Preparation of Fe/C-Mt composite catalyst and ofloxacin removal by peroxymonosulfate activation

Construction and regulation of high active sites in montmorillonite composite catalyst for the removal of ofloxacin via persulfate activation

In this study, ionic liquids (ILs) were used as organic modifiers by introducing montmorillonite nanolayers containing potential C and N active sites between the montmorillonite nanolayers. Organically modified montmorillonite (ILs-Mt-p) was further prepared by high-temperature pyrolysis under N2 and used for the removal of ofloxacin (OFL) by activated peroxymonosulfate (PMS). Combined with XPS and other characterization analyses, it was found that the catalyst materials prepared from different organic modifiers had similar surface functional groups and graphitized structures, but contained differences in the types and numbers of C and N active sites. The catalyst (3CPC-Mt-p) obtained after pyrolysis of montmorillonite modified with cetylpyridinium chloride (CPC) had optimal catalytic performance, in which graphitic C, graphitic N, and carbonyl group (C[bond, double bond]O) could synergistically promote the activation of PMS by electron transfer, and 77.3 % of OFL could be removed within 60 min. The effects of OFL concentration, initial pH, and anions on the effects of OFL removal by the 3CPC-Mt-p/PMS system were further investigated. Satisfactory degradation results were obtained over a wide pH range. Cl- promoted the system to degrade OFL, while the presence of SO42-, H2PO4- and HA showed some inhibition, but overall the 3CPC-Mt-p catalysts had a strong anti-interference ability, showing good application prospects. The quenching experiments and EPR tests showed that O2-- and 1O2 in the 3CPC-Mt-p/PMS system were the main reactive oxygen species for the degradation of OFL, and •OH was also involved in the reaction. This study provides ideas for the construction and modulation of active sites in mineral materials such as montmorillonite and broadens the application of montmorillonite composite catalysts in advanced oxidation processes for the treatment of antibiotic wastewater.

Facile synthesis of pyrite FeS2 on carbon spheres for high-efficiency Fenton-like reaction

Designing iron-based catalysts for Fenton-like reactions with peroxymonosulfate (PMS) as oxidants have attracted growing attentions. Herein, pyrite FeS2 supported on carbon spheres (FeS2@C) is synthesized by a facile low-temperature method. The FeS2@C/PMS system can degrade carbamazepine (CBZ) effectively in a wide pH range. Sulfate radicals (SO4·-), hydroxyl radicals (·OH), superoxide radical (O2·-), and singlet oxygen (1O2) are the responsible reactive oxygen species (ROSs) for CBZ degradation. Moreover, in the simulated fixed-bed reactor, the FeS2@C/PMS system can maintain a high CBZ removal ratio of >95% for than 8 h, exhibiting its excellent stability. The outstanding performance of FeS2@C/PMS system is attributed to the presence of carbon spheres and lattice S2-, which together promote the Fe(III)/Fe(II) redox cycle. The FeS2@C is a promising catalyst due to its facile synthesis, low cost, high efficiency, and excellent stability to activate PMS for organics degradation.

A novel montmorillonite clay-cetylpyridinium chloride material for reducing PFAS leachability and bioavailability from soils

Soils contaminated by per- and polyfluoroalkyl substances (PFAS) present a significant threat to both ecological and human health. Extensive research efforts are currently underway to develop effective strategies for immobilizing these chemicals in soils. In this study, calcium montmorillonite was modified with cetylpyridinium chloride (CPC-CM) to enhance its electrostatic and hydrophobic interactions with PFAS. CPC-CM exhibited high adsorption for perfluorooctanoate acid (PFOA), perfluorooctane sulfonate (PFOS) and 8:2 fluorotelomer sulfonic acids (8:2 FTSA) across initial concentrations of 50-1000 μg/L, outperforming both the parent CM and L-carnitine modified CM. Soil leaching tests demonstrated the superior immobilization capabilities of the CPC-CM, maintaining an average PFAS leaching rate below 7% after 120-day incubation. In the context of human exposure scenarios, the in vitro bioaccessibility and in vivo bioavailability of PFAS in soils were measured by gastrointestinal extraction and mouse assay. CPC-CM treatment effectively reduced the bioaccessibility (by up to 84%) and bioavailability (by up to 76%) of PFAS in soils. Furthermore, the safety and efficacy of CPC-CM were evaluated using enteric microorganisms of mice. CPC-CM treatment mitigated PFAS-induced changes in the abundance of Bacteroidetes and Firmicutes, thereby reducing PFAS-induced health risks for humans. Overall, CPC-CM synthesized in this study demonstrated superior adsorption performance and application safety, offering a highly promising approach for remediating PFAS-contaminated soil.

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.