Chromium(VI) removal from aqueous solution by untreated rubber wood sawdust

The ability of untreated local rubber wood sawdust (RWS) to remove Cr(VI) was carried out under a bench-scale shaking condition by varying parameters such as initial Cr(VI) concentrations, adsorbent dosage, pH, temperature and eluting agent. Complete Cr(VI) removal was achieved at pH less than 2, initial Cr(VI) of 100 mg/L and RWS dosage of greater than 1.5% (w/v). The point of zero charge (pH(PZC)) of 4.90 explained the decrease in Cr(VI) removal capacity by RWS when pH (3-9) and initial Cr(VI) concentrations (200-500 mg/L) were increased. Shorter time was needed when 1 M HCI was used to recover Cr from RWS. FTIR analysis suggests the importance of functional groups such as amino, hydroxyl and carboxyl during Cr(VI) removal. Results suggest that the Cr(VI) removal by RWS is an endothermic process with positive entropy and occurs non-spontaneously.