Apatite is an important mineral resource that plays an important role in many fields such as production of phosphoric acid and phosphate fertilizer.
Flotation technology is the most important method for beneficiation of apatite, and anionic fatty acid and their salt collectors are most-commonly used collectors in the direct flotation of phosphate ores.
Anionic fatty acid collectors have been proven both theoretically and in plant practice to be highly efficient in the flotation of apatite. Under basic conditions (pH10), fatty acid is saponified, which results in a negatively charged carboxylate ion. The negatively charged carboxylate ion then reacts with calcium on the apatite surface to form calcium carboxylate. This chemisorption method is generally considered to be the primary method of fatty acid adsorption onto the apatite surface in alkaline conditions.
Although a flotation mechanism of apatite using sodium oleate as a collector has been studied by several investigators, the flotation mechanism, reaction processes and associated surface reaction products still remain controversial.
Jong Kwang Sok, a researcher at the Faculty of Mining Engineering, synthesized a new collector for apatite flotation by a series of reactions including sulfation and amidation, using sodium oleate as raw material. Then, he carried out an investigation on the flotation behavior and mechanism of oleic acid amide onto apatite by micro flotation tests, zeta potential measurements, and XPS analysis.
The flotation results showed that mixing sodium oleate and oleic acid amide could float apatite well in a pH range of 7.5–9.5 even at the acid number of 120 mgKOH/g and it exhibited better collecting capacity on apatite than a sodium oleate collector. The XPS analysis data correlated with zeta potential showed that the zeta potential of apatite became more negatively charged at around pH8.5 and the oleic ions (C17H33COO−, (C17H33COO)22− and C17H33CONH−) in the mixing collector suspension could get chemisorbed by Ca-O bond formation on the apatite surface, and that the molecular (C17H33CONH2) and micelles ((C17H33CONH2)m) in oleic acid amide could get chemisorbed on the apatite surface by Ca-O or Ca-N bond formation.
You can find more information about this in his paper “Flotation mechanism of oleic acid amide on apatite” published in the SCI Journal “Colloids and Surfaces A: Physicochemical and Engineering Aspects”.
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