锰钾矿氧化硫化物特性与动力学研究

锰钾矿是表生环境中常见的氧化锰矿物，影响土壤溶液中硫化物的迁移、转化和归趋,考察了无氧条件下锰钾矿氧化硫化钠溶液的反应过程，采用分光光度法、离子色谱法分析S^2-及其氧化产物的浓度和变化趋势，用XRD、SEM表征锰钾矿粉末反应前后的晶体结构和微观形貌，探讨了溶液温度、pH值、矿物用量以及锰钾矿锰氧化度（AOS）对S。初...

Investigation on the Oxidation Behaviors and Kinetics of Sulfide by Cryptomelane

As one of the common manganese oxide minerals in supergene environment, cryptomelane affects the migration, transformation and environmental fate of sulfur in soil. In this work, oxidation process of sodium sulfide solution by cryptomelane was investigated without oxygen gas. The species and concentration of oxidation products of sulfide in solution were determined by spectrophotometry and ion chromatography, and the crystal structures and micro-morphologies of solid oxidation products of sulfide were characterized by XRD and SEM. The influence of solution temperature, pH value of solution, manganese average oxidation state (AOS) and the amount of added cryptomelane on the initial oxidation rate of S2- was studied. It was observed that the oxidation products of sulfide were S2O3(2-), SO3(2-), SO4(2-) and S, and S was the main one for that the total transformation rate of S2- to S2O3(2-), SO3(2-) and SO4(2-) was below 13.4%. The initial oxidation rate of S2- follows a pseudo-first-order law. Oxidation rate increased with elevating reaction temperature, decreasing pH value of solution and the increase of the amount of added mineral. The oxidation capacity of cryptomelane increased with the increase of Mn(III) content, and the initial oxidation rate constants (K(obs)) of S2- were 0.220 3 min(-1) and 0.1729 min(-1) when cryptomelane was applied with AOS about 3.81 and 3.98, respectively. During the redox process, cryptomelane was reduced to Mn(OH)2, which could be oxidized into Mn3O4, by O2 in air, and Mn3O4 was further transformed into MnOOH likely due to the reaction of surface-adsorbed water on manganese oxide and O2 and Mn3O4.