Intercalation of the natural pigments, betalains, in a Tunisian smectitic clay: a green synthesis

Abstract Green chemistry is one of the preferred environmental approaches to protect the planet and human health, as it is based on the use of natural compounds such as pigments, clays, and bio-hybrids. The aim of the present study was to synthesize new colored biohybrids obtained from betalains (extracted from Opuntia , commonly known as prickly pear) and a purified smectite. The mineralogical composition and the chemical properties of the hybrids synthesized were determined using a variety of analytical methods. The maximum concentration of betalains adsorbed on the clay, as determined by UV spectroscopy, was 30.80 mg L –1 . The change of the position and intensity of the infrared H–O–H stretching bands from 3405 to 3315–3352 cm –1 indicated that the adsorption of the betalains took place in the interlayer space of the clay. The amount of betalains intercalated did not affect the texture of the clay, as the particle size of the clay was unchanged. Fluorescence analysis revealed the characteristic emission and excitation peaks of the betalain compounds. Successful synthesis of bio-hybrids was achieved, increasing the potential for their possible use in cosmetic or industrial applications.