Mechanochemical intercalation of low reactivity kaolinite

• 2 h co-grinding of low reactivity kaolinite with urea caused 100% intercalation.
• 12% intercalation of low reactivity kaolinite was achieved in aqueous urea solution.
• 1/4 h co-grinding resulted in 40% intercalation without any amorphization.
• Longer grinding caused higher intercalation rate but significant amorphization.

Complete urea-intercalation of a low reactivity kaolinite from Birdwood has been carried out by co-grinding with urea in the absence of water (mechanochemical intercalation). The effectiveness of mechanochemical intercalation was compared to solution intercalation by X-ray diffraction (XRD), thermal analysis (TG, DTG), diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy and scanning electron microscopy (SEM). In aqueous solution of urea the Birdwood kaolinite was intercalated with difficulty and only 12% intercalation was achieved. After 2 h of co-grinding with solid urea, complete (100%) intercalation was attained. The possible explanation of complete intercalation is that co-grinding of Birdwood kaolin with solid urea can remove the high-defect kaolinite coating, which prevents the intercalation of the low-defect kaolinite particles. The mechanochemical treatment increased the degree of intercalation and in parallel reduced the amount of the crystalline kaolinite phase.