The effects of radiofrequency electromagnetic radiation on the adhesion behavior of aqueous suspensions

The effect of radiofrequency treatment on the adhesion behavior of amidine and carboxylated polystyrene latexes was investigated. The isoelectric poin ts pH(IEP) of copper and zinc were initially measured as 9.4 and 9.5, respe ctively, using a technique proposed by N. Kallay, Z. Torbic, M. Golic, and E. Matijevic [J. Phys. Chem. 95, 7028 (1991)] based on the attachment of ch arged colloids to metallic surfaces in an aqueous medium. Statistical analy sis showed that the technique was repeatable with a coefficient of variatio n less than 6% and an accuracy greater than 95%. The effect of a radiofrequ ency signal (27 MHz) on adhesion behavior was evaluated and it was found th at there was reduced attachment at pH values when the colloid and metallic surface were oppositely charged and enhanced attachment between similarly c harged particles. It is proposed that this is due to a reduction in the sur face potential of the charged particles due to thickening of the adsorbed l ayer by hydrogen and hydroxyl ions. (C) 2000 Academic Press.