Study On Controlled Oxidation Of Sulfur In Sulfur - Containing Wastewater

High concentration hydrogen sulfide wastewater is present in a wide range of industry such as petroleum and gas industry. The sulfide is toxic, effluvial, caustic and reducible,which may threaten environment, production safety and human health if it cannot be disposed properly. Desulfurization by chemical method was designed to obtain elemental sulfur as main oxidation products of sulfide,which can not only reduce harm of sulfide but also recover resource. In this paper, the impacts of factors and degradation efficiency of sulfide wastewater treatment with different oxidants were investigated with sulfide concentration and sulfur production as main control objectives,and the structure and microstructure of elemental sulfur was analyzed and observed. The oxidation products were determined under the optimum conditions. The sulfide conversion rate and the xidation progress were analyzed.Reaction-Centrifugation technology was studied to improve sulfide transformation to sulfur,and the optimal operating parameters were determined.The results showed that under the optimal conditions, the sulfide removal rates could reach above97%by oxidation with Na2S2O5, H2O2and Na2S2O8respectively.The sulfide oxidation reaction could finish mainly in15to35minutes. The effect of oxidant dosage and initial pH were outstanding. The results indicated that the sulfide concentration could be decreased to24.16mg/L and sulfur production could be802.57mg/L while Na2S2O5dosage was4.5g/L(m(Na2S2O5):m(S2-)4.5) and initial pH was6.Under the conditions of H2O2dosage14mL/L(m(H2O2):m(S2-)4.62) and initial pH7, the sulfide concentration could reach4.46mg/L and sulfur production could be574.84mg/L.While Na2S2O8dosage was10g/L(m(Na2S2O8):m(S2-)10) and initial pH was7, the sulfide concentration could reach4.84mg/L and sulfur production could be732.19mg/L. The results of XRD showed that the elemental sulfur was orthorhombic crystal system sulfur formed by Sg, which was rhombic sulfur (a-sulfur). By electron microscope.most of the sulfur particles were spherical body of different sizes about1～10μm, and the phenomenon of agglomeration was found..By oxidation with Na2S2O5, S2O32-and S accounted for a large proportion of the main product, but in the treatment of sulfide wastewater by oxidation with H2O2and (NH4)2S2O8, S and SO42-were main product. The corresponding S conversion rate was54.5%and33.1%、58.1%and34.1%、73.3%and20.0%. Extending reaction time of oxidation with Na2S2O5, the amount of S2O32-and S2-has a increasing tendency, the amount of SO32-reduced slightly. The results indicated that the existence of S2O32-and SO32-is the main reason for elemental sulfur consume. Extending reaction time of oxidation with H2O2, the amount of SO42-continued increasing while the content of sulfide reduced, and the content of S2O32-and SO32-was low and changed slightly. This indicated that the oxidability of H2O2itself resulted in the decomposition of elemental sulfur. By oxidation with (NH4)2S2O8, the effect on transformation of elemental sulfur was because of strong oxidant and the middle valence state of sulfur oxyacid salts.Based on the first two steps experiment, reaction-centrifugation technology was designed to reduce side reactions and improve the conversion rate of elemental sulfur. When separation factor was small, the centrifugal force was too low to separate elemental sulfur from the reaction solution, which made elemental sulfur particles uniformly disperse in the solution containing sulfur oxyacid salts, then it promoted side reaction. The optimal centrifugation time was similar to the optimal reaction time under normal conditions. Under the condition of separation factor692, the concentration of elemental sulfur could increase162.23mg/L、106.4mg/L and209.72mg/L by oxidation with Na2S2O5、H2O2and (NH4)2S2O8respectively, and corresponding conversion rate could increase6.6%、10.7%and5.1%.