Ultrasound, pulsed electric fields, and high-voltage electrical discharges assisted extraction of cellulose and lignin from walnut shells

Abstract

Extracting The extraction of cellulose and lignin from biomass is essential for the development of sustainable bio-based materials. This study examines the effects of physical pretreatment techniques-ultrasound (US), pulsed electric fields (PEF), and high-voltage electrical discharges (HVED)-on the efficiency of alkali treatment for cellulose and lignin extraction from walnut shells. The primary objective was to enhance extraction yields and improve extract quality while evaluating the effectiveness of these methods. The results revealed that the combined treatments achieved lignin and cellulose yields of up to 17.03 % and 33.40 %, respectively, with US and HVED showing significantly higher extraction efficiencies compared to other techniques. Characterization of the extracted materials using FTIR, XRD, 2D HSQC NMR, TGA/DTG, and DSC confirmed the presence of key functional groups, crystalline structures, and detailed molecular features, while also providing insights into thermal stability. These findings underscore the potential of walnut shells as a sustainable source for bio-based materials and demonstrate the influence of physical pretreatments on the structural and thermal properties of extracted cellulose and lignin. This study paves the way for further research into industrial applications, such as wood adhesives. Future work should focus on optimizing extraction processes, scaling up operations, and investigating the effects of biomass variability on extraction outcomes.