Adsorptive removal of nickel from aqueous solutions by activated carbons from doum seed (Hyphaenethebaica) coat

The present study investigates the possibility of using low cost agriculture waste as doum-palm seed coat for the removal of nickel ions from aqueous solutions. Two activated carbons had been prepared from raw doum-palm seed coat (DACI and DACII); as well, the raw material was used as an adsorbent (RD). Batch adsorption experiments were performed as a function of pH of solution, initial nickel ions concentration, dose of adsorbent and contact time. Adsorption data were modeled using Langmuir, Freundlich, Temkin and D–R Models. Different error analysis conforms that the isotherm data followed Freundlich models for all adsorbents. Adsorption kinetic data were tested using pseudo-first order, pseudo-second order and Elovich model. Adsorption mechanism was investigated using the intra-particle diffusion model. Diffusion coefficients were calculated using the film and intraparticle diffusion models. Kinetic studies showed that the adsorption of Ni^2+ ions onto RD, DACI and DACII followed pseudo-second order kinetic model, and indicates that the intra-particle diffusion controls the rate of adsorption but it is not the rate limiting step.