Fig. 6. (a) Kinetics of As(V) adsorption on goethite as a function of pH, (b) Kinetics of As(V) adsorption alone at pH 9 and 10 and at pH 8 in the presence of 0.10 and 1.0 mM silicic acid. As(V) = 0.10 mM, ionic strength (I) = 0.01 M, and goethite suspension of 1.0 g L^-1.