Role of some organic inhibitors on the oxidation of dissolved sulfur dioxide by oxygen in rainwater medium.

In August 2012, eight rainwater samples were collected and analyzed for pH and metal ions, viz., iron, copper, and manganese. The pH was within the range 6.84-7.65. The rate of oxidation of dissolved sulfur dioxide was determined using these rainwater samples as reaction medium. Kinetics was defined by the rate law: -d[S(IV)]/dt = R o = k o[S(IV)]], where k o is the first-order rate constant and R o is the rate of the reaction. The effect of two volatile organic compounds-ethanol and 2-butanol-was examined and found to inhibit the oxidation as defined by the rate law: k obs = k o/(1 + B [Inh]), where k obs is the first-order rate constant in the presence of the inhibitor, [Inh] is the concentration of the inhibitor, and B is the inhibitor parameter-an empirical constant. In the pH range of collected rainwater samples, the values of first-order rate constants ranged from 3.1 × 10(-5) to 1.5 × 10(-4) s(-1) at 25 °C. The values of inhibition parameter were found to be (5.99 ± 3.91 × 10(4)) (ethanol) and (3.95 ± 2.36) × 10(4) (2-butanol) at 25 °C.