Abstract
Depressants are essential additives, to increase the separation selectivity, in the reverse flotation of phosphate by fatty acid collectors. In the current study, the rice starch is used, as a phosphate depressant, in the reverse flotation of calcareous phosphate by oleic acid. The operating parameters affecting the starch depressing action such as: collector dosage, pH and starch dosage are studied using statistical design of experiments. The design analysis showed that the starch dose has the most significant effect on the concentrate grade. A concentrate containing 30.6% P2O5 with a recovery of 91.6% was achieved at the optimum values of studied parameters, i.e., 4, 4kg/t, and 4kg/t for pH, starch dosage, and collector dosage, respectively. The FTIR analysis was used to characterize the interaction between the collector and starch as well as the starch and phosphate ore. It was found that the oleic - ore interaction was chemical, whereas the starch interaction with either phosphate or oleic acid was physical.