Extraction of Mercury(ii) by Thiourea-Based Reagents

The extraction of mercury(II) by novel thiourea-based extraction reagents: nonylthiourea (NTH), dodecy I thiourea (DTH), benzylthiourea (BTH), dinonylthiourea (DNTH) and dioctylthiourea (DOTH) from hydrochloric acid solutions has been studied. The kinetics of extraction of Hg(II) by these reagents were found to be very fast, where equilibrium can be achieved in two minutes. The extraction of mercury(II) extracted by DTH was studied in more details and the equilibrium data have been analyzed by graphical as well as numerical methods. The extraction of mercury(II) by DTH is explained by the formation of HgCI2DTH and HgCl2(DTH)3 complexes. The other reagents have been also found to form the same type of complexes and the stability constants were inversely proportional to the chain length. The stability constants of the Hg(II) complexes formed with different reagents are summarized in Table 3. Two of the reagents were found to be very selective for the extraction of mercury over cadmium(II) and zinc(II).