Preliminary studies on Cr(VI) removal from aqueous solution using grape stalk wastes encapsulated in calcium alginate beads in a packed bed up-flow column

Cr(VI) sorption on 2% grape stalks encapsulated in calcium alginate beads was examined in a continuous packed bed column. The effect of operating parameters as flow rate, inlet metal ions concentration and bed height on the sorption characteristics was investigated. The total amount of metal sorbed, equilibrium uptake and total removal percent of Cr(VI) related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different flow rates and different inlet chromium (VI) concentration. Data confirmed that the total uptake decreased with increasing flow rate and increased with increasing inlet Cr(VI) concentration. The obtained results were modeled by the application of a mass transfer and diffusion model and mass transfer coefficient (kf) and diffusion coefficient (De) for Cr(VI) adsorption on calcium alginate beads containing 2% grape stalk wastes were determined. The bed depth service time (BDST) model was used to analyze the experimental data obtained at different bed depths. The model failed in predicting the service time when changing operating parameters due to the complexity of the sorption process.