Valorisation of Mixed Food Wastes using a Green Deep Eutectic Solvent System to Recover Lignin as a Value-added Product and its Utilization in the Fabrication of Nanofibrous Mats

Abstract

Valorising food waste using an eco-friendly solvent is proven to be an efficient strategy for the recovery of lignin as a value-added product together with alleviating adverse impact of this waste on the environment. The present study reports the recovery of lignin from mixed pomegranate and banana peels using a green deep eutectic solvent (DES) system composed of choline chloride and oxalic acid and its subsequent use in the fabrication of nanofibrous mats via electrospinning technique. The recovered lignin was comprehensively characterized by various analytical techniques to confirm its structural and morphological properties. A blend of lignin and polyvinyl alcohol was successfully electrospun into nanofibrous mats at an applied voltage of 14 kV and a flow rate of 0.3 ml/hr. The fabricated mats were characterized to assess their structure, morphology, and chemical content. Fourier Transform Infrared Spectroscopy revealed the presence of key lignin functional groups including syringyl, hydroxyl, and aromatic groups, in the mats, whereas X-Ray Diffraction verified their amorphous nature. Field Emission Scanning Electron Microscopy images clearly demonstrated the formation of uniform nanofibrous mats having interconnected pores. The elemental composition of the fabricated mats was confirmed from Energy Dispersive X-ray spectroscopy. In conclusion, lignin was successfully recovered from mixed food wastes using DES, and lignin based polymeric nanofibrous mats were fabricated by electrospinning, which can be further tested as membrane adsorbents for pollutant remediation.