Thermochemistry of triboactivated natural and NH4-exchanged clinoptilolite mixed with Tunisian apatite

Mechanical tribo- and thermo-chemical methods applied for remodeling phosphate raw materials manifest a number of advantages over the conventional technologies. They are related to the reduction of soil contamination and minimization of the released gas emissions in the environment and generate solid wastes. In this work, natural and NH₄-exchanged clinoptilolite are used for increasing the transition of P₂O₅ into assimilated by plants form during tribochemical activation (TCA). Better nutrients assimilation as well as green production could be achieved by applying such a treatment based on the ion-exchange reactions taking place in the soil. The occurring upon TCA structural changes and phase transformations of the used Tunisian phosphorite, natural and NH₄-exchanged clinoptilolite as well as their mixtures are investigated by means of X-ray powder diffraction, IR spectroscopy, and thermal analysis. The thermal method gives evidence for solid phase reactions and increased reactivity as a result of the tribochemical treatment. This treatment leads also to minimization of the size of crystallites, amorfization of the samples, and increasing amount of hydroxyl and carbonate ions in the apatite structure. Treated samples are highly soluble. In addition, conditions for almost complete solubility of P₂O₅ were found. This study shows that some of the produced compositions are suitable for fertilizers or soil conditioners.