Enrichment of low-grade phosphate coarse particles by froth-flotation process, at the Kef-Eddur washing plant, Tunisia

Low-grade phosphate ore with impurities is becoming the primary source for phosphate; thus, more efficient methods are required for upgrading. Flotation is the predominant method for the processing of low-grade phosphate ore. The phosphate coarse particles of Kef-Eddur washing plant (southern Tunisia), having a low-grade phosphate, were studied to improve the recovery of phosphate flotation, lost during the washing process. The results of the chemical analysis of phosphate samples showed a grade of 12.51 % P2O5 with a carbonation rate of 2.9 %. Mineralogical study of a sample by X-ray diffraction showed the presence of the following minerals: the carbonate-fluorapatite, calcite, quartz, clinoptilolite (zeolite), and dolomite. Testing of dry grinding showed that the work index is of 10.39 kWh/t achieving an economical consumption of energy. Milling tests having high values of recovery are accompanied by a raised rate of carbonation, non-tolerable to enter the flotation circuits, dictated an intermediate determination of parameters simultaneously providing considerable recovery while having a tolerable rate of carbonation. Optimizing the operating parameters of flotation (3 scavengers, 320 g/t ester and 340 g/t amine), specifications of the best flow-sheet obtained are as follows: crushing 10 mm and ball milling (T = 5.5 min, Cs = 45 %, Rc = 3/1, Vbr = 60 tr/min). Attrition released during the first 10 min, second attrition of the same fraction for 20 min and reverse flotation render a grade of 26.80 % P2O5. The results of Kef-Eddur enrichment tests present an increase of 12.51 to 26.80 % P2O5. Application of flotation process is an alternative for this phosphate type.