INFLUENCE OF THE PRECURSOR AND THE TEMPERATURE OF SYNTHESIS ON THE STRUCTURE OF SAPONITE

Abstract

Several procedures for hydrothermal synthesis of saponite can be found in the literature. They differ in terms of the preparation conditions of the precursor and of the synthesis temperature. The objective of the present study was to investigate how these two parameters influence the structure of the final synthesis product. The precursor was prepared from Mg(NO3)2, Al(NO3)3, and Na4SiO4 in three different ways: as a gel, a dried gel, and a calcined gel. The influence of the synthesis temperature on the structure of saponite was investigated in the range 90–200°C. The results showed that the use of a calcined precursor yielded a single mineral phase, saponite, with up to 90% aluminum in tetrahedral configuration. In comparison, the use of a gel precursor resulted in a product with only 60% aluminum in the tetrahedral configuration. The synthesis temperature had no significant effect on the saponite structure. The reported synthesis method showed the possibility of obtaining saponite with superior characteristics, in terms of crystallinity, surface acidity, and thermal stability compared to the natural mineral, even at 90°C, and thus with greater potential for industrial application.