Study On S(Ⅳ) Oxidation Mechanism And One-step Technology Of Adsorption And Catalytic Oxidation In Seawater Desulfurization Process

S(IV) oxidation process is a very important issue in seawater desulfurization process (SFGD). This paper systematically studied the desulfurization effluent in SFGD process and S(IV) oxidation mechanism in seawater. Experiment results found that trace amount of transition metal ions have variable valence states can greatly catalyze S(IV) oxidation. According to the results, an one-step SFGD technology combine absorption and catalyzed oxidation process had been raised. This technology could simplify traditional SFGD process, save capital cost and energy consumption.Firstly, characteristic of desulfurization effluent had been investigated through semi-batch adsorption experiments. Experiment results indicated that S(IV) oxidation in natural seawater is greatly influenced by pH and transition metal ions which have catalytic effects. The seawater absorption capacity of SO2was studied and an ion equilibrium model which describe the relationship between HCO3-, S(IV), S(VI) and pH value was established to forecast the effluent seawater quality.Secondly, kinetics of uncatalyzed, Fe2+catalyzed, and Mn2+catalyzed oxidation of S(IV) in seawater were studied separately using acetic buffer. Reaction path was discussed through analyzing the valence states of Fe ion and using methanol as radical scavenger. Results indicated that the reaction order with respect to dissolved oxygen is zero. Non-radical oxidation pathway does not exist in both catalyzed and uncatalyzed conditions. Reaction order with respect to S(Ⅳ) is variable:second-order under uncatalyzed condition(4.0≤pH≤7.0); first-order under Fe2+-catalyzed oxidation (2.5≤pH≤3.5); first-order (4.0≤pH≤5.0and second-order (5.5≤pH≤5.9) under Mn2+-catalyzed oxidation. Kinetic experiments found that Fe and Mn ion greatly accelerate S(IV) oxidation, this catalytic effect can be utilized to design one-step SFGD process combine the absorption and oxidation.Finally, technical studies of one-step SFGD process was carried out. Two kind of method: adding Fe2+or Mn2+to seawater, and prepare Fe2O3and MnO2supported artificial zeolite packing, all achieved combination of high absorption and oxidation efficiency. Furthermore, MnO2immobilized catalyst has no shortage which cause chroma increase in seawater. This study offered new ideas for the design of SFGD process.