Micropollutant removal and disinfection byproduct control by sequential peroxymonosulfate-UV treatment in water: A case study with sulfamethoxazole

Enhanced reproductive toxicity of photodegraded polylactic acid microplastics in zebrafish

Microplastics are widely used due to their numerous advantages. However, they can have detrimental effects on marine ecosystems. When microplastics enter the ocean, they can be absorbed by marine organisms, leading to toxic effects. Additionally, the transformation of microplastics during natural degradation can alter their toxicity, necessitating further investigation. Polylactic acid (PLA) biodegradable plastics are commonly used, yet research on their toxicity, particularly their reproductive effects on aquatic organisms, remains limited. In this study, we conducted photodegradation of PLA using potassium persulfate as a catalyst to simulate natural degradation conditions. Our objective was to assess the reproductive toxicity of photodegraded PLA microplastics on zebrafish. The results revealed that photodegraded PLA exhibited elevated reproductive toxicity, resulting in abnormal oocyte differentiation, disruption of sexual hormone levels, and alterations in ovarian tissue metabolism. Metabolomics analysis indicated that both unphotodegraded PLA (UPLA) and photodegraded PLA (DPLA) disrupted oxidative stress homeostasis in zebrafish ovarian tissue by influencing pathways such as purine metabolism, phenylalanine metabolism, glutathione metabolism, and riboflavin metabolism. Furthermore, the DPLA treatment induced abnormal biosynthesis of taurocholic acid, which was not observed in the UPLA treatment group. Importantly, the DPLA treatment group exhibited more pronounced effects on offspring development compared to the UPLA treatment group, characterized by higher mortality rates, inhibition of embryo hatching, accelerated heart rates, and reduced larval body length. These findings underscore the varying levels of toxicity to zebrafish ovaries before and after PLA photodegradation, along with evidence of intergenerational toxicity.

Effect of UV/peroxymonosulfate pretreatment on disinfection byproduct (DBP) formation during post-chlorination of humic acid

UV/peroxymonosulfate (UV/PMS) is a promising advanced oxidation technology in water treatment. This study aimed to investigate the impact of UV/PMS on humic acid (HA) and the influence of PMS dosage, pretreatment time, pH pretreatment, nitrate, nitrite, ammonium, and bicarbonate influencing factors on disinfection byproduct (DBP) formation during post-chlorination. With increased PMS dosage or pretreatment time, the UV/PMS treatment significantly reduced ultraviolet absorbance and increased mineralization. It altered the fractional constituent as humic substances were gradually transformed into building blocks and low-molecular-weight acids. However, most DBP formation increased initially and then decreased after subsequent chlorination. Rising nitrate or nitrite concentrations markedly promoted halonitromethane (HNM) formation. The presence of ammonia had a more significant impact on dichloroacetonitrile (DCAN) formation. Bicarbonate in UV/PMS pretreatment increased carbonated disinfection byproduct (C-DBP) formation, whereas it had a negligible impact on nitrogenous disinfection byproduct (N-DBP) formation. The present study revealed the impact of a series of influencing factors on DBP formation in UV/PMS reaction systems, providing comprehensive insights on applying UV/PMS in actual practice.

Co-based MOF heterogeneous catalyst for the efficient degradation of organic dye via peroxymonosulfate activation

In this study, a new cobalt-based metal-organic framework (JLNU-500), [Co2(OH)(PBA)(AIP)]·3DMA·0.75H2O (4-(pyridin-4-yl) benzoic acid (HPBA), 5-aminoisophthalic acid (H2AIP) and N,N-dimethylacetamide (DMA)), was fabricated using a solvothermal method. JLNU-500 has 3D network architecture with 1D nanopore channels. The prepared JLNU-500 can activate peroxymonosulfate (PMS) for Rhodamine B (RhB) dye decolorization. Interestingly, catalyst JLNU-500 exhibited high efficiency for PMS activation, and nearly 100% (above 99.8%) removal of RhB with a high concentration (50.0 mg L-1, 100 mL) was achieved within 6 min. The reaction rate constant of the JLNU-500/PMS system was 1.02 min-1 calculated based on the pseudo-first-order kinetics, which is higher than that of the other reported catalysts. Furthermore, the factors, which could influence PMS activation were also investigated, such as PMS dosage, catalyst dosage, pollutant RhB concentration, reaction temperature and solution pH. More importantly, the radical trapping experiments ferreted out that sulfate (SO4˙-) and hydroxyl (˙OH) radicals were the dominating oxidants in the removal of RhB. Moreover, the possible degradation mechanism was elucidated. This study provides new prospects for fabricating new MOFs that can potentially be employed for high-efficiency catalytic oxidation as heterogeneous catalysts.

Utilization of Fe-Ethylenediamine-N,N'-Disuccinic Acid Complex for Electrochemical Co-Catalytic Activation of Peroxymonosulfate under Neutral Initial pH Conditions

The ethylenediamine-N,N'-disuccinic acid (EDDS) was utilized to form Fe-EDDS complex to activate peroxymonosulfate (PMS) in the electrochemical (EC) co-catalytic system for effective oxidation of naphthenic acids (NAs) under neutral pH conditions. 1-adamantanecarboxylic acid (ACA) was used as a model compound to represent NAs, which are persistent pollutants that are abundantly present in oil and gas field wastewater. The ACA degradation rate was significantly enhanced in the EC/PMS/Fe(III)-EDDS system (96.6%) compared to that of the EC/PMS/Fe(III) system (65.4%). The addition of EDDS led to the formation of a stable complex of Fe-EDDS under neutral pH conditions, which effectively promoted the redox cycle of Fe(III)-EDDS/Fe(II)-EDDS to activate PMS to generate oxidative species for ACA degradation. The results of quenching and chemical probe experiments, as well as electron paramagnetic resonance (EPR) analysis, identified significant contributions of •OH, 1O2, and SO4•- in the removal of ACA. The ACA degradation pathways were revealed based on the results of high resolution mass spectrometry analysis and calculation of the Fukui index. The presence of anions, such as NO3-, Cl-, and HCO3-, as well as humic acids, induced nonsignificant influence on the ACA degradation, indicating the robustness of the current system for applications in authentic scenarios. Overall results indicated the EC/PMS/Fe(III)-EDDS system is a promising strategy for the practical treatment of NAs in oil and gas field wastewater.

Overlooked Contribution of the Indole Moiety to the Formation of Haloacetonitrile Disinfection Byproducts

Haloacetonitriles (HANs) are a group of disinfection byproducts with high toxicity and frequent occurrence. Past studies have focused on the free amine groups, especially those in amino acids, as HAN precursors. This study reports, for the first time, that the indole moiety such as that in the tryptophan side chain is also a potent precursor for the most common HANs dichloroacetonitrile, bromochloroacetonitrile, and dibromoacetonitrile. 3-Indolepropionic acid, differing from tryptophan only in the absence of the free amine group, formed HANs at levels 57-76% of those by tryptophan at a halogen/nitrogen molar ratio of 10. Experiments with tryptophan-(amino-¹⁵N) showed that the indole contributed to 28-51% of the HANs formed by tryptophan. At low oxidant excess (e.g., halogen/precursor = 5), 3-indolepropionic acid even formed more HANs than Trp by 3.5-, 2.5-, and 1.8-fold during free chlorination, free bromination, and chlorination in the presence of bromide (0.6 mg/L), respectively. Indole's HAN formation pathway was investigated by exploring the chlorination/bromination products of 3-indolepropionic acid using liquid chromatography-orbitrap high-resolution mass spectrometry. A total of 22 intermediates were detected, including pyrrole ring-opening products with an N-formyl group, 2-substituted anilines with different hydroxyl/halogen substitutions, and an intermediate with a postulated non-aromatic ring structure.