Removal of Cu(II) from aqueoussolution by adsorption onto acid-activatedpalygorskite

A series of activatedpalygorskite clay by HCl with different concentrations was prepared and applied as adsorbents for removal of Cu(II) from aqueoussolutions. The effects of contact time, adsorbent dosages and pHs of suspension on the adsorption capacities for Cu(II) were investigated. The results showed that adsorption capacity of activated palygorskites increased with increasing the HCl concentration and the maximum adsorption capacity with 32.24 mg/g for Cu(II) is obtained at 12 mol/L of HCl concentration. The variations in IR spectra and pH of solution after adsorption Cu(II) confirmed that the numerous amount of silanol groups (Si–OH) originated by acid treatment were mainly responsible for Cu(II) adsorption onto acid-activatedpalygorskite. Kinetic studies indicated that the adsorption mechanisms in the Cu(II)/acid-activatedpalygorskite system followed the pseudo-second-order kinetic model with a relatively small contribution of film diffusion. Equilibrium data fitted well with Freundlich isotherm model compared to Langmuir isotherm model, indicating that adsorption takes place on heterogeneous surfaces of the acid-activatedpalygorskite. Adsorption–desorption studies presented that activatedpalygorskite has lower adsorption and desorption efficiencies using Cu(CH3COO)2 than that of other inorganic copper salts, such as CuSO4, Cu(NO3)2, and CuCl2.