Eco-dyeing with biocolorant from spent coffee ground on low molecular weight chitosan crosslinked cotton

Growing concern about the environmental effects of synthetic dyes is encouraging the use of natural dyes. Spent coffee ground (SCG), a potential renewable source of natural dye, was investigated as a biocolorant for dyeing of cotton. SCG contains the brown pigment melanoidin. Low molecular weight chitosan (LMWCTS) was used to introduce amino groups, with citric acid (CA) as a crosslinker. LMWCTS was applied to cotton at various concentrations using a simple pad-dry-cure technique, followed by dyeing with SCG extract using an exhaustion process. Fourier transform infrared spectrometry analysis confirmed the formation of ester linkages between the citric acid and cellulose or chitosan. The dyed fabrics were also evaluated for color properties using CIELAB (L*, a* and b*) and K/S values, color fastness, and whiteness index, for physical properties (wrinkle recovery angle, drape coefficient, and tensile strength), and for surface morphology. The combination of chitosan and citric acid provided fabrics with a rich natural brown shade. The samples showed the increase in color strength and wrinkle resistance compared with untreated and alum-mordanted samples. Fabrics treated with CA/LMWCTS had the ability to retain drape and exhibited good wrinkle resistance through 20 wash cycles. Color fastness to washing and rubbing was good.