Preparation and characterization of lake pigments from sappan wood using Thai local clays

Abstract

Thai local clays: Munpoo clay (MC) and Dindang clay (DC) were utilized as the adsorbents for preparation of the lake pigments from sappan wood. The lake pigment which was prepared by using MC as the adsorbent (L-MC) appeared reddish-brown while a deeper reddish-brown color of the lake pigment (L-DC) was obtained by using DC as the adsorbent. Characterization of MC, DC, L-MC, and L-DC was accomplished by XRD, SEM, FT-IR, BET, TGA and UV-Vis DRS. The effects of adsorbent dosage, pH of sappan wood extract and time on the adsorption were also investigated. The results revealed that silicon oxide and aluminium silicate hydroxide were identified as the main component of MC and DC. L-MC and L-DC exhibited similar XRD pattern compared to MC and DC but with the lower crystallinities. Brazilein from sappan wood could not only form complexes with Al and Si on the surface of the clays but also interact with clay surface via electrostatic interactions, which led to the reddish-brown color of L-MC and L-DC. Furthermore, our method could benefit and promote uses of natural clays in the production of lake pigment which could be used in paints and textile dyeing processes.