Kationische Tenside als Sammler bei der Flotation / Cationic surfactants as flotation collectors

Abstract

Three cationic surfactants were prepared by condensing 1-chlorododecane with stoichiometric amounts of either mono-, di- or triethanol amine. They were: N-dodecyl-N-monoethanol ammonium chloride, N-dodecyl-N,N-diethanol ammonium chloride and N-dodecyl-N,N,N-triethanol ammonium chloride. The surface and thermodynamic properties of these surfactants were examined to find the relationship between the structure of the hydrophilic portions of such compounds and their efficiency as collectors in the flotation process. The properties examined were surface excess concentration (Γ max ), critical micelle concentration (c.m.c.), free energy of micellization (ΔG0 mic ) and adsorption (ΔG0 ads, ) in addition to the surface tension (y c.m.c. ) at c.m.c., effectiveness (Π c.m.c. ) and efficiency (pC 20 ) of a surfactant to reduce the surface tension of water. The effect of temperature on surface and themodynamic properties were also checked at 25, 35, 45 and 55°C The results showed that the number of the hydrophilic portions of the prepared cationic surfactants play a major role in determining their thermodynamic properties. Each of Γ max , ΔG0 mic . and ΔG0 ads were found to increase with increasing the number of ethanol groups substituted on the nitrogen atom from one to three, while the c.m.c. and surface area occupied by one molecule (A max ) were decreased. The results suggest that the surfactant N-dodecyl-N,N,N-triethanol ammonium chloride may be preferable as a flotation collector than the other surfactants with fewer ethanol groups.