Abstract
The flotation of-10μm diameter hematite particles using dodecyltrimethylammonium bromide (DTAB) was carried out at various pH 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 were incorporated in order to analyze the flotation results. The results obtained are summarized as follows.1. The adsorption density of DTA+ increases linearly with DTAB equilibrium concentration in the range of 1×10-4 to 1×10-2 mol·drri-3 at various pH values, such as 5, 7.4, 9, 10 and 11. This behavior is similar to that of quartz-DTAB system at pH 5. The higher the pH, the larger the adsorption density at a given DTAB concentration.2. The free energy change of specific adsorption, ΔGsp, of DTA+ on hematite, calculated at isoelectric points by using Stern-Langmuir adsorption isotherm, was obtained to be-4.4-5 kcal·mol-1 in the range of pH 7-11. These values of ΔGsp are close in magnitude to those of quartz-DTAB system at pH 5 and 7.4.3. Flotation recovery of more than 90% is achieved at 2% surface coverage (θ) of DTA+ at pH 7.4 and 10. The floatability decreases when θ reaches 4-5 and 30% at pH 7.4 and 10, respectively.4. No steady flotation is obtained at pH 5, where hematite is positively charged, in spite of the fact that DTA+ adsorption (θ-5%) takes place.
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