adsorption of ni(ii) and cd(ii) from aqueous solutions using modified rice husk

background and purpose: recently, release of pollutants such as heavy metal ions to the environment becomes one of the most important problems for soil and water. the present study was conducted to introduce modified rice husk (rh) as a new low-cost adsorbent. materials and methods: in this study, tartaric acid modified rh (tarh), was used as an adsorbent for removal of ni(ii) and cd(ii) from water samples. this study was conducted in laboratory scale. employing batch method, solution ph, adsorbent dose, contact time, and initial metals concentration were optimized. results: the optimum ph for removing of both the investigated metal ions from water solutions was found to be 4.0. the process of ni(ii) and cd(ii) adsorption on tarh reached equilibrium within 45 min. the isotherm evaluations revealed that the langmuir model attained better fits of the experimental equilibrium data than the freundlich model. in addition, adsorption kinetics data were well-fitted by the pseudo-second-order rate model with high regression coefficients. conclusion: it was found that tarh is a highly efficient adsorbent for ni and cd from aqueous solution, and the maximum predicted adsorption capacities for ni(ii) and cd(ii) were obtained as 55.5 and 45.5 mg/g, respectively.