Study On Comprehensive Utilization Of Sulfate In Desulfurization And Denitrification Absorption Solution Based On Electrolysis To Generate Persulfate

Persulfate（PDS）,as the strongest oxidant in peroxide,has been widely used in chemical industry,light industry,electronics,environmental protection and other fields.Electrochemical production of PDS is currently widely used in industrial production.The absorption solution of amino wet desulfurization and denitrification contains high concentration of sulfate.If it is used as raw material to prepare PDS by electrochemical method,it will not only make waste resource utilization,but also have important significance for environmental protection and cost reduction.The purpose of this study is to generate PDS from sulfate in the absorption solution of electrolytic desulfurization and denitrification.With single sulfate as electrolyte,the formation path and reaction mechanism of PDS on Si/BDD,Ti/Sn O₂,Ti/Pb O₂and Ti/Pt four typical anodes were investigated by cyclic voltammetry and hydroxyl radical generation experiment,and the influence of different additives on the electrochemical behavior of sulfate on different anodes was investigated.In the split-cell reactor,the effects of electrolyte concentration,current density,additives and anode materials on the formation of PDS by electrolytic sulfate were investigated.The optimal anode of single sulfate electrolyte experiment was used to investigate the influencing factors of PDS formation in simulated electrolyte and the influence of impurities in simulated electrolyte on PDS formation with simulated amine wet desulfurization and denitrification absorption liquid as electrolysis object.The research conclusions are summarized as follows:（1）The reaction paths of electrochemical synthesis of PDS on different anodes were studied by cyclic voltammetry and OH generation experiments.It was found that in the CV curve of Si/BDD electrode,a weak oxidation peak appeared at about 2.0 V,indicating that SO₄^2-can be directly oxidized on the Si/BDD anode,but the oxidation ability is weak,while the other three anodes have no obvious SO₄^2-oxidation peak in the cyclic voltammetry curves.Under the condition of low current density,the four main pathways of anodic electrolysis to generate PDS may be mediated by OH-mediated oxidation through electrolysis of water.（2）Through the constant current mode electrolysis of sulfate solution in H-type split-tank reactor,it was found that the PDS prepared by Si/BDD anode was significantly better than that prepared by Ti/Sn O₂,Ti/Pt and Ti/Pb O₂.Under the condition of 0.9 mol·L^-1Na₂SO₄concentration and 60 m A·cm^-2current density,the PDS production reached 24.12 mmol·L^-1at60 min.For Si/BDD and Ti/Sn O₂anodes,the increase of Na₂SO₄concentration and current density is conducive to the formation of PDS and the improvement of current efficiency.The addition of H₂SO₄to the cathode solution is conducive to reducing the cell voltage;adding PDS in the anode liquid is beneficial to improve the PDS production and current efficiency to a certain extent.The addition of NH₄SCN can inhibit the occurrence of oxygen evolution side reactions and promote the formation of PDS by SO₄^2-oxidation.The orthogonal experiment was used to optimize the reaction conditions,and it was found that the dominant influence of various factors on the formation of PDS by electrolysis was:current density>Na₂SO₄concentration>PDS concentration.（3）The experimental study on the preparation of PDS by electrolytic desulfurization and denitrification simulated absorption liquid with optimized BDD anode shows that the higher the current density,the faster the reaction rate of PDS formation.NH₄SCN addition inhibited the formation of PDS in the simulated absorption solution;adding H₂SO₄to the electrolyte can reduce the external cell voltage,but it has little effect on the PDS production and current efficiency.After adding（NH₄）₂S₂O₈into the simulated solution,the formation of PDS was slightly affected,and the production and current efficiency of PDS were improved in a short time.Under the same reaction conditions,the effect of electrolysis simulated absorption solution to generate PDS is better than that of（NH₄）₂SO₄solution.At the current density of60 m A·cm^-2,after 60 min reaction,the amount of PDS can be increased by 18.8%.（4）Impurities in the desulfurization and denitration absorbing liquid have certain influence on the electrolysis of（NH₄）₂SO₄to generate PDS.Both urea and SO₃^2-inhibited the formation of PDS.However,the NO₃^-impurity in the simulated absorption solution of desulfurization and denitrification significantly improved the current efficiency of PDS generation and the amount of PDS generation.The amount of PDS generated can be increased by 26.81%.