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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S2-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S2-初始氧化速率的影响.结果表明,pH为8.0～12.0、温度为20～40℃的Na2S溶液(含S2-为200 mg/L)被锰钾矿氧化成S2O23-、SO32-、SO42-和S,转化生成前三者的S2-所占质量分数不足13.4%,可见,单质S为主要产物,S2-初始氧化速率符合准一级动力学规律,且氧化速率随着温度升高、pH降低和矿物用量增加而增大;Mn(Ⅲ)含量高,有利于提高锰钾矿氧化能力,如AOS为3.81和3.98的锰钾矿氧化S2-的初始表观速率常数分别为0.220 3 min-1和0.172 9 min-1;锰钾矿首先被还原生成Mn(OH)2,其在空气中与O2作用转化成Mn3O4和H2O,Mn3O4可进一步转化生成MnOOH,可能为锰氧化物表面吸附水和O2共同与Mn3O4作用的结果.
Manganite is a common manganese oxide mineral in epigenetic environment, which affects the migration, transformation and fate of sulfides in soil solution. The reaction process of oxidation of sodium sulfide solution by cryptomelane in anaerobic conditions was investigated. Spectrophotometry, Ion chromatography was used to analyze the concentration and trend of S2- and its oxidized products. The crystal structure and morphology of S2-Mn-Mn powder before and after reaction were characterized by XRD and SEM. The effects of solution temperature, pH value, (AOS) on the initial oxidation rate of S2- was investigated.The results showed that the Na2S solution (S2-containing 200 mg / L) with pH value of 8.0-12.0 and temperature of 20-40 ℃ was oxidized to S2O23- , SO32-, SO42- and S, the mass fraction of S2- converted into the first three is less than 13.4%. It can be seen that the elemental S is the main product, and the S2-initial oxidation rate is in accordance with quasi-first order kinetics, and the oxidation rate With the increase of temperature, pH and the increase of mineral content, the content of Mn (Ⅲ) is high, which is helpful to improve the oxidation capacity of cryptomelane. For example, the initial apparent rate constant of oxidation of S2- by cryptomelane with AOS of 3.81 and 3.98 0.220 3 min-1 and 0.172 9 min-1, respectively. The cryptomelane was first reduced to Mn (OH) 2, Its role in the air and O2 into Mn3O4 and H2O, Mn3O4 can be further converted into MnOOH, manganese oxide surface adsorption of water and O2 may be the result of the role of Mn3O4.