The inhibition of atmospheric aqueous phase autoxidation of sulfur dioxide by volatile organic compounds : Benzene, toluene, o-xylene, m-xylene, p-xylene, n-hexane and dichloromethane

Atmospheric Chemistry Lab, Department of Chemistry, University of Rajasthan, Jaipur-302 004,

Rajasthan, India

E-mail : guptaks14@rediffmail.com, yokschem@gmail.com

Manuscript received 06 January 2017, revised 17 February 2017, accepted 21 February 2017

This comprehensive study examines the effect of seven volatile organic compounds (VOCs), viz. benzene, toluene, o-xylene, m-xylene, p-xylene, n-hexane, dichloromethane. The disappearance of aqueous sulfur(IV), [S^IV], follows a first order kinetics.

The nature of the dependence of k_obs on the concentration of inhibitor, [Inh], was defined by eq. (A).

k_obs = k_o /(1 + B [Inh])

where k_o and k_obs are the first order rate constant in the absence and the presence of VOCs, respectively and B is an empirical inhibition parameter. Among VOCs, whereas p-xylene, n-hexane and dichloromethane had no effect, o-xylene and m–xylene displayed strong inhibition. Addition of benzene and toluene resulted in the introduction of induction period indicating a very high value of B. The experimental B values, are (1.4±0.83)×10⁴ and (2.33±1.4)×10⁴ L mol^–1 for o-xylene and m-xylene, respectively.