oa South African Journal of Chemical Engineering - Optimising the extraction of a natural dye from



Natural dyes, from botanical sources, for colouring textiles is fast achieving a niche market in the textile industry necessitating optimised scaled-up extraction processes. The extraction of a natural dye, Badie, from the stem bark of the plant by leaching via an aqueous solvent in a batch stirred tank reactor is reported. The inner bark of the plant tissue with a plate-like morphology retained on a 5 mm mesh size with effective thickness of 500 microns, a liquid solid ratio of 5 mL/g and an effective leaching time of 2 h resulted in an optimum yield of 21% without encumbering the process with limitations in pressure drop during filtration. We identified from infrared and UV spectroscopic analysis that the dye has similar functional features of a flavonol. The effective diffusion coefficient was determined to be 1.6×10-10 m2/. The formation of pigments by complexation with a variety of cations: Al3+, Zn2+, Cu2+, Fe2+, Ba2+, Ca2+, Mg2+, Mn2+, Cr6+ to extend the range of colours of the pigments is reported. Thus, simplified model derived for this work to optimise contact time in the design and operation of a commercial scale extraction and enhance value is reported.


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