Cashew (Anacardium occidentale L) bark extract for eco-safe dyeing of mordanted cotton fabric: Colorimetric and biomedical functional properties

Abstract

Large volume of wastewater containing toxic chemicals often discharged into the environment by textile industry is adversely damaging the quality of the ecosystem. This study aimed to circumvent this unfortunate practice through replacement of toxic chemical-mordants with eco-safe herbal-mordants in the cashew bark (CB) naturally dyed cotton fabric. The high dye yield obtained within short period of time vindicated microwave (MW) radiator as a cost, time and labor efficient modern heating tool in dye extraction from natural source. The MW-assisted CB dye extract was chosen for dyeing cotton fabric based on its desired properties (like high yield, low moisture content and bulk density). It was discovered that dye exhaustion, dye-uptake and tint strength of cotton fabric were enhanced after 4 min MW treatment. Utilization of calcium (II) chloride (CaCl2) and iron (II) sulfate (FeSO4) as chemical mordants, Vernonia amygdalina and Sorghum bicolor leaf extracts as bio-mordants has given a set of attractive shades (yellow to chocolate). The mordanted CB dyed cotton fabrics have desired dye exhaustion, dye-uptake and tint strength. The good colorfastness and biomedical functional properties of MW induced CB dyed cotton fabric were enhanced to excellent after post-mordanted with the herbal-anchors. Overall, MW treatment and exploitation of herbal-anchors have showcased the cotton natural dyeing process as the potential industrial cleaner, ecological-friendly and sustainable practice.