Valorization of mahogany sawdust waste for dyeing of cotton knitted fabrics using aloe vera and banana sap bio-mordants

Abstract Growing environmental concerns and the need to reduce dependence on synthetic dyes have intensified the search for sustainable colorant sources and bio-based mordanting systems derived from renewable resources. In this study, mahogany sawdust, a wood industry by-product, was used as a natural dye source for cotton knitted fabric coloration. Aloe vera, banana sap, and their combination served as bio-mordants. Pre-mordanting was performed at 100 °C for 60 min, followed by 24 h of conditioning. The dye was extracted by heating a mahogany sawdust-water mixture at 100 °C for 1 h. The UV–Visible spectrum of the extract showed a maximum absorption at 275 nm, consistent with the absorption characteristics of flavonoid-related chromophoric compounds. FTIR spectra revealed intensified characteristic peaks in the combined bio-mordant sample, indicating improved intermolecular interaction and dye absorption behavior within the dye–fiber system. The highest color strength value of 7.1 was obtained with the aloe vera and banana sap combination, compared to 4.1 for the unmordanted fabric. Washing fastness improved from 2–3 in the control to 3–4 in mordanted samples, while wet rubbing fastness increased from 2–3 to 3–4, and light fastness reached a rating of 3 in the combined treatment. Comparatively lower weight-loss behavior during washing-based mechanical treatment was observed in bio-mordanted fabrics. Saliva fastness ratings of 3–4 for color change and 4–5 for staining demonstrated acceptable color resistance under saliva exposure conditions. The combined bio-mordant treatment demonstrates improved dye absorption behavior and durability, supporting potential application of mahogany sawdust-based coloration systems in sustainable cotton dyeing.