Effects of operating parameters on efficiency of cadmium and zinc removal by the complexation–filtration process

A process for purifying wastewaters containing heavy and toxic metals such as cadmium and zinc by the complexation–filtration process was studied. From previous research, diethylaminoethyl cellulose (DEAE23) was selected as the complexing agent. The experiments were carried out in a Millipore ultrafiltration stirred dead-end cell at room temperature. Factors such as pH, concentration of the ligand and of the metal ion, membrane pore size and applied pressure were investigated. Experimental results indicate a considerable influence of the pH of the solution on the rejection coefficient. Also, the complexing ability of DEAE23 towards zinc ions is higher than towards cadmium ions. An increase of the concentration of the complexing agent at constant initial concentration of metal increases metal retention. An increase of initial metal concentration at constant concentration of the complexing agent decreases metal retention. When both metals are present in the same solution, retention decreases compared to single metal solutions, which is more significant in the case of cadmium ions.

The results confirm that there is a possibility for applying low-pressure-driven processes to the separation of Zn and Cd ions from water after their prior linking with macromolecular ligands. Experimental results indicate a considerable influence of pH of the solution on the rejection coefficient. By changing the pH values appropriately, it is possible to carry out the separation of metal ions obtaining high retention coefficients or to decompose polymer–metal complexes, which may result in recovery of the concentrated metal or regeneration of the complexing polymer applied. The complexing agent used in research