Characterization of Iranian bentonites to be used as pharmaceutical materials

Ten Iranian bentonites, sampled from the deposits of Chah-Golestan, Chah-Pirouz, Chah-Keshmir and Chah-Taleb (Sarayan), Gholeh-Gelia and Kharman-Sar (Ferdows, Khorasan), Mehrejan (Khoor) and Manian (Zagros) were analyzed to evaluate their potentialities as pharmaceutical products. The mineralogy, chemistry, pH, microbial content, powder flow characteristics, swelling capacity, cation exchange capacity, specific surface area, sedimentation volume, and rheological properties of all samples were determined. The bentonite located in carbonate rocks (Zagros) is made up of calcium montmorillonite (97%) and quartz (3%). The rest of the bentonites are hosted by Eocene volcanic rocks and are mainly made up of sodium montmorillonite (47%-84%) and cristobalite (up to 39%), with lesser quantities of quartz, calcite, plagioclase, zeolites and halite. Two of the samples (those located at Manian and Chah-Golestan C) showed appropriate composition, purity and technical properties to be used in pharmaceutical applications, whereas the rest would require purification or improvement of their properties. In particular, the samples could be used for topical dosage forms as rheological additives.