THE OXIDATION OF MERCURY(I) BY OZONE IN ACIDIC AQUEOUS-SOLUTIONS

The oxidation of mercury(I) (Hg2(2+) by ozone (O3) in acidic aqueous solutions has been investigated using stopped-flow techniques. The reaction is essentially second order, and the rate was found to be independent of pH and temperature for the conditions employed (pH 1-3, T = 283-293 K) with a rate coefficient k(Hg2(2+) + O3) = (9.2 +/- 0.9) x 10(6) M-1 s-1. A small first-order component is attributed to the dissociation of Hg2(2+), with k(Hg2(2+) --> Hg0 + Hg2+) = 4.5 +/- 3.5 s-1 (pH 1, T = 293 K). Elemental mercury is subsequently oxidised by ozone at a rate which appears to approach the diffusion-controlled limit.