Effect of alkyl chain length of amines on fluorapatite and aluminium phosphates floatabilities

Abstract

Microflotation experiments and zeta potential measurements of fluorapatite, wavellite, and turquoise with the use of alkyl amines and amylopectin were conducted. The highest floatability values were achieved in the presence of dodecylamine, exceeding the floatabilities with octylamine between 30% and 90%. Above their respective isoelectric points, the phosphates reached approximately 100% of floatability with dodecylamine. The strong dependence of surfactant adsorption on hydrocarbon chain length was also evidenced by zeta potential results. In the presence of 1 × 10−3 M dodecylamine solution, the surface charge of the phosphates changes from negative to positive until approximately pH 12, while the octylamine was not able to reverse the surface charges. The fluorapatite and wavellite floatabilities were not significantly affected by the amylopectin; however, in the presence of this depressant, the turquoise floatability, with octylamine as collector, decreases abruptly from 93% to 30%. The greater differences observed between turquoise and the other phosphates can be ascribed to their extremely complex structures, chemical composition and its dissolution in aqueous media. Keywords: Fluorapatite, Wavellite, Turquoise, Floatability, Alkyl amine, Zeta potential