Biosorption of Cr(VI) on immobilized Hydrilla verticillata in a continuous up-flow packed bed: prediction of kinetic parameters and breakthrough curves

In this work, biomass of Hydrilla verticillata, a waste weed was used in its immobilized form to remove hexavalent chromium from aqueous solutions. The powdered biomass was entrapped in polyvinyl alcohol and packed bed studies were carried out using beads of immobilized H. verticillata. Bed height, influent Cr(VI) concentrations, and influent flow rate were variable parameters for the present study. The overall performance of the biosorbent was satisfactory as very high Cr(VI) uptake (45.83 mg g(-1)) was observed. Three different models-Bed depth service time (BDST), Yoon-Nelson, and Thomas-were studied and fitted to the experimental data. The correlation coefficient values were all above 0.96, whereas the BDST model fitted the data best. From the Thomas model, Thomas rate constant, K-Th was calculated and found to be 0.0215 L mg(-1) h(-1). The data obtained from the Yoon-Nelson model indicated that tau (148 min at 5 mg L-1) values were very similar to experimental (140 min at 5 mg L-1) results. Desorption studies of Cr(VI) were also carried out to find out the recovery of the metal ion.