Kinetics of Hydrolysis and Oxidation of Carbon Disulfide by Hydrogen

Environ. Sci. Technol. 1987, 21, 170-177

Kinetics of Hydrolysis and Oxidation of Carbon Disulfide by Hydrogen Peroxide in Alkaline Medium and Application to Carbonyl Sulfide Yusuf Gbadebo Adewuyl and Gregory R. Carmichael*

Chemical and Materials Engineering Program, University of Iowa, Iowa City, Iowa 52242

Kinetic studies of the oxidation of carbon disulfide by hydrogen peroxide in alkaline medium were made spectrophotometrically. The reaction of CS2with OH- ion was found to be rate controlling and proceeded by the formation of a dithiocarbonate complex. The major reaction product was sulfate with sulfur occurring as colloidal suspensions only at pH values less than 8. The formation of sulfate increased exponentially with time and was also found to be dependent on the rate of hydrolysis of CS2. In addition, the production of sulfate showed large induction periods, suggesting either a complex mechanism or formation by secondary reactions. The results obtained for carbon disulfide were extended to carbonyl sulfide (OCS) oxidation in alkaline solutions. The removal of OCS (acid gas) from mixtures of gases by alkaline liquid absorbents (e.g., NaOH) and oxidation of subsequent solutions to sulfate is an important industrial practice.

only at pH >13 (10, 11). However, the hydrolysis has been found to involve the formation of an unstable intermediate dithiocarbonate (DTC), which can exist as CS20H- or CS202-(12). The intermediate can disproportionate in one or more rapid steps into carbonate and sulfide. The sequence of reactions depends on the pH of the solution. With pH >11, Philipp et al. (II) and Hovenkamp (7)obtained CS,

= on-

CSzOH-

onC_+_ C S z 0 2 n

With pH