The phenomenology and the mathematical modeling of the silicone-supported chemical oxidation of aqueous sulfide to elemental sulfur by ferric sulphate

When pumping a sulfide solution through a silicone cylinder immersed in a s olution of ferric sulfate, a cloud of elemental sulfur is formed in the fer ric sulfate if the pH of the sulfide solution is below about 8.5. The eleme ntal sulfur subsequently sediments as orthorhombic alpha-sulfur particles. H2S(aq) diffuses through the pores of the hydrophobic silicone membrane and simultaneously reacts to become sulfur. This was confirmed by a mass balan ce between the amount of sulfide removed from the sulfide solution and the amount of solid product formed in the ferric solution. During the experimen t, the pH of the non-buffered sulfide solution rises up to a maximum of 8.5 ; this is explained by the continuous protonation of HS caused by the remov al of H2S(aq). The pH of the strongly acidic (pH 1.5) ferric sulfate soluti on hardly decreased. A mathematical model has been developed to quantify th e phenomena related to the removal of H2S(aq). The model has been succesful ly validated with the data of batch experiments. An Arrhenius-like relation ship was found between the process temperature and the overall mass transfe r coefficient K. A sulfide oxidation rate of 2.5 g S dm(-3) day(-1) was pre dicted for a plug flow reactor. The integration of the novel process with b iological sulfate reduction was studied. (C) 1999 Society of Chemical Indus try.