One-step degumming and bleaching of flax fibers by thermal–alkaline activation of peroxydisulfate: Mechanisms and environmental implications

In this study, a thermal-alkaline activated peroxydisulfate (TA-PDS) process with integrated degumming and bleaching functions was developed for flax fiber treatment. Under the optimized conditions of a NaOH/PDS molar ratio of 6:1, a PDS concentration of 8.8 g/L, and a reaction time of 2.7 h, the residual gum content of the treated fibers was as low as 5.8%, while the fiber retained a tenacity of 2.1 cN/dtex, a whiteness of 48.7%, and a fiber yield of 75.0%. Compared with the traditional alkaline degumming process, TA-PDS achieved more effective removal of non-cellulosic components while preserving favorable fiber properties. Mechanistic investigation demonstrated that radical oxidation and alkaline hydrolysis played synergistic roles in lignin degradation, with electrophilic •OH acting as the dominant oxidative species. The preferential attack of •OH on the electron-rich structures of lignin, together with OH⁻-promoted cleavage of β-O-4 ether linkages, contributed to selective lignin removal and preservation of fiber integrity. Environmental assessment further demonstrated that TA-PDS reduced water consumption from 45.0 to 15.0 m 3 per ton of raw flax and lowered the global warming potential from 766.2 to 285.4 kg CO₂ eq, together with reductions in wastewater pollutant load, and overall environmental burdens. These findings indicate that TA-PDS provides a feasible strategy for simultaneously achieving efficient degumming and favorable fiber properties while improving the environmental sustainability of the process. • One-step flax degumming and simultaneous bleaching were achieved by TA-PDS. • High degumming efficiency was obtained while fiber properties were preserved. • Selective lignin degradation was promoted by electrophilic •OH. • Wastewater loads, water footprint, and life-cycle burdens were reduced.