Fig. 3. Changes in -potential of pure and PGA-coated goethite during phosphate sorption (I = 0.01 M KNO₃, pH = 5). Note that x-axis is log scale. Error bars indicating the standard error of 10 replicate measurements are within the symbol size. Initial -potentials of the samples (no phosphate contact) are presented in Table 1. Figures after ‘G’ refer to the rounded C content of the sample in milligram C per gram.