Removal of metal pollution in waters by natural adsorbents

In this research; unmodified and locally obtained low cost natural adsorbents which consisted Kazımkarabekir natural building stone, Karaman grape molasses soil and oak acorn cap were used. These adsorbents was briefly named T, PT and P respectively. One of the aims of this study was investigation of removal of Zn (II), Cu and Al (III) metals which have low initial concentrations from waters by the T, PT and P natural adsorbents and determination of adsorption capacity, kinetics and thermodynamic parameters. Another aim was to determination of the chemical composition, surface structures and morphology (structural properties) of adsorbents and the mechanisms that effected to the adsorption of polluting metals. In the decision process for the selection of natural adsorbents and polluting metals, the adsorbent-contaminant metal relationship matrix, inspired by the Quality Function Deployment matrix, was used. The removal efficiencies of T, PT and P low cost natural adsorbents with Zn (II), Cu and Al (III) adsorption were investigated by batch experiments. The effects of pH, initial metal concentration, temperature, contact time, adsorbent dose, mixing speed and adsorbent size were investigated within the factors affecting the adsorption equilibrium. Langmuir, Freundlich, D-R and Temkin isotherm models were used to determination the fit equilibrium isotherm for adsorbents. Lagergren pseudo-first order kinetic model, pseudo second order kinetic model as reaction-based models for determination of adsorption kinetics; Boyd equation and liquid film diffusion model were examined as diffusion based models. Adsorption thermodynamics were investigated using Gibbs equation and Van't Hoff graph. ∆G, ∆H and ∆S values were calculated. The characterization of the adsorbents before and after adsorption with polluting metals by SEM + EDX and XRD methods, surface structures and morphology (structural properties) and adsorption mechanisms of adsorbents were determined. For the organic adsorbent P, the efficiency of the tannins in the removal of contaminating metals was investigated. Finally, it was found that low cost natural adsorbents T, PT and P can be used successfully for removal of Zn (II), Cu and Al (III) metals which have low initial concentrations from water by adsorption. Keywords: Adsorbent characterization, equilibrium isotherm, low cost adsorbents, low initial concentration, kinetics, quality function deployment, tannin, thermodynamic