As a fundamental study of non-sulfide mineral flotation using dodecylammonium chloride as a collector, the amine adsorption on calcium minerals such as apatite, calcite, wollastonite, scheelite, fluorite, and gypsum was surface-chemically investigated.
An amino acid analyser was successfully used to analyse the concentration of dodecylammonium chloride in solutions and to determine the amine adsorption on the minerals.
The dodecylamine adsorption was remarkable in alkaline solution for all calcium minerals used in the experiments and showed the maximum amount at the pH region around 10.6 which corresponds to the pK
aof the dodecylamine.It was considered that the existence of neutral amine molecule in solution contributed to the marked increase in amine adsorption at around pH 10.6.
The pH dependence of surface tension for amine solutions was investigated. The minimum value in the surface tension was found also at pH 10.6. Accordingly, the dodecylamine adsorption at the liquid-air interface was closely related to its adsorption at the solid-liquid interface.
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