Experimental Study of the Distribution of Gold and Zinc between Liquid and Vapor at 300–360°C in the H2O–H2S ± HCl System

The distribution coefficients of Au and Zn between liquid and vapor in the H2O–H2S and H2O–H2S–HCl systems at 300–360°C have been experimentally determined. The experiments were performed using an autoclave, which allows for taking liquid and vapor samples at the experimental conditions. The activity of the metals was controlled by the solid phases Au(cr) and ZnS(cr); the total concentration of H2S was 0.3–1.0 m mol (kg H2O)–1], and that of HCl was 0.1 m. The Zn(HS)2 complex has the maximum distribution coefficient KD(V/L) (vapor/liquid concentration ratio), AuHS has an intermediate value, and ZnCl2 has the minimum. The values of the Krichevsky parameter for these complexes were calculated: Zn(HS)2 AKr = –103 ± 33 MPa; AuHS AKr = –195 ± 41 MPa; ZnCl2 AKr = –240 ± 8 MPa. Using these values, the values log K_D(V/L)_Zn(HS)₂ = –1.7 (250°C), –1.3 (300°C), –0.8 (350°C); logKD(V/L)AuHS = –3.2 (250°C), –2.4 (300°C), –1.4 (350°C); log KD(V/L)_ZnCl₂ = –4.0 (250°C), –3.0 (300°C), –1.8 (350°C) were obtained. The obtained data were used to calculate the total amount of metals in liquid and vapor, formed during heterogenization (boiling) of a homogeneous fluid containing 1 m NaCl + 0.1 m H2S + 0.01 m HCl The calculations showed that vapor can transport significant amounts of Au only at temperatures above 450°C. For Zn,over the entire temperature range (200–600°C), with the exception of a narrow range near 450°C, the bulk of the metal is distributed into the liquid phase (brine).