The extraction of cadmium from waste waters using poly(iminoethylene) containing N‐dithiocarboxylato groups

Highly branched poly(iminoethylene) containing N‐dithiocarboxylato groups (polymer 1) has been used to extract cadmium from simulated waste waters. Two conditional stability constants (logK1 = 11, logK2 = 4 to 5) have been related to binding by NHCS2⊖ and nitrogen‐containing groups. Polymer 1 is selective for cadmium over zinc in a solution containing Cd (11,2 mg · dm−3) and Zn (13 mg · dm−3) at pH = 2(H2SO4). The time for half of the available sites to be used by bonding to cadmium (t1/2) is in the order of 20 s. The total NHCS groups on polymer 1 is ca. 3,5 · 10−3 mol · g−1 (22,3% S) and the mole ratio of S: Cd has a limiting value of 3,7.