In this research, chitosan based membrane blended with rice hull ash (RHA) silica and polyethylene glycol (PEG) has been applied as adsorbent of Ca(II), Mg(II), Zn(II) and Cd(II)
based on the adsorption data at initial metal ion concentration and contact time variations, respectively. Results showed that the optimum condition of adsorption was at pH 9.0 for Ca(II), 6.0 for both Mg(II) and Zn(II) and 5.5 for Cd(II), and contact time of 24 h for all ions investigated. Kinetics of all investigated metal ion adsorption followed a kinetic model of pseudo-second-order. Adsorption of Ca(II) and Mg(II) on the membrane fitted toFreundlich model with the affinity of 1.266 and 1.099, respectively; and Zn(II)