Efficent removal of nickel(II) salts from aqueous solution using carboxymethylchitosan-coated silica particles as adsorbent.

Three types of organo-mineral composites have been probed as adsorbents for the removal of Ni(II) ions from aqueous solution. Native Aerosil 200 silica particles have been encapsulated with carboxymethylchitosan (CM-CS) providing SiO+CM-CS, surface-silanized silica particles SiONH+CM-CS were obtained by treatment with APTES and subsequent encapsulation by CM-CS. Alternatively, surface-carboxylated Aerosil 200 was coated by CM-CS affording SiOCOH+CM-CS. The materials have been characterized by various techniques. The effects of counter ions (Cl, Br, CHCOO, NO and SO), pH and initial Ni(II) concentration on the adsorption capacities have been systematically investigated. The maximum adsorption capacity q of CM-CS-coated silica was determined using the Langmuir adsorption isotherm. For SiOCOH+CM-CS, SiO+CM-CS and SiONH+CM-CS, they decrease at pH 7 in the order 256mg/g>140mg/g>105mg/g. The adsorption kinetic fits well with a pseudo-second order model. These carbohydrate-derived biosorbents are excellent adsorbents with capacities superior to most other adsorbents reported in the literature.