| Groundwater contamination by hexavalent chromium is a problem around the world. Various technologies are being used to immobilize hexavalent chromium in situ, thus minimizing exposure risks to the general public. One means of immobilizing heavy hexavalent chromium is to stimulate growth of bacteria that can transform the oxidized forms, which are soluble and thus mobile, to reduced forms, which are insoluble and thus immobile. The oxidized hexavalent chromium, however, can also biosorb to the microbial biomass without undergoing reduction.; The objective of this study was to quantify the biosorption of hexavalent chromium to microbial biomass. The microbial biomass was grown in a chemostat under controlled conditions with the addition of methanol as carbon source and a nitrate nutrient solution at regular intervals. The microbial culture was harvested from the chemostat and it was used in a biosorption method known as "subsequent additions method" to quantify the adsorption of hexavalent chromium as a function of pH and equilibrium aqueous chromate concentration. The nature and concentration of adsorption sites on the biomass was also characterized using a potentiometric titration analysis. |
