Efficient removal of Cu(II) from an aqueous solution using a novel chitosan assisted EDTA-intercalated hydrotalcite-like compound composite: Preparation, characterization, and adsorption mechanism

Adsorption is recognized as one of the most promising methods for heavy metal removal from contaminated water. However, the adsorption efficiency often decreases because of easy aggregation and an inevitable certain loss of adsorbents during the adsorption process. Herein, a highly efficient chitosan (CS) assisted ethylenediaminetetraacetate-intercalated Mg-Al hydrotalcite-like compound (EDTA-HTlc) composite absorbent (CS-EDTA-HTlc) was synthesized by using a simple ion-exchange/chemical crosslinking process to remove Cu(II), used as a template heavy metal, from an aqueous solution. Characterization by FESEM, PXRD, FTIR, TG-DTG, BET specific surface area, and pore volume revealed that CS-EDTA-HTlc had a high specific surface area and many different functional groups (such as carboxyl, hydroxyl, and amino) with strong complexing ability. The adsorption capacity of CS-EDTA-HTlc for Cu(II) was investigated by varying experimental conditions such as adsorbent dosage, initial solution pH, adsorption time, initial Cu(II) concentration, and temperature. The adsorption equilibrium was reached within 120 min. The Cu(II) removal efficiency came 98% with the initial Cu(II) concentration of 200 mg·L-1 and the adsorbent dosage of 1.0 g·L-1. The adsorption kinetics and isotherms data of Cu(II) on CS-EDTA-HTlc were well described by the pseudo-second-order kinetic equation and the Freundlich model, respectively. The adsorption was a spontaneous exothermic process, and the possible adsorption mechanisms analyzed by the XPS and PXRD spectra involved the complexation of Cu(II) ions by carboxyl/hydroxyl/amino groups and the isomorphic substitution of Mg(II) in brucite-like layers. The results suggest that CS-EDTA-HTlc has potential applications in natural Cu(II) contaminated wastewater treatment.