model A: presence of B and MH species; S/L ratio = 3 g/L (0.4 mM ini. PO4 conc., <0.001, 0.05, 0.10, 0.30, 0.40, 0.50 M NaNO3); S/L ratio = 3 - 9 g/L (0.4 - 0.8 mM ini. PO4 conc., 0.5 M NaNO3); »Fe-OH<0.5-> + PO4<3-> + 2 H<1+> = »Fe-O<-1/2+Δz0>-PO2(OH)<Δz1> + H2O, Δz0 = 0.32±0.008, Δz1 = -1.32±0.008)