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Organic dyes and colouring textile agents are persistent pollutant materials that are difficult to decompose by microbiological treatment processes. Their oxidation through photocatalysis is an alternative way to prevent contamination of the environment. In this work, calcium deficient hydroxyapatite (HAP) was synthesized and doped with different amounts of titanium. Its performance in photocatalytic degradation of -methylene blue dye (MB) was then demonstrated. The main parameters which govern the photocatalytic treatment efficiency, such as doped titanium amount, pH, initial concentration of MB, weight of catalyst added to solution, UV-irradiation period and bubbling oxygen-have been-investigated. Photodegradation of MB is found to be effective with HAP/11 wt. %Ti in oxygenated medium. However, pH has no significant effect on the yield of discoloration.

In the present study, nano-calcium carbonate (NCC) was prepared from phosphogypsum (PG) as waste material from phosphate industry using Na2CO3 and Al(HCO3)3 as carbonates precursors. The physicochemical characteristics of the prepared nano-calcite CaCO3 were studied using various methods, including X-ray diffraction (XRD), scanning electron microscope (SEM), chemical analysis, plasma spectrometry with inductive coupling (ICP), as well as the Bernard calcimeter. The size of the pure nanocalcite particles produced differs according to the nature of the carbonate precursor; they are 51 nm and 68 with the use of sodium carbonate and aluminum hydrogen carbonate, respectively.