Study On Removal Of Phosphate And Fluoride From Water By Magnetic Mesoporous LDHs

In order to remove P that caused eutrophication and F that are harmful to human on water,in all of remove methods adsorption has been used widely.However,the traditional adsorption method not only inefficiency but also the adsorbent is difficult to recycle.To overcome these drawbacks,our research will synthesis adsoebent that have pefered adsorption capacity and can be recycled by magnet.Layered double hydroxides(LDHs)coated magnetic cores were synthesised by co-precipitation method,Prepared magnetic mesoporous Mg/Al-LDHs?Mg/La-LDHs and Ni/Al-LDHs that calcined at high temperature.Adsorbents were characterized by XRD,FTIR,BET,etc.that the adsorbents have layered structure of LDHs,fast magnetic response,large specific surface area,and mesoporous pores.Study the adsorption performance of magnetic mesoporous LDHs on water which riched phosphate and fluoride.As the pH and backgroud electrolyts increased,the adsorption capacity of magnetic mesoporous LDHs weaked.In low pH with the concentration of phosphate increased,adsorption capacity of magnetic mesoporous LDHs better,and the concentration of fluoride raised,adsorption capacity of magnetic mesoporous LDHs lowered.Adsorption isotherms of Mg/Al-LDHs were proceed in pH = 7.5 temperature at 25 ?,By Langmuir fitting that the maximum capacity of Fe3O4@SiO2@LDHs350(Mg/Al)for P and F were 50.97 mg/g and 23.28 mg/g,the maximum capacity of Fe3O4@SiO2@mLDHs350(Mg/Al)for P and F were 53.88 mg/g and 24.04 mg/g,the maximum capacity of Fe3O4@mSiO2@mLDHs350(Mg/Al)for P and F were 55.09 mg/g and 27 mg/g.The magnetic mesoporous LDHs were recycled through five adsorpted-desorpted,the removal(%)of phosphate remained above 90%,while the removal(%)of fluorine decreased to about 50%after five times.By analyzed FTIR and XRD before and after adsorption,the adsorption of phosphate and fluoride mainly depends on the structural regeneration and ion exchange of LDHs.The mesopores and the high specific surface area of LDHs,increased the adsorption sites of LDHs,the adsorption process get more effectively.