Simplified synthesis of silicophosphate materials using an activated metakaolin as a natural source of active silica

• Published in: Applied clay science 2018-06, Vol.158, p.169-176
• Main Authors: Khabbouchi, Mohamed, Hosni, Khaled, Mezni, Mohamed, Srasra, Ezzeddine
• Format: Article
• Language: English
• Subjects: Acid activation; Interaction; Metakaolin; Phosphoric acid; Silicophosphate
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2018.03.027

In this study, silicophosphate phase was synthesized from an activated metakaolin as a natural source of silica using a simple and new method. The preparation consists to react the activated metakaolin with phosphoric acid at high temperature. The structure of activated metakaolin–H3PO4 mixtures (A-MKP) with various percentages of P2O5 (15–55%wt) was investigated by X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM). The XRD results showed the formation of an AlSi2(PO4)3 phase for the A-MKP mixture containing 15 wt% P2O5 and the Si5O(PO4)6 phase for the A-MKP mixtures containing 25 and 35 wt% P2O5. While for the mixture containing 55 wt% P2O5, two phases have been formed; Si5O(PO4)6 and SiP2O7. These results were confirmed by 31P and 29Si MAS-NMR techniques. •Silicophosphate synthesis is possible using natural source of active silica.•Activated metakaolin is a potential material for the synthesis of silicophosphate.•Si5O(PO4)6 was obtained for the mixture contains 25, 35 wt% P2O5 regardless of the heat treating temperature.•The SiP2O7 phase was formed for the mixture wt% 55 P2O5 content since 500 °C.