Removal Of Cd(?) And Pb(?) In Aqueous Solution By Amino And Carboxyl Functionalized Magnetic Microspheres

With the rapid development of industrialization,the problem of environmental pollution has become increasingly prominent,in which water pollution has seriously dangerous effects on human health.The problem of heavy metal pollution has attracted extensive attention among water pollution.Global attention has been focused on the pollution of Pb?II?and Cd?II?on water.In the contaminated water,they can be enriched through the food chain into the animal body and produce a strong cytotoxicity,teratogenic and carcinogenic,has been listed as priority heavy metal pollutants which is seriously harm to human health.A large number of studies have shown that the magnetic adsorbents can not only effectively remove the heavy metals in the water,but also easy of operation and recovery.In addition,amino?-NH₂?and carboxyl?-COOH?show a strong chelating ability to heavy metals,the silanol groups?Si-OH?on the SiO₂ surface are easily modify functional groups.In this paper,amino groups,carboxyl functional microspheres were prepared in the conditions of initiator potassium persulfate?KPS?,crosslinking agent N,N-methylene bisacrylamide?NMBA?,reaction time and reaction temperature as the single factor.Their structures were characterized by Fourier transform infrared spectroscopy?FT-IR?,and in this study,the removal of Cd?II?and Pb?II?in aqueous solution by amino and carboxyl bi-functional magnetic microspheres was investigated.The main researches of this paper are listed as follows:1.The preparation conditions of amino and carboxyl bi-functional magnetic microsphere were studied.Adsorption capacity of Fe₃O₄@SiO₂-NH₂/COOH adsorbent on Pb?II?was selected as an indicator,the optimal preparation parameters were: monomer?methacrylic acid and acrylamide?28.6 mol/L,the crosslinking agent 85.7 mol/L,and the initiator 48.6mmol/L,reaction temperature 70 °C,reaction time 8 h.Under the above conditions,an adsorbent with the best adsorption performance for Pb?II?can be prepared.2.The adsorption properties of Fe₃O₄@SiO₂-NH₂/COOH to Cd?II?and Pb?II?in monobasic aqueous solution was studied.The results showed that the amount of Cd?II?and Cd?II?increased first and then stabilized before pH=7.0,and increased rapidly to Cd?II?after pH>8.0.The adsorption kinetics of Cd?II?and Pb?II?is up to 207.807 and 168.995 mg/g,respectively,which indicates that the two kinds of heavy metals The adsorption of ions is a dual effect of physical and chemical adsorption,adsorption for the adsorption process and uniform monolayer adsorption.3.The effects of the concentration of cation?Ca2+ and Mg2+?on the competitive adsorption of Cd?II?and Pb?II?in binary solution were studied.The results show that the higher the concentration of Ca2+ and Mg2+ in the coexisting conditions,the greater the competitive adsorption of Cd?II?and Pb?II?,and the effect of Ca2+ with Mg2+ on Cd?II?and Pb?II?more intense.4.20 mL 0.1mol/L HCl was selected as eluent to elute the adsorbent absorbed Cd?II?and Pb?II?.The elution rates of Cd?II?and Pb?II?were respectively about 94% and 73% after one adsorption-elution,the elution rates of the eluents to Cd?II?and Pb?II?were about 84% and 30%,respectively,after three adsorption elution.5.The adsorption properties of the Fe₃O₄@SiO₂-NH₂/COOH adsorbent for Cd?II?and Pb?II?in drinking water were studied.The results showed that the removal rates of as-prepared adsorbent for Cd?II?and Pb?II?in drinking water were up to 94% and 97%,respectively.Moreover,Fe₃O₄@SiO₂-NH₂/COOH adsorbent lead to the effluent content of Cd?II?and Pb?II?decreasing to ppb level,which is below the drinking water standard recommended by the WHO.All these results demonstrate that the as-synthesis bi-functionlized adsorbent can be applied in drinking water treatment owing to the high adsorption capacity,ease of magnetic separation,and recycling potential.Thus it can be used to remove heavy metal ions from drinking water samples to provide an adsorbent material.