The green preparation of sugarcane trash nanolignin isolated by maleic acid for biosurfactant application.

Sugarcane trash (SCT), with moderate lignin and high cellulose, is a promising feedstock for valuable chemicals and advanced materials. SCT underwent sequential pretreatment using microwave irradiation followed by autoclave heating before alkali lignin extraction. Lignin was isolated using maleic acid (MA) with varying concentrations and pH levels. Optimum lignin was converted into nanolignin using a self-assembly method with THF: ethanol solvent ratios of 1:1 (nanolignin A) and 1:2 (nanolignin B). The best-performing nanolignin and polyvinyl alcohol (PVA) were synthesized into a biosurfactant using the grafting method. The results showed that lignin isolated using high acid concentrations and low pH conditions exhibits inferior characteristics. Nanolignin A exhibited superior characteristics in terms of particle size and morphology, surface charge, and surface tension. The synthesis of the PVA-nanolignin A biosurfactant was successfully achieved, as evidenced by the appearance of a transmittance peak at 1723 cm and 1219 cm-1 in the infrared spectra, indicating the formation of ester bonds. This study demonstrates the efficient use of SCT chemical components through an environmentally friendly process to produce nanolignin-based biosurfactants, thereby may be beneficial in enhancing enzymatic hydrolysis and improving the bioethanol production process. This method aligns with biorefinery strategies by converting waste materials into valuable products, supporting the principles of a circular economy.