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

Total reduced sulfurs quartet (H2S, CH3SH, CH3SCH3 and CH3S2CH3) 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 H2S and CH3SH 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.