Abstract :
Metal cations were removed from water by coagulation-flocculation of the chitosan-montmorillonite system. Co2+, Ni2+ and Cu2+ were used as probe cations. It was found that both chitosan and montmorillonite contribute to the metal ion removal, when used separately, and that coagulation-flocculation strongly depends on the pH and composition of the liquid medium. When used simultaneously, chitosan and montmorillonite displayed a synergy phenomenon, likely due to interactions between the main parameters. Such interactions were investigated through factorial 3^3 experimental designs. The results show that the highest cation removal yields can be obtained for optimal (chitosan/Mt-K) weight ratio of ca. 5%, pH 6.8, and concentration of 20-100 ppm of Co2+, Ni2+ and Cu2+, while the lowest residual turbidity is attained at pH 5.4 and a (chitosan/Mt-K) of 0.6%. A chitosan excess with respect to the optimal amount may affect the cation removal yields. The results obtained herein provide valuable data that enable to assert that chitosan/montmorillonite are effective coagulating agents and that the presence of organic matter or of dispersed clays is an essential requirement for the effective removal of the metal cation from wastewaters.
