Kinetics and mechanism of oxidation of hydrogen sulfide by hydrogen peroxide in acidic solution

The kinetics of the oxidation of hydrogen sulfide and hydrosulfide ion to sulfur and sulfate in aqueous solution by hydrogen peroxide is studied potentiometrically. In the pH range 8-3, the rate law for the oxidation of H_2S is -d[H_2S]/dt = k_1[H_2S] [H_2O_2] + k_2K_(a1)[H_2S] [H_2O_2]/[H+] where K_(a1) is the first acid dissociation constant of H_S, k_2 = 29.0 M^(-1) min^(-1), and k_1= 0.5 M^(-1) min^(-1). The rate law and other data indicate that the reaction proceeds via a nucleophilic displacement by sulfide on hydrogen peroxide with the formation of polysulfide intermediates.