Sustainable scouring of Cotton with Kaolin clay and optimisation by response surface methodology

Abstract This research aims to develop an alkali‐free cotton scouring process using a kaolin clay paste. The application parameters, including process time, temperature and concentration of the clay paste, were optimised using a Box–Behnken response surface methodology design. Considering absorbency time as the primary response, the response surface methodology revealed optimum scouring efficiency with a clay paste concentration of 6% at 89°C for 45 minutes. Greige cotton fabric treated under the optimised clay‐cleaning process exhibited absorbency within 5 seconds and a 1.9° contact angle, which is comparable to traditional caustic soda‐scoured fabrics. Cotton scoured with caustic lye showed higher weight loss than the developed clay‐cleaning process. The prepared clay paste showed adequate detergency properties against a variety of stains such as wine, carbon, turmeric, sebum and chocolate, with a maximum detergency of 78.5% against sebum, confirming effectiveness in the removal of oil‐based impurities during the scouring process. To evaluate the environmental impact, the clay‐cleaning effluent water was compared with traditional caustic scouring effluent. The drained liquor from the clay‐cleaning bath showed lower biological oxygen demand, chemical oxygen demand, total dissolved solids, eutrophication potential (phosphorus content) and pH. Moreover, the clay‐cleaning process does not hamper the treated cotton fabric's hand‐feel and mechanical properties. The developed clay‐cleaning process can be used as an eco‐friendly alternative to traditional caustic scouring in the pretreatment process of cotton fabrics, especially for dyeing medium and dark shades.