in the study: »Si-(OH)2; logarithmic deprotonation constant of the silica surface was assumed to be 6.94 in accordance with the literature; total conc. of surface sites [»Si-(OH)2]tot = 0.51 mM [O95b]; »Si-(OH)2 is a hypothetical average surface adsorption site: »Si-(OH)2 = »SiO2H<1-> + H<1+>