Extraction mechanism for palladium(II) from hydrochloric acid solution with 2-dodecylthiomethylpyridine using a stirred transfer cell.

2-Dodecylthiomethylpyridine (DTP) was newly synthesized to study its extraction properties for precious metals. DTP was a selective extractant for palladium(II) and gold(III) over base metals. The loading test for palladium(II) showed that one palladium ion reacted with one molecule of DTP. The extraction rate of palladium with DTP was measured using a Lewis-type transfer cell at 303 K. The extraction reaction of palladium with DTP has been found to be a first order reaction with respect to palladium ion, DTP, and hydrogen ion concentrations. This reaction is inversely proportional to chloride ion concentration. The rate-determining step was the parallel reactions of DTP with PdCl3(-) and PdCl4(2-) in the aqueous phase.