Functional cellulosic materials in precision oil-water separation for fatberg point source control
File(s)
Author(s)
Gosiamemang, Tsaone
Type
Thesis
Abstract
Fatbergs, composed of congealed fat, oil, grease, wet wipes, and other non-biodegradable waste, pose a multitude of problems for urban areas. These conglomerations obstruct sewer systems, causing backups and overflows that result in sewage spills onto streets, homes, and water bodies, leading to environmental contamination and health hazards. Additionally, their removal requires significant resources, including specialised equipment and manpower, increasing maintenance costs for sewage infrastructure. Despite existing solutions such as the use of grease interceptors, the fatberg issue persists. This study explores the efficacy of superhydrophobic/superoleophilic and superhydrophilic/superoleophobic cellulose-based materials in extracting fats, oils, and grease (FOGs) from wastewater before its discharge into sewers. By eliminating FOGs from wastewater that contribute to fatberg formation, these materials offer a promising solution. Superhydrophobic materials were synthesised using the silica sol-gel method, employing octadecyltrimethoxysilane (ODTMS) as a surface modifier, through both a two-step post-grafting process and a one-pot synthesis approach. The resulting superhydrophobic cotton exhibited superior water contact angle (WCA) (> 154°) and demonstrated remarkable durability even in harsh chemical environments, including laundering tests. Furthermore, the modified cotton demonstrated outstanding oil-water separation efficiency, exceeding 99% for immiscible oil-water mixtures, and achieved over 90% efficiency for surfactant-free oil-in-water emulsion separation. For effective separation of both surfactant-free and surfactant-stabilised emulsions, superhydrophilic cellulose-based materials were developed via dip coating in a solution of Polyethylenimine (PEI) and polyvinylpyrrolidone (PVP) polymers. These materials, including cotton wool, tissue paper, and used tea bags, exhibited excellent separation performance, achieving efficiencies exceeding 99% with high fluxes exceeding 8000 L m-2 h-1 bar-1 for pressure-driven filtration. Additionally, the modified cotton displayed enhanced stability, maintaining separation efficiencies above 97% even after 20 reuse cycles. In conclusion, this study demonstrates that sorption and filtration-based separation methods, employing superhydrophilic and superhydrophobic materials, offer viable solutions for removing FOGs from wastewater and mitigating fatberg formation.
Version
Open Access
Date Issued
2024-04
Date Awarded
2024-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Heng, Jerry
Sponsor
Government of Botswana
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)