Fundamentals of oleic acid adsorption on phosphate flotation feed during anionic conditioning

Abstract

Anionic conditioning of phosphate ores prior to fatty acid flotation is a critical step that determines the selectivity, recovery and, hence, the economics of the process. However, the chemical mechanisms operating during this conditioning step are not very well established. In this work, a comprehensive survey of plant practice was conducted. Then, adsorption on flotation feed and francolite were studied under simulated plant conditions. Different adsorption mechanisms were found to be dominant under laboratory and plant conditions. In plant water, there was some physisorption of oleic acid on phosphate flotation feed and franc olite, in addition to chemisorption. However, in distilled water under laboratory conditions, only chemisorption was detected. Fuel oil reduces the residual oleic acid in solution after adsorption, which explains the beneficial role of extender in phosphate flotation. The dissolved species in solution arising from the flotation feed or plant processing water are shown to clearly play a major role in determining the adsorption of oleic acid on the substrates. The study also specifically demonstrates that, for the results to be used commercially, it is important to conduct the tests under plant mixing conditions and with the same plant water chemistry.