Preparation Of Amino Acid Anion Substituted Hydrotalcite And Study On Adsorption Of Heavy Metal Ions

With the rapid development of industrialization and urbanization,the contamination of heavy metals in water was worsening,which posed a severe hazard to plant,animal and human health.Heavy metals were toxic and non-biodegradable and existed for long period in the environment.Adsorption was regarded as a promising approach for the removal of heavy metal ions from the wastewater compared with other techniques.Hydrotalcite?LDHs?was a type of anionic clay mineral with layer structures,and used as adsorbent,catalyst and fire retardant.In this study,the hybrid has been synthesized by incorporating L-cys or PASP anion into the interlayer of hydrotalcite,The structure and morphology of L-cys/LDHs and PASP/LDHs were characterized by XRD,FTIR,SEM and BET.The experimental result showed that the successful incorporation of L-cysteine and PASP into the interlayered of LDHs and the layer structure of LDHs were retained.The zeta potentials of adsorbents revealed that the surface of adsorbents become more electronegative after intercalating L-cys and PASP anion,which promotes the combination of heavy metal ions and the adsorbents.The adsorption capacity of the L-cysteine/LDHs are compared with that of the pristine LDHs.The maximum adsorption capacities of L-cysteine/LDHs for Cu²⁺,Pb²⁺and Hg²⁺are171.31,86.44 and 233.71mg/g.The effects of various physic-chemical factors such as p H,adsorbent dosage and contact time are investigated.As confirmed by XRD and XPS analysis,a mechanism for adsorbed Cu²⁺in the form of coordinated complexes and isomorphous substitution is proposed.In contrast,a precipitation mechanism is suggested for adsorbed Hg²⁺The adsorption capacity of PASP/LDHs was very excellent.The maximum adsorption capacities of PASP/LDHs for Pb²⁺and Hg²⁺are 240.29 and 210.30mg/g.the adsorption kinetics are fitted by the pseudo-second order model.The adsorption isotherms are well described by the Langmuir equation.The results demonstrate that L-cys/LDHs and PASP/LDHs were the promising adsorbents for efficient elimination toxic metal ions from wastewater.