Preparation Of EDTA Functional Meterials For The Removal Of Pb(?) And Cu(?) From Aqueous Solution

Functional materials as adsorption to remove the heavy metals in the water were attracted more and more attention.There are various functional groups were used to function materials,among them,an aminopolycarboxylic acids?APCAs?can be adopted as a potential candidate due to several carboxylate linkages through one or more nitrogen atoms in the compound and also the ability to sequester metal ions.EDTA as a six-coordinate ligand and a modification agent for adsorbents has attracted more research attentions due to the formation of stable chelates with metal ions.In this study,Fe₃O₄@SiO₂-EDTA?SiO₂-EDTA and BAC@SiO₂-EDTA were prepared by silanization reaction between N-?trimethoxysilylpropyl?ethylenediamine triacetic acid?EDTA-silane?and hydroxyl groups for heavy metals removal from aqueous solutions.To investigate the effect of different SiO₂ ratios on the sorbent,different amounts of SiO₂ assembled with the same amount of EDTA in Fe₃O₄@SiO₂-EDTA were analyzed by Pb???adsorption.Also,the three composites were characterized using SEM,TEM,EDX,FTIR,XPS,TGA and saturated magnetization techniques to investage their morphology structure,chemical composition.Moreover,the adsorption performance and influencing factors of the three matierials for the removal of Pb???,Cu???and complexing state of lead?Pb???-EDTA and Pb???-Cit?,Finally,adsorption mechanism of the materials and its separation and reuse were also studied.After the linkage of EDTA onto the surface of matierials through-OH,the surface area decreased drastically and TGA weight loss increased.Also,in XPS and FTIR spectra,the characteristic peaks of EDTA were found.All of this suggested that EDTA has successfully load.The maximum adsorption capacity was found to increase with TEOS increased from 1 to 2.5 mL,and deceased with further increasing of TEOS.Maximum Pb???and Cu???adsorption capacity was found to be 114.94 mg g^-1 and 37.59 mg g^-1 on Fe₃O₄@SiO₂-EDTA,123.45 and 42.19 mg g^-1 on BAC@SiO₂-EDTA.For Pb???and Pb???-Cit,the the maximum adsorption capacity were 147.06 and 123.95 mg g^-1 on SiO₂-EDTA.Kinetics study revealed that the adsorption rate was significantly high at the beginning and then reached to equilibrium within 10 min with Fe₃O₄@SiO₂-EDTA,20 min with SiO₂-EDTA and 20 min with BAC@SiO₂-EDTA.And the all adsorption data were fitted well to the pseudo-second-order kinetic model.The initial pH had a significant effect on the adsorption.For Fe₃O₄@SiO₂-EDTA,from pH 2 to 5,the adsorption capacity increased with the increasing of pH,and reached the maximum in pH=5;for SiO₂-EDTA and BAC@SiO₂-EDTA,from pH 2 to 6,adsorption capacity increased with the pH increasing.Contrary to the influence of pH,the higher the temperature,the adsorption effect is poorer.Coexisting ions and the impact of natural organic matter on heavy metal adsorption experimental results show that high concentration of cationic smaller influence on adsorption,but as a whole,the influence of adsorption capacity is relatively large,and natural organic matter on adsorption basic no effect.Finally the regeneration properties of the materials for research,found that it could be used to regenerate.The study of solution pH effect on the adsorption found that electrostatic adsorption was involved.Moreover,according to Zeta potential,at pH<pH_pzc,the surface of adsorbent was positively charged and exhibited electrostatic repulsion towards Pb???.At pH>pH_pzc,the adsorbent possessed negative surface charge,so the removal efficiency of heavy metal increasing.The result of XPS showed that C =O and C-N binding energy increased,the binding energy of Pb decreased and the Na absorption peak disappeared after adsorption heavy metals.So,ion exchange and complexation mechanisms were also involved in adsorption process.Physical adsorption was also comfirmed to be involved in the adsorption process via studying the adsorption of three competitive ions.Therefor,there could be electrostatic adsorption,ion exchange and complexation mechanisms of Pb???removal from aqueous solutions.