Fig. 3. (A) Effect of contact time (h) on the sorption of PO₄ and AsO₄ on Andisol-16 at pH 5.0. The oxyanions were added alone (filled symbols) or as a mixture at an initial AsO₄/PO₄ molar ratio of 1 (open symbols). (B) Effect of contact time (h) on rf (rf = sorbed AsO₄/sorbed PO₄ molar ratio).