Strong degradation of orange II by activation of peroxymonosulfate using combination of ferrous ion and zero-valent copper

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.

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^-, SO₄^2- 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.

Nanoscale zerovalent copper (nZVC) catalyzed environmental remediation of organic and inorganic contaminants: A review

Over the past decade, the nano zerovalent copper has emerged as an effective nano-catalyst for the environment remediation processes due to its ease of synthesis, low cost, controllable particle size and high reactivity despite its release during the remediation process and related concentration dependent toxicities. However, the improvised techniques involving the use of supports or immobilizer for the synthesis of Cu⁰ has significantly increased its stability and motivated the researchers to explore the applicability of Cu⁰ for the environment remediation processes, which is evident from access to numerous reports on nano zerovalent copper mediated remediation of contaminants. Initially, this review allows the understanding of the various resources used to synthesize zerovalent copper nanomaterial and the structure of Cu⁰ nanoparticles, followed by focus on the reaction mechanism and the species involved in the contaminant remediation process. The studies comprehensively presented the application of nano zerovalent copper for remediation of organic/inorganic contaminants in combination with various oxidizing and reducing agents under oxic and anoxic conditions. Further, it was evaluated that the immobilizers or support combined with various irradiation sources originates a synergistic effect and have a significant effect on the stability and the redox properties of nZVC in the remediation process. Therefore, the review proposed that the future scope of research should include rigorous focus on deriving an exact mechanism for synergistic effect for the removal of contaminants by supported nZVC.

Zero-Valent Copper-Mediated Peroxymonosulfate Activation for Efficient Degradation of Azo Dye Orange G

Zero-valent metal (ZVMs)-based persulfate activation systems are extensively applied for the elimination of organic pollutants in aqueous environments. In this study, for the first time, zero-valent copper (ZVC) was employed as the peroxymonosulfate (PMS) activator for the efficient degradation of Orange G (OG). The physicochemical properties of ZVC were systematically characterized by FESEM, EDX, TEM, XRD and XPS measurements. Furthermore, the effects of catalyst loading, PMS dosage, OG concentration and inorganic anions on the ZVC/PMS system were, respectively, investigated and explicated. The formation of •OH and SO4•− in the system was verified by quenching experiments and then the possible reaction mechanism was proposed. This work can provide insight into water treatment technology based on ZVMs.