Sustainable and efficient scouring/bleaching strategy for cotton fabric using sucrose octaacetate/peroxide activated system: Mechanistic insights, performance optimizations, and environmental benefits

Abstract

The activator/H2O2 system is able to achieve a low-temperature and near-neutral bleaching by producing of peroxyacids through activators' perhydrolysis. In order to develop a sustainable and efficient pre-treatment process, sucrose octaacetate (SOA) as a biomass-derived activator was initially introduced in the one-step scouring and bleaching for cotton fabric. Despite the documentation of various activators, limited researches focus on the perhydrolysis pathway and bleaching mechanism of bio-based activators. Consequently, the performances of SOA/H2O2 system were investigated by testing the color features, hydrophilicity, and tensile property of the treated fabric. Furthermore, density functional theory (DFT) and liquid chromatography-mass spectrometry (LC-MS) were employed to clarify the perhydrolysis pathway of SOA. Afterwards, a central composite design (CCD) experiment and mathematical modeling was conducted to optimize the bleaching process and analyse the factors significantly influencing the whiteness index (WI) of fabrics. Finally, the energy and water consumption as well as the life cycle assessment (LCA) of SOA/H2O2 bleaching was discussed. Results show that the addition of SOA further increased the fabric's WI from 74.96 to 78.78. The fabric's hydrophilicity enhanced distinctly after removing cotton wax, as confirmed by X-ray photoelectron spectrometer analysis. The bleached fabric exhibited less than 5% mechanical loss and undamaged morphology owing to the moderate SOA/H2O2 system. DFT and LC-MS analyses revealed that three acyl carbon atoms with higher atomic charge in SOA preferentially underwent perhydrolysis, resulting in the release of equal chemical equivalents of peracetic acid as the primary bleaching substance. Besides, the important role of HO· in SOA/H2O2 bleaching was confirmed through fluorescent labeling and radical trapping experiments. The most significant factor affecting WI was temperature, followed by H2O2 concentration, NaHCO3 concentration, and time. Implementing the SOA/H2O2 system led to approximately 35.5% energy savings, 36.4% water savings, and reduced environmental impact by the LCA. Considering the overall evaluation of CCD's outcome, fabric characteristics, and environmental benefits, the WI of 80.64 which is 93% higher than greige fabric, can be achieved when utilizing the optimized parameters (82.73 mmol/L H2O2, 64.14 mmol/L NaHCO3, a temperature of 70 °C, and a duration of 60 min).