ELECTROKINETIC CHARACTERISTICS OF FUSED QUARTZ IN SOLUTIONS OF 1 1-ELECTROLYTES, 2/1-ELECTROLYTES, AND 3/1-ELECTROLYTES/

The electrokinetic characteristics of silicon oxide were investigated on the model system - a plane-parallel capillary in solutions of chlor ides containing singly-(H+, Na+, Ca+), doubly-(Ba2+), and triply-(La3) charged counterions - in wide ranges of pH and concentrations. It wa s discovered that the isoelectric point (IEP) of the investigated sili con oxide coincides with that usually reported in literature and corre sponds to pH 2 in the absence of specific adsorption. The zeta-pH depe ndences for 1:1 and 2:1 electrolytes are linear in the first approxima tion (up to pH 6); their slopes decrease with an increase in concentra tion of the electrolyte and counterion charge in accordance with theor etical concepts. The specific adsorption of cesium ions was discovered , which lead to a shift in IEP to pH 3.3 in the presence of 0.1 M CsCl solution. The specific adsorption of lanthanum ions increases with th e surface charge, thus resulting in the appearance of the positive ran ge of electrokinetic potential at pH > 3.3 in the presence of 0.1 g-eq uiv/l LaCl3 solution. It was established that the specific surface con ductivity on the SiO2 surface is observed only in dilute solutions (c less than or equal to 10(-4) M) and equals about 10(-8) Omega(-1). A c omparison of the values of K-S with those calculated by Bikerman's equ ations (at psi>(1) = zeta) indicates that the experimental values exce ed the calculated ones by more than an order of magnitude. The results of the electrokinetic measurements were used to calculate the charge of a diffuse layer, th constants of the dissociation of surface groups , the adsorption potentials of potential-determining and specifically sorbing ions, and the dependences of the surface potential on pH and t he concentration of 1:1 electrolyte.