Mechanism and security of UV driven sodium percarbonate for sulfamethoxazole degradation using DFT and metabolomic analysis.

Recently, sodium percarbonate (SPC) as a solid substitute for H2O2 has aroused extensive attention in advanced oxidation processes. In current work, the degradation kinetics and mechanisms of antibiotic sulfamethoxazole (SMX) by ultraviolet (UV) driven SPC system were explored. The removal efficiency of SMX was enhanced as the increasing dosage of SPC. Moreover, hydroxyl radical (•OH), carbonate radical (CO3•-) and superoxide radical (O2•-) were verified to be presented by scavenger experiments and •OH, CO3•- exhibited a significant role in SMX degradation. Reactions mediated by these radicals were affected by anions and natural organic matters, implying that an incomplete mineralization of SMX would be ubiquitous. The screening four intermediates and transformation patterns of SMX were verified by DFT analysis. Metabolomic analysis demonstrated that a decreasing negative effect in E. coli after 24 h exposure was induced by intermediates products. In detail, SMX interfered in some key functional metabolic pathways including carbohydrate metabolism, pentose and glucuronate metabolism, nucleotide metabolism, arginine and proline metabolism, sphingolipid metabolism, which were mitigated after UV/SPC oxidation treatment, suggesting a declining environmental risk of SMX. This work provided new insights into biological impacts of SMX and its transformation products and vital guidance for SMX pollution control using UV/SPC technology.

Enhanced degradation of atrazine through UV/bisulfite: Mechanism, reaction pathways and toxicological analysis.

Atrazine residue in the environment continues to threaten aquatic ecosystem and human health owing to its adverse effect. However, limited researches focused on degradation mechanism of atrazine by UV/bisulfite, especially risk of intermediates at cellular and molecular level has not been seriously elaborated. In current work, transformation patterns and residual toxicity of intermediates of atrazine by UV/bisulfite were systematically investigated. The atrazine degradation was described by a pseudo first-order kinetic model (Kobs = 0.1053 min-1). The presence of H2PO4-, HCO3- and HA had a powerful inhibition. Scavenging test of radicals illustrated that SO4•-, •OH and O2•- existed in UV/bisulfite system, SO4•- and •OH were mainly responsible for atrazine degradation. Eight degradation intermediates were identified, which were involved in dealkylation, alkyl oxidation, dechlorination-hydroxylation, and alkylic-hydroxylation. E. coli as a model microorganism was selected to assess the risk of degradation intermediates. The levels of reactive oxygen species, MDA and Na+/K+-ATPase were declined, suggesting that oxidative damage induced by these intermediates was weakened. According to differential metabolites expression analysis, several key metabolites including aspartate, L-tryptophan, L-asparagine, cytidine, cytosin, stearic acid, behenic acid, were up-regulated, and glutathione, cadaverin, L-2-hydroxyglutaric acid and phytosphingosine were downregulated, clarifying that effective detoxification of atrazine can be performed by UV/bisulfite.

UV activated sodium percarbonate to accelerate degradation of atrazine: Mechanism, intermediates, and evaluation on residual toxicity by metabolomics.

Efficient and safe removal of widely used herbicides such as atrazine has become a recent hotspot. Herein, UV driven sodium percarbonate system (UV/SPC) was established to have many advantages in remediation of atrazine contamination. The mechanism and environmental risk of intermediates were explored, which provided information for the feasibility of UV/SPC. The degradation efficiency of atrazine was significantly enhanced as the increasing dosage of SPC. Quenching assay identified that •OH and CO3•- were committed to degrading atrazine. Humic acid and HPO42- remarkably inhibited atrazine degradation. Several intermediates were generated through the dealkylation, dechlorination-hydroxylation, alkylic-hydroxylation, alkyl oxidation and olefination reactions. Toxicity prediction proved that acute toxicity and bioaccumulation of intermediates were mitigated comparing with atrazine. Based on metabolomics results, the alteration of key metabolites such as citrate, L-kynurenine, malic acid, putrescine, glutamine, spermine, ethanolamine and phytosphingosine in various metabolic pathways of E.coli verified that the toxicity of atrazine was weakened after UV/SPC treatment. The application of UV/SPC on atrazine removal in real waters was influenced by environmental factors, and might be improved through coupling with other treatment technologies.

Highly Efficient Liquid-Phase Hydrogenation of Naringin Using a Recyclable Pd/C Catalyst.

A highly efficient liquid-phase hydrogenation reaction using a recyclable palladium on carbon (Pd/C) catalyst has been used for the transformation of naringin to its corresponding dihydrochalcone. The effects of various solvents on the hydrogenation process were studied, with water being identified as the optimal solvent. The analysis also revealed that sodium hydroxide (NaOH) can accumulate on the surface of the Pd/C catalyst in alcoholic solvents, leading to its inactivation. The higher solubility of NaOH in water implies that it remains in solution and does not accumulate on the Pd/C catalyst surface, ensuring the catalytic activity and stability.

Mechanism of extractive/oxidative desulfurization using the ionic liquid inimidazole acetate: a computational study.

The dual role of the ionic liquid 1-butyl-3-methyl-imidazolium trifluoroacetic acid ([C4mim]TFA) as an extractant for thiophene (TH) and a catalyst for the oxidation of TH was explored at the molecular level by performing density functional theory (DFT) calculations. The calculated interaction energies demonstrated why [C4mim]TFA is a better extractant for thiophene sulfone (THO2) than for TH. Two pathways were proposed for the oxidation of TH to THO2 with [C4mim]TFA acting as a catalyst. In the dominant pathway, a peracid is formed which then oxidizes TH to the sulfoxide and sulfones. The presence of [C4mim]TFA was found to greatly reduce the barrier to the oxidative desulfurization (ODS) of TH using H2O2 as an oxidant. Graphical Abstract Possible reaction mechanisms of TH with the aid of [C4mim]TFAᅟ.

A comparative DFT study on aquation and nucleobase binding of ruthenium (II) and osmium (II) arene complexes.

The potential energy surfaces of the reactions of organometallic arene complexes of the type [(η (6)-arene)M(II)(pic)Cl] (where pic = 2-picolinic acid, M = Ru or Os) were examined by a DFT computational study. Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes. The reactions and binding energies of Ru(II) and Os(II) arene complexes with both 9EtG and 9EtA were studied to gain insight into the reactivity of these types of organometallic complexes with DNA. The obtained data rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes.

Di-n-butyl 5-amino-isophthalate.

The title compound, C(16)H(23)NO(4), is essentially planar except for the last two C atoms in each n-butyl group (r.m.s. deviation from the least-squares plane = 0.02 Šfor 17 non-H atoms). In the crystal, inter-molecular N-H⋯O hydrogen bonds between the amine and carbonyl groups link the mol-ecules into one-dimensional chains.

cyclo-Tris[µ-5-(2-pyrid-yl)pyrazol-1-ido-κN,N:N]tris-ilver(I).

In the title compound, [Ag(3)(C(8)H(6)N(3))(3)], the asymmetric unit contains three silver cations and three depronated 5-(2-pyrid-yl)pyrazol-1-ide ligands. Each silver cation is chelated by one 5-(2-pyrid-yl)pyrazol-1-ide ligand, which also acts as a bridging ligand towards the next silver ion via the second pyrazole N atom. In summary, three silver cations and three deprotonated 3-(2-pyrid-yl)-1H-pyrazole ligands produce a macrocyclic trimeric coordination oligomer that exhibits an almost planar conformation (mean deviation 0.1483 Å). In addition, short non-bonding Ag⋯Ag inter-actions [3.127 (2) Å] are observed.

Bis(µ-biphenyl-2,2'-dicarboxyl-ato)bis-[(2,2'-bipyridine)copper(II)].

The title compound, [Cu(2)(C(14)H(8)O(4))(2)(C(10)H(8)N(2))(2)], was obtained by solvothermal synthesis. The Cu(II) atom is coordinated by one chelating 2,2'-bipyridine ligand and two carboxyl groups from different biphenyl-2,2'-dicarboxyl-ate ligands, leading to a distorted octahedral environment. Each carboxyl-ate group makes one short Cu-O bond [1.9608 (14) and 1.9701 (14) Å] and one longer Cu-O contact [2.4338 (17) and 2.5541 (17) Å] to each Cu(II) atom. The biphenyl-2,2'-dicarboxyl-ate ligands bridge between Cu(II) atoms, forming a dinuclear complex around a crystallographic inversion centre.

Bis(6-meth-oxy-2-{[tris-(hydroxy-meth-yl)methyl-κO]imino-meth-yl}phenolato-κN,O)nickel(II) dihydrate.

In the title compound, [Ni(C(12)H(16)NO(5))(2)]·2H(2)O, the Ni(II) atom is coordinated by four O atoms and two N atoms from the two 6-meth-oxy-2-{[tris-(hydroxy-meth-yl)meth-yl]imino-meth-yl}phenolate ligands in a distorted octa-hedral coordination geometry. O-H⋯O hydrogen bonds link the complexes and uncoordinated water mol-ecules into two-dimensional networks parallel to (001).