THE STREAMING CURRENT DETECTOR - A COMPARISON WITH CONVENTIONAL ELECTROKINETIC TECHNIQUES

The streaming current detector (SCD) is an instrument showing increasing application for the in-situ monitoring of colloidal flocculation processes. The mechanism of operation of the SCD is examined by the use of well characterized surfaces and dispersed colloidal particles. The response of the instrument in the presence of various electrolytes and with the addition of colloids of known electrokinetic properties indicates that the apparatus is measuring a quantity that shows contributions from the charge on both the walls and piston of the apparatus and from colloidal material associated with the surfaces. Analysis of the output of the instrument in terms of the magnitude of the current is poorly accounted for by theory. The efficiency of adsorption of colloids, polymers and other simple reagents to the walls and/or piston and the ease of removal of these substrates was found to be critical to the response of the instrument. Streaming potential measurements were used to obtain reference zeta potentials.