Leaching of some lanthanides from phosphogypsum fertilizers by mineral acids

الملخص EN

The phosphate rock contains trace amounts of uranium and lanthanides.

When treating this rock with H2SO4 produces phosphoric acid together with 5 times of its quantity of phosphogypsum (PG) precipitate as a by-product.

The lanthanides in the rock are mostly present in the PG.

After a slight modification of the precipitated PG, some portion of the PG is used as a low-grade phosphate fertilizer (PGF) containing ~ 2% P2O5.

Leaching of different lanthanides from PGF by the mineral acids solutions namely; HCl, H2SO4 and HNO3 is investigated in relation the acid concentration, the mixing time, and acid volume to mass of PGF ratio (L/S) as well as temperature.

It is found that the highest leaching efficiency was obtained using 3.0 M HNO3, L/S = 3.0 and mixing time of 3.0 hr, at room temperature.

The total lanthanides content in the PGF, was found to be about 480 mg/kg.

After three cycle of leaching, the leached out lanthanides from PGF was more than 66 %.