Selective mesoporous adsorbents for and Cu separation

NH₂–MCM-41 and COONa–MCM-41 were prepared by grafting aminopropyls and propionates on the pore wall of the mesoporous silica MCM-41 for the separation of and Cu²⁺. Single and binary component adsorptions show that has a 100% selectivity for adsorption at low pH (<3.5 i.e., point of zero charge, p.z.c.), while COO⁻Na⁺–MCM-41 adsorbs only Cu²⁺ over the entire pH range of the study (i.e., pH 1.5–5.5). Adsorption uptakes were rapid on both adsorbents reaching equilibrium in less than 3 h and in most cases less than 10 min. The adsorption capacity of for is high, approaching the theoretical values of two aminopropyls for one , the Cu²⁺ adsorption on COO⁻Na⁺–MCM-41 was less efficient requiring five propionates to adsorb one Cu²⁺. High purity hydrogen dichromate and copper chloride solutions were respectively recovered by a simple acid wash and the regenerated adsorbents were reused without a loss of performance.