A Comparative Study of Ni (II) Removal from Aqueous Solutions on Ca-Alginate Beads and Alginate-Impregnated Hemp Fibers

Ca-alginate particles (CA) and alginate-impregnated hemp fibers (AH) (both, as prepared, dried, and rehydrated) were used as adsorbents for removal of Ni (II) ions from water. Adsorption was examined in the batch system and experimentally obtained data were analyzed by both linear and nonlinear curve fitting using pseudo-first and pseudo-second-order rate, as well as Langmuir, Freundlich, and Sips equations. The concentration of Ni (II) ions was measured by atomic absorption spectrophotometry, while the Fourier transform infrared spectroscopy was used for characterization of adsorbent surface, before and after the adsorption. Although all tested samples showed similar adsorption capacities of 12 mg/g, it was found that rehydration improves adsorption characteristics of AH and increases the removal efficiency above 90 %. Adsorption of Ni (II) ions can be sufficiently described by both kinetic models and Sips isotherm equation, and this relatively fast process presumably occurs through the mechanism of physisorption and ion-exchange. The obtained results proved that Ca-alginate particles and alginate-impregnated hemp fibers have good potential to reduce nickel concentrations in a cost-effective and efficient manner.