Study On The Removal Of Antimonate And Bromate From Water By Binary Micro-electrolysis Of Iron-spent Bleaching Earth Carbon

In recent years,water pollution caused by antimonate and bromate has been paid more and more attention.Excessive exploitation of antimony ore will produce a large amount of antimony-containing wastewater,which is discharged into the water environment and then poses a serious threat to human living environment.At the same time,in the process of ozone disinfection of tap water,bromate,a disinfection by-product,is inevitably produced,which is toxic and potentially carcinogenic,and has the serious potential safety hazards to human health.Therefore,there is an urgent need for a safe and effective scientific method to remove antimonate and bromate in water.In the research of removing the oxyacid salts from water,the iron-carbon micro-electrolysis technology has attracted more and more attention because of its simple operation and no secondary pollution.In this study,antimonate and bromate in water were removed by micro-electrolysis composed of iron and spent bleaching earth carbon（SBE@C）.The effects of dosage,Fe/SBE@C dosage ratio,temperature,initial p H value and coexisting anions on the micro-electrolysis reaction were studied.Furthermore,cationic surfactant cetyltrimethylammonium chloride（CTAC）was used to modify SBE@C to enhance the micro-electrolysis reaction to remove bromate in water.The research contents mainly include:（1）SBE@C was prepared by anoxic pyrolysis of spent bleaching earth（SBE）,and the zero-valent iron supported spent bleaching earth carbon composite（Fe⁰/SBE@C）was prepared through the liquid phase reduction method.The removal of antimonate in water by Fe⁰/SBE@C binary micro-electrolysis system was studied.The results of influencing factors（dosage,temperature,p H,etc.）showed that when the dosage increased from 0.05g/L to0.2g/L,for antimonate solution with an initial concentration of 20mg/L,the removal efficiency of antimonate increased from 41.6%to 88.7%.When the temperature rises from25℃to 45℃,the removal efficiency of antimonate increases from 71.55%to 83.25%.Acidic conditions are more conducive to the micro-electrolysis reaction.When the initial p H value of the solution is equal to 3,the removal efficiency of antimonate is as high as 91.93%.The response surface methodology（RSM）predicted that the best conditions for antimonate removal（the removal efficiency of 98%）were dosage of 0.19g/L,temperature of 45℃and initial p H of 4.The data of three repeated experiments show that under this condition,the removal efficiency of antimonate is 97.4%,which is consistent with the predicted results.In the study of the influence of coexisting anions,SO₄^2-and Cl^-hardly affect the removal of antimonate,while NO₃^-inhibits the removal of antimonate to a certain extent,while CO₃^2-,PO₄^3-and Si O₃^2-obviously inhibit antimonate removal.The morphology,structure and properties of Fe⁰/SBE@C were characterized by SEM,FTIR,XRD,XPS and BET.The characterization results indicate that zero-valent iron is successfully loaded on SBE@C,and its specific surface area and pore volume decrease.The Fe⁰/SBE@C has the similar surface functional groups and crystal structure with SBE@C.Based on experimental data and characterization results,it is speculated that the reaction mechanism of removing antimonate from water by Fe⁰/SBE@C binary micro-electrolysis system mainly includes the surface adsorption,electrostatic attraction,hydrogen bonding and surface complexation.（2）The removal of bromate in water by the binary micro-electrolysis of iron powder and cationic surfactant cetyltrimethylammonium chloride modified spent bleaching earth carbon（CTAC-SBE@C）was studied.The removal efficiency of bromate in water by the microelectrolysis system composed of iron and spent bleaching earth carbon is higher than that by the sum of iron powder and spent bleaching earth carbon respectively.SBE@C was modified by CTAC with a concentration of 25 mmol/L.The removal of bromate in water by iron-spent bleaching earth carbon binary micro-electrolysis was obviously enhanced,and the removal efficiency of bromate increased from 78.69%without modification to 92.25%after modification（The initial bromate concentration was 20mg/L,and the dosage was 2g/L）.The increase of temperature can accelerate the removal efficiency of bromate by the iron-spent bleaching earth carbon binary micro-electrolysis.At 45℃,the equilibrium state is reached in60 min,and almost all bromate is reduced to bromine ion,and the removal efficiency can reach 98%.The influence of initial p H value shows that acidic conditions are more favorable for bromate removal,and when initial p H value is 3,the maximum bromate removal efficiency can reach 98.8%.The results of coexisting anions shows that adding Cl^-,SO₄^2-and NO₃^-can improve the removal efficiency of bromate,while CO₃^2-,PO₄^3-and Si O₃^2-obviously inhibit the removal of bromate.SEM,FTIR,XRD,XPS and other characterization results show that CTAC is successfully loaded onto the SBE@C surface.After modification,specific surface area and pore volume of SBE@C are reduced,and the surface was covered by many fine particles.CTAC-SBE@C has the good crystallinity,and the micro-electrolysis system composed of CTAC-SBE@C and iron powder can effectively remove bromate from water.XPS analysis results show that bromate removal by iron-spent bleaching earth carbon binary micro-electrolysis not only reduces Br O₃^-to Br^-,but also removes bromate by adsorption to the material surface.The reaction mechanism of removing bromate from water by the iron-spent bleaching earth carbon binary micro-electrolysis mainly includes surface adsorption,electrostatic attraction,chemical reduction and complexation.