IMPREGNATION OF ACTIVATED CARBON WITH CHROMIUM AND COPPER-SALTS - EFFECT OF POROSITY AND METAL CONTENT

Activated carbons with different pore size distributions were impregnated with ammoniacal solutions of Cr(VI) and Cu(II) salts to give impregnated carbons with different metal loadings. Original and impregnated carbons were analyzed by means of physical adsorption, simultaneous DTA/TG, and temperature programmed desorption (TPD). Impregnation produces a partial blocking of the porosity of the carbon, which is a function of the original pore size distribution; thus, if the carbon has a relatively important mesoporosity contribution, the loss of microporosity is more pronounced than in essentially microporous carbons. When the impregnated carbons are heat treated in inert atmosphere, there is simultaneous reduction of the metals and oxidation of the carbon. The reduction products are Cr(III) and Cu(0), the reductions taking place in two stages. The simultaneous oxidation of carbon produces oxygen surface groups, which are different from those in the original carbon.