Enhanced Cotton Dyeing With Turmeric Rhizome Extracts by Cashew Flesh Juice ( <i>Anacardium occidentale</i> L.) as a Natural Mordant

ABSTRACT The study aimed to investigate the potential of cashew ( Anacardium occidentale L.) flesh as a tannin‐based mordant for cellulosic dyeing. Herein, cotton was dyed with turmeric ethanol extracts in combination with cashew apple juice. The highest curcumin exhaustion (≈87%) was obtained after 60 min of dyeing at 70°C, with a liquor ratio of 1:50 and 30 g/L of Na 2 SO 4 . The incorporation of cashew juice was proven to enhance fixation and improve the washing fastness of the dyed fabric from grade 2–3 to 3. The product, after being treated with eco‐friendly KAl(SO 4 ) 2 mordant, exhibited high washing fastness, with a rating of 4–5, comparable to that of synthetic dyes. Additionally, the strong antimicrobial capacity of cashew juice against Staphylococcus aureus and Escherichia coli enhanced the fabric's antibacterial potential, boosting the product's functional attributes. A quantitative test (AATCC 100) showed a significant reduction in bacterial count after 18 h: 73.68% for S. aureus and 85.71% for E. coli . Unfortunately, the lightfastness assessment of the fabric only reached grade 1, indicating that the combination of tannin and metal ions could not help improve curcumin's intrinsically high sensitivity to light. Overall, this study suggests that cashew apples could serve as an effective green mordant for natural dyeing, showcasing the prospect to utilize this valuable agri‐food waste.