Comparative study of the adsorption properties of several micropollutants on natural phosphate from Tahoua/Niger and activated carbon based on Hyphaene thebaica shells

This study compares the adsorption properties of dyes on natural phosphate from Tahoua and activated carbon. The phosphate used is natural phosphate powder from Tahoua calcined at 850°C for two hours to increase the orthophosphate (P₂O₅) content. The activated carbons used were obtained from the shell of the Hyphaene thebaica (HT) nut by chemical activation with orthophosphoric acid (H₃PO₄) at 10% and 40% at a pyrolysis temperature of 450°C with an isothermal plateau of 1 hour 30 minutes. The shell was first characterized. The moisture content obtained was 5.002 %, the ash content was 5.828 % and the volatile matter content (loss on ignition) was 98.9587 %. The activated carbons produced (ACEs) have mass yields of around 42.85 % and 47.05 % when impregnated at 10% and 40%, respectively. Next, tests were conducted to determine the adsorption capacities of diiodine (I₂), methylene blue (MB), and methyl orange (MO) on the activated carbons produced (ACPs) and on natural phosphate from Tahoua (NPT). The results obtained show that the adsorption equilibrium time for methyl orange is 40 minutes and around 25 minutes for the developed activated carbon (CAE) and Tahoua natural phosphate (PNT), respectively. Finally, the surface functions and pH at zero charge point were determined using the Boehm method and the first bisector method, respectively. The surface functions of CAEs are acidic in nature and the pH at zero charge point is below neutrality. For Tahoua natural phosphate (PNT), the pH at zero charge point is slightly above neutrality.