Study of Chromium(VI) Adsorption from Aqueous Solution on to Activated Carbon

Abstract

The adsorption of chromium(VI) from dilute aqueous solutions on to activated carbons at natural pH values was investigated. The activated carbons were modified to obtain materials with a well-defined surface containing inorganic impurities at ppb or ppm level. Measurements of the adsorption kinetics relative to the degree of granulation were undertaken. It was found that the reaction rate of the ions on the surface of the activated carbon rather than diffusion was the major process influencing the equilibrium. Surface reduction of Cr VI to Cr III appeared to be the principal mechanism for the adsorption of chromium on the activated carbons studied. It was demonstrated experimentally that the presence of oxidizing agents dramatically changed the adsorption capacity of Cr VI on the studied carbons. The influence of the ionic strength (controlled by the addition of NaCl) on the adsorption capacity was also studied. Variable and complex influences of the ionic strength on the adsorption capacity were observed.