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% P 2 O 5). 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 m 2 /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: (() − − = ln 1 α m kt). 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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The present work aims to study the effect of weathering-produced sands across the area in the weathering damage of sandstones in Madâin Sâlih (Saudi Arabia). Our approach is to investigate some chemical and physical properties of sand samples from the study area. The weathered point in this arid area is Qsar al Bint or Place of the daughter monument in which five different samples have been collected. The analysis of scanning electron microscope images reveals that sand surfaces have different roughness and some surface areas were broken except for the rock samples. According to energy dispersive spectroscopy analysis, the rock samples reveal the presence of Ca, Mg, Na, K, Al and Fe at the surface. Mineralogy study using X-ray diffraction revealed that sandstones are clay-cemented sandstone. Fourier Transform Infrared spectroscopy analysis confirmed that the inorganic binding agent of silica grains is essentially Kaolonite (Al 2 Si 2 O 5 (OH) 4).

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