Degradation of tetracycline by FeNi-LDH/Ti3C2 photo-Fenton system in water: From performance to mechanism

Hollow layered double hydroxide nanoreactor activated peroxymonosulfate to efficiently degrade dye wastewater

The conventional preparation of layered double hydroxide (LDH) often limits its catalytic effectiveness in advanced oxidation processes due to agglomeration and inadequate exposure of active sites. In this work, we present a simplified synthesis approach that utilizes zeolitic imidazolate frameworks (ZIF)-67 (Co) as a sacrificial template to in situ fabricate hollow polyhedral CoFe-LDH (HP-LDH), aimed at enhancing the degradation of dye contaminants in aqueous systems. The unique porous and polyhedral structure of HP-LDH, derived from the template, facilitates contact efficiency between the substrate and active metal sites, acting as an effective nanoreactor. The comparative degradation experiments of Acid Red 27 (AR27) in peroxymonosulfate (PMS) revealed that the degradation efficiency of HP-LDH was nearly twice that of conventional flake LDH (F-LDH). Under optimal conditions, the HP-LDH/PMS system attained a removal rate of 95% in just 15 min. The degradation of the dye relies on the action of both radical and non-radical species, particularly 1O2. Furthermore, the robust adaptability and versatility of HP-LDH/PMS to real water bodies, with a wide range of pH levels and coexisting inorganic anions, demonstrates its potential as a superior catalyst in wastewater treatment, offering a novel pathway for structural innovation of LDH materials in environmental applications.

Pomegranate peel adsorbents for water pollutants removal: preparation, characterization and applications

Pomegranate peel waste in the forms of raw biomass, biochar and activated carbon has been explored as adsorbents in water treatment. This review examined and discussed published works between 2008 and 2024 that focused on the utilization of pomegranate peel waste adsorbents with emphasis on preparation strategies, characterization techniques and applications. The thermal and chemical activation have shown to improve the structural and chemical properties of the resultant adsorbent materials to effectively adsorb various pollutants such as dyes, heavy metals, organics, inorganic nonmetals, and pharmaceuticals from water. The performance was compared and the avenues for future research was highlighted to shed insight into the potential of pomegranate peel adsorbents for environmental protection.

S-Cu Doubly Doped NiFe LDH@Diatomite with Adjustable Surface Characteristics for the Efficient Removal of Tetracycline

Overuse of antibiotics can lead to increased bacterial resistance; therefore, there is a need to develop efficient nanomaterials for removing antibiotics from water. NiFe bimetallic hydroxide nanosheets doped with S-Cu were prepared on diatomite (S-CuNiFe LDH@diatomite) by using a two-step hydrothermal method. The surface of CuNiFe LDH@DE has a layered structure with an increased specific surface area and pore volume. The average pore size of S-CuNiFe LDH@De increases from 13.3 to 24.7 nm, and a more stereoscopic channel structure is obtained. Tetracycline removal experiments were performed on CuNiFe LDH@De and S-CuNiFe LDH@De. It was found that CuNiFe LDH@De had excellent photocatalytic performance and S-CuNiFe LDH@De had excellent adsorption performance. After CuNiFe LDH@De had been in contact with tetracycline (TC) for 2 h, the TC removal rate reached 95.6%. After S-CuNiFe LDH@De had been in contact with TC for 1 h, the adsorption capacity of TC was 145.5 mg/g. The pseudo-first-order kinetics and Sips isotherm model can be used to describe the adsorption process more accurately. The response surface method was used to optimize the adsorption conditions. According to the optimized conditions, a better adsorption performance of 166.9 mg/g was obtained. The two prepared materials showed good performance in the removal of tetracycline. This study provides a way to synthesize low-cost adsorbents and photocatalysts, which has value in the treatment of TC wastewater.

Heterointerface engineering of MXene: Advanced applications in environmental remediation

Contemporary global industrialization, coupled with the relentless growth of the population, has led to a persistent escalation in the emission and accumulation of various toxic and harmful chemicals in the environment, severely disrupting the ecological balance. The development of efficient environmental cleanup materials is a crucial scientific and technological concern. Since the groundbreaking work on Ti3C2Tx in 2011, there has been a huge growing interest in MXene-based composites developed through heterointerface engineering due to its high surface area, hydrophilicity, eco-friendliness, biocompatibility, easy functionalization, excellent thermal/mechanical properties, metal conductivity and rich electronic density. In the area of environmental remediation, MXene-based composites obtained through heterointerface engineering strategies have the ability to effectively remove and systematically monitor contaminants in comparison to virgin MXene, thanks to the synergistic effects and complementary benefits. Heterointerface engineering strategy increases specific surface area, introduces catalytic sites, constructs heterojunctions/Schottky junctions, and facilitates carrier migration and electron-hole separation. These novel MXene-based composites represent significant advances in MXene research and deserve a comprehensive review. Although several excellent reviews and perspectives on the application of MXene-based composites in environmental remediation have been published, there is still a scarcity of comprehensive and systematic assessments on the reliable data and mechanisms of various MXene-based composite materials for pollutant removal and monitoring. In this focused review, the first part briefly introduces the common preparation strategies and characterization methods of single MXene and MXene-based composites, and the second part details the innovative application of MXene-based composites (involving the amalgamation of MXene with metal oxides, metal sulfide, g-C3N4, layered double hydroxides, metal-organic frameworks, single atom/quantum dots, polymers, etc.) in the field of environmental remediation, including carbon dioxide reduction, nitrogen monoxide and volatile organic compounds removal, antibiotic and heavy metal ions degradation, summarizing the relevant performance and mechanisms. Furthermore, the recent advancements in the utilization of MXene-based composites for the sensing of emerging environmental contaminants (antibiotic and antibiotic resistance genes) are summarized. Finally, an outline of the existing challenges and future prospects on this exciting field was narrated for plausible real-world use. This review will help to inspire the diverse design of MXene-based composites and to advance research related to their application in the environmental sector.

A review of the degradation of antibiotic contaminants using advanced oxidation processes: modification and application of layered double hydroxides based materials

In recent years, the treatment of organic pollutants has become a global concern due to the threat to human health posed by emerging contaminants, especially antibiotic contamination. Advanced oxidation processes (AOPs) can solve the organic pollution problem well, which have been identified as a promising solution for the treatment of hard-to-handle organic compounds including antibiotic contaminants. Layered double hydroxides (LDHs) are excellent catalysts because of their flexible tunability, favorable thermal stability, abundant active sites, and facile exchangeability of intercalated anions. This paper conducted a systematic review of LDHs-based materials used for common antibiotic removal by three significant AOP technologies, such as photocatalysis, the Fenton-like processes, and peroxymonosulfate catalysis. The degradation effects studied in various studies were reviewed, and the mechanisms were discussed in detail based on the type of AOPs. Finally, the challenges and the application trends of AOPs that may arise were prospected. The aim of this study is to suggest ways to provide practical guidance for the screening and improvement of LDH materials and the rational selection of AOPs to achieve efficient antibiotic degradation. This could lead to the development of more efficient and environmentally friendly materials and processes for degrading antibiotics, with significant implications for our ecological conservation by addressing water pollution.

Ferrocenylselenoether and its cuprous cluster modified TiO2 as visible-light photocatalyst for the synergistic transformation of N-cyclic organics and Cr(vi)

In this study, fcSe@TiO2 and [Cu2I2(fcSe)2]n@TiO2 nanosystems based on ferrocenylselenoether and its cuprous cluster were developed and characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), and electron paramagnetic resonance (EPR). Under optimized conditions, 0.2 g L-1 catalyst, 20 mM H2O2, and initial pH 7, good synergistic visible light photocatalytic tetracycline degradation and Cr(vi) reduction were achieved, with 92.1% of tetracycline and 64.5% of Cr(vi) removal efficiency within 30 minutes. Mechanistic studies revealed that the reactive species ˙OH, ˙O2-, and h+ were produced in both systems through the mutual promotion of Fenton reactions and photogenerated charge separation. The [Cu2I2(fcSe)2]n@TiO2 system additionally produced 1O2 from Cu+ and ˙O2-. The advantages of the developed nanosystems include an acidic surface microenvironment provided by Se⋯H+, resourceful product formation, tolerance of complex environments, and excellent adaptability in refractory N-cyclic organics.

Cu0@CuOx-NC modified Zn2In2S5 for photo-self-Fenton system coupling H2O2 in-situ production and decomposition

Although many concerns have been put into photocatalytic hydrogen peroxide (H₂O₂) production, multifunctional catalysis suitable for continuously in-situ H₂O₂ consumption in the field has rarely been investigated. Herein, Cu⁰@CuO_x@nitrogen-doped graphitic carbon (Cu⁰@CuO_x-NC) decorated Zn₂In₂S₅ was successfully prepared for in-situ production and activation H₂O₂, which could achieve effectively photocatalytic self-Fenton degradation of tetracycline (TC). Under visible light irradiation, 5wt% Cu⁰@CuO_x-NC/Zn₂In₂S₅ (CuZS-5) efficiently generated a high yield of H₂O₂ (0.13 mmol L^-1), and Cu⁰@CuO_x-NC could in-situ consume H₂O₂ to generate hydroxyl radicals (•OH), accelerating the oxidation of TC. As a result, the 5 wt% Cu⁰@CuO_x-NC/Zn₂In₂S₅ degraded about 89.3% of TC within 60 min, and the cycle experiments also exhibited sufficient stability. This study achieves a delicate combination of in-situ production and activation of H₂O₂, which is regarded as a promising strategy to eco-friendly promote pollutant degradation in wastewater.

Visible-light-driven iron-based heterogeneous photo-Fenton catalysts for wastewater decontamination: A review of recent advances

Visible-light-driven heterogeneous photo-Fenton process has emerged as the most promising Fenton-derived technology for wastewater decontamination, owing to its prominent superiorities including the potential utilization of clean energy (solar light), and acceleration of ≡Fe(II)/≡Fe(III) dynamic cycle. As the core constituent, catalysts play a pivotal role in the photocatalytic activation of H₂O₂ to yield reactive oxidative species (ROS). To date, all types of iron-based heterogeneous photo-Fenton catalysts (Fe-HPFCs) have been extensively reported by the scientific community, and exhibited satisfactory catalytic performance towards pollutants decomposition, sometimes even exceeding the homogeneous counterparts (Fe(II)/H₂O₂). However, the relevant reviews on Fe-HPFCs, especially from the viewpoint of catalyst-self design are extremely limited. Therefore, this state-of-the-art review focuses on the available Fe-HPFCs in literatures, and gives their classification based on their self-characteristics and modification strategies for the first time. Two classes of representative Fe-HPFCs, conventional inorganic semiconductors of Fe-containing minerals and newly emerging Fe-based metal-organic frameworks (Fe-MOFs) are comprehensively summarized. Moreover, three universal strategies including (i) transition metal (TMs) doping, (ii) construction of heterojunctions with other semiconductors or plasmonic materials, and (iii) combination with supporters were proposed to tackle their inherent defects, viz., inferior light-harvesting capacity, fast recombination of photogenerated carriers, slow mass transfer and low exposure and uneven dispersion of active sites. Lastly, a critical emphasis was also made on the challenges and prospects of Fe-HPFCs in wastewater treatment, providing valuable guidance to researchers for the reasonable construction of high-performance Fe-HPFCs.

Synthesis, characterization and photocatalytic properties of In2.77S4/Ti3C2 composites

Recently, the problem of water pollution, caused by antibiotics, is becoming more and more serious. Photocatalysis is one of the promising technologies for removing antibiotics from water. Herein, the In_2.77S₄/Ti₃C₂ composites were prepared by an in-situ hydrothermal growth method for photocatalytic degradation of tetracycline (TC). The as-developed composites were characterized by various methods. The UV-Vis DRS spectra reveals that the introduction of Ti₃C₂ makes the bandgap of the as-prepared composites smaller and the visible light absorption ability improved. The photocatalytic degradation efficiency of the as-prepared composite is enhanced under visible light illumination. It is shown as first increasing and then decreasing with increasing the content of Ti₃C₂ in the composite and reaches to the maximum of 89.3% in 90 min, which is higher than 75.1% of In_2.77S₄ and 6.7% of Ti₃C₂. The reason of improvement is the interface between In_2.77S₄ and Ti₃C₂ is tightly combined to form a heterojunction. Moreover, the photocurrent intensity of the as-obtained composite is improved, while its Nyquist arc radius is decreased. In addition, holes are the main active species and ·OH and ·O₂ ^- play an auxiliary role during the degradation of TC.

A self-sufficient photo-Fenton system with coupling in-situ production H2O2 of ultrathin porous g-C3N4 nanosheets and amorphous FeOOH quantum dots

Photo-Fenton degradation of pollutants in wastewater involving hydrogen peroxide (H₂O₂) and Fe²⁺ ions to produce hydroxyl radicals (·OH) with high oxidative activity is an ideal and feasible choice in advanced oxidation processes (AOPs). However, the photo-Fenton degradation application is limited by the range of acidic pH and the external introduction of H₂O₂ and Fe²⁺ ions. Herein, a self-sufficient photo-Fenton system was developed by coupled ultrathin porous g-C₃N₄ (UPCN) nanosheets that spontaneously produce H₂O₂ with amorphous FeOOH quantum dots (QDs) via in-situ deposition method for efficient photo-Fenton degradation of oxytetracycline (OTC) under natural pH condition. The enhancement of photocatalytic degradation activity comes from the synergistic effect of amorphous FeOOH QDs and UPCN nanosheets as follows: on the one hand, the formation of photo-Fenton system combining in-situ generation H₂O₂ of UPCN with amorphous FeOOH QDs can better boost photocatalytic activity for degrading OTC solution in natural pH under light illumination; on the other hand, the ultrathin porous structure of UPCN can better promote the rapid transfer and dispersion of photo-generated electrons from UPCN to amorphous FeOOH QDs and then Fe³⁺ is reduced to Fe²⁺ to participate in the Fenton catalytic reaction.