Synergistic action of photocatalytic oxidation and alkaline degumming of hemp fibres under simulated sunlight

Efficient degumming is crucial for valorisation of bast fibres. However, severer conditions and high energy consumption hinder their practical application. This work developed a photocatalytic degumming method assisted by both ZnIn2S4 catalysis and lignin autocatalysis at mild conditions. The method achieved high lignin removal rate (71.6%) and cellulose yield (94.8%) in degumming of hemp fibres, decreasing the major content of β-O-4 bond and β-β bond in lignin from 32.0% to 10.7% and 6.8% to 3.4%, respectively. The pretreated fibres possessed excellent breaking strength (4.46 cN/dtex) and fineness (6.83 dtex). Moreover, the pretreated fibres were readily hydrolysed by cellulase, improving the glucose concentration by 58.3% compared to the alkaline degumming. Furthermore, the synergistic action of ZnIn2S4 and lignin on generation of free radicals was observed. Thus, this work explored the potential of photocatalysis degumming of bast fibres, and discovered the synergistic action of ZnIn2S4 and lignin autocatalysis.