Facile fabrication of sustainable and superhydrophobic aerogels from waste agricultural materials for use in oil adsorption applications

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

This study set out to improve the adsorption capacity performance of dry corn cobs, banana peels, orange rind, and watermelon rind by fabricating aerogels in a facile manner using the sol-gel process from these materials. To achieve this aim, several research questions were put forward by the study. The study asked questions about the existence of differences in adsorption capacity performance between the dry precursor materials for the different oils and organic liquids chosen for the study. The existence of differences in adsorption capacity performance between aerogels from the precursor materials for the oils and organic liquids was examined, along with the differences in adsorption capacity performance between the dry precursor materials and the aerogels from these dry precursor materials for the oils and organic liquids. Also, the existence of differences between the aerogels from dry corn cobs and the cellulose aerogels using cellulose extracted from dry corn cobs, was examined.
The experimental methods employed by the study include the sol-gel process for the fabrication of the aerogels, chemical vapour deposition for inducing hydrophobicity, delignification, and hemi-cellulose removal to obtain cellulose, and characterisation experiments. The characterisation experiments included adsorption capacity (modified version of the ASTM-F726-60 method), selective adsorption capacity, water contact angle tests, and surface morphology tests. The results were displayed using tables and graphs, while the statistical analysis was carried out using the two-way Analysis of Variance (ANOVA) with repeated measures tool.
The adsorption capacity results revealed better performances across the board by all sorbents for the oils when compared with the organic liquids. Fabricated aerogels from the dry ground precursor materials had up to 10 times better adsorption capacity when compared with the adsorption capacity results of the dry precursor materials for the chosen oils and organic liquids. The maximum adsorption capacity went from 1.18g/g for the dry precursor materials to 10.64g/g for the aerogels fabricated from these materials. Extracting cellulose from the chosen precursor material (corn cob) also yielded increased adsorption capacity from the resulting cellulose aerogels when compared with corn cob aerogels. The maximum adsorption capacity recorded went from 8.51g/g for the corn cob aerogel to 13g/g for the cellulose aerogel from corn cob representing a 35% increase in adsorption capacity performance. The hydrophobicity experiment successfully made the aerogels hydrophobic with an average water contact angle result of 118.5°. The surface morphology results showed the development of three-dimensional structures serving as sites for adsorption.
Date of Award2023
Original languageEnglish
Awarding Institution
  • Coventry University
SupervisorStephen Theophilus (Supervisor)

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