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.
Chemical reagents used in traditional mineral processing can be toxic and hazardous for the environment. Therefore, the use of biotechnological methods is becoming increasingly important. Great hopes are being placed in the use of microorganisms for bio-beneficiation of raw materials. However, assessment of adhesion abilities of bacteria onto minerals surface as well as biosorption of metals are essential steps before designing final process of each ore beneficiation. The main aim of this work was an investigation of biosorption of Cd and Mg, as well as adhesion abilities of five microorganism species with minerals included in the natural mixture of phosphate ore form Djebel Onk, Algeria. The ore, due to its unique composition, created conditions for adhesion of all five tested microbial strains onto apatite surface during incubation at pH 3. Moreover, Rhodococcus erythropolis CD 130, Pseudomonas fluorescens and Escherichia coli adhered distinctly onto apatite surface during incubation at pH 7. Incubation lasting 20 min at pH 4-6 created the most favorable conditions for biosorption of metals by B. subtilis and adhesion of cells. In case of C. albicans, biosorption of metals as well as adhesion of cells onto the mineral surface were more effective after longer time and in a wider pH range.
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