The chelating properties of two polymers: chitosan (a biopolymer) and polyethyleneimine (PEI, synthetic polymer) have been used for the binding of metal ions, and more specifically mercury. The PEUF (polymer enhanced ultrafiltration) process allowed reaching retention yields higher than 95 % under optimum experimental conditions. In the case of chitosan the efficiency of the process is strongly controlled by the pH : negligible retention below pH 4, and highest retention at pH 5.5. In the case of PEI, pH effect is much less marked. The retention of mercury has been also tested in binary solutions (containing Ni, Zn, Pb and Cu). Both chitosan and PEI show a greater affinity for mercury compared to Zn, Ni and Pb. Obviously, the cake filtration model appeared the most appropriate for describing the clogging of the membranes in these experiments performed using a static ultrafiltration cell.
