CH3COO Research Articles

Peracetic acid combined with ultraviolet for ibuprofen degradation: Activation mechanism and reactive species contribution

As an emerging advanced oxidation technology, ultraviolet/peracetic acid (UV/PAA) shows great potential in removing pharmaceuticals and personal care products (PPCPs) in the field of wastewater treatment. In this work, ibuprofen (IBP) was chosen as the contaminant to study the degradation effects and PAA activation mechanisms by UV irradiation. The experimental results showed that UV/PAA had an excellent degradation efficiency (99.22 %) of IBP after 15 min reaction, and the synergistic effect between UV and PAA was also observed. Increasing the dosage of PAA caused the increase in IBP degradation reaction rate. Under acidic conditions, the increase in pH values increased the degradation reaction rate, whereas the opposite was true in alkaline conditions. In addition, the coexisting substrates (e.g., NO3-, CO32-, Ca2+, and HA) could exert inhibition on the degradation. Quenching experiments were carried out using various quenchers to identify reactive oxygen species (ROSs) in the system. The results demonstrated that ·OH and carbon centered radicals (R-C·) played a dominant part in the degradation, and the contribution of CH3C(O)OO·,·O2-, CH3C(O)O·, ·OH, and direct photolysis were estimated to be 29.9 %, 26.9 %, 21.5 %, 14.5 %, and 7.2 %, respectively. The results of IBP intermediates identification indicated that the degradation process was mainly related to its side chain decarboxylation, oxidative dehydrogenation, demethylation, and the oxidation of the aromatic ring. Furthermore, Toxicity Estimation Software Tool (T.E.S.T.) and ECOSAR were applied to evaluate the toxicity of the intermediate products was further evaluated. This study enriched the understanding of the PAA activation mechanism by UV involved, and improved the theory and technology of removing PPCPs by UV/PAA process.

Hydroxylamine enhanced the degradation of diclofenac in Cu(II)/peracetic acid system: Formation and contributions of CH3C(O)O•, CH3C(O)OO•, Cu(III) and •OH

The slow reduction of Cu(II) into Cu(I) through peracetic acid (PAA) heavily limited the widespread application of Cu(II)/PAA system. Herein, hydroxylamine (HA) was proposed to boost the oxidative capacity of Cu(II)/PAA system by facilitating the redox cycle of Cu(I)/Cu(II). HA/Cu(II)/PAA system was quite rapid in the removal of diclofenac within a broad pH range of 4.5–9.5, with a 10-fold increase in the removal rate of diclofenac compared with the Cu(II)/PAA system at an optimal initial pH of 8.5. Results of UV−Vis spectra, electron paramagnetic resonance, and alcohol quenching experiments demonstrated that CH3C(O)O•, CH3C(O)OO•, Cu(III), and •OH were involved in HA/Cu(II)/PAA system, while CH3C(O)OO• was verified as the predominant reactive species of diclofenac elimination. Different from previously reported Cu-catalyzed PAA processes, CH3C(O)OO• mainly generated from the reaction of PAA with Cu(III) rather than CH3C(O)O• and •OH. Four possible elimination pathways for diclofenac were proposed, and the acute toxicity of treated diclofenac solution with HA/Cu(II)/PAA system significantly decreased. Moreover, HA/Cu(II)/PAA system possessed a strong anti-interference ability towards the commonly existent water matrix. This research proposed an effective strategy to boost the oxidative capacity of Cu(II)/PAA system and might promote its potential application, especially in copper-contained wastewater.

Using Fe(II)/Fe(VI) activated peracetic acid as pretreatment of ultrafiltration for secondary effluent treatment: Water quality improvement and membrane fouling mitigation

Ultrafiltration (UF) is a technology commonly used to treat secondary effluents in wastewater reuse; however, it faces two main challenges: 1) membrane fouling and 2) inadequate nitrogen (N), phosphorus (P), and organic micropollutants (OMPs) removal. To address these two issues, in this study, we applied peracetic acid (PAA), Fe(VI)/PAA, and Fe(II)/PAA as UF pretreatments. The results showed that the most effective pretreatment was Fe(II)/200 μM PAA, which reduced the total fouling resistance by 90.2%. In comparison, the reduction was only 29.7% with 200 μM PAA alone and 64.3% with Fe(VI)/200 μM PAA. Fe(II)/200 μM PAA could effectively remove fluorescent components and hydrophobic organics in effluent organic matter (EfOM), and enhance the repulsive force between foulants and membrane (according to XDLVO analysis), and consequently, mitigate pore blocking and delay cake layer formation. Regarding pollutant removal, Fe(II)/200 μM PAA effectively degraded OMPs (>85%) and improved P removal by 58.2% via in-situ Fe(Ⅲ) co-precipitation. The quencher and probe experiments indicated that FeIVO2+, •OH, and CH3C(O)OO•/CH3C(O)O• all played important roles in micropollutant degradation with Fe(II)/PAA. Interestingly, PAA oxidation produced highly biodegradable products such as acetic acid, which significantly elevated the BOD5 level and increased the BOD5/total nitrogen (BOD5/TN) ratio from 0.8 to 8.6, benefiting N removal with subsequent denitrification. Overall, the Fe(II)/PAA process exhibits great potential as a UF pretreatment to control membrane fouling and improve water quality during secondary effluent treatment.

Highly efficient activation of peracetic acid via zero-valent iron-copper bimetallic nanoparticles (nZVIC) for the oxidation of sulfamethazine in aqueous solution under neutral condition

Herein, zero-valent iron-copper bimetallic nanoparticles were firstly applied to efficiently activate peracetic acid (PAA) for the removal of sulfamethazine (SMT) under neutral condition. Compared with the system of nano zero-valent iron (nZVI)-activated PAA, nZVIC/PAA system could significantly increase the removal efficiency of SMT by 70.8% at pH 7.0. It was demonstrated that the doped Cu could greatly accelerated Fe2+/Fe3+ cycle on the surface of the nZVIC and triggered the interaction between iron and copper. CH3C(O)OO• and 1O2 acted a dominant role on SMT removal in the nZVIC/PAA system. The transformation pathways of SMT were inferred based on DFT theory calculations and determined intermediates, and the luminescent bacteria test and toxicity prediction of degradation intermediates showed that the biotoxicity of SMT was reduced during degradation. Finally, based on the results of the practicability evaluation, the proposed nZVIC/PAA process is a promising approach for the rapid decontamination of antibiotic-polluted water.

Citric acid enhanced oxytetracycline degradation by Fe(Ⅲ)/peracetic acid: Performance, mechanism and influence factors

Citric acid (CA) can effectively complex with Fe(Ⅲ) to improve the solubility of Fe(Ⅲ) and accelerate the reduction of Fe(Ⅲ) to Fe(II), while its use in Fe(Ⅲ)-activated peracetic acid (PAA) system has not been reported so far. Therefore, CA was introduced into Fe(Ⅲ)/PAA system in this study to degrade oxytetracycline (OTC), and the degradation efficiency and mechanism of OTC in this system were systematically investigated. The results showed that the removal efficiency of OTC in Fe(Ⅲ)-CA/PAA system at pH 7.0 could reach 81.5% after 20 min, and the degradation of OTC followed pseudo-first-order kinetic. The addition of CA into Fe(Ⅲ)/PAA system could effectively reduce Fe(Ⅲ) to Fe(Ⅱ) driving the cycle of Fe(Ⅲ)/Fe(Ⅱ) and accordingly enhance the OTC removal in this system. According to the results of electron paramagnetic resonance (EPR) and scavenging experiments, hydroxyl radical (HO•) and organic radicals (CH3C(O)O• and CH3C(O)OO•) played major roles for the degradation of OTC in Fe(Ⅲ)-CA/PAA system. Four possible transformation paths of OTC in this system were proposed, including demethylation, hydroxylation, dehydrogenation and dehydration, based on five detected degradation products. This study provides an idea to improve PAA activation by Fe(Ⅲ) and broadens the practical application of Fe(Ⅲ) in advanced oxidation processes.

Proton/Mg2+ Co-Insertion Chemistry in Aqueous Mg-Ion Batteries: From the Interface to the Inner.

Co-insertion of protons happens widely and enables divalent-ion aqueous batteries to achieve high performances. However, detailed investigations and comprehensive understandings of proton co-insertion are scarce. Herein, we demonstrate that proton co-insertion into tunnel materials is determined jointly by interface derivation and inner diffusion: at the interface, hdrated Mg2+ has poor insertion kinetics, and therefore accumulates and hydrolyzes to produce protons; in the tunnels, co-inserted/lattice H2 O molecules block the Mg2+ diffusion while facilitate the proton diffusion. When monoclinic vanadium dioxide (VO2 (B)) anode is tested in Mg(CH3 COO)2 aqueous solution, the formation of Mg-rich solid electrolyte interphase on the VO2 (B) electrode and co-insertion of derived protons are probed; in the tunnels, the diffusion energy barrier of Mg2+ +H2 O is 2.7 eV, while that of the protons is 0.37 eV. Thus, protons dominate the subsequent insertion and inner diffusion. As a consequence, the VO2 (B) achieves a high capacity of 257.0 mAh g-1 at 1 A g-1 , a high rate retention of 59.1 % from 1 to 8 A g-1 , and stable cyclability of 3000 times with a capacity retention of 81.5 %. This work provides an in-depth understanding of the proton co-insertion and may promote the development of rechargeable aqueous batteries.

Natural tourmaline activated peracetic acid for efficient degradation of sulfadiazine: Reaction mechanisms and catalyst reusability

Peracetic acid (PAA) has received extensive attention in the water treatment due to its high oxidation potential and low toxicity of by-products. In this study, natural non-toxic mineral tourmaline (TM) was used to activate PAA to remove sulfadiazine (SDZ). The TM/PAA system could remove 92 ​% SDZ in 120 ​min. The radical analysis confirmed the co-existence of both free radical and non-free radical degradation pathways in the TM/PAA system, indicating that singlet oxygen (1O2) and acetyl(per)oxy radicals (CH3C(O)O· and CH3C(O)OO·) were the main reactive oxygen species. The Fe2+/Fe3+ ratio on the TM surface decreased during the degradation of SDZ due to Fe2+ consumption. The effect of water matrix on SDZ removal indicated that Cl−, SO42− and NO3− posed little effect on SDZ removal, while CO32− inhibited SDZ removal by affecting pH. Particularly, humic acid (HA) slightly promoted SDZ removal. Ten by-products of SDZ were identified by HPLC-MS/MS, and four possible transformation pathways (SO2 detachment, S–N breakage, amino acid oxidation, and hydroxylation) were proposed. TM was recycled five times and the removal of SDZ remained above 85 ​%, confirming its excellent reusability. This work indicates the TM/PAA system is of great potential for the application on the organic contaminant removal.

Heat induced superfast diclofenac removal in Cu(II)–activated peracetic acid system: Mediation from non-radical to radical pathway

A Cu(II)/heat coactivated peracetic acid (PAA) system for enhancing diclofenac (DCF) degradation was proposed in this work. The superiority of this synergetic activation strategy for PAA, working reactive species, catalytic mechanism and effects of reaction parameters on DCF elimination in this system were simultaneously investigated. Based on our results, the DCF loss rate in Cu(II)-heat/PAA process at pH 8.0 was about 49.3 and 4.2 times of that in Cu(II)/PAA and heat/PAA processes, respectively. Increasing the reaction temperature to 60 оC not only motivated the conversion of Cu(II) to Cu(I) but also facilitated the one-electron transfer between Cu(I) and PAA, boosting the generation of radicals. Organic radicals (mainly CH3C(O)O• and CH3C(O)OO•) were evidenced to be the core oxidizing substances dominating in the destruction of DCF while hydroxyl radical (•OH) made a minor contribution in this system by electron paramagnetic resonance (EPR) method together with scavenging experiments. This study broads the eyes into enhanced PAA activation initiated by homogenous Cu(II), providing a simple but efficient tool to degrade micropollutants.

Achieving Highly Proton-Resistant Zn-Pb Anode through Low Hydrogen Affinity and Strong Bonding for Long-Life Electrolytic Zn//MnO2 Battery.

High-energy electrolytic Zn//MnO2 batteries show potential for grid-scale energy storage, but the severe hydrogen evolution corrosion (HEC) caused by acidic electrolytes results in subdued durability. Here, we report an all-around protection strategy for achieving stable metal Zn anode. Firstly, a proton-resistant Pb-containing (Pb and Pb(OH)2) interface is constructed on Zn anode (denoted as Zn@Pb), which will in-situ form PbSO4 during H2SO4 corrosion and protect the Zn substrate from HEC. Secondly, to improve the plating/stripping reversibility of Zn@Pb, Pb(CH3COO)2 additive (denoted as Zn@Pb-Ad) is introduced, which will convert to PbSO4 precipitation and release trace Pb2+ that can dynamically deposit Pb layer on Zn plating layer to suppress HEC. The superior HEC resistance stems from the low affinity of PbSO4 and Pb for H+ as well as strong bonding between Pb-Zn or Pb-Pb, which increase the hydrogen evolution reaction overpotential and the H+ corrosion energy barrier. Consequently, the Zn@Pb-Ad//MnO2 battery runs stably for 630 and 795h in 0.2 and 0.1M H2SO4 electrolytes, respectively, which are >40 times than that of bare Zn. The as-prepared A h-level battery achieves the one-month calendar life, opening the door to the next generation of high-durable grid-scale Zn batteries. This article is protected by copyright. All rights reserved.

Kinetics study of chloride-activated peracetic acid for purifying bisphenol A: Role of Cl2/HClO and carbon-centered radicals

Peracetic acid is an emerging oxidant and disinfectant for wastewater purification. In this study, we first developed a comprehensive and accurate model to elucidate the reaction mechanisms and simulate reaction kinetics of peracetic acid (PAA, CH3C(=O)OOH) activated by chloride (Cl–) based on experimental results and literature. A diversity of experiments methods (e.g., quenching experiments, probe compounds degradation, electron paramagnetic resonance (EPR) measurements) and kinetic modeling were used to determine the reactive species. As a result, carbon-centered radicals and free chlorine reactive species (Cl2 and HClO) were devoted to BPA degradation in the PAA/Cl− system. The carbon-centered radicals CH3C(=O)OO•, CH3C(=O)O•, CH3OO•, and •CH3 greatly accelerated BPA degradation with their corresponding kinetics of kCH3C(=O)OO•, BPA = 2 × 108 M−1 s−1, kCH3C(=O)O•, BPA = 2 × 107 M−1 s−1, k•CH3, BPA = 2 × 106 M−1 s−1 and kCH3OO•, BPA = 2 × 104 M−1 s−1. Dissolved Cl2(l) species was also important for BPA degradation with kCl2, BPA of 2 × 107 M−1 s−1, much higher than HClO/ClO− of kHClO, BPA = 1.2 × 101 M−1 s−1 and kClO−, BPA = 9 × 10−3 M−1 s−1. While free chlorine tends to transform BPA to estrogenic chlorinated organic products, the primary degradation of BPA by carbon-centered radicals results in chlorine-free products, reducing the production of disinfection byproducts during the treatment of saline wastewater. This study improves the knowledge of reaction kinetics and mechanism and reactive species generation in the PAA/Cl– system.

Porous Salts Containing Cationic Al24 -Hydroxide-Acetate Clusters from Scalable, Green and Aqueous Synthesis Routes.

The solution chemistry of aluminum is highly complex and various polyoxocations are known. Here we report on the facile synthesis of a cationic Al24 cluster that forms porous salts of composition [Al24 (OH)56 (CH3 COO)12 ]X4 , denoted CAU-55-X, with X=Cl- , Br- , I- , HSO4 - . Three-dimensional electron diffraction was employed to determine the crystal structures. Various robust and mild synthesis routes for the chloride salt [Al24 (OH)56 (CH3 COO)12 ]Cl4 in water were established resulting in high yields (>95 %, 215 g per batch) within minutes. Specific surface areas and H2 O capacities with maximum values of up to 930 m2 g-1 and 430 mg g-1 are observed. The particle size of CAU-55-X can be tuned between 140 nm and 1250 nm, permitting its synthesis as stable dispersions or as highly crystalline powders. The positive surface charge of the particles, allow fast and effective adsorption of anionic dye molecules and adsorption of poly- and perfluoroalkyl substances (PFAS).

Phosphate enhanced Cu(II)/peracetic acid process for diclofenac removal: Performance and mechanism

Since limitedly existing researches suggested Cu(II) had deficiently catalytic ability to PAA, in this work, we tested the oxidation performance of Cu(II)/PAA system on diclofenac (DCF) degradation under neutral conditions. It was found that overwhelming DCF removal could be obtained in Cu(II)/PAA system at pH 7.4 using phosphate buffer solution (PBS) compared to poor loss of DCF without PBS, and the apparent rate constant of DCF removal in PBS/Cu(II)/PAA system was 0.0359 min−1, 6.53 times of that in Cu(II)/PAA system. Organic radicals (i.e., CH3C(O)O• and CH3C(O)OO•) were evidenced as the dominant contributors to DCF destruction in PBS/Cu(II)/PAA system. PBS motivated the reduction of Cu(II) to Cu(I) through chelation effect, and then the activation of PAA by Cu(I) was facilitated. Besides, due to the steric hindrance of Cu(II)-PBS complex (CuHPO4), PAA activation was mediated from non-radical-generating pathway to radical-generating pathway, leading to desirably effective DCF removal by radicals. The transformation of DCF mainly experienced hydroxylation, decarboxylation, formylation and dehydrogenation in PBS/Cu(II)/PAA system. This work proposes the potential of coupling of phosphate and Cu(II) in optimizing PAA activation for organic pollutants elimination.

Enhanced tetracycline abatement by peracetic acid activation with sulfidation of nanoscale zerovalent iron.

Iron-based heterogeneous catalysts due to the environmental friendliness have been widely studied for activation of peracetic acid (PAA) for abatement of organic contaminants in the water and wastewater treatment. However, the slow reduction from Fe(III) to Fe(II) of the iron-based catalysts as the rate-limiting step results in the low PAA activation efficiency. With regard to the excellent electron-donating capability of the reductive sulfur species, sulfidized nanoscale zerovalent iron is proposed for PAA activation (simplified as the S-nZVI/PAA process) and the tetracycline (TC) abatement efficacy and mechanism of this process are elucidated. The optimal sulfidation ratio (S/Fe) of S-nZVI is 0.07, which exhibits superior performance in PAA activation for TC abatement with the efficiency of 80-100% in the pH range of 4.0-10.0. The radical quenching experiments and oxygen release measurements confirm that acetyl(per)oxygen radicals (CH3C(O)OO•) are the main radical contributing to TC abatement. The influence of sulfidation on the crystalline structure, hydrophobicity, corrosion potential, and electron transfer resistance of S-nZVI is evaluated. The main sulfur species on the S-nZVI surface are identified as ferrous sulfide (FeS) and ferrous disulfide (FeS2). The analysis by X-ray photoelectron spectroscopy (XPS) and Fe(II) dissolution suggest that the reductive sulfur species can accelerate the conversion from Fe(III) to Fe(II). In summary, the S-nZVI/PAA process exhibits application prospects for the abatement of antibiotics in the aquatic environments.

Picolinic Acid-Mediated Catalysis of Mn(II) for Peracetic Acid Oxidation Processes: Formation of High-Valent Mn Species.

Metal-based advanced oxidation processes (AOPs) with peracetic acid (PAA) have been extensively studied to degrade micropollutants (MPs) in wastewater. Mn(II) is a commonly used homogeneous metal catalyst for oxidant activation, but it performs poorly with PAA. This study identifies that the biodegradable chelating ligand picolinic acid (PICA) can significantly mediate Mn(II) activation of PAA for accelerated MP degradation. Results show that, while Mn(II) alone has minimal reactivity toward PAA, the presence of PICA accelerates PAA loss by Mn(II). The PAA-Mn(II)-PICA system removes various MPs (methylene blue, bisphenol A, naproxen, sulfamethoxazole, carbamazepine, and trimethoprim) rapidly at neutral pH, achieving >60% removal within 10 min in clean and wastewater matrices. Coexistent H2O2 and acetic acid in PAA play a negligible role in rapid MP degradation. In-depth evaluation with scavengers and probe compounds (tert-butyl alcohol, methanol, methyl phenyl sulfoxide, and methyl phenyl sulfone) suggested that high-valent Mn species (Mn(V)) is a likely main reactive species leading to rapid MP degradation, whereas soluble Mn(III)-PICA and radicals (CH3C(O)O• and CH3C(O)OO•) are minor reactive species. This study broadens the mechanistic understanding of metal-based AOPs using PAA in combination with chelating agents and indicates the PAA-Mn(II)-PICA system as a novel AOP for wastewater treatment.

Advanced oxidation processes for pharmaceutical degradation and disinfection of wastewater: peracetic acid and graphene oxide quantum dots

A combination of graphene oxide quantum dots and peracetic acid (GQDs/PAA) was used to degrade sulfasalazine in municipal wastewater. The impact of reaction parameters such as initial concentrations of oxidant (peracetic acid) and drug (sulfasalazine) and different water matrices was evaluated. The degradation efficiency when using GQDs/PAA (50 mg/L: 0.10 mM) was almost 100% in synthetic water and 80% in municipal wastewater. The primary reactive radicals that caused the degradation of sulfasalazine in wastewater were identified as hydroxy (·OH) as well as the peroxy radicals (CH3C(=O)OO·, CH3C(=O)O·). 83.7% of total organic carbon were eliminated when 0.15 mM PAA was used while nearly 100% degradation of SZZ was achieved. A degradation pathway was proposed using the degradation intermediates obtained on quadrupole time-of-flight liquid chromatography mass spectrometry. The genotoxic and mutagenic potential of the degradation products formed during the degradation of sulfasalazine was assessed using the Ames test. It was demonstrated that none of the intermediates were mutagenic. GQDs/PAA was further tested as a potential disinfectant, and S. aureus was completely inactivated as verified by using LIVE/DEAD Baclight staining. In raw municipal wastewater, GQDs/PAA eliminated more than 90% of bacteria, thus confirming the synergy of GQDs/PAA as both a disinfectant and a photocatalyst.

Efficient activation of peracetic acid for abatement of tetracycline by W-doped CuS via regulating copper redox cycling

Recently, activation of peracetic acid (PAA) with the copper-based heterogeneous catalysts has been applied for organic pollutant abatement, yet the efficiency is limited by the sluggish Cu(II)/Cu(I) redox cycling. Regarding that reductive W(IV) can continuously effectively promote the regeneration of Cu(I) via the redox-reversible W(IV)/W(VI) couple, the W(IV) component is introduced to copper sulfide for efficient activation of PAA (simplified as the W-CuS/PAA process). Morphological and structural characterizations validate the incorporation of W(IV) component into the CuS lattice structure. Under neutral conditions, tetracycline (TC) can be completely removed within 30 min with the apparent first-order rate constant 5 times higher than that of the CuS/PAA process. CH3C(=O)OO is demonstrated as the main radical responsible for TC abatement by radical quenching experiment and electron paramagnetic resonance (EPR). The redox properties and electron transfer capacity of CuS are significantly improved by the W(IV) component. The reductive W(IV) and S(–II) components facilitate the Cu(II)/Cu(I) redox cycling with the concomitant generation of reactive radicals. In addition, the influence of various parameters and coexisting anions on TC abatement is systematically investigated. Four degradation pathways of TC are put forward and the toxicity of intermediates is evaluated. The W-CuS/PAA process shows superior reuse performance and excellent adaptability in different water matrices. This study highlights the capability of the W(IV) to modulate the Cu(II)/Cu(I) redox cycle and proposes a feasible activator amelioration strategy for the efficient activation of PAA.

The dual pathway mechanisms of peroxyacetic acid activation by CoMn2O4 spinel for efficient levofloxacin degradation

In this work, CoMn2O4 spinel catalyst was used for the first time to activate peroxyacetic acid (PAA) for the degradation of fluoroquinolone antibiotic levofloxacin (LVF). The results showed that the degradation efficiency of CoMn2O4/PAA system reached 93% within 15 min at initial LVF concentration of 20 mg/L. In addition, the bimetallic oxide CoMn2O4 with spinel structure showed significantly higher activation performance than the single metal oxide (Co3O4 and MnO2). The excellent PAA activation performance by CoMn2O4 was attributed to the redox cycles between Co3+/Co2+, Mn3+/Mn2+, and Mn4+/Mn3+, as well as the synergistic interaction between Co and Mn species. Radical quenching and electron paramagnetic resonance (EPR) spectra results indicated that acetylperoxyl radical (CH3C(O)OO·) was the dominant radical species, and this work highlighted that 1O2 played an important role in non-radical process in PAA-based AOPs for the first time. The production of 1O2 may be attributed to the interaction between reactive oxygen (O*) and PAA. In addition, the CoMn2O4/PAA system has been proved to have great stability and reusability, and exhibit selective degradation of organic pollutants which contained electron-rich groups. Overall, this work presents perspective for the application of antibiotic remediation by CoMn2O4/PAA process.

Vitamin C promoted refractory organic contaminant elimination in the zero-valent iron/peracetic acid system: Efficiency, mechanism and effects of various parameters

The conventional zero-valent iron/peracetic acid (ZVI/PAA) system is severely limited owing to the passivation of ZVI and the low recovery of Fe2+. In this study, a reducing agent, vitamin C (H2A), was used for the first time to enhance the ZVI/PAA system as a way to improve its degradation performance. Under optimal conditions, the removal efficiency of the H2A/ZVI/PAA system was 82.9%, while that of the H2A/PAA and ZVI/PAA systems were only 19.0% and 25.6%. Free radical quenching and electron paramagnetic experiments (EPR) confirmed that CH3C(O)O•, •OH and CH3C(O)OO• were the major active species for acid orange 7 (AO7) degradation with contributions of 9.7%, 75% and 14.4%, respectively. The degradation mechanism was proposed through UV–vis full-wavelength scanning and chemical oxygen demand (COD) experiments. The removal of AO7 was not affected in the presence of Cl−, SO42− and HCO3−, while inhibition occurred with humic acid. ZVI exhibited excellent catalytic properties and stability, and the removal efficiency of AO7 exceeded 70% after three cycles. Additionally, the H2A/ZVI/PAA system showed good ability to remove AO7 in well water, lake water, river water and reservoir water, and the elimination efficiency of MO, DCF and ACE also exceeded 70%. Overall, this study contributes new cognition for enhancing the ZVI/PAA system to degrade contaminants, which is expected to achieve a cleaner water environment.

Ultra-rapid and long-lasting activation of peracetic acid by Cu-Co spinel oxides for eliminating organic contamination: Role of radical and non-radical catalytic oxidation

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have attracted considerable attention in organic wastewater purification for yielding reactive oxidative species (ROS) with high performance and long lifetime. However, searching for economical and stable activators is a huge obstacle. In this work, we used a facile second transition metal embedding approach to prepare bimetallic spinel oxides (CuCo2O4) through embedding Cu to Co3O4, which was used as the activator for the rapid and durable activation of PAA to remove model organic pollutant bisphenol A (BPA). Under identical conditions, the rate constant of the constructed CuCo2O4/PAA system (0.0412 min−1) was 21.7 and 3.3 times that of CuO/PAA (0.0019 min−1) and Co3O4/PAA (0.0125 min−1) system alone, respectively. The CuCo2O4/PAA system had better resistance to co-existed ions and natural organic compounds. Meanwhile, the as-prepared materials maintained excellent stability during four-cycle tests and gradient experiments, confirming their perfect application potential. Combining the capture experiments, chemical probe, electron paramagnetic resonance, and theoretical calculations, the singlet oxygen (1O2) and organic radicals (R-O•, e.g., CH3C(O)O• and CH3C(O)OO•) were validated to be the dominant ROS. The density functional theory (DFT) calculations indicated that both BPA and PAA were more easily adsorbed onto the CuCo2O4 surface and bimetallic internal cycle opening was more likely to occur, which accelerated the PAA activation and the contaminants decomposition for rapid electron supply. This study provides new ideas for the design of alternative alloy oxides as efficient PAA activators, and further broadens the applicability of non-homogeneous PAA-based AOPs in wastewater decontamination.

Comprehensive understanding of fluoroquinolone degradation via MPUV/PAA process: Radical chemistry, matrix effects, degradation pathways, and toxicity.

The wide occurrence of fluoroquinolones (FQs) in aquatic environments has aroused increasing concern about their potential adverse effects on human health. In this study, an emerging advanced oxidation process, i.e., the Medium-Pressure Ultraviolet/Peracetic Acid (MPUV/PAA) process, was used to degrade FQs (e.g., levofloxacin (LEV), norfloxacin, and ciprofloxacin). Compared with the MPUV process alone and the PAA process alone, the MPUV/PAA process significantly promoted degradation of FQs due to the considerable contribution of reactive radicals. Probe experiments revealed that PAA-specific organic radicals (e.g., CH3C(O)O• and CH3C(O)OO•) were the major radicals responsible for FQ elimination. Rapid degradation of FQs via the MPUV/PAA process was achieved within a wide range of pH values (5-9) by selecting LEV as the target compound, and higher pH values were more favorable for the reaction. The slight impacts of Cl- and CO32-/HCO3- on LEV removal were observed. The transformation products and pathways of LEV were identified, and nearly all of the transformation pathways occurred on the piperazine ring. Based on Quantitative Structure-Activity Relationship (QSAR) analysis, most of the products had lower toxicities than LEV. Overall, these findings improve our understanding and application of the MPUV/PAA process for degrading emerging contaminants in (waste)water treatment.