Toxicity evolution and control for the UV/H2O2 degradation of nitrogen-containing heterocyclic compounds: SDZ and PMM.

This study aimed to achieve toxicity control of sulfadiazine (SDZ) and pirimiphos-methyl (PMM) via the UV/H2O2 process by optimizing the reaction parameters. The results show that both drugs had a good degradation effect under the following parameters: a H2O2 molar ratio of 1:200, and neutral conditions. SDZ and PMM could be degraded by more than 99% within 3 min, respectively. In the Daphnia magna acute toxicity assay and Vibrio fischeri inhibition assay, both SDZ and PMM exhibited a phenomenon of increasing toxicity. Additionally, through the use of density functional theory (DFT) calculation and HPLC-QTOF-MS, 21 transformation products (TPs) were identified, and the principal degradation pathways were proposed. The toxicity of the TPs was determined by comparing the QSAR prediction results with toxicity test data. As a result, under the higher UV light intensity (2300 µW/cm2) and neutral conditions, SDZ showed highest toxicity, whereas PMM showed lowest toxicity under the lowest UV light intensity (450 µW/cm2) and neutral conditions. Four main toxic TPs were identified, and their yields could be reduced by adjusting the reaction parameters. Therefore, the selection of appropriate reaction parameters could reduce the production of toxic TPs and ensure the safety of water environment.

Identification and regulation of ecotoxicity of polychlorinated naphthalenes to aquatic food Chain (green algae-Daphnia magna-fish).

Polychlorinated naphthalenes (PCNs) are widely distributed in the aquatic environment and can be transmitted through the food chain, which can amplify their toxic effects on human. To inhibit their transmission in the trophic level, this study aimed to predict the joint toxicity mechanism of polychlorinated naphthalenes (PCNs) to the key organisms and control scheme of its toxicity in the aquatic food chain (green algae-Daphnia magna-fish). The toxic effect grade and mode of action (MoA) of PCNs on the food chain were first predicted to guide the establishment of toxic mechanism model. QSAR models were constructed to quantify the mechanism of aquatic toxicity due to PCNs. The results showed the PCN compounds studied were highly toxic at all the trophic levels of the aquatic food chain. The binding ability of PCNs to the aquatic organisms was the main factor causing the toxicity of PCNs in the food chain, followed by electronic parameters EHOMO and ELUMO. Moreover, the binding ability between PCNs and food chain receptors was related to the molecular hydrophobicity, the hydrophobicity can be changed by adjusting the ability of PCNs to be adsorbed by sediment and their chlorine substituents, while the effect of PCNs electronic parameters (EHOMO and ELUMO) can be adjusted by their solvation effect. In addition, the macro-control scheme of PCN-based aquatic toxicity mechanism was established, and the molecular dynamics (MD) simulation confirmed its effectiveness and accessibility. The MD simulation showed the inhibition effect of nutrition-grade toxicity in the food chain was significant when the external stimulation conditions of solvation, anaerobic dechlorination and molecular adsorption were improved, with the decrease range of 66.26-263.16%, 198.93-323.98% and 189.24-549.48%, respectively. This work reveals new insights into the mechanism of PCNs joint toxicity to aquatic ecosystem food chain and develop appropriate strategies for its ecological risk management.

[Adsorption Effect and Mechanism of Aqueous Arsenic on FeMnNi-LDHs].

Removing As(Ⅲ)from water steadily and efficiently is still a challenging global issue. In this study, novel FeMnNi-LDHs were prepared by a co-precipitation method using Fe, Mn, and Ni as lamellar cations, and the structure were characterized by XRD, TEM, FT-IR, and XPS techniques, and the adsorption performance and mechanism of As(Ⅲ)was explored. The results showed that FeMnNi-LDHs have typical characteristic peaks of layered double hydroxides, with sharp peaks and high crystallinity. The TEM images also show obvious layered structures. The adsorption kinetics of As(Ⅲ)on FeMnNi-LDHs agree with the quasi second-order kinetic model, and the isotherm adsorption curve agrees with the Freundlich isotherm equation. The maximum adsorption capacity at 45℃ was 240.86 mg·g-1, which is significantly higher than other similar layered double hydroxides. Acidity had little effect on the adsorption performance of As(Ⅲ), and it had a good adsorption effect in the range of pH 2-9. The coexistence of PO43- and CO32- ions in water showed adverse effects on the As(Ⅲ) adsorption capacity, and NO3-, Cd2+, and Pb2+ had less influence. The adsorption mechanism of FeMnNi-LDHs for As(Ⅲ) includes ion exchange, oxidation, and coordination complexation, in which Mn plays a major role in the oxidation process of As(Ⅲ). The prepared FeMnNi-LDHs exhibited good application potential in the adsorption of As(Ⅲ) from water and toxicity control.