removal of zn(ii) and cr(vi) from aqueous solutions using rice husk

rice husk is as an organic solid waste material that has high adsorbing capacity in removal of heavy metal ions from wastewater, and can be very effective in treating industrial aqueous solutions that are important sources of water and soil pollution. in this study, the removal of zn(ii) and cr(vi) ions from aqueous solutions using rice husk was investigated. the investigated parameters included acidity, initial concentrations of ions in aqueous solution, contact time, temperature and the amount of adsorbent matter used for treatment. with increasing ph of the solution, the adsorption of zinc and chromium ions by rice husk were increased and decreased, respectively. the maximum adsorption was occurred in ph 7 and 2. moreover, with increasing initial concentration of metals, the removal efficiencies of zinc and chromium were decreased. while, with increasing the contact time, the removal efficiencies were increased and reached an equilibrium after 2 and 3 hours for zinc and chromium, respectively. the metal adsorption is also dependent on the reaction temperature, so that by increasing temperature the percentage of adsorption was increased. with increasing the amount of husk rice to the solution, the percentages of adsorption of zinc and chromuim were increased. rice husk showed to be a proper absorbent for the removal of zn (ii) and cr (vi) from aqueous solutions.