Caractérisation physico-chimique du gypse synthétisé et du phosphogypse

Abstract

The phosphogypsum is a waste sub-product of the production of the phosphoric acid, and a

basic component in the manufacture of modern manures. It allows the concentration of the impurities

of the basic ore, and often poses problems of storage and safeguarding of the environment. On the

other hand, this gypsum can be used as raw materialto manufacture plaster after purification.

Our work was focused on a comparative study of thephysicochemical characterisatization of

two synthesized samples referred respectively GSHCa, GSNaCa and the phosphogypsum which

result of the attack of the ore of phosphate by thesulphuric acid. The synthesized gypsum (CaSO

4

2H

2O) was elaborated starting from calcium nitrate Ca(NO3)2 4H

2O, the sulphuric acid (H2SO4) or

sulphate sodium (Na

2SO4

). The studied products were characterized by various physicochemical

techniques and analysis (granulometry, X-Ray Diffraction (XRD), Infra Red, X-ray fluorescence,

Scanning Electron Microscopy (SEM) and DifferentialScanning Calorimeter (DSC).

The results obtained show that the synthesized samples and the phosphogypsum are made

up mainly of gypsum (CaSO

4, 2H2

O). Thermal treatment under dry conditions of thesesamples led to

the formation of semi-hydrated (CaSO4, ½H 2O) at 200°C and anhydrous CaSO 4II at 450°C and

CaSO4I at 1200°C.