Development of a novel photocatalytic reactor for the treatment of polycyclic aromatic hydrocarbons.

Gbadamosi, Taiye Gbenga

Abstract

Water pollution through the discharge of contaminated water into the environment has been a major problem, both to humans and aquatic life. These potential consequences mean that water pollution has therefore received major attention. In industry, a group of contaminants still facing challenges with regards to effective remediation are the polycyclic aromatic hydrocarbons (PAH) present in water. These PAHs impose significant risk due to their carcinogenic, mutagenic and teratogenic potential. 18 of these PAHs are classified as high priority by the Environmental Protection Agency (EPA) due to their toxic and harmful nature. This research investigated two remediation methods - coagulation-flocculation and photocatalysis - for the remediation of these 18 PAHs in water. In each remediation method investigated, preliminary works were first carried out on 3 PAHs (naphthalene, phenanthrene and fluorene) before then applying the method to the other 15 PAHs. The coagulation-flocculation remediation method was investigated because the literature review proved that it was an effective method in the adsorption of pollutants from water. Also in the investigation, powder and solubilized (in acetone) chitosan were used as an adsorbent to remove the PAHs in water. Results from this investigation showed little significance in the removal of PAHs with a removal efficiency of 15% attained for phenanthrene using powder chitosan (25 ppm) at 30 minutes contact time. An increase in contact time to 120 hours increased the removal efficiency to 88%. To attain sustainable removal from an industrial treatment point of view, a fast and effective remediation method is required. At 120 hours duration, this method is too slow, meaning that further investigation for a more rapid and effective method required. The photocatalysis remediation method was identified as an alternative. Investigation carried out using the photocatalytic remediation method involved the design and construction of a photocatalytic reactor. Preliminary work was first carried out in a constructed batch suspended photocatalytic reactor to investigate the photodegradation of naphthalene, phenantharene and fluorene, in order to confirm the photocatalytic ability of TiO2 to photodegrade PAH under the influence of UV light. A high removal efficiency of 99% was achieved, but with the limitation of needing to subsequently remove the TiO2. Due to the secondary treatment required to remove TiO2, an immobilized photocatalyst reactor was then investigated. Preliminary work was first carried out on a batch immobilized TiO2 coated photoreactor. This achieved significant results with 83% removal of naphthalene from water over 20 minutes. As a result of this investigation, this study then moved to focus on the design and construction of a flow-through photocatalytic reactor. The developed reactor included both an immobilized TiO2 photocatalyst and UV light radiation. In testing, the novel reactor achieved a high removal rate of 84% in the removal of naphthalene in water. Further investigation with the PAH present in synthesized sea water achieved a similarly high removal rate of 77%. This novel flow-through photocatalytic reactor therefore provides a solution to the challenge of effective removal of PAHs in water.

Citation

GBADAMOSI, T.G. 2019. Development of a novel photocatalytic reactor for the treatment of polycyclic aromatic hydrocarbon. Robert Gordon University [online], PhD thesis. Available from: https://openair.rgu.ac.uk

• Thesis Type: Thesis
• Deposit Date: Aug 12, 2019
• Publicly Available Date: Aug 12, 2019
• Keywords: Water pollution; Polycyclic aromatic hydrocarbons; Photocatalysis; Coagulation-flocculation; Titanium dioxide; Photocatalytic reactors
• Public URL: https://rgu-repository.worktribe.com/output/346584
• Award Date: Feb 28, 2019