Removal of hexavalent chromium from wastewaters by bone charcoal

The adsorption of hexavalent chromium onto bone charcoal was studied as a f unction of time, amount of charcoal, pH, concentration of chromium and samp le volume. The cross interference with other elements was also investigated . Tests were carried our with solutions of chromium(VI) at concentrations b etween 5 and 25 mg . L-1 Chromium removal efficiencies higher than 90% were achieved at pH = 1 using 2 g of bone charcoal and a stirring time in the o rder of 30 min. Acid and alkaline pretreatments of bone charcoal did not im prove the sorption capacity of bone charcoal against Cr(VI). The presence o f other ions had practically no influence on the chromium removal. The pres ence of a matrix of tannery effluents did not reduce the removal capacity o f bone charcoal for Cr(VI), but it was confirmed that only 47% of Cr(III) c an be removed using these conditions.