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Abstract

For decades, the primary concern regarding excess nitrate concentrations has centred around safeguarding human health. However, deterioration in surface water quality and the widespread issue of eutrophication has prompted a shift in focus. Now, efforts are directed toward remediating and achieving good ecological status of water bodies. Despite progress, current remediation technologies face challenges in combining cost-effectiveness with environmental impact. Hence, agricultural wastes have gained traction as potential adsorbents to due to their abundance and easy disposal. However, in their raw state, they have been found to exhibit low capacities. Thus, this study focused on assessing the feasibility of modified orange-peels as cost-effective adsorbents and their effectiveness in removing nitrates from a multiple-ion solution in a batch system. To improve the physicochemical properties, the orange-peels were soaked in potassium hydroxide (KOH) for 2 hours. The chemically treated orange-peels were thermally decomposed using pyrolysis at 300℃ and hydrothermal carbonization at 180℃ at 4 hours each to produce highly reactive adsorbents; namely, OPBC and OPHC. Characterization showed the clear effect of thermal modification on the surface properties of orange-peels. The highest adsorption capacity was obtained using OPHC (22.25 mg/g) whereas OPBC achieved a capacity of 14.75 mg/g. However, adsorptive performance in the presence of other anions significantly reduced to 7.8 mg/g and 12 mg/g for the OPBC and OPHC respectively. Furthermore, kinetic studies revealed that the adsorption mechanism for both adsorbents followed chemisorption possibly through cationic exchange or complexation. Overall, this work shows the adsorptive potential of orange-peels in remediating affected waters, however they are not as effective. Thus, by varying carbonizing temperatures and chemical treatment methods, agricultural adsorbents with a high affinity towards nitrate can be developed.

Course: Water and Environmental Engineering - MSc - P3422FTC

Date Deposited: 2025-01-16

URI/permalink: https://library.port.ac.uk/dissert/dis14666.html