A new adsorbent, polyacrylonitrile/organobentonite composite with amidoxime functionality was prepared using in situ intercalation polymerization technique and characterized by Fourier transform infrared spectroscopy, X-ray diffraction pattern, scanning electron microscopy, surface area analyzer, thermogravimetry, and potentiometric analysis. The adsorption of Cu(II), Zn(II), and Cd(II) ions was examined by batch-equilibrium technique with respect to the initial pH, adsorbent dose, ionic strength, contact time, and initial metal concentration. Adsorption-complexation, in addition to ion exchange, must be involved in the sorption process. Maximum adsorption of 99.8% Cu(II), 98.9% Zn(II), and 97.4% Cd (II) with 2 g/L of the adsorbent was observed at pH 6.0 for an initial metal concentration of 25 mg/ L. The kinetic data were reasonably correlated with pseudosecond-order kinetic equation. An increase of ionic strength on the medium caused a decrease in metal adsorption, indicating the occurrence of outer-sphere surface complex mechanism for the metal. The equilibrium isotherm data were analyzed using Langmuir, Freundlich, and Scatchard isotherm models; however, the Langmuir model was found to provide the best correlation. The maximum monolayer adsorption capacity was 77.43, 65.40, and 52.61 mg/g for Cu(II), Zn(II), and Cd(II) ions, respectively, at 30 °C. The adsorption efficiency toward heavy metals removal was tested using different industry wastewaters. Acid regeneration was tried for several cycles with a view to recover the adsorbed metals and also to restore the adsorbent to its original state.
