College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Water Res. 2017 Mar 15;111:234-243. doi: 10.1016/j.watres.2017.01.013. Epub 2017 Jan 7.
Mn(III) is a strong oxidant for one electron transfer, which may be important in the transformation of organic contaminants during water/wastewater treatment and biogeochemical redox processes. This study explored the reaction mechanisms of dissolved Mn(III) with organics. The role of dissolved Mn(III) either as a catalyst or an oxidant in reactions with organics was recognized. Aquo and/or hydroxo (or free) Mn(III), generated from the bisulfite activated permanganate process, facilitated efficient N-dealkylation of atrazine via a β-elimination mechanism, resulting no net redox reaction. In contrast, free Mn(III) degraded 4-chlorophenol via intramolecular redox processes, the same as hydroxyl radical (OH), resulting in dechlorination,OH substitution, ring-opening and mineralization. Mn(III)-pyrophosphate compounds did not react with atrazine because complexation by pyrophosphate rendered Mn(III) unable to bond with atrazine, thus the electron and proton transfers between the reactants couldn't occur. However, it degraded 4-chlorophenol at a slower rate compared to free Mn(III), due to its reduced oxidation potential. These results showed two distinct mechanisms on the degradation of organic contaminants and the insights may be applied in natural manganese-rich environments and water treatment processes with manganese compounds.
锰（III）是一电子转移的强氧化剂，这在水/废水处理和生物地球化学氧化还原过程中有机污染物的转化中可能很重要。本研究探讨了溶解的 Mn(III)与有机物的反应机制。认识到溶解的 Mn(III)在与有机物的反应中既可以作为催化剂，也可以作为氧化剂。亚硫酸氢盐激活高锰酸盐过程中产生的水合和/或氢氧根（或游离）Mn(III)，通过β消除机制促进莠去津的有效 N-脱烷基化，导致没有净氧化还原反应。相比之下，游离 Mn(III)通过分子内氧化还原过程降解 4-氯苯酚，与羟基自由基 (OH) 相同，导致脱氯、OH 取代、开环和矿化。Mn(III)-焦磷酸化合物与莠去津不反应，因为焦磷酸盐的络合作用使 Mn(III)无法与莠去津键合，因此反应物之间的电子和质子转移无法发生。然而，由于其氧化还原电位降低，它比游离 Mn(III)以更慢的速率降解 4-氯苯酚。这些结果表明，在有机污染物的降解中有两种不同的机制，这些见解可能适用于富含天然锰的环境和使用锰化合物的水处理过程。
