Purification of montmorillonite and the influence of the purification method on textural properties

Abstract This work aimed to investigate the effect of a hybrid chemico-physical purification method on swelling properties of montmorillonite interlayer in bentonite samples from China. This method assumes a chemical treatment with NaOH with subsequent physical size-fractionation. X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), and Fourier-Transform infrared (FTIR) spectroscopy methods were applied to examine raw and purified samples. In comparison with the untreated samples, feldspar, mordenite, and quartz, which have a bigger size than opaline silica, were not present in the purified samples. The chemical dissolution in NaOH effectively removed the nano-scale opaline silica particles. Besides, further studies confirmed that the coordination structure and the interlayer swelling properties of montmorillonite layers are not primarily affected by the chemical treatment. These results confirm that the chemico-physical hybrid method is an effective and non-destructive method for the purification of opal-rich bentonites.