Effect of natural deep eutectic solvent molar ratio variation on cowpea shell pretreatment

Authors

  • C M Onyelucheya Department of Chemical Engineering, School of Engineering and Engineering Technology, Federal University of Technology, Owerri, Imo state, Nigeria PMB1526
  • J T Nwabanne Department of Chemical Engineering, Faculty of Engineering, Nnamdi Azikiwe University, PMB 5025 Awka, Anambra state, Nigeria
  • M O Daramola Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Hatfield Campus, Pretoria 0028, South Africa.
  • S A Iwarere Department of Chemical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, Hatfield Campus, Pretoria 0028, South Africa.

Abstract

This research investigated the effect of pretreatment on cowpea shells using lactic acid-choline chloride (L: C) solvent with varying molar ratios (L: C 5:1, L: C 9:1, and L: C 10:1). The chemical composition of the pretreated samples was analysed, and their surface morphology was evaluated using scanning electron microscopy (SEM). In addition, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction were used to study the structural changes in the functional groups and crystallinity of the pretreated cowpea shells. The results obtained showed that the pretreatment process made a significant impact on the chemical composition of the cowpea shells. The solvent of L: C (10: 1) made the highest impact with an increase in the percentage of glucan in the pretreated samples by 33 % and a decrease in acid-insoluble lignin by 11. 5 %. Acid-soluble lignin and xylan remained relatively constant in different molar ratios. SEM analysis revealed surface erosions and biomass deconstruction in the pretreated samples, with the degree of erosion increasing with higher acid molar ratios.  FTIR analysis identified distinct changes in the functional groups of pretreated cowpea shells compared to those of untreated shells. Specific peaks at different wavelengths 2936 cm-1, 1034 cm-1, and 1693 cm-1 were identified, indicating variations in cellulose, hemicellulose, and lignin content. The pretreatment of samples with varying ratios (L: C 5:1, L: C 9:1, and L: C 10:1) exhibited increased crystalline indices of 78%, 79%, and 81%, respectively, compared to the untreated sample with a crystalline index of 66%. The pretreatment of cowpea shells with lactic acid: choline chloride solvent induced significant changes in their chemical composition, surface morphology, functional group structure, and crystallinity index. These findings contribute to our understanding of the potential applications of pretreated cowpea shells.

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Published

2023-12-31

Issue

Vol. 2 No. 3 (2023): UNIZIK Journal of Engineering and Applied Sciences

Section

Articles