Some additional aspects of gold(III) extraction by dibutyl carbitol

From changes of volumes of the aqueous and organic phases it was found that the extraction of HAuCl4 from hydrochloric medium by dibutyl carbitol (DBC) involves co-extraction of about 6 mol of water per one mole of gold(III). The changes of phase volumes are equal to Delta V-org = 0.17 n(Au), Delta V-aq = -0.20 n(Au), where n(Au) is the number of moles of gold(III) extracted. Distribution coefficients have been obtained for C-Au org = 10(-6)-1.25 M, C-HCl = 1 M and for some other conditions. The electro-conductivity of extracts and solutions of HAuCl4 center dot 3.3H(2)O in dry DBC has been measured. In the organic phase the contribution of the ionic subsystem increases with the concentration of gold(III) and at high C-Au org exceeds 50%. A set of species in the organic phase H+, AuCl4-, HAuCl4, (HAuCl4)(2), H(AuCl4)(2)(-), and H-2(AuCl4)(+) containing molecules of DBC and water, is sufficient to adequately explain the experimental data on distribution and electro-conductivity of extracts. However, it is necessary to take into account medium effects, which were simulated using simple models by Born and Debye. It has been shown that for this system the method based on the correspondence of the organic phases (equality of C-Au org) gives satisfactory results in recalculating data from 1 m to other C-HCl. (c) 2012 Elsevier B.V. All rights reserved.