Evaluation of Efficiency of Rice Bran in the Removal of Heavy Metals from Wastewater

Rice bran, as an organic solid waste material, has a high adsorption potential in removal of heavy metal ions from wastewater and can be very effective in treating the industrial wastewater which is the main source of water and soil contamination with heavy metals. In this study, the efficiency of Cr(III) and C (II) removals from heavy metals containing solutions was evaluated. Afterwards by adding rice bran to reaction environment, the amount of metal ions removed by rice bran in acidities, amount of adsorbent used, contact times and different initial concentrations of ions in wastewater were investigated. The results indicated that with an increase in the solution pH, the percentage heavy metal ions adsorption by rice bran increased and reach the amount maximum in pH=5. Also, percentage of adsorption was dependent on metal type, so that percentages of C (III) and Cu(II) adsorption from wastewater were 84.2% and 89.5% in pH=5, respectively.To increase the wastewater initial concentration, first percentage of adsorption was increased and then it was decreased due to saturation of rice bran particles. According to the obtained results, the calculated saturation capacities of rice bran for Cr (III) and Cu (II) were 71and 78 mg/g-1 respectively. Moreover, percentage of ions adsorption was increased with the increase of contact time. Due to rapid reaction, 50-60% of metal ions was adsorbed after 5 min from start of reaction. In this study, contact time of 30 min was offered as an appropriate contact time. The experimental data were analyzed using the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model.