The development of biosorbents from agricultural waste sources for the separation of fat-based particles from water
Date
2020-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The presence of hydrocarbons and triglycerides in water pose a technical challenge for wastewater processing or re-use. Hydrocarbon contamination reduces the water quality for available for human consumption and marine life. The available petrochemical-based oil-removing technologies either have negative environmental impacts or are non-selective and ineffective for oil removal. However, plant-based biosorbents, tailored for selective oil removal by surface acetylation reactions can overcome some of the challenges posed by traditional petrochemical-based sorbents.Therefore, the aim of this study entailed the production of bio-based sorbents from corncob (CC) and wheat straw(WS)and their respective cellulose andnanofibrillated cellulose(NFC)constituents, whichwerefunctionalised via acetylation methods that follow the greenchemistry principles, in order to increase selective oil sorption (OS, g/g). The functionalitiesof these feedstocks were critically dependant onthe replacement of hydrophilic hydroxylgroups on the molecular surface with hydrophobic acetyl groups to attainoleophilicity.
The CCand WSwere tuned to become oleophilic via greenand non-greenacetylations. The greenmodification implemented acetic an hydride and iodine,and was optimised via central composite design (CCD),by varying temperature (50 –150 °C), time (0.6 –7.4 h)an diodine concentration (0.7 –7.4 % (w/w)).The optimal performances were compared to a cetylations achieved by the non-green methodology, which replaced the green iodine catalyst with non-green N-bromosuccinimide. The green acetylationyielded CC and WS with a selective OSofapproximately17 –18g/g, while the non-green modified CC and WSexhibitedOS of 17–20g/g. These OS performances were statistically similar(p < 0.05). Cellulose was extracted from unmodified biomass to improve the surface area for sorption. Oleophilic films were developed from CC and WS celluloseretrospective tosurface acetylation.The green acetylation was catalysed by a 50 % (w/w) NaOH-solutionand was optimised via CCDbyvarying temperature (40 –140 °C), time(3.8 –44.2 h) and catalyst volume (1.2 –13.8 % (v/v) NaOH-solution). Concurrently, the non-green acetylation implemented H2SO4as catalyst. The green modification yielded hydrophobic CC and WS films with OSof12 –13g/g, while the non-green CC and WS films had OS of 20 –21g/g.These results revealed that CC and WS had an analogous reaction when subjected to the same type of modification (i.e. greenor non-green). However, the non-green modifications outperformed the green modifications by 65 –69 %based on selective OS.
AFRIKAANSE OPSOMMING: Raadpleeg teks vir opsomming
AFRIKAANSE OPSOMMING: Raadpleeg teks vir opsomming
Description
Thesis (MEng)--Stellenbosch University, 2020.
Keywords
Acetylated nanocellulose, UCTD, Corncobs, hydrophobic-oleophilic, Water contamination, Aerogels, Wheat straw, Agricultural wastes -- Recycling