Characterization and Assessment of Natural Amazonian Clays for Cosmetics-Industry Applications

摘要

Clays are abundant materials in the Amazon region and have been used historically by ancient Amazonian people to produce ceramic and cosmetics products. The current study aimed to evaluate the potential of four clays from the metropolitan area of Manaus, each with a different color, for cosmetics applications. Two clays were collected in the Ponta Negra region (red and gray in color) in Manaus, one in Careiro (white), and one in Itacoatiara (black). After drying in an oven for 24 h at 105℃, the four clays were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared (IR) spectroscopy, thermogravim-etry (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), particle-size analysis,and detection of microorganisms. The amounts of Al, Si, Cl, K, Ca, Ti, Cr, Fe, Zn, P, and S in all samples were below the limits for use in cosmetics. The main phases identified were kaolinite 1A, quartz, gibbsite, and the rare kaolinite 2M. Approximately 40 wt. of each sample was in the < 20 μm particle-size range. Analyses by SEM revealed pseudo-hexagonal kaolinite structures with nano-islands and nanocrystallites. The low toxicity, mineralogic compositions, and particle-size findings suggest that Amazonian clays are promising for cosmetics applications.