Electronic Theses and Dissertations (Masters)
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Item Development and Application of activated carbons from Avocado waste: Resource recovery for sustainable applications(University of the Witwatersrand, Johannesburg, 2023) Mohale, Lehlohonolo; Mulopo, JeanThis research sought to produce activated carbons that could be used for hydrogen storage. The effect of hydrothermal pretreatment of the char, the effect of varying the activation ratio of KOH as the activation agent and the effect of activation temperature in producing these activated carbons were evaluated. Hydrothermal pretreatment of the char enhanced the properties of the resulting activated carbons. The best performing activated carbon was produced from the hydrochar pretreated at 200℃. It was observed that activation improved with increased activation agent concentration and activation temperature, to a point, and the best activated carbon was produced at 1:3 activation ratio and 800℃ activation temperature. This activated carbon had the highest total pore and micropore volumes of 1.45cm3/g and 1.16 cm3/g, respectively. The highest surface area of 2529.8m2/g was obtained, which is relatively higher than previously reported surface areas obtained from activated carbons created from coal or biomass. The porosity and the high surface area show well developed activated carbons that have desirable gas adsorption performance. The activated carbons had oxygen containing functional groups that aid in hydrogen sorption, the highest hydrogen sorption at 77K and 1 bar was 352 cm3/g, which supports the use of the produced activated carbons in the hydrogen economy. These activated carbons enable the circular economy. Well developed micropores were observed in the activated carbons produced through this work and their gravimetric capacity meets the DOE targets for hydrogen storage.