Fig. 2. Sorption of iron–cyanide complexes and sulfate on goethite at variable iron–cyanide complex and constant sulfate concentrations at pH 3.5 (a, ferricyanide; b, ferrocyanide). Experimental conditions: c_i ([Fe(CN)₆]) = 0.025 to 0.48 mmol L^-1; c_i = 0.23 mmol L^-1; I = 0.01 M. Regression equations for sorption data: ferricyanide, S = 20.5 - 19.8 exp; ferrocyanide, S = 22.2 - 24.1 exp; sulfate (presence of ferricyanide), S = 15 + 7.91 exp; sulfate (presence of ferrocyanide), S = 7.99 + 21.9 exp.