Fig. 2. Adsorption isotherms for PO₄ on boehmite, ferrihydrite, and mixed boehmite/ferrihydrite (1:1 mass basis) at pH 6.0 ± 0.1, along with Freundlich isotherm models as solid lines for the June 2002 data. Data for the mixed mineral isotherm for June 2002 are fit using a mass weighted (1:1) linear combination of Freundlich models from the single-mineral systems (dashed line, see text). Some additional data collected in October 2002 for PO₄ adsorbed on ferrihydrite and mixed-mineral systems are shown. q_f, q_m, q_b, denote the Freundlich model predicted PO₄ adsorption for ferrihydrite (f), mineral mixtures (m), and boehmite (b) as a function of dissolved PO₄ concentration (c).