用硫化氢气体分解硫化钠阳极电解液的热力学分析

直接电解硫化氢碱性溶液(通常用Na2S溶液表示)产生单质硫和氢气的关键问题是单质硫在阳极表面上沉积而导致的阳极钝化. 用硫化氢气体分解Na2S的阳极电解液可以很好地解决这一问题,并对这一方法进行了热力学分析.对简化S-H2O 系的电势-pH图的分析表明,多硫化物Sx2-在碱性溶液中稳定,且随着体系中溶解态物质的总硫浓度T(s)的增加,高级多硫化物的优势区增大.当Na2S阳极电解液与硫化氢气体反应时,固相硫稳定存在于pH较低和H2S 分压较小的环境中.分析表明,当H2S 分压为1atm,溶液pH值小于8时,大多数多硫化物分解为单质硫S、S2-, HS-或H2S(aq.).分析结果对电解产生多硫化物以及用H2S气体分解多硫化物的实际过程具有重要指导意义.图6,表1,参10.

Thermodynamic analysis for a new process of electrochemical decomposition of aqueous hydrogen sulfide solution into sulfur and hydrogen gas

The difficulty for electrochemical decomposition of aqueous hydrogen sulfide solution into elemental sulfur and hydrogen gas is the anode passivation caused by deposition of solid sulfur on the anode surface.Thermodynamic analyses for a novel approach to get rid of the anode passivation are presented in this paper. Pourbaix diagrams for the simplified sulfur-H_2O system show that polysulfide ions in alkaline solution are stable species and dominant regions of higher polysulfide ions become bigger with the increase of total sulfur concentration T(s) of all dissolved species.When the anolyte is reacted with H_2S gas,solid sulfur phase is stable if both pH of the solution and partial pressure of H_2S gas are lower.Thermodynamic calculations show that the appropriate H_2S gas partial pressure is chosen to be 1 atm,and that,when the solution pH is less than 8,most of the polysulfide ions are decomposed into elemental sulfur and S~(2-),HS~- or H_2S(aq.).The result is useful both for determining optimum electrolytic conditions in electrochemical formation of the polysulfide ions and for decomposition of the polysulfide ions by H_2S gas into elemental sulfur.6figs.,1tab.,10refs.