Fig. 3. Sorption of iron–cyanide complexes and sulfate on goethite at variable sulfate and constant iron–cyanide complex concentrations at pH 3.5 (a, ferricyanide; b, ferrocyanide). Experimental conditions: c_i = 0.05 to 0.9 mmol L^-1; c_i = 0.24 mmol L^-1; I = 0.01 M. Regression equations for sorption data: ferricyanide, S = 18.5 - 18.3 exp; ferrocyanide, S = 17.5 - 1.5 exp; sulfate (presence of ferricyanide), S = 6.9 + 6.32 exp; sulfate (presence of ferrocyanide), S = 3.39 - 4.72 exp.