Homogeneous activation of bisulfite by transition metals for micro-pollutant degradation: Mn(VII) versus Cr(VI)
| Autor: | Mirna Habuda Stanić, Shule Duan, Pin Hou, Huiyu Dong, Xiangjuan Yuan, Zhimin Qiang |
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| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Chemistry
General Chemical Engineering chemistry.chemical_element S(IV)-based process kinetics radical species transformation products 02 engineering and technology General Chemistry Manganese 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Chloride Industrial and Manufacturing Engineering 0104 chemical sciences Hydroxylation chemistry.chemical_compound Reaction rate constant Transition metal Carboxylation medicine Environmental Chemistry Reactivity (chemistry) 0210 nano-technology Stoichiometry medicine.drug Nuclear chemistry |
| Popis: | In this study, the oxidation kinetics, mechanisms, effects and products of metalaxyl (MTL) by two different S(IV)-based processes (i.e., Mn(VII)/S(IV) and Cr(VI)/S(IV)) were systematically investigated and compared. The results showed that the concentration of S(IV) was primarily responsible for driving Mn(VII) and Cr(VI) consumption with a measured second order rate constant (k), and the k of Mn(VII) was less dependent on pH than that of Cr(VI), ranging from 104.7 M−1 s−1 to 104.9 M−1 s−1 and 10−0.4 M−1 s−1 to 101.6 M−1 s−1, respectively. Moreover, the reaction stoichiometry of [Cr(VI)]0:[S(IV)]0 was estimated to about 1:30–1:40 in the presence of O2, which was significantly different from the molar ratio of [Mn(VII)]0 to [S(IV]0 (1:5–1:10). Sulfur radical (SO4 −) was determined to be a major active oxidant in both the systems based on the chemical probes and radical scavenging experiments. Besides, carbonate and chloride have greater inhibitory effects than other coexisting solutes (e.g., nitrate and organic matter) because of the higher reactivity with radical species. In addition, the proposed degradation of MTL mainly proceeded through hydroxylation, demethylation, and carboxylation reactions. All these results indicated that Mn(VII) outperforms Cr(VI) in the activation of S(IV) auto-oxidation for the degradation of MTL. An extremely fast degradation rate, high mineralization and strong adaptation to the water matrices were observed in the process, which were attributed to ultra-fast production of high concentrations of radical species such as SO4 −, HO and high valent manganese intermediates (e.g., Mn(III) and Mn(V)). |
| Databáze: | OpenAIRE |
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