Abstract :
[en] Our study aims to decompose phosphogypsum (PG), mainly composed of CaSO4.2H2O, by reduction in an acidic medium. We evaluated the decomposition of PG by various reaction mechanisms.
Sulfate ions from the acid digestion of PG are reduced to sulfide by the hydrogen gas produced
in the solution by hydrochloric attack of the metal iron. The solid residues obtained have been
determined and monitored by X-Ray Diffraction, Fourier-Transform Infrared spectroscopy and
Ultraviolet-visible spectroscopy. The microstructure of residues was observed by scanning electron
microscope (SEM). The results show that hydrogen gas formed by hydrochloric acid attack of iron
reduces the sulfur from S(VI) to S(-II). CaSO4.2H2O, insoluble in water, gives a residue containing
CaS, which is only sparingly soluble in water. The residue also contains anhydrite, bassanite and
ferrous chloride. The monitoring of the quantities of residue obtained under varying experimental
conditions (temperature, attack time, mass of iron and PG and volume of acid on PG) and volume
of HCl showed that the amounts of residue obtained are less than 32% of mass. When the volume
of the HCl added increases, the obtained mass of the solid residue decreases sharply. The residue
stabilizes at 10% of mass when the volume of HCl added is higher than that required to attack
metal iron.
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