Study On Controlled Oxidation Of High Sulfur Wastewater And Formation Characteristics Of Elemental Sulfur

Sulfur-containing wastewater may not only cause corrosion to equipment, make great effect to water treatment systems, and the hydrogen sulfide will cause harm to human body. There is a need to find an effective treatment method to abate the environmental pollution, realize pollutant resource recycling simultaneously for the high concentration Sulfur-containing wastewater. The simulative sulfur-containing wastewater was used in the single experiment by chemical oxidation. The desulfurization effect of Na2S2O5, Na2SO3and H2O2was evaluated to select the best oxidant, with the removal rate of S2-and conversion rate of elemental sulfur as the indicators, and the influence factors of sulfide oxidation kinetics also studied, and the oxidation reaction conditions were optimized by the Response Surface Methodology on the basis of the best oxidant. The conversion of elemental sulfur was intensified by changing dosing method of oxidant, controlling the ORP of reaction system and coupling between reaction and separation. The structure and morphology of solid phase product were analyzed by X-Ray Diffraction, scanning electron microscope and granulometer.(1) The results indicated that under the optimal condition of9g/L Na2S2O5, initial pH6and30min the removal rate of S2-and conversion rate of elemental sulfur were95.16%and42.32%respectively, and under the optimal condition of5g/L Na2SO3, initial pH5and20min,the removal rate of S2-and conversion rate of elemental sulfur were78.71%and26.68%respectively, and under the optimal condition of10mL/L H2O2, initial pH6and14min, the removal rate of S2-and conversion rate of elemental sulfur were95.68%and60.78%respectively. H2O2is the oxidant, with best desulfurization effect. The sulfide oxidation by H2O2followed the second-order reaction kinetics, the reaction rate constant was determined as1.0669L.g-1.min-1. The reaction rate constant was affected by dosage of H2O2, reaction temperature and initial pH. The reaction rate constant increased with the increase of dosage of H2O2, and it increased with temperature rise, decreased with the increase of the initial pH.(2) The Response Surface Methodology was used to optimize the reaction condition for H2O2oxidation sulfur-containing wastewater based on the results of single factor experiments, the optimized condtions were that the dosage of H2O2was9mL/L, initial pH was6.5, reaction time is15min. The conversion of elemental sulfur reached65.85%, increased by5.07%compared with that before optimum.(3) Compared with one step system, the conversion rate of elemental sulfur was decreased by8.25～26.05%by taking separate addition. With the method of reaction separation coupling, the conversion rate of elemental sulfur was reached74.98%under the condition of separation factor1082, increased by9.13%compared with that before intensification. Controlling ORP has the best strengthening effect for elemental sulfur conversion. The conversion rate of elemental sulfur was reached76.35%under the condition of ORP (30±5) mV, up from10.50%before intensification.(4) The result of X-Ray Diffraction indicated that the solid phase product was constitutionally stable S8at room temperature. The result of scanning electron microscope and granulometer indicated that the layer composed of tiny sulfide nanoparticls became larger sulfur particles because of reunion convolution with the reaction time. The analysis results showed that the mechanism of elemental sulfur particles increase caused by crystal growth and agglomeration of nanoparticles. It was concluded that the formation mechanism of Ss is using Sx2-as the intermediate product.