Uptake of chromium cations and anions by milled peat

Abstract

The biosorption of chromium by milled peat from aqueous solution was investigated between pH 2 and 7. Peat was chosen as an inexpensive and readily available biomass. Adsorption of both the cationic Cr(III) and the anionic Cr(VI) was studied. Maximum uptake of Cr(III) occurred at pH 4. At this pH, approximately 50% of the Cr(III) present was in the form of Cr3+ and 50% was in the form of Cr(OH)2+ as predicted by MINEQL, a chemical speciation prediction program. The maximum uptake was 0.27 mmol/g which occurred at a final concentration of approximately 3 mmol. In contrast, maximum adsorption of Cr(VI) occurred at pH 2, to a level of 0.59 mmol/g for a 3-mmol final concentration. The predominant species at this pH was HCrO4−.