Fig. 3. Effects of particle size, pH, and time on (a) Mg concentration, (b) B/Mg molar ratio of release, (c) Si concentration, and (d) K concentration for Morris illite. The cation-exchange capacity (CEC) was 30.2 and 18.5 cmmol(+) kg^–1 for the <2- and 2- to 20-µm fractions of Morris illite, respectively.