The adsorption of divalent metal cations on mesoporous silicate MCM-41

MCM-41 is a synthetic, mesoporous silicate material, which currently has limited use as an industrial catalyst. This material is considered to have good potential for adsorption/separation applications due to its regular hexagonal structure, uniform pore distribution, large surface area and large pore volume. In order to enhance the adsorption of metal ions on MCM-41, a metal ion chelating agent, acetylacetone is added and the capacity of the adsorbent for three divalent metal cations in aqueous solutions; Cu(II), Ni(II) and Co(II) determined. Adsorption isotherms for these metal ions are presented, along with adsorption selectivity with respect to pH. Metal ion adsorption results are compared with published data for solvent extraction systems utilising pure acetylacetone and acetylacetone in benzene. It was found that the MCM-41/acetylacetone system produced equal or better metals removal in comparison to solvent extraction methods for some of the metal species tested. Further, the pH of maximum adsorption is shifted in the MCM-41 system compared with the solvent extraction case, thus presenting the possibility of processing under different conditions.