Experimental Study And Safety Analysis Of Sulfate And H₂S Treatment By Iron-carbon Micro-electrolysis

Sulfur as an important raw material is widely used in industrial production,the production process often produces a large number of sulfur compounds,such as sulfate and H₂S,which brings serious pollution to the environment,and also produces some safety problems.Therefore,it is necessary to treat sulfate and H₂S before being discharged.The research group found that sulfate can be removed by iron-carbon micro-electrolysis in the process of industrial wastewater treatment.According to the literature review,there is no report on the treatment of sulfide by iron-carbon micro-electrolysis.Therefore,iron-carbon microelectrolysis was used to treat sulfate and H₂S in this paper.First of all,the removal experiment and mechanism of sulfate radical in wastewater were studied by iron-carbon micro-electrolysis.Five factors including reaction time,aeration rate,pH,iron-carbon ratio and initial concentration of sulfate radical were selected for single factor experiment.The initial concentration of sulfate radical,pH and iron-carbon ratio were optimized by response surface method.The optimal conditions were as follows:the initial concentration of sulfate radical was 500 mg·L^-1,pH was2 and iron-carbon ratio was 1.45:1.The sulfate radical removal rate predicted by the model was 80.96%.The experimental result showed that the removal rate of H₂S was 73.08%,which was within the 95%confidence interval.SEM,EDS,XRD,XPS and Raman spectroscopy were used to study the removal mechanism of sulfate radical by iron-carbon micro-electrolysis.The experimental results showed that sulfate radical could be removed through the following two ways:1)firstly,sulfate radical was reduced to sulfite under the action of redox,and then further reduced to sulfur ions.Sulfur ions formed Fe S precipitation and H₂S with Fe²⁺and H⁺in the solution,respectively.2)Fe（OH）₂ and Fe（OH）₃ flocs were generated with the reaction in the solution,and sulfate radical was removed under the flocculation and precipitation of Fe（OH）₂ and Fe（OH）₃.On the basis of the above experiments,iron-carbon micro-electrolysis was used to treat sulfate in actual landfill leachate.Firstly,the effects of reaction time,aeration rate,pH and iron carbon ratio on treatment were explored.Then,response surface method was used to optimize the reaction time,pH and iron-carbon ratio.The optimized reaction conditions were as follows:reaction time was 297 min,pH was 2.2 and iron-carbon ratio was1:1.67.The sulfate removal rate predicted by the model was 55.25%.The experimental results showed that the sulfate removal rate was 49.37%,which was within the 95%confidence interval.Then,the iron-carbon micro-electrolysis was used to degrade H₂S in natural gas.Four factors including reaction time,aeration rate,iron-carbon ratio and pH were selected for single factor experiment.Response surface method was used to optimize the iron-carbon ratio,pH and aeration rate.The optimized reaction conditions were as follows:aeration rate was 0.33m³·h^-1,iron-carbon ratio was 3:2,pH was 6.1.And the H₂S removal rate predicted by the model was 92.66%.The experimental result showed that the removal rate of H₂S was 84.6%,which was within the 95%confidence interval.Finally,the process safety of iron-carbon micro-electrolysis for sulfate and H₂S treatment was qualitatively and quantitatively analyzed by using safety checklist and fuzzy comprehensive evaluation method.The result shows that the safety of iron-carbon micro-electrolysis process for treating sulfate radical in wastewater is relatively safe,and the safety of iron-carbon micro-electrolysis process for treating H₂S in natural gas is generally safe.