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Electrokinetic Flotation of Paint Solids in a Continuous Flow Tank

Julie Q. Shang and Y. (Bruce) Xu. Civil and Environmental Engineering, University of Western Ontario, SEB3082, Western Road, London, ON N6A5B9, Canada

A study was carried out to explore alternative solutions for separating paint solids from circulating water in paint operation systems. Electrokinetic flotation (EKF hereafter) was tested for removing suspended paint solids from water. The EKF is based on principles of electrostatics and electrochemistry, including (1) directional movement of electrically charged particles in an electric field (electrophoresis and dielectrophoresis), (2) oxygen and hydrogen gas bubbles generated by an electric current through conducting electrodes (electrolysis) and (3) flocculation generated by changes of surface charges of suspended solids under the influence of the electric filed. As a result, when a DC field is applied via submerged electrodes in the circulating water with suspended paint solids, electrophoresis and dielectrophoresis generates movement of paint particles, the electrical field generates flocculation of paint solids to form larger flocs, and electrolysis generates gas bubbles at the both cathode and anode that carry paint particles and flocs to the water surface. The influencing parameters of EKF treatment include the water electrical conductivity (EC), electrode type and layout, type of paints, paint solid loading, and applied DC current. The results showed that the EKF process generated quick floatation of paint particles without using any flocculants. The suspended solids (SS) in the sludge water are significantly reduced along with significant color and COD removal. This paper presents the results of a study using a lab-scale continuous flow tank that simulates the paint spray operation in an automatic assembly plant.