Adsorption Isotherms and Kinetics of Ni(II) and Pb(II) Ions on New Layered Double Hydroxides-Nitrilotriacetate Composite in Aqueous Media

摘要

Anionic layered double hydroxides (LDH) known to have high adsorption capacities and are easily synthesized in the laboratory. With nitrilotriacetate (NTA) anions inclusion as ligand, which is incorporated as interlayer anion in the LDH structure via ion-exchange or coprecipitation reaction, this inclusion would give the Zn-Al LDH material considerable potential as chelate for metal cation contaminants in the aqueous environment by changing the regular behavior of anion exchange to cationic exchanger or serpent. The characterization of the new sorbent is carried out by FTIR spectroscopy (FT-IR), powder x-ray diffraction and scanning electron microscope (SEM). The potential capacity of uptake of Ni(II) and Pb(II) at pH of 5 is attributed to the complex formation between metal ions and NTA in the interlayer of LDH as well as surface adsorption. This work aimed to investigate the kinetics of the sorption mechanism using batch technique at different temperature, pH and various metal concentrations. In addition to the kinetic study of adsorption isotherms and the interaction of adsorbent-adsorbate time as parameters, using a pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. The results show better correspondence to a pseudo-second-order kinetics model with high correlation coefficients (R²= 0.997 for the initial concentrations). The model of Freundlich is appropriate to describe the experimental adsorption results with sorption capacities of 7.153, 6.807 mg/g for Ni(II) and Pb(II) respectively. These behaviors are attributed to the structural construction of the Zn-Al-NTA material. All these results have shown the high efficiency of Zn-Al-NTA adsorbent for the fast removal of Ni(II) and Pb(II) from aqueous solution.