Orientated construction of visible-light-assisted peroxymonosulfate activation system for antibiotic removal: Significant enhancing effect of Cl. J Hazard Mater 2023;445:130476. [PMID: 36455327 DOI: 10.1016/j.jhazmat.2022.130476]

2D/2D heterojunctions for rapid and self-cleaning removal of antibiotics via visible light-assisted peroxymonosulfate activation: Efficiency, synergistic effects, and applications

Developing eco-friendly and efficient technologies for treating antibiotic wastewater is crucial. Traditional methods face challenges in incomplete removal, high costs, and secondary pollution. Heterogeneous peroxymonosulfate (PMS) activation assisted by visible light shows promise, but suitable activators remain a huge challenge. Here, we synthesized cost-effective carbon nitride/bismuth bromide oxide (CN/BiOBr) heterojunctions. Such a heterojunction achieved rapid PMS activation, achieving over 90.00% tetracycline (TC) removal only within 1 min (kobs of 2.23 min-1), surpassing previous systems by nearly 1-2 orders of magnitude and even remarkably superior to the popular single-atom catalysts. The system exhibited self-cleaning properties, maintaining activity after 8 cycles and stability across a wide pH range (3.01 to 9.03). Quenching experiments and theoretical calculations elucidated the exclusive •O2- species involvement and removal pathways. Eco-toxicity assessment and total organic carbon results confirmed simultaneous degradation, detoxification, and mineralization. This system also showed excellent resistance to environmental factors, e.g., coexisting anions, varying pH, and water sources, and demonstrated potential in coking and medical wastewater purification. This study presents a novel technique for rapidly decontaminating antibiotic wastewater through visible light-assisted PMS activation and introduces innovative bionic catalytic oxidation combining light and darkness for practical applications.

Ce/N @BC prepared based on plant metallurgy strategy: A novel activator of peroxymonosulfate for the degradation of sulfamethoxazole

A novel carbon catalyst was created based on plant metallurgy strategy for organic pollutants removal. Plants rich in CeO2 NPs in water were used as carbon precursors and pyrolyzed with urea to obtain Ce/N co-doped carbon catalysts, which were used in the degradation of sulfamethoxazole (SMX) by active peroxymonosulfate (PMS). The results showed that the Ce/N @BC/PMS system achieved to 94.5% degradation of SMX in 40 min at a rate constant of 0.0602 cm-1. The activation center of PMS is widely dispersed Ce oxide nanocrystals, and CeO2 NPs promote the formation of oxygen centered PFR with enhanced catalytic ability and longer half-life. In addition, N-doping facilitates the transfer of π-electrons within the sp2 carbon of biochar, increasing active sites and thus improving PMS activation efficiency. The degradation process was contributed to by both radical and non-radical activation mechanisms including 1O2 and direct electron transfer, with O2•- serving as 1O2's precursor. Through the DFT calculations, LC-MS and toxicological analyses, the degradation pathway of pollutants and the toxicity changes throughout the entire degradation process were further revealed, indicating that the degradation of SMX could effectively reduce ecological toxicity.

A novel DBD/VUV/PMS process for efficient sulfadiazine degradation in wastewater: Singlet oxygen-dominated nonradical oxidation

In this study, a novel process of dielectric barrier discharge plasma/vacuum ultraviolet/peroxymonosulfate (DBD/VUV/PMS) for the nonradical-dominated degradation of sulfadiazine (SDZ) was investigated. The hybrid system has significant synergistic effects, with 95.5% SDZ and 68.3% TOC removal within 10 min. The activation efficiency of DBD/VUV (69.0%) on PMS via multipath was 2.07 times higher than that of single DBD (33.3%) under alkaline conditions. Electron paramagnetic resonance analyses and trapping experiments showed 1O2 was the primary active substance in the DBD/VUV/PMS process. The predominant role of 1O2 revealed that SDZ removal mainly followed the nonradical reaction pathway, contrary to the previously reported non-thermal plasma (NTP)-based radical-dominated process. Multiple spectroscopy analysis showed the efficient degradation process of SDZ. Unlike the radical attack sites, the SDZ transformation pathway by nonradical 1O2 was probably initiated by an aniline ring site attack based on density functional theory (DFT) calculations and product analyses. The DBD/VUV/PMS process reduced energy consumption by 69% compared to DBD. Finally, the evaluation of ecotoxicity and PMS utilization demonstrated the advantages and application prospects of the DBD/VUV/PMS process. This research developed a new nonradical-dominated pathway for antibiotic degradation by the photo/plasma/persulfate process.

Differences between reductive defluorination of perfluorooctanoic acid by chlorination, bromination, and iodization in the vacuum-ultraviolet/sulfite process

The introduction of iodide (I-) has broad perspectives on the decomposition of perfluorocarboxylates (PFCAs, CnF2n+1COO-). However, the iodinated substances produced are highly toxic synthetic chemicals, hence, it is urgent to find a similar alternative with less toxicity. In this work, the defluorination of perfluorooctanoic acid (PFOA) by I-, bromide (Br-) and chlorine (Cl-) was systematically compared in the VUV/sulfite process. Results indicated that the PFOA defluorination rates increased with increasing nucleophilicity of halogens (I > Br > Cl). Meanwhile, the introduction of I-, Br-, and Cl- reduced the interference of the coexisting water matrix on the degrading influence of PFOA. The in situ produced eaq-, SO3•-, H•, and HO• were recognized, among the addition of I- maximized the relative contribution of eaq- but Br- and Cl- decreased that of H• and other radicals. Additionally, HPLC/MS analysis revealed the presence of I-, Br-, and Cl- had a vital impact on the difference in product concentrations, while they had a negligible effect on the change in the pathway of degradation. Overall, this study demonstrated the similarities and differences between I-, Br-, and Cl-, which has significant implications for further understanding VUV/sulfite degradation.

Chlorinated nucleotides and analogs as potential disinfection byproducts in drinking water

Identification of emerging disinfection byproducts (DBPs) of health relevance is important to uncover the health risk of drinking water observed in epidemiology studies. In this study, mutagenic chlorinated nucleotides were proposed as potential DBPs in drinking water, and the formation and transformation pathways of these DBPs in chlorination of nucleotides were carefully investigated. A total of eleven chlorinated nucleotides and analogs were provisionally identified as potential DBPs, such as monochloro uridine/cytidine/adenosine acid and dichloro cytidine acid, and the formation mechanisms involved chlorination, decarbonization, hydrolysis, oxidation and decarboxylation. The active sites of nucleotides that reacted with chlorine were on the aromatic heterocyclic rings of nucleobases, and the carbon among the two nitrogen atoms in the nucleobases tended to be transformed into carboxyl group or be eliminated, further forming ring-opening or reorganization products. Approximately 0.2-4.0 % (mol/mol) of these chlorinated nucleotides and analogs finally decomposed to small-molecule aliphatic DBPs, primarily including haloacetic acids, trichloromethane, and trichloroacetaldehyde. Eight intermediates, particularly chlorinated imino-D-ribose and imino-D-ribose, were tentatively identified in chlorination of uridine. This study provides the first set of preliminary evidence for indicating the promising occurrence of chlorinated nucleotides and analogs as potential toxicological-relevant DBPs after disinfection of drinking water.