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 ΔVorg = 0.17 nAu, ΔVaq = − 0.20 nAu, where nAu is the number of moles of gold(III) extracted. Distribution coefficients have been obtained for CAu org = 10− 6–1.25 M, CHCl = 1 M and for some other conditions. The electro-conductivity of extracts and solutions of HAuCl4·3.3H2O 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 CAu org exceeds 50%. A set of species in the organic phase H+, AuCl4−, HAuCl4, (HAuCl4)2, H(AuCl4)2−, and H2(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 CAu org) gives satisfactory results in recalculating data from 1 M to other CHCl.

► Extraction of gold(III) by dibutyl carbitol was studied
► Volume changes of phases and co-extraction of water were determined
► Electro-conductivity of the organic phase was measured.
► The contribution of the ionic subsystem in the organic phase is considerable.
► The modeling equilibrium was performed taking into account medium effect.