MIXED ADSORPTION OF IONIC AND NONIONIC SURFACTANTS ON CALCIUM-CARBONATE

The adsorption of dodecylamine hydrochloride (DDAHC) and polyoxyethyle ne (20) sorbitan monolaurate (Tween-20) from their single aqueous solu tions and from DDAHC-Tween-20 mixed binary solutions on calcium carbon ate at 20-degrees-C has been investigated. The results show that indiv idual cationic surfactants can be adsorbed on the negatively charged s urface of calcium carbonate, leading to a change in the sign of the ze ta potential of the calcium carbonate particles to positive. The adsor ption of non-ionic surfactants reduces the zeta potential to zero. How ever, no significant adsorption of DDAHC from mixed binary DDAHC-Tween -20 solutions can be detected. The adsorption of Tween-20 from mixed b inary solutions decreases when the concentration of DDAHC in the mixtu re increases. Intensive flocculation of the calcium carbonate particle s is found in all the mixed solutions.