Recrystallization of magadiite into offretite in the presence of tetramethylammonium cations

BACKGROUND: This study was aimed at investigating the recrystallization of magadiite into offretite in the presence of tetra methylammonium cations (TMA). The offretite was characterized by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, N-2 adsorption analysis, thermogravimetry and differential thermal analysis. The influence of key reaction parameters on the formation of offretite, including reaction time, TMA cations, potassium cations and the SiO2/Al2O3 reactant ratio, were examined. RESULTS: Well-crystallized offretite, which was composed of agglomerated samples, was prepared from a dispersion with the molar composition: 3.6 K2O: 3.6 Na2O: 1.0 Al2O3: 6.5 SiO2: 320 H2O: 1.5 TMA(+) by heating at 140 degrees C for 3 days. The structure of offretite collapsed when the temperature rose above 1000 degrees C. The organic template was removed when the sample was calcined at 550 degrees C for 10 h. CONCLUSION: Magadiite has been used to synthesize offretite with a high purity and well crystallized in the presence of tetramethylammonium cations. The results of the present study indicate the feasibility of a synthetic route to offretite through recrystallization of magadiite in the presence of tetramethylammonium cations. (C) 2009 Society of Chemical Industry