Kinetic and mechanistic study of aqueous sulfide-sulfite-thiosulfate system.

摘要

Aiming at the development of a new sulfur-producing flue gas desulfurization (SP-FGD) technology, a systematic kinetic study of aqueous sulfide-sulfite-thiosulfate system has been performed. A simplified reaction scheme has been proposed to describe the system, and the investigation strategies were set up accordingly. The reaction between sulfide and thiosulfate was studied at pH 5--7, and its rate equation was found to be -d[S2O 32-]/dt = k C[S2O32-][H2S]. Thiosulfate formation by reaction between sulfide and sulfite was studied at pH 8--9, of which the rate equation is d[S2 O32-]/dt = kB[HS-][HSO3- ]2. Mechanisms for the above two reactions have been postulated. Other reactions of sulfide and sulfite were treated as a single reaction and its rate equation was found to be -d[HSO 3-]/dt = k A[HS-]0.7[HSO3 -]1.5[H+]-0.6 in pH range 8--9. A kinetic model was established to predict the system behavior at pH 7. The experimental data agreed with the model prediction in a satisfactory manner, indicating the same reaction mechanisms apply at this pH value.