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 SiO2 +CM - CS, surface-silanized silica particles SiO2NH2 +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 SiO2CO2H + CM CS. The materials have been characterized by various techniques. The effects of counter ions (Cl-, Br-, CH3COO-, NO3- and SO42-), pH and initial Ni(II) concentration on the adsorption capacities have been systematically investigated. The maximum adsorption capacity q(m) of CM-CS-coated silica was determined using the Langmuir adsorption isotherm. For SiO2CO2H +CM - CS, SiO2 +CM - CS and SiO2NH2 +CM - CS, they decrease at pH 7 in the order 256 mg/g > 140 mg/g > 105 mg/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. (C) 2017 Elsevier Ltd. All rights reserved.