Parametric study on microwave-assisted extraction of runo (Miscanthus sinensis Andersson) dye and its application to paper and cotton fabric

The study was designed to devise a high-yielding, microwave-assisted extraction of the colored material from the core tissue of runo (Miscanthus sinensis Andersson) stem. Soxhlet extraction of M. sinensis core tissue gave yields ranging from 1.04 % with dichloromethane to 11.91 % from 1:1 ethanol-water mixture. Folin-Ciocalteau tests showed that the extracts were primarily flavonoid compounds, accounting for 66.05 ppm of the total 1:1 ethanol-water extractable material. Initial application trials of the ethanol, ethyl acetate, and ethanol-water extracts followed by color fastness tests showed poor retention on both paper and cotton fabric, suggesting the need for a mordant. Subsequent trials with aluminum acetate as mordant showed greatly improved binding of the ethanol-water extracted dye onto the cotton fabric following wash, rubbing, and light fastness tests. A two-level, full factorial model extraction procedure to determine the effects of extraction time (15 s – 90 s), solvent volume (50 mL – 150 mL), and microwave power level (90 W – 540 W) was done for all solvents used. All three factors had a significant effect on the dye extraction yield, along with the interactions between duration-power level and volume-power level. The highest yield for microwave assisted extraction was at 15 s −150 mL – 540 W setting. Results suggest that microwave extraction can potentially produce dye extracts from M. sinensis core material with a faster throughput than simple soaking and Soxhlet extraction.