New Maya Blue-like Pigments Obtained in the Presence of Green Seaweed Extract

Abstract

Nanopigments consisting of organic/inorganic hybrid composites represent a convenient alternative for pigments, combining the qualities of organic dyes with those of inorganic materials. We obtained Maya blue pigments from methylene blue and modified bentonites, using Ulva lactuca aqueous extract. Structural modifications of bentonites during the synthesis of nanopigments were evidenced by the interplanar distance and the basal peak position in X-ray diffraction patterns. The presence of methylene blue in Maya blue nanopigments was also confirmed by UV-vis and FTIR spectra. The adsorption study revealed a higher adsorption capacity in the presence of Ulva lactuca extract compared to water, and two adsorption models, Langmuir and Freundlich, were applied for studying the adsorption of methylene blue onto bentonite. The stability and seed germination effect of the resulting nanopigments were assessed. Accordingly, it was found that the nanopigments obtained in Ulva lactuca extract had superior redox stability compared to those obtained in water or methylene blue solution. The ability of bentonite-based nanopigments to be used in seed treatment is another interesting feature that can be exploited.