Polydithiocarbamate resin, abbreviated as DTC-resin hereafter, was prepared from polyethyleneimine (10 g), carbon disulfide (34 g), and sodium hydroxide (9 g) (reaction( 1 ) in the text). In order to allow an aqueous solution to pass effectively through the resin, polyethyleneimine (10 g) is necessary to be mixed with powdered silica gel(60 g) and treated with 1, 2-dibromoethane (reaction( 2 ) in the text), prior to the reaction ( 1 ).
DTC-resin readily captures various heavy metal ions forming dithiocarbamate chelates. There are remarkable differences among metal ions in the readiness of chelation. The experiment was carried out for the competitive adsorption of various binary metal ion systems on DTCresin. The results are shown in Table 1. The order of the ability of metal ions to bind with the resin is Mg"Ni"Cd2+CZnCPb2+, which is consistent with the order of increasing softness of Lewis acids except for that of Cd2+ and Zn".
In conclusion, DTC-resin will be utilized for collecting some heavy metal ions from a dilute solution in the presence of a relatively large amount of light metal ions, such as Na+, K+ and mg2+.