Investigation of Mineralogy and Porosity of Two Pakistani Bentonites and Its Corresponding Purified Bentonites

Bentonite samples from Peshawar and Nowshera regions of Khyber Pakhtunkhwa (Pakistan) were collected, and their mineralogy and textural studies were carried out. It was examined by X-ray diffraction that, besides containing clay minerals such as montmorillonite and illite, both the original bentonites also contained albite and quartz. The clay fraction of \({<}2\,\upmu \hbox {m}\) (purified sample) of original bentonites was separated by Stoke’s law of sedimentation from its aqueous dispersions. The equipment used for particle size analysis was Malvern Master-sizer 2000. The particle size of Nowshera samples both in raw and purified form was found smaller in comparison with Peshawar samples. The particles size difference in the two samples, even in purified form, may be attributed to the variation in particle shape. The \(\hbox {N}_{2}\) adsorption–desorption on bentonites samples at 77 K was carried out by Micromeritics ASAP 2010 surface analyzer. The pore size distributions revealed that the selected bentonites were highly porous in nature even in raw form; however, their behavior in this regard was also found incredibly different. The specific surface area, mesopore size distribution, micropore volume/area and mesopore volume/area of Peshawar raw sample were found considerably lower than Nowshera raw sample, however, they change greatly, as a result of purification. The lower porous raw sample, i.e., Peshawar raw sample, reached to the highest porous material in purified form. The high surface area and high porous structure of bentonite especially in case of purified samples suggest their use as adsorbents, catalysts, and cosmetics raw material.