Kinetics of degradation of sulphur mustard on impregnated carbons

Abstract

Kinetics of degradation of sulphur mustard (HD) on the surface of NaOH/CrO 3/C, NaOH/CrO 3/EDA/C and RuCl 3/C systems has been examined by using gas chromatography technique by extracting and analyzing the residual HD periodically. The carbons were prepared by impregnating activated carbon with 4% sodium hydroxide plus 3% Cr(VI) as CrO 3 with and without 5% ethylene diamine (EDA) and 5% ruthenium chloride by using their aqueous solutions. Obtained carbons were characterized for surface area analysis by BET conventional method. Kinetic plots reveal that the observed reactions are fast at the initial stages, slow at the later stages and progress to a steady state indicating the first order behavior. Effect of moisture on kinetic rate is also observed. In the case of NaOH/CrO 3/C system the rate constant is decreased from 13.36 to 5.53 × 10 −2 h −1 and half life is increased from 5.2 to 12.54 h while moisture content is increased from 1.9% to 11.2%. Whereas, the rate constant of HD degradation reaction is decreased from 10.4 to 4.14 × 10 −2 h −1 and half life is increased from 6.7 to 16.72 h while moisture content is increased from 2.1% to 10.8% on NaOH/CrO 3/EDA/C. Reaction on RuCl 3/C system also behaves in the similar manner. Extracted reaction products were characterized by GC/MS and it is found that on NaOH/CrO 3/C, HD degrades to hemisulphur mustard, thiodiglycol and 1,4-oxathiane. Whereas, on NaOH/CrO 3/EDA/C, HD is degraded to 1,4-thiazane and it is degraded to divinyl sulphone on RuCl 3/C. All these investigations reveal that above mentioned carbons can be used in nuclear, biological and chemical (NBC) filtration systems for protection against sulphur mustard.