Sustainable scouring of cotton using extracts from wood ash and soapnut and its optimisation by response surface methodology

The non‐cellulosic impurities like oil, wax, and pectins present in the cotton fibre adversely impact wetting. Consequently, these impurities must be removed during the pretreatment process to prevent unevenness of subsequent coloration. Generally, an alkaline treatment with petroleum‐based synthetic surfactants is done, which is called scouring. This study attempts to develop an environmentally safe alternative using alkali from wood ash extract (WAE) and surfactant from soapnut extract (SE). The factors of WAE (10%–30%), SE (5–15 g/L), temperature (75–95°C), and time (20–60 min) were optimised using response surface methodology. A concentration of 20% WAE and 10 g/L SE at 90°C for 30 min was found to be adequate to remove impurities. The statistically optimised method showed good hydrophilicity, indicated by an average wetting time of 15 s, and 2.7% weight loss. The scoured fabric was subsequently dyed with natural dye extracted from marigold flowers and reactive dye. The scoured cotton was evaluated by weight loss, wettability, tensile strength, whiteness index, and colour value (K/S) and showed comparable results to conventional scouring.