Preparation of porous material from talc by mechanochemical treatment and subsequent leaching

Synthesis of porous silica via mechanochemical treatment of talc and subsequent acid leaching was investigated by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and N₂ adsorption techniques. Raw talc was ground for different times and then leached with 4 M hydrochloric acid (HCl) at 80 °C. Grinding for 6 h and subsequent leaching for 2 h of raw talc produced the porous silica with a specific surface area of 133 m²/g and total pore volume of 0.22 ml/g. The increase in specific surface area (S_BET) of the porous silica reflected the formation of micropores of 1.21.8 nm and mesopores of 4.05.5 nm in diameter inside the porous structure. The number of micropores decreased with prolonged leaching time, which can be attributed to a condensation reaction. The characteristic of hysteresis loop indicated mainly slit-shaped pores. The apparent activation energy for the leaching process was calculated to be about 21.6 kJ/mol, indicating that the kinetic process of talc leaching was the diffusion-controlled reaction. Mechanochemical treatment may promote the amorphization of talc, being greatly favorable to the subsequent leaching.