Abstract
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.
Highlights
Phosphate rocks are complex raw materials and are mainly used in the manufacture of phosphate fertilizers
Sardisco et al [1] investigated the digestion of low-grade phosphate ores using phosphoric acid
Several studies [2,3,4,5,6,7,8], have shown that the calcium carbonate content of phosphate rocks can be reduced by calcinations or by acid leaching Ben Brahim et al [9] this can affect the particle’s texture
Summary
Phosphate rocks are complex raw materials and are mainly used in the manufacture of phosphate fertilizers. The composition of this rock varied from ore deposit to another and cannot be used directly as fertilizers because of their solubility in humid soil. Several studies [2,3,4,5,6,7,8], have shown that the calcium carbonate content of phosphate rocks can be reduced by calcinations or by acid leaching Ben Brahim et al [9] this can affect the particle’s texture. According to Sengul et al [6], calcinations may lead to almost complete disposal of carbonates present in the phosphate rock
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