GB793801A - Process for the recovery of values from phosphate rock - Google Patents

Abstract

A fertilizer containing dicalcium phosphate is obtained from phosphate rock containing rare earth compounds and fluorine compounds by reacting with 14-62 per cent sulphuric acid to obtain a solution containing monocalcium phosphate, fluorine and rare earth compounds, separating the precipitated calcium sulphate, adding calcium carbonate or lime before or after heating to 85 DEG C, to give a P2O5; Ca weight ratio of 10 : 1 to 4 : 1, allowing the solution to stand, if necessary, to insolubilize a fluorine-rare earth compound, separating said compound, if desired, and adding a further quantity of calcium carbonate or lime to precipitate dicalcium phosphate. Preferably hydrated or another form of reactive silica is arranged to be present during the acid treatment: it is then not necessary for the solution to stand to precipitate the fluorine compound. If necessary due to deficiency in the phosphate rock, a rare earth containing ore such as monazite may be added prior to acidulation or a rare earth compound in solution may be added during or after acidulation, a sulphate, e.g., calcium sulphate may be added to the solution from which the fluorine compound is precipitated and sufficient calcium and aluminium to effect complete removal of the fluorine compound should also be present. In the acidulation, preferably 80 per cent of the sulphuric acid necessary to convert the P2O5 content of the rock to H3PO4 is used. In an example details are given of a process using silica and pH and other conditions are specified. The fluorine-rare earth compound which may be present in the product may contain F, Ca, p SO4, Al, Si, Sr, water and rare earths; e.g., La and Y, and when monazite is added (v.s.) Ce and Yb may also be present: Zr has also been observed. U.S.A. Specifications 1,809,473, 2,013,970, and 2,164,627 are referred to.