Removal of hexavalent chromium from aqueous solution by crosslinked mangosteen peel biosorbent

In present study the potential of a new biosorbent obtained from mangosteen peel was investigated for the removal of hexavalent chromium and trivalent chromium from the aqueous solutions. The biosorbent was modified by using concentrated sulphuric acid as the crosslinking reagent. Various batch experiments were carried out testing different values of several parameters such as pH, contact time, adsorbent dosages, and metal ion concentration to identify the optimum conditions. The effect of these parameters on the adsorption capacity and selectivity was studied. Results showed that optimum pH for hexavalent chromium adsorption was 3.0 and adsorption equilibrium was attained in 120 min. The adsorption data were found to fit Langmuir model and pseudo-secondorder equation. The adsorption mechanism for hexavalent chromium was found to be a complex process involving esterification, reduction and ion exchange, while cation exchange is the main route for trivalent chromium adsorption. From the above results, the crosslinked mangosteen peel gel appears to be a potential low-cost and effective adsorbent for hexavalent chromium and trivalent chromium removal from the waste water.