Enriching Clay For Cosmetic Applications

Clays are low-cost materials that can be found abundantly in natural deposits distributed around the world. Clays are known as a versatile material used for various purposes, such as oil and gas extraction exploration and building construction, which are the most traditional industries that use the highest amount of clays. The versatility of clay applications has been evaluated through generations, confirming the clays as an important raw material for catalysis, nanocomposites, pharmaceuticals, and cosmetics, etc.

In the area of cosmetics and health, many studies have revealed the potential use of clays by describing their physical and chemical properties, such as color, swelling capacity and adsorption, chemical inertia, antibacterial action etc [Carretero et al., 2013; Carretero and Pozo, 2010; Legido et al., 2007; Mattioli et al., 2016; Rautureau et al., 2017; Roselli et al., 2015; Williams and Haydel, 2010]. One of the reasons to use clays for such applications is to take advantage of their physical and chemical properties to contribute to the generation of environmentally friendly products.

The purity of the mineral is an important feature when choosing a clay for pharmaceuticals and cosmetics. Generally, clays consist of a mixture of two or more clay minerals, and may also contain non-clay minerals (for example, quartz, feldspar, mica) and organic matter. When necessary, it is possible to submit the clay to purification processes to obtain a clay free of unwanted products and enriched in clay minerals, presenting characteristics suitable for specific applications.

The article investigated a clay usually destined for traditional applications, for use in pharmaceuticals and cosmetics. We received a sample of the raw clay coming from the city of Vitória da Conquista, state of Bahia, northeast region of Brazil. The off-green clay, codified as VM, was first submitted to a fractionation process, yielding three different grain-size fractions, each one corresponding to the colors pink, red, and green, as observed in Figure 1, and named VMF1, VMF2, and VMF3, respectively. The clay fractions showed homogeneous and interesting pleasant colors, especially the pink and red colors, which presented a particle size smaller than the green grain-size fraction and raw clay.

Figure 1. Images of the colors of VM raw clay and its different grain-size fractions. Credit: Maria das Graças da Silva-Valenzuela

The mineralogical analyzes of the original clay and the three grain-size fractions obtained were performed by X-ray diffraction and the Rietveld method, indicating that each fraction was composed mainly of smectite and kaolin in a significant concentration ranging 32-46 mass%, as shown in Table 1. The chemical analysis showed that the original clay and the three grain-size fractions presented smectites with a significant content of Fe₂O₃ and MgO. Kaolin and smectites are the two clay minerals most used by the pharmaceutical and cosmetic industries.

Table 1. Quantitative results of clay minerals in the samples (mass%). Credit: Maria das Graças da Silva-Valenzuela

Further analyzes were performed for more detailed observations on the structure and physical and chemical properties of clays analyzed, such as scanning electron microscopy, Fourier transform infrared spectroscopy, specific surface area, oil adsorption etc .; besides pharmaceutical tests recommended by United States, European, British, and Brazilian Pharmacopoeias, which are swelling capacity, heavy metal content, and microbiological tests.

The complete analysis of the raw clay and the three clays originated from its fractionation, showed that all of them have adequate characteristics for use in cosmetics, but the pink and red grain-size fractions are the most indicated because they presented swelling capacities in agreement to those recommended by Pharmacopoeia.

The article shows how a crude green clay of low added value, after being submitted to a fractionation process, gave rise to three clays of different physical and chemical properties, and higher added value. Two of the grain-size fractions originated, the pink and red clays, presented properties for use in pharmaceuticals and cosmetics. Its colors and the fact that these clays have a high kaolinite content corroborate to the final intended use.

These findings are described in the article entitled Enrichment of clay from Vitoria da Conquista (Brazil) for applications in cosmetics, recently published in the journal Applied Clay Science. This work was conducted by Maria das Graças da Silva-Valenzuela, Isaac Jamil Sayeg, Flávio Machado de Souza Carvalho, Shu Hui Wang, and Francisco Rolando Valenzuela-Díaz from the University of São Paulo (Brazil), and Marvin Marco Chambi-Peralta from the University Center of United Metropolitan Colleges (Brazil) and the National University of San Agustin (Peru).

References:

1. Carretero, M.I., Gomes, C.S.F., Tateo, F., 2013. Clays, drugs, and human health. In:Bergaya, F., Lagaly, G. (Eds.), Handbook of Clay Science. Elsevier, Amsterdam, pp. 711–764.
2. Carretero, M.I., Pozo, M., 2010. Clay and non-clay minerals in the pharmaceutical and cosmetic industries part II. Active ingredients. Appl. Clay Sci. 47, 171–181.
3. Legido, J.L., Medina, C., Mourelle, M.L., Carretero, M.I., Pozo, M., 2007. Comparative study of the cooling rates of bentonite, sepiolite and common clays for their use in pelotherapy. Appl. Clay Sci. 36, 148–160.
4. Mattioli, M., Giardini, L., Roselli, C., Desideri, D., 2016. Mineralogical characterization of commercial clays used in cosmetics and possible risk for health. Appl. Clay Sci. 119 (part 2), 449–454.Rautureau et al., 2017;
5. Roselli, C., Desideri, D., Cantaluppi, C., Mattioli, M., Fasson, A., Meli, M.A., 2015. Essential and toxic elements in clays for pharmaceutical and cosmetics use. J. Toxic. Environ. Health A 78, 316–324.
6. Williams, L.B., Haydel, S.E., 2010. Evaluation of the medicinal use of clay minerals as antibacterial agents. Int. Geol. Rev. 52, 745–770.