Grape Stalks Wastes Encapsulated in Calcium Alginate Beads for Cr(VI) Removal from Aqueous Solutions

Abstract

In this study, a low‐cost effective adsorbent based on grape stalks encapsulated in calcium alginate beads was investigated as a possible sorbent for the removal of Cr(VI) from aqueous solution. The present paper deals with the procedure for the preparation of calcium alginate beads and the encapsulation of grape stalks powder into calcium alginate beads, the characterization of these beads and the study of their behavior on Cr(VI) adsorption from aqueous solutions. The influence of grape stalks powder concentration in the calcium alginate beads, metal solution pH, sodium chloride, and metal concentration on metal removal has been studied. Uptake showed a pH‐dependent profile. Maximum Cr(VI) sorption was achieved at pH 3.0. High NaCl concentrations significantly reduce the mechanical resistance of the beads, however, this does not have a significant effect on metal removal. Langmuir and Freundlich isotherms were used to describe sorption equilibrium data. The experimental data were fitted better by the Langmuir adsorption isotherm. The Langmuir adsorption capacity for calcium alginate beads containing 2% (w/v) grape stalks powder was found to be 71.98 10−3 mg/bead (≈225 mg Cr(VI)/g grape stalks).