Solubility of dimethyldisulfide (DMDS) in aqueous solutions of Fe(III) complexes of trans-1,2-cyclohexanediaminetetraacetic acid (CDTA) using the static headspace method

Abstract

Total reduced sulfurs quartet (H 2S, CH 3SH, CH 3SCH 3 and CH 3S 2CH 3) is part of a well-known environmental problem afflicting pulp mills exploiting the Kraft mill sulfate-pulp process. Utilization of ferric chelate complex of trans-1,2-cyclohexanediaminetetraacetic acid (CDTA) for the oxidative scrubbing of H 2S and CH 3SH in Kraft mill streams is beneficial from the standpoints of iron protection against precipitation and oxygen-mediated regenerative oxidation of the ferrous chelate CDTA. The remaining two sulfur-bearing compounds, considered not oxidizable by CDTA–Fe(III), undergo only physical absorption in such solutions, so their solubility in aqueous CDTA–Fe(III) alkaline solutions is a crucial parameter for designing the complete scrubbing-absorption process. This investigation was carried out to determine the Henry's law constants of dimethyldisulfide (DMDS) in pure water, in aqueous iron-free CDTA solutions and CDTA–Fe(III) complex solutions using the static headspace method with an estimated accuracy of 2%. Experiments with aqueous solutions of chelate concentrations varying between 38 and 300 mol m −3 were carried out at temperatures between 298 and 333 K and atmospheric pressure. It was shown that DMDS solubility decreases with increasing temperature for all systems and is not much influenced by the CDTA concentration and solution pH.