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Fig. 4. Calculated charge of amphoteric sites of clay minerals (bold lines represent the sum of all species bearing the same type of charge—positive, negative or neutral) compared with measured values of adsorption to these minerals (dotted lines) vs. pH. (a) Ca-montmorillonite; (b) Ca-kaolinite (note different scales compared with montmorillonite in Fig. 4a). Experimental conditions: two replicates; 1.0 mM of desferrioxamine B (DFOB), the ferric complex of DFOB (FOB), ethylenediamine di-o-hydroxyphenylacetic acid (EDDHA), and FeEDDHA; 5 g L–1 clay minerals; pH values 4.0, 6.0, 7.5, 9.0; I = 0.01 M (KClO4).
