Study On Removal Of Bromate And Chromate From Water By Iron Modified Bleaching Earth Carbon-based Material

The main components of activated clay are Al₂O₃ and SiO₂.Because of its porous structure and large surface area,it is widely used in the refining of oils.The activated clay after adsorption of oils is called carbon based spend bleaching earth.A large amount of grease remains on the surface of the spend bleaching earth,which needs to be properly handled,otherwise it will cause environmental pollution and waste of resources.Under anoxic conditions,the spend bleaching earth is made into the carbon of spend bleaching earth?C/SBE?,which can be used as a new type of water treatment material to achieve the purpose of waste treatment.In this study,the iron-modified spend bleaching earth carbon-based materials?Fe_xO_y@C/SBE?were prepared removal the typical pollutants of water,bromate and chromate.Investigate the removal characteristics of pollutants and influencing factors.The material physicochemical properties and surface functional groups were characterized,and the removal mechanism was further explored.The research content mainly includes:?1?Bromate is a by-product of water disinfection,at 25^oC,the removal capacity of bromate by Fe_xO_y@C/SBE can reach 225.90mg/g.The kinetic process conforms to pseudo-second-order kinetics,indicating a chemical reaction control the removal of bromate.The correlation coefficient of Langmuir model fitting is better than that of Freundlich model,indicating that the removal process of bromate conforms to the assumption of monolayer reaction.At a pH of 3.12,either C/SBE or Fe_xO_y@C/SBE can completely remove 20mg/L of bromate.The XRD and FTIR results confirmed that the main components of the iron oxide loaded on the surface of Fe_x O_y@C/SBE are Fe⁰ and Fe₃O₄,and the XPS test results showed that the ratio was Fe²⁺/Fe³⁺=1.3,According to the mechanism analysis results,the removal process of bromate is dominated by chemical reduction,and part of the bromate removed by adsorption.?2?In order to further remove the chromate reducing substances,the modification conditions of the material are further controlled.The design iron content is increased from0.03mol to 0.05mol,the ratio of BH₄-/Fe²⁺is 6.When the initial concentration of hexavalent chromium is 5 mg/L?calculated as Cr?,the amount of dosage added is 0.2g/L.,the temperature is 25 ^oC.After 4 hours of reaction,the removal rate reaches 91.2%.The reaction process is more fitted with pseudo-secondary kinetics,indicating that the removal of hexavalent chromate is also a chemical adsorption reaction as a control step.When the initial dichromate concentration is 10mg/L,the removal capacity of dichromate can reach102.42mg/g.The Langmuir model better fits the adsorption isotherm equilibrium data.Comparing the removal effect of the material Fe_xO_y@C/SBE before and after optimization,the results show that:after optimization,when the initial dichromate concentration is10mg/L,the removal rate is increased from 60.21%to 81.25%.The removed dichromate is converted to Cr?OH?₃ and removed.Next investigate the influence of coexisting anions in water,and the order of influence of each ion is:PO₄^3->SO₄^2->BrO₃^-.XRD and FTIR characterization results show that the iron in the optimized material mainly exists in the form of Fe⁰ and Fe₂O₃.XPS analysis results show that Fe²⁺/Fe³⁺in the material is 1,and the content of Fe⁰ is 10.03%.After the reaction,trivalent chromium is detected in the material,which confirms that the dichromate is reduced to Cr?III?.In an anaerobic environment,dichromate can be completely removed,and hexavalent chromium can be removed more quickly.This provides reference value in the practical application of materials.