Direct flotation of low-grade Moroccan phosphate ores: a preliminary micro-flotation study to develop new beneficiation routes

Moroccan high-grade phosphate has so far always been upgraded by reverse flotation. Within a major project to go back to the deposits considered as sterile or low grade, this preliminary study was conducted in a micro-flotation cell to find new routes for their beneficiation by direct flotation. Three collectors, alone and combined to modifiers, were evaluated for a potential direct flotation of apatite from calcite and quartz minerals. The obtained results demonstrated that sodium oleate (NaOl) and ATRAC 50S have an affinity toward both apatite and calcite, but not quartz. In the opposite, Phospholan PE 169 has an affinity toward the three minerals even when it is combined with depressants. NaOl and ATRAC 50S flotation selectivity of apatite can be improved by their combination at dosages of 5.56 to 3.7 mg/L sodium alginate or CMC at pH 9.5. Apatite recovery exceeded 95%, and calcite buoyancy decreased from about 50% to only 19.20% and 19.39% using sodium alginate and CMC as prior depressants, respectively. On the other hand, when ethylene glycol was added as a synergist with the collector ATRAC 50S and sodium alginate as a depressant, 78.10% apatite recovery was obtained with 23.78% and 1.47% for calcite and quartz, respectively. These results were correlated to adsorption tests, zeta potential measurements, and FTIR analysis.