Preparation Of Aminopolycarboxylic Acid Modified Magnetic Mesoporous Materials And Its Adsorption Of Cr(Ⅲ)

In recent years,heavy metal waste water pollution incident has occurred from time to time in China.Heavy metal pollution can induce damage to people’s health and biological system,meanwhile,it has a wide range of social negative impacts.Therefore,strict supervision and rapid treatment of heavy metal wastewater becomes more urgent.Chromium,one typical of heavy metals,was widely used in the industries of leather,metal products processing and electronic equipment manufacturing,etc,which a large scale of contain chromium（Cr（Ⅵ）and Cr（Ш））wastewater was discharged.Due to the cumulative risks and potential hazards of Cr（Ш）and the extensive use of organic complexing agents and inorganic salts in industrial processes,the difficulty of treating wastewater was further increased.Hence,the removal of Cr（Ш）in wastewater has been studied.In this study,three kinds of aminopolycarboxylic acid functionalized superparamagnetic high-magnetization microspheres were prepared for removal of Cr（Ш）from wastewater,respectively（FNMs-EDTA,FNMs-NTA and FNMs-TTHA）.The research contents include the influence of Cr（Ш）concentration,reaction time,pH,cation,organic complexing agent and cation/complexing agent coexisting system on the adsorption performance.According to the characterization and experimental results,the following conclusions can be obtained:（1）FNMs-EDTA remove Cr（Ш）from wastewaterThe adsorption isotherm of FNMs-EDTA followed the Freundlich model,and the adsorption kinetics was well described by the pseudo-second-order model.The amount of Cr（Ш）adsorbed increased dramatically when the pH increased from 2.0 to 5.0,and when pH was over 6.0,the adsorption equilibrium could be obtained.The foreign ions could reduce the adsorption capacity but exhibited only a slight effect.With the increase of complexing agents concentration the amount of Cr（Ш）adsorbed decreased,which influence from promoting adsorption to inhibiting effect was negligible.In the NaCl/EDTA-Na₂coexisting system,there were almost no effect on the adsorption.Ion exchange and surface complexation by functional groups of EDTA was the adsorption mechanism.Moreover,FNMs-EDTA could be reused repeatedly by regeneration using HCl solution.（2）FNMs-NTA remove Cr（Ш）from wastewaterThe adsorption isotherm of FNMs-NTA followed the Freundlich model,and the adsorption kinetics was well described by the pseudo-second-order model.The amount of Cr（Ш）adsorbed increased dramatically when the pH increased from 2.0 to 5.0,and when pH was over 6.0,the adsorption equilibrium could be obtained.The foreign ions could promote the adsorption capacity.With the increase of EDTA-Na₂ concentration the amount of Cr（Ш）adsorbed decreased,which influence from promoting adsorption to inhibiting effect was negligible and the adsorption capacity of Cr（Ш）on the adsorbent decreases with the increase of citric acid concentration.In the NaCl/EDTA-Na₂ coexisting system,the adsorption capacity has a slightly increased.The adsorption mechanism involves ion exchange and surface complexation by functional groups of NTA.Moreover,FNMs-NTA could be reused repeatedly by regeneration using HCl solution.（3）FNMs-TTHA remove Cr（Ш）from wastewaterThe adsorption isotherm of FNMs-TTHA followed the Langmuir and Freundlich model,and the pseudo-second-order model can described the adsorption kinetics.The amount of Cr（Ш）adsorbed increased dramatically when the pH increased from 2.0 to 5.0,and when pH was over 6.0,the adsorption equilibrium could be obtained.The foreign ions could reduce the adsorption capacity but exhibited only a slight effect.With the increase of complexing agents concentration the amount of Cr（Ш）adsorbed decreased,which influence from promoting adsorption to inhibiting effect was negligible.In the NaCl/EDTA-Na₂ coexisting system,the adsorption capacity has a slightly increased.The adsorption mechanism can be confirmed the surface complexation by functional groups of TTHA.These three kinds of materials was found to possess a good adsorption capacity of Cr（III）in aqueous solution,and adsorption capacity was ranked as FNMs-TTHA>FNMs-EDTA>FNMs-NTA.The adsorption mechanism is the complexation of Cr（III）with the amino polycarboxylic acid functional group on the surface of the material.