Removal Of Chromium [Cr(?)] And Cadmium [Cd(?)] By316L Porous Stainless Steel Supported Alumina Membrane

Rescently,water pollution has drawn increasingly attention due to the development of in dustry,abuse of pesticides and intensification of urbanization.Inmany pollution sources,heavy metals is the most harmful,therefore the governance of heavy metal pollution is urgent.There are many methods to removal of heavy metal ions,such as chemical precipitation,electrochemistry,biological method,membrane separation,ion exchange and adsorption etc.Among them,the adsorption has the advantages of high efficiency,low cost and simple operation.However separate adsorbentisoften difficult to be recycled.In order to solve this problem,appropriate carrier is often used to immobilize adsorbent.In this study,?-Al2O3 nanoparticles are immobilized on316 L porous stainless steel to absorb Cr(VI)and Cd(II)in aqueous solution.The main conclusions are as follows.1.Scanning electron microscopy(SEM)and X ray diffraction(XRD)test showed that ?-Al2O3 nanoparticles were uniformly coated on the 316 L porous stainless steel.The alumina has film uniformity,good continuity and does not appear the incomplete coverage,whilethe thickness of film depositionis about 20?m.The isoelectric point of alumina membrane is 8.93 which was measured by titration.The iron and aluminum filtered from aluminum membranes were 0.378mg/L and 0.085mg/L,whichin line with China's national sanitary standard for drinking water,it proves that the film has better chemical stability.2.Alumina films in single aqueous solution of Cr(VI)and Cd(II)adsorption results showed that the optimal pH of Cr(VI)and Cd(II)were 3.0-4.0 and 8.0-9.0,which are in line with the quasi two stage adsorption dynamic model and Langmuir isotherm model,and the maximum adsorption capacity ofCr(VI)and Cd(II)is 0.603 mg/g and 0.399 mg/grespectively.3.Alumina films on the coexistence of Cr(VI)and Cd(II)in aqueous solution competitive adsorption showed that theequilibrium adsorption film of two kinds of single heavy metal ions in solution were 0.307mg/g and 0.181 mg/g,respectively,on the adsorption of two kinds of ions in the solution were 0.244 mg/g and 0.063mg/g.Thus,the adsorption ability of the film can be reduced because of the existence of another ion.4.The alumina film adsorbed on Cd(II)was eluted by HNO3,and the film adsorbed on Cr(VI)was eluted by NaOH.After three times of adsorption-elution cycle,the elution rate of Cd(II)was about 30% and the elution rate of Cr(VI)was about 90%.5.In drinking water samples,alumina films lead to the effluent content of Cr(VI)and Cd(II)decreasing to ppb level,which is below the drinking water standard recommended by the WHO.The porous stainless steel based alumina membrane has better removal effect for Cr(VI)and Cd(II)in aqueous solution,and the stability of the membrane is better.Thisstudy solves the problem that the adsorbent has no supports and is difficult to recover.In addition,it provides theoretical and practical basis for the practical application of alumina membrane in the adsorption of heavy metals injuice andwastewater.