No abstract

Leonardite was used as an adsorbent for the removal of Cd(II) and Zn(II) from aqueous solutions. The characteristics of leonardite were determined using XRD, XRF, FTIR, and SEM. Adsorption of Cd(II) and Zn(II) on leonardite, in batch system at 30 °C, was investigated to achieve the optimum condition for metals removal. Studies were carried out at different pH, contact time, and initial metal concentration. It was found that adsorption of metals ions was strongly influenced by pH value. The optimum adsorption conditions obtained were pH 6 and contact time of 60 min. Adsorption data were interpreted to kinetic models, including pseudo-first-order, pseudo-second-order, intra-particle diffusion, and adsorption isotherm models, including Langmuir isotherm and Freundlich isotherm. Pseudo-second-order kinetic model was suitable for describing adsorption of Cd(II) and Zn(II) on leonardite. Both Langmuir and Freundlich isotherms fitted well with the adsorption data of Zn(II) whereas the adsorption of Cd(II) better fitted to Freundlich isotherm.