Analysis and Equilibrium Constant of Polysulfides in Desulfurization Solution

Abstract

Polysulfides play key roles to thorough understanding of the desulfurization mechanism. The analysis and equilibrium constant of polysulfides from dissolved sodium sulfide and inorganic sulfur has been studied. Polysulfides with different chain length are prepared. The influence of absorption wavelength, pH value and other components in the desulfurization solution on the determination of polysulfide concentration by UV spectrophotometry is investigated. The optimum absorption wavelength of polysulfide is 285 nm. The molar extinction coefficient is 1,458 L·mol-1cm-1. Using the proposed UV spectrophotometric, the polysufide concentration in PDS desulfurization solutions is determined under different the total amount of divalent sulfur and the total amount of zero valent sulfur. In addition, the total negative bivalent sulfur is measured by the iodimetry method. The activity coefficients of all ions are calculated by the Debye-Huckel law. At 80 ℃, The calculated average chain length of polysulfides is 5.64. The equilibrium constant of the polysulfide with elemental sulfur and polysulfide in the desulfurization solution is 9.362.