Earliest Results in the Use of Activated Composite Membranes for the Transport of Silver Ions from Aqueous Solutions

Table 1

Values of global equilibrium constants for silver complexation under different stripping conditions [20].

Stripping solution constituent^a	Silver complex		Presence of Ag in the stripping solution^b
NH3	Ag(NH3)^2+	7.22	−
EDTA (Y)	AgY^3−	5.84	−
HNO3	—	—	−
NaSCN		10.00	−
tu		13.41	+

Chemical conditions: NH₃ = ammonia buffer (/NH₃ 0.5 mol L⁻¹), pH 9.4; EDTA (Y) = ethylenediaminetetraacetic acid 0.1 mol L⁻¹ in tris (tris(hydroxymethyl)aminomethane), 0.1 mol L⁻¹ pH 9.6; HNO₃ 2 mol L⁻¹; NaSCN 0.5 mol L⁻¹; tu = thiourea 0.3 mol L⁻¹ in sulfuric acid 2 mol L⁻¹.
^bIt was considered positive when its concentration in the receiving phase after three hours of experimentation was higher than the detection limit (2.40 × 10⁻⁷ mol L⁻¹).