Fig. 3. The (a) pH and (b) buffer capacity of arsenated kaolinite determined by addition of KOH (0.05 M) to 0.25 g substrate suspended in 50 mL nutrient solution (same as that used in desorption experiment). KOH (0.05 M) was added in small increments (0.02 mL when dE was <0.0004 mV s^–1) to the suspensions by a pH-stat apparatus.