Activated Carbon Adsorption of Cobalt from Aqueous Solutions

6 ACTIVATED CARBON ADSORPTION OF COBALT FROM AQUEOUS SOLUTIONS 

Cobalt is one of the heavy metal toxic pollutants that is present in trace amounts in natural waters, the amount usually being less than 1 g/L. Consequently, its removal by adsorption using suitable adsorbents has been studied by a number of 

FIGURE 6.28 Speciation diagram of O.IM cadmimn chloride aqueous solution. (Source Ferro-Garcia, M.A., Rivera-Utrilla, J., Rodriguez-GoidiUo, J., and Bautista-Toledo, I., Carbon, 26, 363, 1988. With permission.) 

Rivera-Utrilla and coworkers carried out adsorption studies of Co(ll) ions from aqueous solutions using activated carbons prepared from almond shell activated to different degrees by activation in CO2 at 1123 K, and after the formation of carbon-oxygen acidic surface groups on treatment with nitric acid, hydrogen peroxide, and in air, and carbon-nitrogen basic surface groups on treatment with ammonia. The surface acidity and the surface basicity of each carbon was determined by titration with sodium hydroxide and HCl solutions, respectively. The adsorption isotherms of Co(II) ions on three typical samples of carbons, namely commercial 

FIGURE 6.29 Adsorption of Co(II) ions on different activated carbons as a function of solution pH. (1) A-5 (2) A-8 (3) A-24 carbons activated in CO2 at 1123 K, (4) as-received activated carbon, (5) A-5 oxidized with HNO3. (Source Rivera-Utrilla, 1. and Ferro-Garcia, M.A., Carbon, 25, 645, 1987. With permission.) 

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