The flotation of -10 μm diameter quartz particles using dodecyltrimethylammonium bromide (DTAB), one of the typical complete ionizable collectors, was carried out at pH 5, 7.4 and 10 by varying the ...DTAB concentration in the presence of 1×10-3 mol·dm-3 KNO3 as a supporting electrolyte. The adsorption density of dodecyltrimethylammonium ions (DTA+) and zeta potential of quartz were also measured in order to analyze the flotation results. The results obtained are summarized as follows. 1. Almost complete flotation is achieved at a surface coverage of DTA+ of the order of several percent on quartz surfaces. 2. The negative zeta potential of quartz decreases with DTAB concentration and changes its sign after passing through an isoelectric point (iep) at some particular DTAB concentration depending upon the pH of the solution. By analyzing the adsorption data at the iep using Stern-Langmuir adsorption isotherm, the free energy change of specific adsorption of DTA+, ΔGsp, was obtained as follows: pH 5, -4.4 kcal·mol-1; pH 7.4, -4.7 kcal·mol-1; pH 10-5.9 kcal·mol-1. 3. The bilayer adsorption of DTA+ occurs simultaneously on top of the first monolayer formed patchwise on the surface even at low surface coverage of DTA+, whereby the quartz surfaces are made hydrophilic and flotation ceases. No flotation occurred at an adsorption density of DTA+ corresponding to θDTA+=100%(corresponding. to the first monolayer coverage of 50%) at pH 10. This contrasts with the result of dodecylammonium acetate (DAA) at pH 9.8, in which quartz showed complete flotation even at an adsorption density of DAA corresponding to a bilayer adsorption. This is in support of the capillary condensation of undissociated dodecylamine at the point of contact between fine grained quartz particles. 4. There was no significant difference in the adsorption and flotation behavior at pH 5 between DTAB and DAA.
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