In the present study, porous structure of raw
and calcined phosphate ore particles was examined. The specific surface area
and the pore volume were determined by nitrogen adsorption. Raw particles and
calcined ores were leached using dilute phosphoric acid solution (4% P2O5).
In all cases, the ESEM (Environmental Scanning Electron
Microscopy) observations show
that the grain of phosphate holds its shape ovoidale. The sample heated at 780?C presented
the lowest specific surface area 0.6 m2/g at each reaction time, and
the unreacted phases were analysed using XRD, FT-IR, Nitrogen adsorption and
ESEM observations. The selective leaching curves were evaluated in order to
test the validity of kinetics models. A mathematical model in the following
form was applied.The dissolution of the two samples (raw and
calcined phosphate) has been observed to take place in two steps: the first
being fast and the second being slow.
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