The influence of hydroxyl volatile organic compounds on the oxidation of aqueous sulfur dioxide by oxygen

Although the effect of volatile organic compounds (VOCs) on the oxidation of dissolved sulfur dioxide by oxygen has been the subject of many investigations, this is the first study which examines the effect of a large number of precisely 16 hydroxy compounds. The kinetics both in the absence and the presence of VOCs was defined by rate laws (A and B): $$ \hbox{-} \mathrm{d}\left[\mathrm{S}\left(\mathrm{IV}\right)\right]/\mathrm{dt}={R}_o={k}_o\left[\mathrm{S}\left(\mathrm{IV}\right)\right] $$ (A) $$ \hbox{-} \mathrm{d}\left[\mathrm{S}\left(\mathrm{IV}\right)\right]/\mathrm{dt}={R}_i={k}_i\left[\mathrm{S}\left(\mathrm{IV}\right)\right] $$ (B) where R o and k o are the initial rate and first-order rate constant, respectively, in the absence of VOCs, R i , and k i are the initial rate and the first-order rate constant, respectively, in the presence of VOCs, and [S(IV)] is the concentration of dissolved sulfur dioxide, sulfur(IV). The nature of the dependence of k i on the concentration of inhibitor, [Inh], was defined by Eq. (C). $$ {k}_i={k}_0/\left(1+B\left[\mathrm{Inh}\right]\right) $$ (C) where B is an empirical inhibition parameter. The values of B have been determined from the plots of 1/k i versus [Inh]. Among aliphatic and aromatic hydroxy compounds studied, t-butyl alcohol and pinacol were without any inhibition effect due to the absence of secondary or tertiary hydrogen. The values of inhibition parameter, B, were related to k inh , the rate constant for the reaction of SO4 − radical with the inhibitor, by Eq. (D). $$ B=\left(9\pm 2\right)\times 1{0}^{-4}\times {k}_{inh} $$ (D)