Processing Florida dolomitic phosphate pebble in a double reverse fine flotation process

Abstract

A double reverse fine flotation process was employed to process Florida high-dolomitic phosphate pebbles. In this study, the dolomitic phosphate pebble sample was ground to −150 μm (100 mesh) for liberating the phosphate to achieve the maximum phosphate grade and recovery. The selective fatty-acid-type collector for dolomite and H3PO4/H2SO4, in the ratio of 2:1, as both phosphate depressant and pH modifier, were used to effectively float dolomite at pH 5 to 5.5. The dolomite flotation sink product, rich in phosphate, was sized at 37 μm (400 mesh). The oversized fraction was further subjected to a siliceous flotation using a fatty-acid amine collector to reject silica. The amine flotation sink product was combined with the undersized fraction of dolomite flotation sink product to form a composite phosphate concentrate. The final composite phosphate concentrate had the grade of 31.6% P2O5 and 0.8% MgO, with a 92% P2O5 recovery, from the fine feed containing 26.7% P2O5 and 2.2% MgO. The effects of pH and reagent dosages on the efficiency of dolomite separation were studied. Two fatty-acid-type collectors were evaluated by flotation rates. This double reverse fine flotation process was also used effectively in processing Florida high dolomitic phosphate pebble samples obtained from various locations.