Naslov
Homogeneous activation of bisulfite by transition metals for micro-pollutant degradation: Mn(VII) versus Cr(VI)

Autori
Duan, Shule ; Hou, Pin ; Yuan, Xiangjuan ; Habuda- Stanić, Mirna ; Qiang, Zhimin ; Dong, Huiyu

Izvornik
Chemical engineering journal (1385-8947) 394 (2020); 124814, 9

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
S(IV)-based process ; kinetics ; radical species ; transformation products

Sažetak
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)).

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

POVEZANOST RADA