MgO-supported CuO with encapsulated structure for enhanced peroxymonosulfate activation to remove thiamphenicol

Efficient activation of peroxymonosulfate by CoMg2Mn-LDO for the degradation of orange Ⅱ: The important synergy of Mg

Advanced oxidation process (AOP) based on peroxymonosulfate (PMS) has aroused extensive discussion in the degradation of organic pollutants due to the strong oxidative ability of SO4•-. Great attention has been paid to developing transition metal catalysts for PMS activation. Still, few studies focused on the co-catalysis effect of non-redox metals. To study the co-catalysis of Mg and develop a more efficient metal catalyst, the CoMg2Mn-LDO was prepared by a co-precipitation method accompanied by calcination. The material showed an excellent ability for PMS activation. 97.1% of Orange Ⅱ was degraded within 15 min with the reaction rate constant (kobs) of 0.539 min-1 when pH equals 6.7, the dosages of CoMg2Mn-LDO and PMS were 90 mg L-1 and 100 mg L-1, respectively. By contrast, the value of kobs was 0.375 min-1 for the system of Co3Mn-LDO/PMS at the same experimental conditions. The electron paramagnetic resonance (EPR) and quenching experiments results proved the existence of O2•-, SO4•- and HO• in the CoMg2Mn-LDO/PMS system and the dominant role of SO4•- in Orange Ⅱ degradation. The synergistic effects among Co, Mn, and Mg were found to be responsible for the outstanding catalytic ability of CoMg2Mn-LDO. The presence of Mg could not only promote the formation of Mg-HSO5- and CoOH+ complexes but also reduce the leaching of Co and Mn, which accelerated the generation of free radicals and decreased secondary pollution risk. Based on the overall analysis, reasonable activation mechanisms of PMS and possible degradation pathways of Orange Ⅱ in this reaction system were proposed. This work proves that Mg could be applied as an effective co-catalytic element and provides new insight into developing transition metal catalysts for PMS-based AOPs.

MgxCu-biochar activated peroxydisulfate triggers reductive species for the reduction and enhanced electron-transfer degradation of electron-deficient aromatic pollutants

In wastewater treatment by persulfate-based advanced oxidation processes (PS-AOPs), electron-deficient aromatic pollutants (EDAPs) are refractory to nonradical pathway. To explore an efficient degradation pathway for EDAPs, Mg_xCu-biochar (BC) (x = 0.5, 1, 1.5) activated peroxydisulfate (PDS) was developed, which could trigger reductive species (•H) to reduce EDAPs first, and subsequently facilitate electron-transfer degradation of reduced intermediates. The roles of Mg-doping in Mg_xCu-BC to promote PDS activation and 2,4-dibromophenol (DBP) degradation were investigated. The mechanisms were then explored via electron paramagnetic resonance (EPR), chemical probes and Density Functional Theory (DFT) calculations. The results showed that Mg-doping improved metal-support interactions (MSIs) of Mg_xCu-BC, inducing •H formation via electron transfer from Cu atoms during PDS activation, which was thermodynamically favorable. The degradation rate of DBP (k_obs, 0.0494 min^-1) and Br^- release (5.35 mg L^-1) in Mg₁Cu-BC systems were more 31 and 33 times than that in Cu-BC/PDS system, respectively. The degradation mechanism of •H-enhanced electron transfer processes was that •H attacked one Br group of DBP, and then debrominated intermediates were mineralized by electron transfer processes in the Mg₁Cu-BC/PDS system. Overall, this study reports a novel pathway in PS-AOPs for selective degradation of EDAPs in wastewaters.

Insight into radical-nonradical coupling activation pathways of peroxymonosulfate by CuxO for antibiotics degradation

In this work, a heterogeneous catalyst of Cu_xO was rationally designed by using Cu-based metal organic frameworks (marked Cu-BDC) as the template, and was used to degrade tetracycline (TC) via activation of peroxymonosulfate (PMS). The optimal Cu_xO-350 showed excellent catalytic efficiency for TC degradation, and the reaction rate constant (0.104 min^-1) was 8 times higher than that (0.013 min^-1) of raw Cu-BDC. The characterization observations confirmed that Cu_xO-350 possessed multiple valence states (CuO and Cu₂O) and oxygen vacancies (O_v), both of which were favorable for the activation of PMS, resulting in promoting the generation of active species in the Cu_xO-350 + PMS system. Different from the free radical pathway in Cu-BDC + PMS system, a radical-nonradical coupling process was detected in the Cu_xO-350 + PMS system, which was confirmed by quenching experiments and EPR measurements. Moreover, the toxicity prediction showed that the toxicity of degradation intermediates declined compared with TC. This work not only opened up a new strategy for the rational design and preparation of high-efficient catalysts by employing metal organic frameworks precursors, but also offered an insight into the reaction mechanism of PMS activation through a radical-nonradical coupling process catalyzed by Cu_xO-350 derived from Cu-BDC.

Applications of Spent Lithium Battery Electrode Materials in Catalytic Decontamination: A Review

For a large amount of spent lithium battery electrode materials (SLBEMs), direct recycling by traditional hydrometallurgy or pyrometallurgy technologies suffers from high cost and low efficiency and even serious secondary pollution. Therefore, aiming to maximize the benefits of both environmental protection and e-waste resource recovery, the applications of SLBEM containing redox-active transition metals (e.g., Ni, Co, Mn, and Fe) for catalytic decontamination before disposal and recycling has attracted extensive attention. More importantly, the positive effects of innate structural advantages (defects, oxygen vacancies, and metal vacancies) in SLBEMs on catalytic decontamination have gradually been unveiled. This review summarizes the pretreatment and utilization methods to achieve excellent catalytic performance of SLBEMs, the key factors (pH, reaction temperature, coexisting anions, and catalyst dosage) affecting the catalytic activity of SLBEM, the potential application and the outstanding characteristics (detection, reinforcement approaches, and effects of innate structural advantages) of SLBEMs in pollution treatment, and possible reaction mechanisms. In addition, this review proposes the possible problems of SLBEMs in practical decontamination and the future outlook, which can help to provide a broader reference for researchers to better promote the implementation of “treating waste to waste” strategy.

Enhanced Degradation of Rhodamine B through Peroxymonosulfate Activated by a Metal Oxide/Carbon Nitride Composite

The development of high catalytic performance heterogeneous catalysts such as peroxymonosulfate (PMS) activators is important for the practical remediation of organic pollution caused by Rhodamine B (RhB). An economical and facile synthesized composite of copper–magnesium oxide and carbon nitride (CM/g-C3N4) was prepared by the sol-gel/high-temperature pyrolysis method to activate PMS for RhB degradation. CM/g-C3N4 exhibited a splendid structure for PMS activation, and the aggregation of copper–magnesium oxide was decreased when it was combined with carbon nitride. The introduction of magnesium oxide and carbon nitride increased the specific surface area and pore volume of CM/g-C3N4, providing more reaction sites. The low usage of CM/g-C3N4 (0.3 g/L) and PMS (1.0 mM) could rapidly degrade 99.88% of 10 mg/L RhB, and the RhB removal efficiency maintained 99.30% after five cycles, showing the superior catalytic performance and reusability of CM/g-C3N4. The synergistic effect of copper and g-C3N4 improved the PMS activation. According to the analyses of EPR and quenching experiments, SO4•−, •OH and O2•− radicals and 1O2 were generated in the activation of PMS, of which SO4•− and 1O2 were important for RhB removal. The toxicity of RhB was alleviated after being degraded by the CM/g-C3N4/PMS system. This study provides an efficient and promising strategy for removing dyes in water due to the hybrid reaction pathways in the CM/g-C3N4/PMS system.

The synergistic effect of PMS activation by LaCoO3/g-C3N4 for degradation of tetracycline hydrochloride: performance, mechanism and phytotoxicity evaluation

A LaCoO3/g-C3N4 catalyst with high stability was designed and used for PMS activation to degrade TC.

New FeOCl/graphene quantum dots catalyst for peroxymonosulfate activation to efficiently remove organic pollutants and inactivate Escherichia coli

The sulfate radical-based advanced oxidation processes (SR-AOPs) are well-established and efficient techniques for degradation of organic pollutants. Fe2+ is used as an environmentally friendly and cost-effective catalyst for activating peroxymonosulfate...