Influence of drying and calcination on remaining amount and immobile character of titanium on titanium-pillared montmorillonite

Remove of titanium (Ti) from titanium-pillared montmorillont (TIPM) is not expected during its application as adsorbent and photocatalyst, etc. But studies on immobilization of Ti on TIPM are seldom reported. In this work, TIPM was synthesized from TiCl ₄ and Na ⁺-montmorillont (Na ⁺-MMT). Then the prepared TIPM was heated at different temperatures (100, 240 and 450°C) to yield three TIPM samples (TIPM1, TIPM2, and TIPM3). Inductively coupled plasma optical emission spectrometer (ICP-OES) was used to determine the effect of heating temperature on the remaining amount of Ti on TIPMs. A two-step treatment method which is often used in the pretreatment and application of TIPM was developed to investigate the immobile character of Ti on TIPMs. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N ₂ adsorption/desorption isotherm, thermogravimetric analysis and differential scanning calorimetry (TG-DSC) were also used to characterize TIPMs before and after the treatment. The results show that with an increase in heating temperature, the amount of Ti species remained on TIPM decreases gradually and Ti immobilization is strengthened on TIPM. For TIPM3, less than 2% Ti is removed from TIPM3 after the treatment required to simulate the practical conditions of TIPM in its application, while those of TIPM1 and TIPM2 are 6.6% and 8.4%, respectively. The reason may be that when TIPM is heated, Ti species intercalated into MMT become chemically bonded with the framework of MMT and partially migrate into the layer structure, which make Ti immobile on TIPM firmly during the treatment process.