Characterization and purification of Algerian natural bentonite for pharmaceutical and cosmetic applications

Abstract

Introduction Bentonitic clays from the Hammam Boughrara deposit in the Maghnia area (northwestern Algeria) were studied by mineralogical, chemical and physicochemical characterization to evaluate their potential suitability as raw and purified materials in pharmaceutical and cosmetic applications. Methodology Natural bentonite was purified by Na+ ion exchange treatment combined with sedimentation techniques. Before use in the pharmaceutical industry, bentonite samples must be safe and conform to recommendations and directives of pharmacopeia. A set of technological tests were investigated with the samples, such as cation exchange capacity (CEC), specific surface area (SSA), swelling capacity (SC),sedimentation volume (SV) and viscosity, and mineralogical, chemical and microbial properties were also identified by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results Mineralogical data proved that the raw bentonite is mainly composed of smectite and illite with small quantities of gangue minerals such quartz, feldspars (orthoclase and albite) and calcite. The purified bentonite matches the mineralogical properties of Wyoming bentonite as an international standard clay (deposits of high economic value). Quartz and feldspars were successfully eliminated in the absence of illite and calcite after beneficiation. Investigation of chemical analyses indicated that the contents of trace elements (particularly Pb and As) were below the more restrictive limits proposed by major pharmacopeias for raw and purified bentonite clay. For microbiological tests, the absence of Escherichia coli, Salmonella species, Staphylococcus aureus and Pseudomonas aeruginosa was confirmed. Moreover, we note that a high cation exchange capacity, large surface area, and good swelling capacity and sedimentation volume were also obtained for purified bentonite. Conclusion In view of the fundamentals of major pharmacopoeias for the use of bentonite in pharmacies and considering the results obtained, we identified a pharmaceutically acceptable designation for purified Algerian bentonite, which can be used as a pharmaceutical excipient and in cosmetic products such as creams, powders and emulsions.

Comparison of two purification methods of Algerian bentonite: chemical, mineralogical and physicochemical properties

“…Then, the dried bentonite was re-ground to obtain fine powder for experimental purpose. The raw bentonite was chemically purified according to classical purification method of Bergaya et al 2013 [9,10] . About 25 g of raw bentonite was first dispersed in 400 mL of 1 M NaCl solution, stirred magnetically overnight and centrifuged at 3000 r/min for 2 h .…”

“…RBN-1 sample showed a broad particle size distribution with high volume percentages centered at 5 μm and 11 μm, which were attributed to quartz, feldspar and other impurities [10]. (Fig.…”

“…The scan was recorded in the angular range of 2°-30° (2θ) with a step size 0.017° (2θ) and a scanning speed of 2° per minute [10].…”

“…Chemical compositions (major element contents) of all samples were obtained with a Philips X-ray fluorescence spectrometer, model PW2400 [10].…”

“…Morphological characteristics of bentonite samples were checked with scanning electron microscopy (SEM), using QUANTA 250 SEM equipment. The SEM images were acquired with an applied acceleration voltage of 300 kV [10].…”