Fabrication of g-C3N4@N-doped Bi2MoO6 heterostructure for enhanced visible-light-driven photocatalytic degradation of tetracycline pollutant

Efficient degradation of antibiotic pollutants in water by Ca2+/Ce3+ Co-doped Bi2O2CO3 photocatalysts

Aiming at the bottleneck problems of limited visible light response range and high carrier recombination rate of Bi2O2CO3 (BOC) photocatalyst, Ca2+/Ce3+ co-doped Bi2O2CO3 composite photocatalyst was constructed by hydrothermal method. The analysis of different characterization techniques shows that double doping can lead to lattice distortion and induce oxygen defects. Under visible light irradiation, the degradation efficiency of ciprofloxacin (CIP) and levofloxacin (LVX) by BOC-Ca-Ce4 reached 92.56 % and 90.39 %, respectively, and maintained a certain degradation efficiency in complex water bodies such as tap water and lake water. ESR and capture experiments confirmed that •O2- and h+ were the dominant active species. Mechanism analysis showed that the valence cycle of Ce3+/Ce4+ and the local electric field of Ca2+ synergistically promoted the spatial separation of carriers. Through intermediate product analysis, CIP was finally mineralized to CO2/H2O, and the ECOSAR toxicity assessment showed that the ecological toxicity was reduced. This study provides a new design strategy for energy band engineering of two-component doped photocatalysts.

Engineering bandgap energy of MoO3 nanorod heterostructure using AgVO3 for efficient photocatalytic degradation of antibiotic pollutant

The increasing contamination of water bodies with pharmaceutical pollutants, particularly acetaminophen, necessitates innovative and efficient remediation strategies. This study introduces a novel AgVO3@MoO3 (AV@MoO3) nanorod heterostructure synthesized via a hydrothermal process designed to enrich the photocatalytic degradation of antibiotic pollutant using visible light irradiation. The bandgap energy of the optimum AV@MoO3-3 heterostructure is 2.62 eV which is lower than pristine MoO3 nanorod (3.16 eV). The integration of AgVO3 into MoO3 effectively reduced the bandgap energy and created beneficial surface defects, significantly boosting the visible-light absorption and photocatalytic activity. The optimized AV@MoO3-3 nanorod heterostructure achieved a remarkable photocatalytic degradation efficiency of 97.21% for acetaminophen, with a degradation rate constant of 0.0298 min-1, outperforming MoO3 (0.003 min-1) and AgVO3 (0.004 min-1) alone by factors of 9.9 and 7.4, respectively. Transient photocurrent and electrochemical impedance spectroscopy analyses confirmed the enhanced charge separation and reduced recombination. This study provides a comprehensive understanding of bandgap engineering and defect manipulation in heterostructures and highlights the potential for advanced water purification applications.

Defect-assisted surface modification of a g-C3N4@WC heterostructure for tetracycline degradation: DFT calculations, degradation pathways, and nematode-based ecological assessment

Eliminating hazardous antibiotics from aquatic environments has become a major concern in recent years. Tetracycline (TC) compounds pose a challenge for the selective degradation of harmful chemical groups. In this study, we successfully designed carbon vacancies in a gC3N4@WC (GW) heterostructure for the effective removal of TC pollutants under visible light. The carbon vacancies in the GW heterostructure were confirmed using X-ray photoelectron spectroscopy and electron spin resonance spectroscopy (ESR). The introduction of defects into the as-prepared GW heterostructure significantly impacted the photocatalytic performance of the catalyst. Moreover, defect formation results in enhanced light utilization, a large surface area, and the exposure of numerous active sites, thereby improving the redox capability and facilitating the efficiency of charge carriers during the photocatalytic degradation of TC. The photoluminescence and electrochemical analysis revealed that the GW3 heterostructure has a low recombination rate of photogenerated electron-hole pairs, which enhances the consumption of visible light. The as-prepared GW3 catalyst exhibits the highest degradation efficiency and kinetic rate constants of 92.73% and 0.0218 min-1 within 120 min, respectively. ESR and radical trapping experiments confirmed that ˙O2- radicals were the primary active species associated with the remarkable TC photodegradation activity. The degradation mechanism and intermediate reaction pathways of TC were investigated using density functional theory and liquid chromatography-mass spectroscopy studies. An in vivo model of C. elegans was used to investigate the toxicological effects of TC degradation. Therefore, this study proposes a method for the construction of dynamic and pioneering semiconductor catalysts to eliminate organic pollutants via photocatalysis.

Fabrication of 2D/2D Bi2MoO6/Sx@g-C3N(4-y) type-II heterojunction photocatalyst for enhanced visible-light-mediated degradation of tetracycline in wastewater

Aquatic biota and human health are seriously threatened by the dramatic rise in antibiotics in environmental matrices. In this regard, the present study aims to improve knowledge of the combined effects of heterojunction design and defect engineering on the photocatalytic degradation of pharmaceuticals in aqueous matrices. Advantageously, the positioning of the valence band (VB) and conduction band (CB) levels of Sx@g-C3N(4-y), being higher than those of Bi2MoO6, demonstrates the feasibility of forming a type-II heterojunction between these materials. Initially, S and N defects were inserted in S-doped g-C3N4 through an alkali-assisted calcination method (referred to as Sx@g-C3N(4-y)), as affirmed by the reduced concentrations of S and N in the end product. Thereafter, the Bi2MoO6/Sx@g-C3N(4-y) photocatalysts (referred to as BSxNy) were synthesized via a solvothermal method followed by calcination. Among the prepared samples, the integration of 10% Sx@g-C3N(4-y) with Bi2MoO6 (referred to as BSxNy (II)) demonstrated superior photocatalytic performance. Under optimal conditions, BSxNy (II) achieved a remarkable 92.4% degradation efficiency of tetracycline (TCL) in an aqueous solution after 60 min. The degradation rate of BSxNy (II) transcended that of pristine Sx@g-C3N(4-y) and Bi2MoO6 by 4.86 and 3.41 times, respectively. The higher number of active sites and the greater electron-hole pair separation are responsible for this improvement in the rate of TCL degradation. The photocatalyst also exhibited remarkable thermal/chemical stability and possessed reusability, as noted by 84% TCL degradation TCL up to 5 cycles. The radical scavenging experiment indicated O2˙- as the primary contributor towards TCL degradation, with h+ and ˙OH playing a secondary role. Additionally, a seed germination experiment used to measure phytotoxicity determined that the treated effluent was non-phytotoxic, making it suitable for irrigation.

Extended Interfacial Charge Transference in CoFe2O4/WO3 Nanocomposites for the Photocatalytic Degradation of Tetracycline Antibiotics

The large-scale utilization of antibiotics has opened a separate chapter of pollution with the generation of reactive drug-resistant bacteria. To deal with this, in this work, different mass ratios of CoFe2O4/WO3 nanocomposites were prepared following an in situ growth method using the precursors of WO3 and CoFe2O4. The structure, morphology, and optical properties of the nanocomposite photocatalysts were scrutinized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectra (UV-Vis DRS), photoluminescence spectrum (PL), etc. The experimental data signified that the loading of CoFe2O4 obviously changed the optical properties of WO3. The photocatalytic performance of CoFe2O4/WO3 composites was investigated by considering tetracycline as a potential pollutant. The outcome of the analyzed data exposed that the CoFe2O4/WO3 composite with a mass ratio of 5% had the best degradation performance for tetracycline eradication under the solar light, and a degradation efficiency of 77% was achieved in 20 min. The monitored degradation efficiency of the optimized photocatalyst was 45% higher compared with the degradation efficiency of 32% for pure WO3. Capturing experiments and tests revealed that hydroxyl radical (·OH) and hole (h+) were the primary eradicators of the target pollutant. This study demonstrates that a proper mass of CoFe2O4 can significantly push WO3 for enhanced eradication of waterborne pollutants.

Exploring the potential of CoMoO4-modified graphitic carbon nitride to boost oxidation of amoxicillin micropollutants in hospital wastewater

This study investigates the removal of amoxicillin micropollutants (AM) from hospital wastewater using CoMoO4-modified graphitic carbon nitride (CMO/gCN). Consequently, CMO/gCN exhibits notable improvements in visible light absorption and electron-hole separation rates compared to unmodified gCN. Besides, CMO/gCN significantly enhances the removal efficiency of AM, attaining an impressive 96.5%, far surpassing the performance of gCN at 48.6%. Moreover, CMO/gCN showcases outstanding reusability, with AM degradation performance exceeding 70% even after undergoing six cycles of reuse. The removal mechanism of AM employing CMO/gCN involves various photoreactions of radicals (•OH, •O2-) and amoxicillin molecules under light assistance. Furthermore, CMO/gCN demonstrates a noteworthy photodegradation efficiency of AM from hospital wastewater, reaching 92.8%, with a near-complete reduction in total organic carbon levels. Detailed discussions on the practical applications of the CMO/gCN photocatalyst for removal of micropollutants from hospital wastewater are provided. These findings underline the considerable potential of CMO/gCN for effectively removing various pollutants in environmental remediation strategies.

Recent progresses in synthesis and modification of g-C3N4 for improving visible-light-driven photocatalytic degradation of antibiotics

Graphitic carbon nitride (g-C3N4) is a widely studied visible-light-active photocatalyst for low cost, non-toxicity, and facile synthesis. Nonetheless, its photocatalytic efficiency is below par, due to fast recombination of charge carriers, low surface area, and insufficient visible light absorption. Thus, the research on the modification of g-C3N4 targeting at enhanced photocatalytic performance has attracted extensive interest. A considerable amount of review articles have been published on the modification of g-C3N4 for applications. However, limited effort has been specially contributed to providing an overview and comparison on available modification strategies for improved photocatalytic activity of g-C3N4-based catalysts in antibiotics removal. There has been no attempt on the comparison of photocatalytic performances in antibiotics removal between modified g-C3N4 and other known catalysts. To address these, our study reviewed strategies that have been reported to modify g-C3N4, including metal/non-metal doping, defect tuning, structural engineering, heterostructure formation, etc. as well as compared their performances for antibiotics removal. The heterostructure formation was the most widely studied and promising route to modify g-C3N4 with superior activity. As compared to other known photocatalysts, the heterojunction g-C3N4 showed competitive performances in degradation of selected antibiotics. Related mechanisms were discussed, and finally, we revealed current challenges in practical application.

Enhanced photocatalytic degradation of organic pollutants by green-synthesized gold nanoparticles using polysaccharide for environmental remediation

The recent rise in textile dye wastewater discharge into the environment has detrimental effects on living organisms and human health. The present study reports a facile approach to green-synthesized AuNPs employing sesbania gum for catalytic and photocatalytic degradation of organic pollutants. The obtained AuNPs were characterized by various techniques such as UV-vis, FT-IR, SEM, TEM, AFM, zeta potential, LC-MS, and XPS. The XRD patterns revealed a highly crystalline and face-centered cubic structure. XPS and EDX analysis defined the chemical composition and product purity of SBG-AuNPs. Photocatalytic degradation of hazardous dyes congo red and safranin-O using SBG-AuNPs showed a rapid decomposition rate with 94.69 % under visible light irradiation. The effect of pH, dye concentration, and catalyst dose on photodegradation and recyclability was also studied. The kinetic plots were used to calculate the rate constant, showing a pseudo-first-order reaction. Scavenger trap experiments confirmed the role of h+ and superoxide(.O2-) as active species, and LCMS analysis was used to identify the degradation intermediates. The catalytic reduction of SBG-AuNPs was studied for brilliant green (BG) and methylene blue (MB) in the presence of NaBH4, resulting the degradation efficiency of 90.37 % and 84.52 %, respectively. This study presents an innovative approach for designing highly efficient photocatalysts for environmental remediation and wastewater treatment from textile dyes.

WO3-x nanorods/rGO/AgBiS2 Z-scheme heterojunction with comprehensive spectrum response and enhanced Fenton and photocatalytic activities

Tetracycline (TC) antibiotics and dyes are the prevalent water contaminants, and their removal from the water through photocatalysis is a plausible approach. However, most semiconductors in their pristine form need to be improved to be exploited in photocatalysis owing to poor photoresponse, intense carrier recombination, and inertness without irradiation. Herein, we demonstrate the modification of defective WO3-x by rGO and AgBiS2 in the form of WO3-x/rGO/AgBiS2 (R2). It exploits the superior conductivity and synergism of rGO to inhibit carrier recombination; thereby, Z-scheme heterojunction with AgBiS2 provides high redox potential. Defects in WO3-x enable electron (e-) storage in R2, which decomposes H2O2 to generate ROS without irradiation. Owing to these essences and broad-spectrum response, it removed 93.72, 82.77, and 84.82% of TC during photo-Fenton (PFR), night-Fenton (NFR), and photocatalytic (PCR) reactions, respectively. Its removal rates reached 94.74, 81.54, and 87.50% against rhodamine B (RhB) during PFR, NFR, and PCR, respectively. It is superior to memory catalysis (MC) and conventional Fenton reactions (CFR) because it can perform without and with irradiation across a broader pH range. So, this work is conducive to designing WO3-x-based catalysts to combat environmental and energy crises.

All-solid-state Z-scheme ZnFe-LDH/rGO/g-C3N5 heterojunction for enhanced sonophotocatalytic degradation of ciprofloxacin: Performance and mechanistic insights

The fabrication of all-solid-state Z-scheme sonophotocatalysts is vital for improving the transfer rate of photogenerated electrons to remove antibiotics present in wastewater. Herein, a novel indirect Z-scheme ZnFe-layered double hydroxide (LDH)/reduced graphene oxide (rGO)/graphitic carbon nitride (g-C3N5) heterojunction was synthesized using a simple strategy. The ZnFe-LDH/rGO/g-C3N5 (ZF@rGCN) ternary composites were systematically characterized using different techniques. Results revealed that the 15%ZF@rGCN catalyst achieved a ciprofloxacin (CIP) degradation efficiency of 95% via the synergistic effect of sonocatalysis and photocatalysis. The improved sonophotocatalytic performance of the ZF@rGCN heterojunction was attributed to an increase in the number of active sites, a Z-scheme charge-transfer channel in ZF@rGCN, and an extended visible light response range. The introduction of rGO further enhanced the charge-transfer rate and preserved the reductive and oxidative sites of the ZF@rGCN system, thereby affording additional reactive species to participate in CIP removal. In addition, owing to its unique properties, rGO possibly increased the absorption of incident light and served as an electronic bridge in the as-formed ZF@rGCN catalyst. Finally, the possible CIP degradation pathways and the sonophotocatalytic Z-scheme charge-migration route of ZF@rGCN were proposed. This study presents a new approach for fabricating highly efficient Z-scheme sonophotocatalysts for environmental remediation.

Constructing a Titanium Silicon Molecular Sieve-Based Z-Scheme Heterojunction with Enhanced Photocatalytic Activity

Titanium silicon molecular sieve (TS-1) is an oxidation catalyst that possesses a long lifetime of charge transfer excited state, high Ti utilization efficiency, large specific surface area, and good adsorption property; therefore, TS-1 acts as a Ti-based photocatalyst candidate. In this work, TS-1 coupled Bi2MoO6 (TS-1/BMO) photocatalysts were fabricated via a facile hydrothermal route. Interestingly, the optimized TS-1/BMO-1.0 catalyst exhibited a decent photodegradation property toward tetracycline hydrochloride (85.49% in 120 min) under the irradiation of full spectrum light, which were 4.38 and 1.76 times compared to TS-1 and BMO, respectively. The enhanced photodegradation property of the TS-1/BMO-1.0 catalyst could be attributed to the reinforced light-harvesting capacity of the photocatalyst, high charge mobility, and suitable band structure for tetracycline hydrochloride degradation. In addition, the mechanism of photocatalytic degradation of tetracycline hydrochloride by the TS-1/BMO-1.0 catalyst was reasonably proposed based on the band structure, trapping, and ESR tests. This research provided feasible ideas for the design and construction of high-efficiency photocatalysts for contaminant degradation.