently removing organic pollutants is challenging in permoxymonosulfate (PMS) based advanced-oxidation-processes (AOPs) due to the limitation of the high 3d-orbital electronic occupancy of Co and slow conversion from Co(III) to Co(II). Herein, S-scheme BiOCl-OV/CoAl-LDH heterojunction were constructed by ultrathin BiOCl with the oxygen-vacancy (OV) self-assembled with ultrathin CoAl-LDH. OV promoted the formation of charge transfer channel (Bi-O-Co bonds) at the interface of the heterojunction and reduced electron occupation of the Co 3d-orbital to facilitate the generation of Co(IV)=O in the BiOCl-OV/CoAl-LDH/PMS/Visible-light system. S-scheme heterojunction accelerated the photogenerated electrons to allow rapid conversion of Co(III) to Co(II), promoting the fast two-electron transfer from Co(II) to Co(IV)=O. Consequently, the developed BiOCl-OV/CoAl-LDH/PMS/Visible-light system showed excellent degradation efficiency for most of organic pollutions, and exhibited very high removal capability for the actual industrial wastewater. This study provides a new insight into the evolution of Co(IV)=O and the coordinative mechanism for photocatalysis and PMS activation.

Oxygen-deficient AgIO3 for efficiently photodegrading organic contaminants under natural sunlight

Defect engineering is regarded as an effective strategy to boost the photo-activity of photocatalysts for organic contaminants removal. In this work, abundant surface oxygen vacancies (Ov) are created on AgIO3 microsheets (AgIO3-OV) by a facile and controllable hydrogen chemical reduction approach. The introduction of surface Ov on AgIO3 broadens the photo-absorption region from ultraviolet to visible light, accelerates the photoinduced charges separation and migration, and also activates the formation of superoxide radicals (•O2-). The AgIO3-OV possesses an outstanding degradation rate constant of 0.035 min-1, for photocatalytic degrading methyl orange (MO) under illumination of natural sunlight with a light intensity is 50 mW/cm2, which is 7 and 3.5 times that of the pristine AgIO3 and C-AgIO3 (AgIO3 is calcined in air without generating Ov). In addition, the AgIO3-OV also exhibit considerable photoactivity for degrading other diverse organic contaminants, including azo dye (rhodamine B (RhB)), antibiotics (sulflsoxazole (SOX), norfloxacin (NOR), chlortetracycline hydrochloride (CTC), tetracycline hydrochloride (TC) and ofloxacin (OFX)), and even the mixture of organic contaminants (MO-RhB and CTC-OFX). After natural sunlight illumination for 50 min, 41.4% of total organic carbon (TOC) for MO-RhB mixed solution can be decreased over AgIO3-OV. In a broad range of solution pH from 3 to 11 or diverse water bodies of MO solution, AgIO3-OV exhibits attractive activity for decomposing MO. The MO photo-degradation process and mechanism over AgIO3-OV under natural sunlight irradiation has been systemically investigated and proposed. The toxicities of MO and its degradation intermediates over AgIO3-OV are compared using Toxicity Estimation Software (T.E.S.T.). Moreover, the non-toxicity of both AgIO3-OV catalyst and treated antibiotic solution (CTC-OFX mixture) are confirmed by E. coli DH5a cultivation test, supporting the feasibility of AgIO3-OV catalyst to treat organic contaminants in real water under natural sunlight illumination.

Z-scheme heterojunction photocatalyst formed by MOF-derived C-TiO2 and Bi2WO6 for enhancing degradation of oxytetracycline: Mechanistic insights and toxicity evaluation in the presence of a single active species

In the work, Bi2WO6/C-TiO2 photocatalyst was successfully synthesized for the first time by loading narrow bandgap semiconductor Bi2WO6 on MOF-derived carboxyl modified TiO2. The phase structure, morphology, photoelectric properties, surface chemical states and photocatalytic performance of the prepared photocatalysts were systematically investigated using various characterization tools. The degradation efficiency of oxytetracycline by 6BT Z-scheme heterojunction photocatalyst under visible light could reach 93.6 % within 100 min, which was related to the high light harvesting and effective separation and transfer of photo-generated carriers. Furthermore, the effects of various environmental factors in actual wastewater were further investigated, and the results showed that 6BT exhibited good adaptability, durability and resistance to interference. Unlike most works, the degradation system with a different single active species were designed and constructed based on their formation mechanism. In addition, for the first time, a positive study was conducted on the priority attack sites, intermediate products, and degradation pathways for the photocatalytic degradation of oxytetracycline by a single active species through HPLC-MS and Fukui index calculations. The toxicity changes of intermediate products produced in three different single active species oxidation systems were evaluated using toxicity assessment software tools (T.E.S.T.), Escherichia coli growth experiments, and wheat growth experiments. Among them, the intermediate products formed through O2- oxidation had the lowest toxicity and the main active sites it attacked were the 20C, 38O, 18C, 41O, and 55O atoms with high f+ values in the oxytetracycline molecular structure. This work provided the insight into the role of each active species in the degradation of antibiotics and offered new ideas for the design and synthesis of efficient and eco-friendly photocatalysts.

Boosting the activity for organic pollutants removal of In2O3 by loading Ag particles under natural sunlight irradiation

A novel photocatalyst In2O3 with loading Ag particles is prepared via a facile one-step annealing method in air atmosphere. The Ag/In2O3 exhibits considerable photoactivity for decomposing sulfisoxazole (SOX), tetracycline hydrochloride (TC), and rhodamine B (RhB) under natural sunlight irradiation, which is much higher than that of pristine In2O3 and Ag species. After natural sunlight irradiation for 100 min, 70.6% of SOX, 65.6% of TC, and 81.9% of RhB are degraded over Ag/In2O3, and their corresponding chemical oxygen demand (COD) removal ratio achieve 95.4%, 38.4%, and 93.6%, respectively. A batch of experiments for degrading SOX with adjusting pollutant solution pH and adding coexisting anions over Ag/In2O3 are carried out to estimate its practical application prospect. Particularly, the as-prepared Ag/In2O3 possesses a superior stability, which exhibits no noticeable deactivation in decomposing SOX after eight cycles' reactions. In addition, the Ag/In2O3 coated on a frosted glass plate, also possesses a superior activity and stability for SOX removal, which solve the possible second pollution of residual powdered catalyst in water. Ag particles on In2O3 working as electron accepter improve charge separation and transfer efficiency, as well as the photo-absorption and organic pollutants affinity, leading to the boosted photoactivity of Ag/In2O3. The photocatalytic mechanism for degrading SOX and degradation process over Ag/In2O3 has been systemically investigated and proposed. This work offers an archetype for the rational design of highly efficient photocatalysts by metal loading.

Methyl contributes to the directed phosphorus doping of g-C3N4: pH-dependent selective reactive oxygen species enable customized degradation of organic pollutants

In the photocatalytic degradation process, constructing a controllable composite oxidation system with radicals and nonradicals to meet the requirement for efficient and selective degradation of diverse pollutants is significant. Herein, a methylated and phosphorus-doped g-C3N4 (NPEA) can exhibit selective radical and nonradical species formation depending on the pH values. The NPEA can spontaneously switch the production of active species according to the pH value of the reaction system, exhibiting steady-state concentrations of ·O2- for 11.83 × 10-2 µmol L-1 s-1 (with 92.7 % selectivity) under alkaline conditions (pH = 11), and steady-state concentrations of 1O2 for 5.18 × 10-2 µmol L-1 s-1 (with 88.7 % selectivity) under acidic conditions (pH = 3). The NPEA exhibits stability and universality in the degradation of pollutants with rate constant for sulfamethazine (k = 0.261 min-1) and atrazine (k = 0.222 min-1). Moreover, the LC-MS and Fukui function demonstrated that the NPEA can tailor degradation pathways for pollutants, achieving selective degradation. This study offers a comprehensive insight into the mechanism of the photocatalytic oxidation system, elucidating the intricate interplay between pollutants and reactive oxygen species.

Tuning interfacial oxygen vacancy level of bismuth oxybromide to enhance photocatalytic degradation of bisphenol A

Oxygen vacancies (OVs) have garnered significant interest for their role as active sites, enhancing the catalytic efficiency of various catalysts. Despite their widespread application in environmental purification processes, the generation of OVs conventionally depends on high-temperature conditions and strong reducing agents for the extraction of surface partial oxygen atoms from catalysts. In this work, bismuth oxybromide (BiOBr) nanosheets with varying levels of OVs were synthesized via a simple and effective solvothermal method. This novel method affords precise control over the conduction band (CB) and valence band (VB) positions of BiOBr. The presence of different OVs exhibited varying photocatalytic efficiencies in the degradation of bisphenol A (BPA) under visible light irradiation, with higher levels of OVs resulting in superior photocatalytic performance. Furthermore, radical scavenger experiments demonstrated that superoxide oxides (O2•-) and holes (h+) were the primary reactive oxygen species for BPA degradation. Additionally, BiOBr-OVs exhibited excellent anti-interference and stability in water matrices containing diverse inorganic anions and organic compounds. This work provides a simple and effective approach for the fine-regulating of catalysts through interfacial defect engineering, paving the way for their practical application in environmental decontamination.

Rational Design and Synthesis of Fe-Doped Co-Based Coordination Polymer Composite Photocatalysts for the Degradation of Norfloxacin and Ciprofloxacin

The solar light-responsive Fe-doped Co-based coordination polymer (Fe@Co-CP) photocatalyst was synthesized under mild conditions. [Co(4-padpe)(1,3-BDC)]n (Co-CP) was first constructed using mixed ligands through the hydrothermal method. Then, Fe was introduced into the Co-CP framework to achieve the enhanced photocatalytic activity. The optimal Fe@Co-CP-2 exhibited excellent catalytic degradation performance for norfloxacin and ciprofloxacin under sunlight irradiation without auxiliary oxidants, and the degradation rates were 91.25 and 92.66% in 120 min. These excellent photocatalytic properties were ascribed to the generation of the Fe-O bond, which not only enhanced the light absorption intensity but also accelerated the separation efficiency of electrons and holes, and hence significantly improved the photocatalytic property of the composites. Meanwhile, Fe@Co-CP-2 displayed excellent stability and reusability. In addition, the degradation pathways and intermediates of antibiotic molecules were effectively analyzed. The free radical scavenging experiment and ESR results confirmed that •OH, •O2-, and h+ active species were involved in the catalytic degradation reaction; the corresponding mechanisms were deeply investigated. This study provides a fresh approach for constructing Fe-doped Co-CP-based composite materials as photocatalysts for degradation of antibiotic contaminants.

A novel photo-enzyme platform based on non-metallic modified carbon nitride for removal of bisphenol A in water

A nonmetallic composite photocatalyst with 2D/2D structure was prepared by hydrothermal in-situ polymerization and used for the immobilization of cytochrome C (Cyt c). The photo-enzyme coupling system has a very high enzyme load, which can reach 528.29 mg g-1 after optimization. Compared with free Cyt c, Cytc/PEDOT/CN showed better enzymatic activity, stability and catalytic efficiency. Even after being stored at 100 °C for 60 min, the enzyme activity remained at 49.42 % and remained at 57.89 % after 8 cycles. Moreover, Cytc0.5/PEDOT3/CN showed excellent photocatalytic degradation performance in the degradation experiment of bisphenol A (BPA), reaching 68.22 % degradation rate within 60 min, which was 3.9 times higher than that of pure g-C3N4 and 1.61 times higher than that of pure PEDOT3/CN. This study shows that the introduction of conductive polymers is of great significance to the photo-enzyme coupling system and provides a new strategy for the treatment of phenol-containing wastewater.

The diverse roles of halide ions in the degradation of bisphenol A via UV/peracetic acid process at different pH values: Radical chemistry, and transformation pathways

UV/Peracetic Acid (UV/PAA), as an innovative advanced oxidation process (AOP), is employed to treat bisphenol A (BPA) in water through the generation of hydroxyl radicals (•OH) and carbon-centered radicals (R-C•). The impact of halide ions (Cl-; Br-; I-) on the efficiency of UV/PAA was investigated for the first time under varying pH levels. The presence of halide ions exerted an influence on the reactivity of •OH and R-C•, exhibiting varying degrees of impact across different pH conditions. It was discovered that pH exerts a significant influence on its efficiency, with optimal removal performance observed at a pH 9. The degradation of BPA was inhibited by Cl- through the generation of reactive chlorine species (RCS), which triggers the interconversion between •OH and R-C•. Reactive bromine species (RBS) were produced in the presence of Br-, facilitating BPA degradation and generating HOBr as a supplementary source of •OH radicals. I- primarily generate reactive iodine species (RIS) through photolysis, which facilitates the degradation of BPA. The transformation of BPA involves hydroxylation, demethylation, halogenation, and cleavage reactions to form various products and pathways. The toxicity test demonstrates that the UV/PAA treatment of BPA exhibits lower toxicity, thereby indicating its environmentally friendly.

Fabrication of CuFe2O4/Bi12O17Cl2 photocatalyst with intrinsic p-n junction for highly efficient bisphenol A degradation

The construction and application of novel highly efficient photocatalysts have been the focus in the field of environmental pollutant removal. In this work, a novel CuFe2O4/Bi12O17Cl2 photocatalysts were synthesized by simple hydrothermal and chemical precipitation method. The fabricated CuFe2O4/Bi12O17Cl2 composite exhibited much higher photocatalytic activity than pristine CuFe2O4 and Bi12O17Cl2 in the removal of bisphenol A (BPA) under visible-light illumination, which ascribed to the intrinsic p-n junction of CuFe2O4 and Bi12O17Cl2. The photocatalytic degradation rate of BPA on CuFe2O4/Bi12O17Cl2 with an optimized CuFe2O4 content (1.0 wt.%) reached 93.0% within 30 min. The capture experiments of active species confirmed that the hydroxyl radicals (•OH) and superoxide radicals (•O2-) played crucial roles in photocatalytic BPA degradation process. Furthermore, the possible degradation mechanism and pathways of BPA was proposed according to the detected intermediates in photocatalytic reaction process.

Construction of Bi/BiOI/BiOCl Z-scheme photocatalyst with enhanced tetracycline removal under visible light

Bi/BiOI/BiOCl composite photocatalyst was constructed by one-step stirring approach at ambient environment to remove of tetracycline (TC) antibiotics via photodegradation in aqueous medium. A systematic discussion of the architecture, composition, formation, photochemical performance and photocatalytic activity of Bi/BiOI/BiOCl was carried out. By adjusting the experimental conditions, it was found that the Bi/BiOI/BiOCl photocatalyst obtained by using 0.7 mmol NaBH4, I/Cl = 5% and reacting for 6 h had the greatest removal performance. Under visible light irradiation, the photocatalytic degradation efficiency of TC reached 90.3% within 60 min, surpassing that of single BiOCl and BiOI. Through the active species removal experiment, it was determined that •O2- made a primary contribution to the photocatalytic degradation process. Moreover, the formation of Z-scheme heterojunction in Bi/BiOI/BiOCl was discussed, analyzing the photocatalytic mechanism and TC degradation pathway. The ecological toxicity of TC solution before and after degradation to rice seedlings was preliminarily tested. This study provides an idea for one-step synthesis of bismuth-based composite photocatalysts, with potential applications in the photocatalytic degradation of antibiotics.

Photocatalytic degradation of alkyl imidazole ionic liquids by TiO2 nanospheres under simulated solar irradiation: Transformation behavior, DFT calculations and promoting effects of alkali and alkaline earth metal ions

In this study, TiO2 nanospheres prepared by the sol-gel method were found to efficiently catalyze the photodegradation of 1-butyl-2,3-dimethylimidazolium bromide salt ([BMMIm]Br) under simulated solar irradiation through the main attack of hydroxyl radicals (•OH). The promoting effect of alkali metal (Li+→Cs+) and alkaline earth metal ions (Mg2+→Ba2+) was particularly emphasized. In-situ EPR tests showed that the introduction of alkali and alkaline earth metal ions could enhance the formation of •OH thus leading to a 7%-30.3% increase in the degradation efficiency of. [BMMIm]+. Moreover, the removal efficiency of [BMMIm]+ still reached > 96.19% in four real waters. A total of 23 products of [BMMIm]Br were detected, and hydroxyl substitution, bond breaking, direct oxidation and ring opening were considered as the main reactions during the photocatalytic degradation process. The results of toxicity evaluation showed that hydroxylation was a reaction process of increasing toxicity, while the bond breaking reaction had great detoxification capacity for [BMMIm]+. These findings may enhance our understanding on the effects of alkali or alkaline earth metal ions on the photocatalytic activity of TiO2, which could also provide reference for the efficient and green removal of alkylimidazolium ionic liquids in waters.

Enhancing Electrocatalytic Water Oxidation of NiFe-LDH Nanosheets via Bismuth-Induced Electronic Structure Engineering

The design and synthesis of high-efficiency electrocatalysts are of great practical significance in electrocatalytic water splitting, specifically in accelerating the slow oxygen evolution reaction (OER). Herein, a self-supported bismuth-doped NiFe layered double hydroxide (LDH) nanosheet array for water splitting was successfully constructed on nickel foam by a one-step hydrothermal strategy. Benefiting from the abundant active sites of two-dimensional nanosheets and electronic effect of Bi-doped NiFe LDH, the optimal Bi0.2NiFe LDH electrocatalyst exhibits excellent OER performance in basic media. It only requires an overpotential of 255 mV to drive 50 mA cm-2 and a low Tafel slope of 57.49 mV dec-1. The calculation of density functional theory (DFT) further shows that the incorporation of Bi into NiFe LDH could obviously overcome the step of H2O adsorption during OER progress. This work provides a simple and effective strategy for improving the electrocatalytic performance of NiFe LDHs, which is of great practical significance.

Sonochemically assisted the synthesis and catalytic application of bismuth-based photocatalyst: A mini review

Recently, bismuth (Bi)-based photocatalysts have been a well-deserved hotspot in the field of photocatalysis owning to their photoelectrochemical properties driven by the distortion of the Bi 6 s orbital, while their narrow band gap and poor quantum efficiency still restrict their application. With the development of ultrasonic technology, it is expected to become a broom to clear the application obstacles of Bi-based photocatalysts. The special forces and environmental conditions brought by ultrasonic irradiation play beneficial roles in the preparation, modification and performance releasement of Bi-based photocatalysts. In this review, the role and influencing factors of ultrasound in the preparation and modification of Bi-based photocatalysts were introduced. Crucially, the mechanism of the improving the performance for various types of Bi-based photocatalysts by ultrasound in the whole process of photocatalysis was deeply analyzed. Then, the application of ultrasonic synergistic Bi-based photocatalysts in contaminants treatment and energy conversion was briefly introduced. Finally, based on an unambiguous understanding of ultrasonic technology in assisting Bi-based photocatalysts, the future directions and possibilities for ultrasonic synergistic Bi-based photocatalysts are explored.

Enhanced and synergistic catalytic activation by photoexcitation driven S-scheme heterojunction hydrogel interface electric field

The regulation of heterogeneous material properties to enhance the peroxymonosulfate (PMS) activation to degrade emerging organic pollutants remains a challenge. To solve this problem, we synthesize S-scheme heterojunction PBA/MoS2@chitosan hydrogel to achieve photoexcitation synergistic PMS activation. The constructed heterojunction photoexcited carriers undergo redox conversion with PMS through S-scheme transfer pathway driven by the directional interface electric field. Multiple synergistic pathways greatly enhance the reactive oxygen species generation, leading to a significant increase in doxycycline degradation rate. Meanwhile, the 3D polymer chain spatial structure of chitosan hydrogel is conducive to rapid PMS capture and electron transport in advanced oxidation process, reducing the use of transition metal activator and limiting the leaching of metal ions. There is reason to believe that the synergistic activation of PMS by S-scheme heterojunction regulated by photoexcitation will provide a new perspective for future material design and research on enhancing heterologous catalysis oxidation process.

Poly(acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)-grafted chitosan hydrogels for effective adsorption and photocatalytic degradation of dyes

As a result of the growth of industrialization and urbanization, the water ecosystem is contaminated by various pollutants, including heavy metal ions and dyes. The use of low-cost and environmentally friendly dye adsorbents has been investigated. A hydrogel was fabricated via graft polymerization of acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto chitosan. The hydrogel was used as a dye adsorbent and support for a zinc oxide (ZnO) powder photocatalyst. The adsorption capacity of the bare hydrogel was greater towards cationic dyes than anionic dyes. Grafting P(AA-co-AMPS) exhibited a 23-time increase in adsorption capacity towards crystal violet (CV) compared to pristine chitosan. The effect of the AA-AMPS molar ratio on CV adsorption was studied. A hydrogel with an AA-AMPS ratio of 10 : 1 had the highest adsorption capacity towards CV in water, removing 91% of the dye in 12 h. The maximum adsorption capacity was 2023 mg g-1. The adsorption kinetics and isotherm were described by the pseudo-second-order model and the Langmuir model, respectively. ZnO particles were in situ synthesized within the 10 : 1 hydrogel to facilitate the recovery of the photocatalyst. The ZnO hydrogel composite could remove 95% and 92% of CV from solutions on the 1st and 2nd cycle, respectively. In addition, the hydrogel composite containing only 8.7 wt% of ZnO particles effectively degraded adsorbed CV under sunlight and could be reused without requiring a chemical regeneration or photocatalyst recovery procedure. This hydrogel composite is an effective dual-functional material for the adsorption and photodegradation of dye pollutants in wastewater.

Porous cyclopentadiene unit-incorporated graphitic carbon nitride nanosheets for efficient photocatalytic oxidation of recalcitrant organic micropollutants in wastewater

For the purpose of searching for efficient photocatalysts to deal with recalcitrant organic micropollutants in wastewater, here an in-situ supramolecule self-assembly-thermal polymerization strategy is developed to prepare a series of porous cyclopentadiene (CPD) unit-incorporated g-C3N4 ultrathin nanosheets (CCPD-g-C3N4). The CCPD-g-C3N4 demonstrate CPD unit doping level-dependent and remarkably enhanced visible-light photocatalytic oxidation efficiency towards two organic micropollutants, acetaminophen and methylparaben, in which the optimized CCPD-g-C3N4-2 shows 6.1 and 3.5 times higher acetaminophen and methylparaben degradation rate than bulk g-C3N4; moreover, CCPD-g-C3N4-2 is still robust and efficient in the treatment of five mixed organic micropollutants in pharmaceutical wastewater, and the satisfactory micropollutant removal efficiency is obtained in a wide pH window and the presence of high concentrations of inorganic anions and cations as well as dissolved organic matters. Theoretical calculation combined with experimental test reveal that CCPD-g-C3N4 can significantly reduce ecological risk of the target pollutant after the photocatalytic degradation reaction. Such enhanced photocatalytic oxidation efficiency is dominated by the accelerated charge carrier separation dynamics and extended visible-light response region due to the incorporation of CPD units, which finally lead to the generation of abundant reactive oxygen species to degrade and mineralize target micropollutants efficiently.

Exceptional photo-elimination of antibiotic by a novel Z-scheme heterojunction catalyst composed of nanoscale zero valent iron embedded with carbon quantum dots (CQDs)-black TiO2

Passivation of nanoscale zero valent iron (nZVI, Fe0) impaired its longevity while black TiO2 (b-TiO2) suffered from restricted optical properties. Using a facile approach, a novel Z-scheme heterojunction catalyst (Fe0@CQDs-TiO2(b)) of nZVI decorated with carbon quantum dots (CQDs) implanted into b-TiO2 was designed. Characterization results revealed the optical potential of the passivation coating of nZVI. The incorporation of CQDs stimulated the creation of active •OH during the dark reaction, and led to an accelerated mobility of photo-excited carriers of b-TiO2 and optimized its band gap (narrowing from 2.36 eV to 2.15 eV) during the light reaction. The photo-elimination capacity of metronidazole (MNZ) on Fe0@CQDs-TiO2(b) (99.36%) was 2.64, 8.25 and 1.34 fold beyond that on nZVI, b-TiO2 and Fe0@b-TiO2, respectively. The assembled material offered excellent adaptability to environmental substrates, in addition to being virtually unaffected by tap (95.62%) and river water (92.62%). The mechanism of MNZ degradation was elaborated, and the combination of density functional theory (DFT) calculations and LC-MS discerned 12 intermediates and 3 routes. Toxicity assessment of these products was conducted to ensure no inadvertent negative environmental impacts arose. This work proposed an original direction and mechanism for the application of passivation layers in nZVI-based materials for environmental restoration.

Biochar/layered double hydroxides composites as catalysts for treatment of organic wastewater by advanced oxidation processes: A review

Heterogeneous advanced oxidation process has been widely studied as an effective method for removing organic pollutants in wastewater, but the development of efficient catalysts is still challenging. This review summaries the present status of researches on biochar/layered double hydroxides composites (BLDHCs) as catalysts for treatment of organic wastewater. The synthesis methods of layered double hydroxides, the characterizations of BLDHCs, the impacts of process factors influencing catalytic performance, and research advances in various advanced oxidation processes are discussed in this work. The integration of layered double hydroxides and biochar provides synthetic effects for improving pollutant removal. The enhanced pollutant degradation in heterogeneous Fenton, sulfate radical-based, sono-assisted, and photo-assisted processes using BLDHCs have been verified. Pollutant degradation in heterogeneous advanced oxidation processes using BLDHCs is influenced by process factors such as catalyst dosage, oxidant addition, solution pH, reaction time, temperature, and co-existing substances. BLDHCs are promising catalysts due to the unique features including easy preparation, distinct structure, adjustable metal ions, and high stability. Currently, catalytic degradation of organic pollutants using BLDHCs is still in its infancy. More researches should be conducted on the controllable synthesis of BLDHCs, the in-depth understanding of catalytic mechanism, the improvement of catalytic performance, and large-scale application of treating real wastewater.

Layered by layered construction of three novel ZnCo-LDHs/g-C3N4 for the removal of sunset yellow by adsorption-photocatalytic process

The removal of organic dyes has attracted attention by adsorption-photocatalytic synergetic process in water treatment technology. Three novel ZnCo-LDHs/g-C3N4 were successfully prepared for the first time by layered construction technique through the hydrolysis of triethanolamine in this paper. They exhibited high specific surface area which facilitates the adsorption of sunset yellow (SY) from solution to catalyst surface. All the target pollutant dyes are very effectively removed by the three ZnCo-LDHs/g-C3N4 composites through synergetic effect of adsorption and photocatalysis process under UV irradiation (λ = 365 nm). The order of synergistic degradation effect for SY is as follows: ZnCo-LDHs/g-C3N4-3 (99.6%) > ZnCo-LDHs/g-C3N4-2 (99.5%) > ZnCo-LDHs/g-C3N4-1 (99.3%) > pure g-C3N4 (77.4%) > pure ZnCo-LDHs (44.2.6%) at the initial concentration of 75 mg L-1. ZnCo-LDHs/g-C3N4-3 has the largest k value (0.0284 min-1) in SY degradation, which is 2.8 times that of g-C3N4. ZnCo-LDHs/g-C3N4-3 is a very promising adsorption-photocatalyst for the removal of SY from wastewater. The electron spin resonance experiments demonstrate that OH·, 1O2, and O2- are the dominant active species and oxides SY together. This result demonstrates that the three ZnCo-LDHs/g-C3N4 have practical applications as efficient adsorption-photocatalytic materials and also provides a synergetic strategy for the removal of SY wastewater.

Efficient photocatalytic degradation of ciprofloxacin by graphite felt-supported MnS/Polypyrrole composite: Dominant reactive species and reaction mechanisms

The accumulation of antibiotics in aquatic environments poses a serious threat to human health. Photocatalytic degradation is a promising method for removing antibiotics from water, but its practical implementation requires improvements in photocatalyst activity and recovery. Here, a novel graphite felt-supported MnS/Polypyrrole composite (MnS/PPy/GF) was constructed to achieve effective adsorption of antibiotics, stable loading of photocatalyst, and rapid separation of spatial charge. Systematic characterization of composition, structure and photoelectric properties indicated the efficient light absorption, charge separation and migration of the MnS/PPy/GF, which achieved 86.2% removal of antibiotic ciprofloxacin (CFX), higher than that of MnS/GF (73.7%) and PPy/GF (34.8%). The charge transfer-generated 1O2, energy transfer-generated 1O2, and photogenerated h+ were identified as the dominant reactive species, which mainly attacked the piperazine ring in the photodegradation of CFX by MnS/PPy/GF. The •OH was confirmed to participate in the defluorination of CFX via hydroxylation substitution. The MnS/PPy/GF-based photocatalytic process could ultimately achieve the mineralization of CFX. The facile recyclability, robust stability, and excellent adaptability to actual aquatic environments further confirmed MnS/PPy/GF is a promising eco-friendly photocatalyst for antibiotic pollution control.

Photocatalytic degradation of metronidazole and oxytetracycline by novel l-Arginine (C, N codoped)-TiO2/g-C3N4: RSM optimization, photodegradation mechanism, biodegradability evaluation

Removal of Metronidazole (MNZ) and Oxytetracycline (OTC) from wastewater by the prepared (C, N codoped)-TiO₂/g-C₃N₄ (Graphitic carbon nitride) was examined. l-Arginine (C, N codoped)-TiO₂ and l-Arginine (C, N codoped)-TiO₂/g-C₃N₄ photocatalysts were successfully synthesized through the sol-gel method, and optimal ratio of l-arginine:TiO₂, as well as l-arginine/TiO₂:g-C₃N₄, was determined by a kinetic study of photodegradation process. The maximum photocatalytic removal rate (0.065 min^-1 for MNZ removal) was observed using 1% l-Arginine-TiO₂/g-C₃N₄ (1:1) under visible light illumination, 2.2 and 6.5 times greater than those of 1% l-Arginine-TiO₂ and pure TiO₂, respectively. l-Arginine (1%)-TiO₂/g-C₃N₄ (1:1) (co-doped-TCN) was investigated using X-ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), Photo-luminescence (PL), and Differential Reflectance Spectroscopy (DRS) as the best-performing photocatalyst. Response surface methodology (RSM) was used to study the effect of co-doped-TCN dosage (0.5-1.0 g/L), pH of simulated wastewater (4-10), initial concentration of MNZ and OTC (50-100 mg/L), and irradiation time (30-90 min for MNZ and 20-40 min for OTC) on removal efficiency of the antibiotics. Also, their optimum values were determined by RSM. The treated pharmaceutical wastewater showed high biodegradability features with 5-day biological oxygen demand/chemical oxygen demand (BOD₅/COD) of 0.51 and 0.46 after 40 and 100 min reaction for OTC and MNZ, respectively. The order of reactive species responsible for the photodegradation of pollutants was •O₂^─> •OH > h⁺>¹O₂. The effect of inorganic anions showed that all anions decreased the removal efficiency of both antibiotics in order of NO₃^─> Cl^─ >SO₄^2─>HPO₄^2─ >HCO₃^─ for MNZ and NO₃^─> SO₄^2─ > Cl^─ >HPO₄^2─ >HCO₃^─ for OTC. Also, introducing different oxidants improved the photocatalytic removal efficiency with the order of H₂O₂>K₂S₂O₈> KBrO₃.

Lanthanide-doped upconversion glass-ceramic photocatalyst fabricated from fluorine-containing waste for the degradation of organic pollutants

Fluorine-containing waste is one kind of hazardous waste characteristic by hard disposal and utilization, it is an attractive way to prepare for fluoride-based luminescent matrix. In this work, to realize the high value-added utilization of fluorine-containing waste and reduce cost of the raw materials for preparation near-infrared (NIR) glass-ceramic (GC) photocatalyst, the pure fluoride of luminescent matrix was replaced by introducing fluorine-containing waste. The waste contained NIR GC photocatalyst was synthesis by the method of facile in-situ etching of an upconversion GC with HCl, which possesses core-shell structure, where the GC micro-powder including optically active centers lanthanides doped CaF₂ nanocrystals are displayed as the core, and the BiOCl is as the superficial coating. The upconversion emission performance of CaF₂ based luminescent matrix in photocatalyst is not weakened with HCl etching. NIR GC photocatalyst has high methyl orange and enrofloxacin degradation rate of 86 % and 82 % over 180 min after NIR light irradiation, respectively. The UV-Vis-NIR photocatalytic activity was enhanced degradation rate (93 % in 15 min) of enrofloxacin compared with those of commercial P25 and BiOCl. In addition, the photocatalyst had stable photocatalytic activity and it also can be regenerated. The study provided references for high value-added utilization fluorine-containing waste.

Biological and green remediation of heavy metal contaminated water and soils: A state-of-the-art review

Contamination of the natural ecosystem by heavy metals, organic pollutants, and hazardous waste severely impacts on health and survival of humans, animals, plants, and microorganisms. Diverse chemical and physical treatments are employed in many countries, however, the acceptance of these treatments are usually poor because of taking longer time, high cost, and ineffectiveness in contaminated areas with a very high level of metal contents. Bioremediation is an eco-friendly and efficient method of reclaiming contaminated soils and waters with heavy metals through biological mechanisms using potential microorganisms and plant species. Considering the high efficacy, low cost, and abundant availability of biological materials, particularly bacteria, algae, yeasts, and fungi, either in natural or genetically engineered (GE) form, bioremediation is receiving high attention for heavy metal removal. This report comprehensively reviews and critically discusses the biological and green remediation tactics, contemporary technological advances, and their principal applications either in-situ or ex-situ for the remediation of heavy metal contamination in soil and water. A modified PRISMA review protocol is adapted to critically assess the existing research gaps in heavy metals remediation using green and biological drivers. This study pioneers a schematic illustration of the underlying mechanisms of heavy metal bioremediation. Precisely, it pinpoints the research bottleneck during its real-world application as a low-cost and sustainable technology.