pH adjustable MgAl@LDH-coated MOFs-derived Co2.25Mn0.75O4 for SMX degradation in PMS activated system

Novel CoFe-supported UiO-66-derived ZrO2 for rapid activation of peracetic acid for sulfamethoxazole degradation

The leaching of toxic metals is still problematic for heterogeneous metal catalysts in activating peracetic acid (PAA). Herein, CoFe/U-ZrO2 was synthesized by loading CoFe onto the metal-organic framework (UiO-66) derived ZrO2 (U-ZrO2) for PAA activation. The high porosity and specific surface area of UiO-66 enable efficient embedding and uniform dispersion of CoFe particles into pore channels. The supported material effectively activates PAA and significantly reduces Co leaching. CoFe/U-ZrO2-PAA system shows a removal efficiency of sulfamethoxazole reaching 98.9% within 10 min with Co leaching concentrations as low as 0.005 mg/L (equivalent to 1.4% of CoFe-PAA system). Quenching experiments, probe experiments and electron paramagnetic resonance tests identify CH3C(O)OO· as the dominant radical species. The CoFe/U-ZrO2-PAA system maintains high activity in actual water bodies and can resist the interference of HPO42-, Cl-, SO42-, NO3- and humic acid except for the inhibitory effect of HCO3-. The system also displays good stability and high degradability to different pollutants, maintaining consistently outstanding degradation efficiency in the flow-through experiment. Overall, the environmentally friendly, good efficiency, and high stability of the CoFe/U-ZrO2-PAA system makes it potential for broad applications in wastewater treatment.

Self-assembled materials from MXene and polyoxometalates based on polymerization of dopamine in one step for non-radical dominated degradation of sulfamethoxazole

The difficulty in introducing polyoxometalates (POMs) into few-layer MXene (Ti3C2) is caused by POMs dissolution and the easy oxidation of MXene. In this paper, a ternary composite of MXene-SiW9Co3@PDA, was synthesized in a one-step process by the self-polymerization of dopamine (DA) on few-layer MXene. The material was characterized by a large MXene interlayer spacing, low dissolution of POMs, and high oxidation resistance with good adsorption properties, excellent stability, and catalytic activity. MXene-40 %SiW9Co3@PDA degraded 98 % of sulfamethoxazole (SMX) in 30 min with a pseudo-first-order rate constant k of 0.1401 min-1. The redox of Ti2+/Ti3+ or Ti4+ in MXene and Co2+/Co3+ in POMs activated peroxymonosulfate (PMS), which generated large amounts of reactive oxygen species (ROS). As a consequence, the degradation of SMX was not dominated by SO4-·, but by non-radical 1O2. Additionally, this system was also efficient in degrading norfloxacin (30 min, 94 %), amoxicillin (5 min, 99 %), and tetracycline hydrochloride (10 min, 95 %). This study provides a new idea in developing two-dimensional MXene-based POMs composites and is promising in the practical application of advanced oxidation technology in wastewater treatment.

Densely Stacked CoCu-MOFs Coated with CuAl/LDH Enhance Sulfamethoxazole Degradation in PMS-Activated Systems

As the most promising techniques for refractory antibiotic degradation in wastewater management, sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted considerable attention. However, systematic studies on potassium peroxymonosulfate (PMS) activation by MOF-derived metal oxides coated with LDH materials are still lacking. In this work, a series of catalysts consisting of CoCu-MOFs coated with CuAl/LDH were synthesized for PMS activation in the removal of sulfamethoxazole (SMX). As expected, CoCu-MOFs coated with CuAl/LDH catalyst showed high SMX removal and stability in PMS activation. In the CoCu/LDH/PMS reaction, the SMX removal was nearly 100% after 60 min, and the mineralization reached 53.7%. The catalyst showed excellent catalytic stability and low metal leaching concentrations (Co: 0.013 mg/L, Cu: 0.313 mg/L), as detected by ICP. Sulfate radicals and hydroxyl radicals were identified as the dominant reactive species in the CoCu/LDH/PMS system. Moreover, the presence of 1O2 in the process revealed the coupling of non-radical and radical processes. The XPS results showed that the layered structure of CoCu/LDH promoted the recycling of metal ions (high and low valence), which facilitated heterogeneous PMS activation. The effects of different reaction conditions and reuse cycles were also determined. The SMX oxidation pathways were proposed based on the intermediates identified by LC/MS. The high activity and stability of CoCu/LDH provide a new mechanistic understanding of PMS activation catalysts and their potential utilization in practical wastewater treatment.

Regulating the interface electron distribution of iron-based MOFs through ligand functionalization enables efficient peroxymonosulfate utilization and catalytic performance

Ligand functionalization is an effective way to endow Metal-organic frameworks (MOF) with versatility for multiple applications by introducing or displaying substituents without changing the origin framework. In this work, the original MIL-101(Fe) was modified by functional groups, including -NH2, -NO2, -CH3, and -Cl substituents. The Bader charge results and electron localization function (ELF) quantitatively indicated that the functional ligands with different properties can regulate the electron structure of transition-metal centers through interface-charge redistribution. Accompanying the higher adsorption and utilization rate of peroxymonosulfate (PMS), more than 96% of acetaminophen (APAP) was degraded with a mineralization rate of 40.17% under the NH2-BDC/PMS system. In terms of mechanism, the amino group not only accelerated the regeneration of Fe(II) via the NCFe electron-transfer path, but also stimulated the appearance of high-valent Fe species. Meanwhile, the degradation pathways of APAP were proposed by integrating the results of liquid chromatograph-mass spectrometry (LC-MS) and Frontier molecular-orbital theory. Finally, the NH2-BDC/PMS system reveals long-term stability, nonselectivity, low biotoxicity as well as secondary pollution for pollutant degradation, which is a considered candidate for further environmental applications.

Attuning doped ZnO-based composites for an effective light-driven mineralization of pharmaceuticals via PMS activation

Water treatment technologies need to go beyond the current control of organic contaminants and ensure access to potable water. However, existing methods are still costly and often inadequate. In this context, novel catalysts that improve the mineralization degree of a wider range of pharmaceuticals through more benign and less consuming methodologies are highly sought after. ZnO, especially when doped, is a well-known semiconductor that also excels in the photocatalytic removal of persistent organic pollutants. In this study, we investigated the effect of doping ZnO nanoparticles with either copper, gallium or indium on the structure, morphology, photophysical properties and photocatalytic mineralization of pharmaceuticals. Their architecture was further improved through the fabrication of composites, pairing the best performing doped ZnO with either BaFe12O19 or nickel nanoparticles. Their suitability was tested on a complex 60-ppm multi-pollutant solution (tetracycline, levofloxacin and lansoprazole). The activation strategy combined photocatalysis with peroxymonosulfate (PMS) as an environmentally friendly source of highly oxidative sulfate radicals. The alliance of doped ZnO and BaFe12O19 was particularly successful, resulting in magnetic microcroquette-shaped composites with excellent inter-component synergy. In fact, indium outperformed the other proposed metal dopants, exceeding 97% mineralization after 1 h and achieving complete elimination after 3 h. All composites excelled in terms of reusability, with no catalytic loss after 10 consecutive cycles and minimal leakage of metal ions, highlighting their applicability in water remediation.

Peroxymonosulfate activation by nanocomposites towards the removal of sulfamethoxazole: Performance and mechanism

Heterogeneous activation of peroxomonosulfate (PMS) has been extensively studied for the degradation of antibiotics. The cobalt ferrite spinel exhibits good activity in the PMS activation, but suffers from the disadvantage of low PMS utilization efficiency. Herein, the nanocomposites including FeS, CoS2, CoFe2O4 and Fe2O3 were synthesized by hydrothermal method and used for the first time to activate PMS for the removal of sulfamethoxazole (SMX). The nanocomposites showed superior catalytic activity in which the SMX could be completely removed at 40 min, 0.1 g L-1 nanocomposites and 0.4 mM PMS with the first order kinetic constant of 0.2739 min-1. The PMS utilization efficiency was increased by 29.4% compared to CoFe2O4. Both radicals and non-radicals contributed to the SMX degradation in which high-valent metal oxo dominated. The mechanism analysis indicated that sulfur modification, on one hand, enhanced the adsorption of nanocomposites for PMS, and promoted the redox cycles of Fe2+/Fe3+ and Co2+/Co3+ on the other hand. This study provides new way to enhance the catalytic activity and PMS utilization efficiency of spinel cobalt ferrite.

Ce/N @BC prepared based on plant metallurgy strategy: A novel activator of peroxymonosulfate for the degradation of sulfamethoxazole

A novel carbon catalyst was created based on plant metallurgy strategy for organic pollutants removal. Plants rich in CeO2 NPs in water were used as carbon precursors and pyrolyzed with urea to obtain Ce/N co-doped carbon catalysts, which were used in the degradation of sulfamethoxazole (SMX) by active peroxymonosulfate (PMS). The results showed that the Ce/N @BC/PMS system achieved to 94.5% degradation of SMX in 40 min at a rate constant of 0.0602 cm-1. The activation center of PMS is widely dispersed Ce oxide nanocrystals, and CeO2 NPs promote the formation of oxygen centered PFR with enhanced catalytic ability and longer half-life. In addition, N-doping facilitates the transfer of π-electrons within the sp2 carbon of biochar, increasing active sites and thus improving PMS activation efficiency. The degradation process was contributed to by both radical and non-radical activation mechanisms including 1O2 and direct electron transfer, with O2•- serving as 1O2's precursor. Through the DFT calculations, LC-MS and toxicological analyses, the degradation pathway of pollutants and the toxicity changes throughout the entire degradation process were further revealed, indicating that the degradation of SMX could effectively reduce ecological toxicity.

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.

Antibiotic removal from synthetic and real aqueous matrices by peroxymonosulfate-based advanced oxidation processes. A review of recent development

The widespread use of antibiotics for the treatment of bacteriological diseases causes their accumulation at low concentrations in natural waters. This gives health risks to animals and humans since it can increase the damage of the beneficial bacteria, the control of infectious diseases, and the resistance to bacterial infection. Potent oxidation methods are required to remove these pollutants from water because of their inefficient abatement in municipal wastewater treatment plants. Over the last three years in the period 2021-September 2023, powerful peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have been developed to guaranty the effective removal of antibiotics in synthetic and real waters and wastewater. This review presents a comprehensive analysis of the different procedures proposed to activate PMS-producing strong oxidizing agents like sulfate radical (SO4•-), hydroxyl radical (•OH, radical superoxide ion (O2•-), and non-radical singlet oxygen (1O2) at different proportions depending on the experimental conditions. Iron, non-iron transition metals, biochar, and carbonaceous materials catalytic, UVC, photocatalytic, thermal, electrochemical, and other processes for PMS activation are summarized. The fundamentals and characteristics of these procedures are detailed remarking on their oxidation power to remove antibiotics, the influence of operating variables, the production and detection of radical and non-radical oxidizing agents, the effect of added inorganic anions, natural organic matter, and aqueous matrix, and the identification of by-products formed. Finally, the theoretical and experimental analysis of the change of solution toxicity during the PMS-based AOPs are described.