Aung et al. (2014, 2015) described the activation of kaolin samples to remove coloured pigments from rice-bran oil, the effects of various treatments on their decolourization capacity, and the characterization of these kaolin samples by physical methods. This research used a kaolin sample from Ranong in southern Thailand, and investigated the effects of grinding and heat treatment prior to acid activation of the mineral. The various activated mineral phases were then characterized by a combination of X-ray diffraction, Fourier-Transform infrared spectroscopy and X-ray fluorescence. This work represented an extension of research reported previously by Worasith et al. (2011a), in which various samples of the same Ranong kaolin were characterized after grinding and acid activation, and their capacities to decolourize rice-bran oil evaluated (Worasith et al., 2011b). However, despite the similarities in the experiments, there are some important differences in the results presented in these two sets of publications, which raise questions concerning the conduct of this type of research and the generality of any conclusions derived.

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