Coumalic Acid-Enabled Covalent Functionalization of Khadi-Cotton via a Closed-Loop Aqueous Process for Durable Multifunctional Textiles

Abstract The rapid prevalence of vector-borne diseases, microbial infections, UV radiations, and oxidative stress due to free radicals poses significant public health risks, often exacerbated by the environmental footprint of traditional multifunctional textiles. This study investigates a circular and sustainable approach to textile engineering by integrating a biomass-derived molecule, coumalic acid (CA), into Khadi-Cotton fabric. Utilizing an industrially feasible, aqueous-based pad−dry−cure technique, we successfully engineered a multifunctional fabric structure without the need for synthetic crosslinkers or organic solvents. Interestingly, a closed-loop processing strategy was implemented, where the residual CA solution was recovered and reused for subsequent fabrication cycles. The invariant color strengths (K/S) and uniform CA uptake across multiple batches confirmed consistent batch-to-batch reproducibility, maximizing atom utilization and achieving near-zero process waste. Comprehensive characterization through Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA)/derivative thermogravimetric analysis (DTG) validated the successful functionalization of cellulose fibres (Khadi-Cotton) through the formation of covalent ester linkages between the −COOH group of CA and the cellulosic hydroxyls. The engineered textile exhibited excellent antimicrobial activity (>99% against S. aureus and ∼98% against E. coli), ∼96% mosquito repellency against the female Aedes species, and a high ultraviolet protection factor (UPF) of 47.15, with 97.20% UVA and 97.94% UVB blocking. Notably, the multifunctional performance remained consistent across all recycled batches, demonstrating remarkable durability through 25 home laundering cycles and for one year of ambient storage, demonstrating the long-term performance and high washing durability of the functionalized fabric materials. The present study establishes a practical and innovative roadmap for utilizing biomass-derived platform molecules in circular manufacturing, offering a durable, non-toxic solution to widespread environmental health hazards while supporting a sustainable bioeconomy.