Highly efficient activation of peroxymonosulfate by biomass juncus derived carbon decorated with cobalt nanoparticles for the degradation of ofloxacin

Efficient electrochemical oxidation of ofloxacin by IrO2 -RuO2-TiO2 /Ti anode: Parameters optimization, kinetics and degradation pathways

Among various pharmaceutical pollutants, fluoroquinolones broad-spectrum antibiotics are major water pollutants, usually present in the aquatic environment as multicomponent mixtures with potentially deleterious effects on humans and the environment. This study used electrochemical oxidation to remove ofloxacin from aqueous solution using Ti and IrO2-RuO2-TiO2/Ti electrodes as cathode and anode, respectively. We investigated the morphology and electrochemical behavior of the selected anode and analyzed the effects of operational variables on the degradation performance of OFL in detail. The results showed that the electrochemical system for degrading OFL possessed high oxidizing activity and excellent durability, and the hydroxyl and reactive chlorine radicals generated by the electrochemical reaction could effectively degrade OFL. As predicted and optimized by the PSO-SVR model, the removal of OFL could be increased to 99.011 % when the electrolyte concentration was 5.65 mM, current density was 3.9 mA/cm2, initial pH was 7.12, and treatment time was 3.7 min. In addition, four possible degradation pathways, including ring opening and mineralization, were proposed based on the byproducts calculated by DFT and determined by GC-MS. More importantly, this electrochemical process can efficiently degrade various organic pollutants (ciprofloxacin, enrofloxacin, sulfamethoxazole, oxytetracycline, and chloromycetin). This study provides the theoretical basis and essential data for applying this electrochemical system in wastewater treatment.

Catalytic degradation of Rhodamine B through peroxymonosulfate activation by the Co-doped hydroxyapatite

Supported Co-based catalysts have shown attractive prospects for peroxymonosulfate (PMS) activation. In this work, Co-doped hydroxyapatite (H-Co/HAP) composites were prepared by a simple hydrothermal method. The Co content in H-Co/HAP could reach 71.2 mg/g, while the Co leaching rate remained relatively low. By right of the excellent catalytic performance, the as-prepared H-Co/HAP could achieve 99.02% degradation of Rhodamine B (RhB) within 10 min in the presence of 0.5 mM PMS and a first-order kinetic rate constant of 0.876 min-1. Even after 8 cycles, the RhB degradation efficiency remained at 81.96%. In addition, the effects of vital reaction parameters, including catalyst dosage, PMS dosage, initial pH, humic acid, and coexisting anions, on the catalytic performance in the H-Co/HAP10/PMS system were systematically investigated and discussed. The degradation mechanism of a non-radical (1O2) as the dominant active specie and a radical (•O2- and SO4•-) as the minor active specie was identified through quenching experiments and electron paramagnetic resonance testing. Moreover, possible degradation pathways of RhB were proposed in the H-Co/HAP10/PMS system. Overall, this study offers a meaningful strategy for designing high-content Co-based catalysts to degrade dye molecules in wastewater.

Efficient degradation of tetracycline via peroxymonosulfate activation by phosphorus-doped biochar loaded with cobalt nanoparticles

The accumulation of tetracycline hydrochloride (TCH) threatens human health because of its potential biological toxicity. Carbon -based materials with easy isolation and excellent performance that can activate peroxymonosulfate (PMS) to generate reactive oxygen species for TCH degradation are essential, but the development of such materials remains a significant challenge. In this study, based on the idea of treating waste, tricobalt tetraoxide loaded P-doped biochar (Co NP-PBC) was synthesised to activate PMS for the degradation of TCH. Possible degradation pathways and intermediate products of TCH were identified using High performance liquid chromatography tandem mass spectrometry (HPLC-MS) detection and density functional theory analysis. Toxicity analysis software was used to predict the toxicity of the intermediate products. Compared to catalysts loaded with Fe and Mn and other Co-based catalysts, Co NP-PBC exhibited an optimal performance (with a kinetic constant of 0.157 min-1 for TCH degradation), and over 99.0% of TCH can be degraded within 20 min. This mechanism demonstrates that the non-free radical oxidation of 1O2 plays a major role in the degradation of TCH. This study provides insights into the purification of wastewater using BC-based catalysts.

Iron/nitrogen co-doped biochar derived from salvaged cyanobacterial for efficient peroxymonosulfate activation and ofloxacin degradation: Synergistic effect of Fe/N in non-radical path

A green, low-cost, high-performance Fe/N co-doped biochar material (Fe-N@C) was synthesized using salvaged cyanobacteria without other extra precursors for peroxymonosulfate (PMS) activation and ofloxacin (OFX) degradation. With the increased pyrolysis temperature, the graphitization degree, the specific surface area and the corresponding groups like OH, COO etc. for Fe-N@C tended to increase, resulting in a greater OFX adsorption. However, the total amount of Fe-NX and graphitic nitrogen groups in the Fe-N@C composites was firstly increased and then decreased, which reached the highest at 800 °C (Fe-N@C-800). All these changes of functional species ascribed to the strong interaction between Fe, N and C led to the highest defect degree of Fe-N@C-800, resulting the highest OFX removal efficiency of 95.0 %. OFX removal experiments indicated the adsorption process promoted the total OFX degradation for different functional groups on Fe-N@C composites separately dominated the process of OFX adsorption and PMS catalysis. Radical quenching and electron paramagnetic resonance (EPR) measurements proved free radical and non-free radical pathways participated in Fe-N@C/PMS system. The non-free radicals based on 1O2 and high-valent iron-oxo species played a more important role in OFX degradation, leading to the minimal effect of co-existing anions and the high universality for other antibiotic pollutants. Fe-NX was utilized as the main catalytic sites and graphitic nitrogen contributed more to the electron transfer for PMS activation, whose synergistic effect efficiently facilitated OFX degradation. Finally, the possible degradation route of OFX in the Fe-N@C-800/PMS system was proposed. All these results will provide the new insights into the intrinsic mechanism of Fe/N species in carbon-based materials for PMS activation.

Persulfate enhanced removal of bisphenol A by copper oxide/reduced graphene oxide foam: Influencing factors, mechanism and degradation pathway

The CuO/reduced graphene oxide foam (CuO/RGF) with excellent recyclability was prepared via hydrothermal method followed by freeze drying treatment for bisphenol A (BPA) removal via activating peroxydisulfate (PDS). SEM, XRD, XPS, FT-IR, BET, and TG techniques were used to investigate the structure and property of CuO/RGF. The effect of degradation conditions (pH, PDS amount, Cl-, HCO3-, HA and FA) on BPA removal by CuO/RGF were investigated. The result presented that CuO nanosheet was inserted into the RGF carrier with three-dimensional structure. The degradation rate constant of BPA over CuO/RGF (0.00917 min-1) was 1.24 and 6.46 times higher than those of BPA over CuO (0.00714 min-1) and RGF (0.00142 min-1). More importantly, the pore structure of RGF can successfully limit the release of Cu (II) compared to pure CuO. According to quenching test as well as electron spin resonance (EPR) spectra, BPA degradation was triggered by 1O2, •OH and SO4•-, which was the combination of nonradical (1O2) and radical activation of PDS (•OH and SO4•-). The possible degradation route of BPA was proposed based on intermediates obtained by combining solid phase extraction pretreatment technique with high performance liquid-mass spectrometry. After assessing the viability of MCF-7 cells, we can see that the estrogenic activities of treated solution reduced without producing stronger endocrine disruptors.

Theoretical study of local S coordination environment on Fe single atoms for peroxymonosulfate-based advanced oxidation processes

Tuning the electronic structure of single atom catalysts (SACs) is an effective strategy to promote the catalytic activity in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). Herein, a series of Fe-based SACs with S_1/2/3/4-coordination numbers on graphene were designed to regulate the electronic structural of SACs at molecular level, and their effects on PMS activation were investigated via density function theory (DFT). The calculation results demonstrate that the electron structure of the active center can be adjusted by coordination environment, which further affects the activation of PMS. Among the studied Fe-S_X-C_4-X catalysts, with the increase of the S coordination number, the electron density of the Fe-S_X-C_4-X active center was optimized. The active center of the Fe-S₄-C₀ catalyst has a largest positive charge density, exhibiting the highest number of electron transfer. It also has a lower kinetic energy barrier (0.28 eV) for PMS dissociation. Organic pollutant such as bisphenol A (BPA) can achieve stable adsorption on Fe-S_X-C_4-X catalysts, which is conducive to subsequent oxidation by radicals. The dual index ∆f(r) indicates that the para-carbon atom of the hydroxyl group on the benzene ring of BPA is vulnerable to radical attack. This study highlights a theoretical support and a certain guide for designing efficient SACs to activate PMS.

Activation of peroxymonosulfate by palygorskite supported Co-Fe for water treatment

In the present work, palygorskite (PAL) supported Co-Fe oxides (CoFe@PAL) were prepared and used as a peroxymonosulfate (PMS) activator for removal of rhodamine B (RhB) in water. The results showed that CoFe@PAL prepared at impregnation solution of 50 g L^-1 and calcination temperature of 500 °C showed the best catalytic performance. The removal efficiency of RhB (10 mg L^-1) by PMS (0.1 mmol L^-1) activated with CoFe@PAL (1 g L^-1) was above 98% within 60 min. The effects of various environmental factors including initial pH, humic acid (HA) and inorganic anions on the removal effect were simultaneously investigated. The radical quenching experiments and EPR characterization revealed that ˙OH, SO₄˙^-, O₂˙^- and ¹O₂ radicals existed in the CoFe@PAL/PMS system simultaneously. The intermediates during RhB degradation were analyzed by LC-MS and possible degradation pathways of RhB were proposed. Moreover, CoFe@PAL exhibited superior stability and reusability.