adsorption isotherm data from [BL73], site protolysis reference GS84 (average values from literature of various iron oxides); FITEQL/MICROQL; 20+-0.5°C; original equation: »Fe-OH + H3PO4 = »Fe-HPO4<1-> + H2O + H<1+> with log K = 2.06, formation constant in aqueous solution: PO4<3-> + 3H<1+> = H3PO4 logK = 21.702 [GFFGN03]