Removal of Chromium from Aqueous Solution By Biochars Derived from Sugarcane Residue with Pretreatments.

Removal of chromium from aqueous solution by biochars derived from sugarcane residue with pretreatments

Novel modification of biochar structural and surface properties has been a recent research focus for improving its efficacy in order to achieve a specific remediation goal. In this study, MgO impregnated biochars derived from sugarcane harvest residue (SHR) with H₂SO₄ pretreatment were synthesized and evaluated for removing Cr (VI) from aqueous solution under different conditions. Batch adsorption and desorption experiments coupled with surface and structural characterization using FTIR, SEM-EDS and XRD were conducted. Magnesium impregnation and H₂SO₄ pretreatment were found to generally promote the removal of Cr (VI) from aqueous solution, especially at low pH. Cr (VI) adsorption on biochar was best described by Langmuir model, and maximum adsorption capacities increased in the order of biochar prepared from SHR < Mg impregnated material (MgSHR) < Mg impregnated H₂SO₄ pretreated material (MgASHR). Moreover, the maximum adsorbed amount was higher than many other biochars/adsorbents, especially for MgASHR generated biochar. The adsorbed Cr was hardly desorbed by H₂O and KNO₃ but can be desorbed with alkaline solution. Electrostatic interactions were among the main mechanisms contributing to the adsorption of chromium by the improved biochars. Overall, the modified biochars can be used as effective and low-cost adsorbents for the removal of Cr (VI) from aqueous solutions.