Efficient Approach for Cd~(2+) and Ni~(2+) Removal and Recovery Using Mesoporous Adsorbent with Tunable Selectivity

摘要

Cadmium pollution from the manufacture and disposal of NiCd batteries remains an important problem in developing countries. Among the available remedial technologies, adsorption is popular because of its low cost and simplicity. The mesoporous NH_2-MCM-41 displays good adsorption capacities for cadmium and nickel ions. This work demonstrated for the first time the use of the competition between complexant and sorbent to create high adsorption selectivity. The selectivity was manipulated by the judicious use of a chelating agent, thus achieving on-demand 100% selectivity for either Cd~(2+) or Ni~(2+) adsorption. Single and binary components adsorption studies, carried out with different metals and EDTA concentrations, solution compositions and pH, showed that NH_2-MCM-41 adsorbs only cadmium with a capacity of 0.56 mmol g~(-1) from binary mixtures at [EDTA]/[M~(2+)] = 0.5 and pH 5. The NH_2-MCM-41 displays 100% selectivity for nickel adsorption at [EDTA]/[M~(2+)] = 0.5 and pH 2 with a measured adsorption capacity of 0.50 mmol g~(-1). Pure Cd~(2+) and Ni~(2+) solutions were recovered by a simple acid wash, and the regenerated adsorbent could be reused without lost of performance (i.e., adsorption capacity and selectivity).