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Heterogeneous photocatalysis is an advanced oxidation technology widely applied in environmental remediation processes. It is a relatively safe and affordable technology with a low impact on the environment and has found applications in a number of fields from chemical engineering, construction and microbiology to medicine. It is not catalysis in the real sense of the word as the photons which initiate the desired photocatalytic reaction are consumed in the process. The cost of these photons is by far the limiting economic factor in its application. From a technical standpoint, the inefficient use of the aforementioned photons during the photocatalytic reaction is responsible for the limited adoption of its application in industry. This inefficiency is characterised by low quantum yields or photonic efficiencies during its application. The mechanism of the technique of controlled periodic illumination which was previously proposed as a way of enhancing the low photonic efficiency of TiO2 photocatalysis has been investigated using a novel controlled experimental approach; the results showed no advantage of periodic illumination over continuous illumination at equivalent photon flux. When the technique of controlled periodic illumination is applied in a photocatalytic reaction where attraction between substrate molecules and catalyst surface is maximum and photo-oxidation by surface-trapped holes, {TiIVOH•}+ ads is predominant, photonic efficiency is significantly improved. For immobilized reactors which usually have a lower illuminated surface area per unit volume compared to suspended catalyst and mass transfer limitations, the photonic efficiency is even lower. A novel photocatalytic impeller reactor was designed to investigate photonic efficiency in gas–solid photocatalysis of aromatic volatile organic compounds. The results indicate photonic efficiency is a function of mass transfer and catalyst deactivation rate. The development of future reactors which can optimise the use of photons and maximize photonic efficiency is important for the widespread adoption of heterogeneous photocatalysis by industry.

This PhD thesis investigated solid and liquid waste treatment systems for Sureclean, a waste Management company based in the North of Scotland. Sureclean receives a diverse range of waste streams and the increasing need for sustainable development as well as stringent environmental legislation motivated this research to develop an integrated waste treatment system. Waste characterisation was conducted using a range of analytical instrumentation to identify the TPH, COD, heavy metals content, TOC, and particle size of Sureclean waste streams. From there, four treatment systems were investigated utilising Sureclean waste streams: mechanical separation, chemical treatment, electro-coagulation and the advanced oxidation process. Laboratory and field trials were conducted using these different treatment techniques and the analysis was performed to verify the treatment results. The result of these trials led to the development of four modular waste treatment units, that form the outcome of this research: the Sureclean Water Treatment System (SWTS), a filtration based mechanical separation system was shown to reduce the TSS, BOD and TOC content of an oily wastewater; the Sureclean Sludge Separation System (SSSTS), a chemical-enhanced filtration based system was demonstrated to reduce 52.6 % of the sewage sludge volume; the Sureclean Electro-coagulation Water Treatment System (SEWTS), a system that agglomerates colloid particles and demulsifies oil removed 99.9 % of TPH from Sureclean interceptor effluent; and the Sureclean Advanced Water Treatment System (SAWTS), an advanced oxidation process which was demonstrated to reduce the TPH of a contaminated groundwater collected from an ex-gas work. The treated effluent could be discharged to Sureclean interceptor. The four treatment units developed in this research expanded Sureclean waste treatment capabilities and an integrated system was developed to treat different waste streams and to improve the treatment efficiency thus increasing the revenue and future waste stream options for Sureclean.

The synergistic enhancement of oxidative degradation of atrazine (ATZ) using combined electrolysis and ozonation (EO) was investigated in a laboratory-scale system. Initial studies relied on high performance liquid chromatography (HPLC) for analysis of intermediates. These experiments conducted in sulfate electrolyte at pH 2, 7, and 12 for electrolysis only (E), ozonation only (O), and the combination (EO) indicated that the rate constant of ATZ degradation in the (EO) system could not be explained simply from considering the (E) and (O) processes as additive based on rate constants obtained when they were applied separately. At pH 7, the measured first-order rate constant for (EO) was 0.3441 min-1, a rate 4.78 times as large as the estimated additive rate (0.072 min-1) from (E) and (O) separately. Across the pH range, the rate constant increased from 0.0516 min-1 at pH 2 to 0.3441 min-1 at pH 7 and 0.3065 min-1 at pH 12. Use of a radical scavenger elucidated that hydroxyl radical (HO&#9679) oxidation dominated the (EO) treatment at pH 7 and 12.The impact of chloride and bromide ions in the matrix was also investigated using HPLC at pH 7. Bromide and chloride slightly increased the rate of ATZ degradation compared to sulfate alone when (E) was applied. When (O) was applied, the estimated first-order degradation rate of ATZ decreased 20% with chloride and 87% with bromide compared to the rates in sulfate. The degradation rate of ATZ decreased 86% with chloride in (EO) mode and 93% with bromide, both as compared to sulfate. This is significant since (EO) has been shown in previously published works to produce strong synergism for contaminant removal in sulfate. The proposed mechanism for antagonism with a reactive electrolyte such as chloride or bromide is increased competition in the system for (HO&#9679). Free halogen species and bromide are reactive with HO&#9679, decreasing the likelihood of direct reaction between HO&#9679 and ATZ. In addition to the antagonism, all cases except ozonation in chloride generated either bromate or chlorate, undesirable byproducts.Finally, research using Quadrupole Time-of-Flight (QTOF) Mass Spectrometry was used to identify potential degradation products from the application of (E), (O) and (EO) at pH 2, 7, and 12 in a sulfate electrolyte. Dechlorination and dealkylation products were identified in all conditions studied. Detailed reaction pathways for ATZ are proposed. Six distinct oxidative mechanisms are proposed at pH 7: dechlorination, dealkylation, alcohol transformation, imine transformation, acetamide transformation, and aldehyde transformation. In addition to the previous six mechanisms, a carboxyl transformation pathway is proposed at pH 2 and 12 and a deamination pathway is proposed at pH 12. Abstraction of hydrogen atoms by HO&#9679 is notable as it can initiate all oxidative mechanisms except dechlorination and deamination. Molecular ozone (O3), a selective oxidant, is reactive with ATZ, and participates only in the acetamide transformation pathway.

Magnetic spinel cobalt and zinc ferrite nanoparticles with variable composition (M x Fe 3-x ; x= 0.1, 0.5, 0.7 and 1.0; M= Co, Zn) were synthesized. The nanoparticles were characterized by various surface techniques. Average sizes and surface areas of nanoparticles were determined in the ranges of 11-34 nm and 18.5-49.1 m2/g, for cobalt ferrite and of 11-34 nm and 14.4 -r48.7 m2/g for zinc ferrite, respectively. Surface analysis of the nanoparticles confirmed the spinel type structures in which Co(II) incorporated into the crystal lattice for the cobalt ferrite and confirmed the incorporation of Zn(II) into the crystal lattice for the zinc ferrite. Synthesized Co x Fe 3-x O 4 catalysts were used to dissociate peroxomonosulfate (PMS) into reactive sulfate radicals (SO4•–) and further into hydroxyl radicals (HO•) to degrade a target pollutant, 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in absence of heat and light. As the molar ratio of cobalt (i.e., x) in the ferrite catalyst increased from 0.1 to 1.0, PBSA degradation enhanced from 27 to 74%. Significantly, removal of PBSA increased with the increase in PMS concentration up to 0.1 mM, followed by a decrease at PMS levels of > 0.1 mM. Nitrogen content in PBSA was mineralized by the ferrite-PMS system mostly into NO 3 - and NH 4 + ions with minor formation of NO 2 -. Only 32% TOC removal was observed over a 240 min reaction time, indicating carbon content in PBSA was not completely mineralized. A chemical probe method, based on free radical scavenging, revealed the contribution of both SO4•– and HO• species in PBSA degradation. Fifteen reaction intermediates were identified using LC/Q-TOF-ESI-MS analysis. Hydroxylation, elimination of sulfonate moiety, and ring cleavage processes were involved in the major degradation pathways. Catalyst reuse experiments demonstrated PBSA degradation efficiency either retained or increased with each subsequent reuse. The magnetic spinel Co-ferrite nanoparticles can be applied effectively to activate PMS without energy aiding for degrading harmful emerging organic contaminants in water. Synthesized Zn x Fe 3-x O 4 the was capable of degrading 90% of 10 µM initial pharmaceutical Diclofenac (2-(2,6-dichloranilino) phenylacetic acid) also known as DCF in water in 2 min reaction time under dark conditions without the use of PMS or any other oxidant. The most molar ratio of zinc (i.e., x) in the ferrite catalyst increased from 0.1 to 1.0, DCF degradation enhanced from 25 to ~ 90%. However, lower removal percentage was obtained when catalysts with lower zinc content were used. Furthermore, investigation of Zn x Fe 3-x O 4 showed lower ability of Zn xFe3-x O 4 to degrade ability degraded Diclofenac. Moreover, synthesized zinc ferrite demonstrated a strong magnetic property that facilitate the particles collection and separation from reaction medium using a magnetic field. The results revealed zinc ferrite is a promising catalyst for the degradation of diclofenac in contaminated waters under dark conditions in a relatively short reaction time.

The main focus of the present work was to expand the existing knowledge in using an advanced oxidation process for produced water treatment. Produced water is a phrase used in the oil and gas industry to describe water that is produced as a waste byproduct together with oil and gas. Historically produced water was pumped down disposal wells as a waste product. Due to increasing demand, limited supply and stricter regulation on fresh water sources, exploration and production companies have been compelled to recycle produced waters in many parts of their operations around the world. Produced water quality varies dramatically based on geographical location, type of hydrocarbon produced (oil or gas), and the makeup of the producing formation. In general, the total dissolved solids concentration ranges from 100,000 to over 250,000 milligrams per liter. Acid producing and sulfate reducing bacteria are the most commonly occurring microorganisms in produced water. Suspended solids, sodium, bicarbonate, chloride, iron and sulfide are the most commonly occurring inorganic constituents in produced water. Benzene, toluene, ethylbenzene, and xylene compounds are the most commonly occurring organic contaminants in produced water, which contribute to elevated chemical and biological oxygen demand. The advanced oxidation process studied in this work utilized an effective grouping of sciences to provide a high rate treatment for bacteria, organics, hydrogen and/or iron sulfide and volatile compounds; while inhibiting scale through electrochemical oxidation. Key instruments for amplification were apparent hydroxyl free radicals, and the reduction of the mass transfer resistances by efficient distribution of the ozone and hydrogen peroxide. Anticipated benefits of treatment were elimination or better compatibility with oilfield chemicals, e.g. biocides, scale inhibitors, and friction reducers. All results were correlated with oxidation-reduction potential.

In this dissertation, as a monitoring technology for cyanotoxins, a multiwalled carbon nanotube (MWCNT)-based electrochemical biosensor was developed to determine microcystin-LR (MC-LR), a potent cyanobacterial toxin, in sources of drinking water supplies. The performance of the MWCNT array biosensor is evaluated using micro-Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, optical microscopy, and Faradaic electrochemical impedance spectroscopy. A linear dependence of the electron-transfer resistance on the MC-LR concentration is observed in the range of 0.05 to 20 µg L-1, which enables cyanotoxin monitoring well below the World Health Organization provisional concentration limit of 1 µg L-1 for MC-LR in drinking water.In addition to the development of monitoring tools for cyanotoxins, visible light-activated (VLA) TiO2 and monodisperse TiO2 were developed and evaluated for treatment of water contaminants of emerging concern. These materials were synthesized using modified sol-gel methods (i.e., wet chemistry-based methods) such as self-assembly-based and ionic strength-assisted techniques. For this study, first, VLA-sulfur-doped TiO2 (S-TiO2) nanocrystalline films were synthesized by a self-assembly-based sol-gel method using nonionic surfactant to control nanostructure and an inorganic sulfur source for decomposing MC-LR under visible light illumination. Second, the effects of solvent on the synthesis of VLA-S-TiO2 films were scrutinized. Four different polar, protic solvents, isopropanol, 1-butanol, ethanol, and methanol, were chosen as the solvent in four titania sol-gel preparations. Third, monodisperse anatase titania nanoparticles with controllable sizes (typically 10–300 nm) were synthesized using an efficient and straightforward protocol via fine tuning of the ionic strength in the devised sol–gel methodology. Finally, noble metal Ag-decorated, monodisperse TiO2 (TiO2-Ag) aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the pharmaceutical oxytetracycline (OTC) under both UV and visible light irradiation. With a self-assembly-based sol-gel method, nanostructured anatase S-TiO2 with high surface area (> 100 m2 g-1) and porosity (> 30 %) was synthesized and the sample calcined at 350 oC demonstrated the highest visible light absorption and visible light-induced photocatalytic activity in the decomposition of MC-LR. The structural and morphological properties of S-TiO2 could be also tailor-designed using different solvents in the sol-gel synthesis, while inducing negligible effects on the sulfur doping and the visible light activation of TiO2. Thus, it can be concluded that the enhancement of photocatalytic activity of S-TiO2 films can be achieved by judicious choice of the main solvent for the sol-gel method. With an ionic strength-assisted sol-gel method, monodisperse spherical anatase TiO2 (10-300 nm in diameter) as well as monodisperse TiO2-Ag aggregates with 350 nm of diameter were synthesized. For TiO2-Ag, its visible light absorption increased due to the presence of Ag on the surface of monodisperse TiO2, which resulted in the enhancement of the photocatalytic degradation of OTC under both UV-visible light and visible light irradiation compared to pure TiO2. There was an optimal Ag content to obtain the highest photocatalytic degradation of OTC. These newly developed materials demonstrated the efficient decomposition of water contaminants of emerging concern, especially MC-LR and OTC, under UV-visible light and visible light illumination.

To achieve sustainable water resources, new treatment technologies are needed that can be applied to a broad range of undesirable constituents in water over a broad range of water chemistries. In this project, nanomaterials were developed as building blocks for advanced treatment technologies through the controlled material synthesis technique of electrospinning. Electrospun nanofibers are promising materials for nano-integrated systems due to their simple tuning and production, large surface-area-to-volume ratio, and potential substrate integration to prevent incidental release into the environment.In this work, electrospun metal oxide nanofibers were synthesized and optimized for their application in various aspects of water treatment, which include Ag-enriched TiO2 nanofibers for UV-driven photocatalytic oxidation of organic microcontaminants, Al2O3-Fe2O3 composite nanofibers for adsorption of heavy metals, and BiVO4 nanofibers for visible light-activated photocatalytic oxidation.TiO2 nanofibers were developed and tuned to alter morphological, dimensional and optical properties towards optimal photocatalytic performance of contaminant degradation. Electrospinning synthesis yielded nanofibers with controlled diameter, crystal phase, grain size, and band gap. Photoreactivity studies towards the model pollutant phenol showed that diameter and crystal phase composition were the two major factors in optimizing TiO2 nanofibers performance. Additionally, the introduction of Ag led to further enhancement of photoreactivity, where optimization of the composite nanofibers was tied predominantly to Ag content. Fe2O3 nanofibers were developed and tuned to alter morphological and dimensional properties towards optimal adsorption of heavy metals. Electrospinning synthesis yielded nanofibers with controlled diameter, crystal phase, grain size, and specific surface area. Chromate adsorption isotherm studies reveal increased sorption capacity with decreased diameter of the Fe2O3 nanofibers, attributed with the increased surface area. With the addition of Al, Al2O3-Fe2O3 composite nanofibers were produced with even greater sorption capacity due to further enhanced surface area.BiVO4 nanofibers were developed and tuned to control morphological, dimensional and optical properties towards optimal visible-light activated photocatalytic performance. Electrospinning synthesis yielded nanofibers with controlled diameter, crystal phase, grain size, and band gap. Photoreactivity studies towards phenol showed that reactivity increased with decreased nanofiber diameter. The addition of Ag and Au co-catalysts enhanced photoreactivity of the BiVO4 nanofibers, outperforming TiO2 nanomaterials under visible light irradiation.

Abstract: The large volume of oil sands process-affected water (OSPW) produced by the oil sands industries in Northern Alberta, Canada, is an environmental concern. The toxicity of OSPW has been attributed to a complex mixture of naturally occurring acids, including naphthenic acids (NAs). NAs are a broad range of alicyclic and aliphatic compounds that are persistent in the environment. This work focused on the application of advanced oxidation processes (AOPs): UV/H2O2 and O3/H2O2 for degradation of model NA compounds and OSPW NAs. Cyclohexanoic acid (CHA) was selected as a simple model naphthenic acid, and its oxidation and byproduct formation in the UV/H2O2 and ozonation processes was studied. The results indicated that in the UV/H2O2 process, the pH had no significant effect on the degradation, nor on the formation and degradation of byproducts in ultrapure water. A real OSPW matrix had a significant impact by decreasing the CHA degradation rate up to 82% relative to that in ultrapure water. Relative rate measurements using binary mixtures of model NA compounds confirmed that reactivity favoured compounds with more carbons, and also favoured NAs with one saturated ring, relative to the corresponding linear NA. However, for model compound with three rings, no increased reactivity was observed relative to mono-cyclic NA. The mechanism of ozonation of CHA was different at pH 3 and pH 9. At pH 9, oxo-CHA and hydroxy-CHA were both detected by LC-MS/MS, confirming the hydroxyl radical (•OH) pathway in which superoxide CHA radical is a possible intermediate. The results of the O3/H2O2 advanced oxidation process of OSPW NAs showed that in a semi-batch system, approximately 90% of extractable organic acids of OSPW were removed using O3/H2O2 process with 85 mg/L of O3 and O3 to H2O2 ratio of 0.3.

Photocatalysis process, as an environmental application is an advanced oxidation process with tremendous potential in the near future. Previously many researchers, have conducted photocatalysis in different reactor configuration using TiO2 slurry and thin film, using a UV light source, the constraints for these reactors are the need for the removal of TiO2 particles at the outlet stream in a slurry reactor and poor environment for the efficient use of TiO2 film using UV light, as the UV light penetration depth in water is about an inch. Taking all this into consideration, we propose a design for reactor with efficient contact of the aqueous phase to the TiO2 film so that UV light doesn't need to penetrate through water, the TiO2 particles need not be removed from the outlet stream of water. The wok involves the deposition of TiO2 on quartz tubes with TiO2 and TiO2-Fe doped film by sol-gel and ESA (electrostatic self assembly) method and testing the performance of the coated film in proposed photocatalytic reactor in degradation of congo red, KI and Nitro phenol.

This research involved an investigation of the application and reaction mechanisms of UV/H₂O₂ for the simultaneous removal of regulated halogenated disinfection byproducts (DBPs) and odorous aldehydic algal byproducts in the presence of geosmin and 2-methylisoborneol, which are earthy-musty odorants that commonly occur in drinking water. UV/H₂O₂ is an expensive advanced oxidation process that is used to successfully control geosmin and 2-methylisoborneol. The aqueous oxidation of odorous aldehydes and halogenated DPBs were compared to that of the earthy-musty odorants and the changes to the sensory properties of the drinking water were examined. Geosmin, 2-methylisoborneol, heptadienal, decadienal, and nonadienal, hexanal, and the two most prevalent classes of DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were oxidized by UV photolysis alone and the UV/H₂O₂ process with 6 mg/L H₂O₂ and realistic ng/l to μg/L concentrations of the test compounds. The di-, and tri-brominated THMs and HAAs were substantially (80-99%) removed by direct UV photolysis mechanism at the same UV/H₂O₂ dose required for removing 95% of geosmin and 65% of 2-methylisoborneol with faster reaction rates for the more bromine substituted compounds. The C-Br bond cleavage is the first step of brominated HAAs degradation by UV photolysis, and followed by either of two second steps: reaction with oxygen producing peroxyl radical or interaction with water molecule causing O-H insertion/H-Br elimination. Trichloromethane and mono-, di-, and tri-chlorinated HAAs were not substantially removed under the same conditions used for the brominated compounds. The principal removal mechanism was by the reaction with hydroxyl radical for the UV/H₂O₂ process. The second order reaction rate constants were on the order of 10⁶ - 10⁸ M⁻¹ s⁻¹ with faster reaction rates for the less chlorine substituted compounds. Based on the reaction rates, hydrogen and halogen ion balance, and isotope effect, both hydrogen abstraction and electron transfer reaction were involved in the first steps of the chlorinated HAA degradation. Three odorous aldehydes - heptadienal, decadienal, and nonadienal - were removed faster than geosmin or 2-methylisoborneol, and direct UV photolysis was the principal reaction mechanism for the removal of these unsaturated aldehydes. Hexanal was poorly removed. In sensory tests, new odors such as sweet or chalky odors were produced while the concentration and initial odor intensity of these fishy/grassy-smelling aldehydes were reduced with increasing exposure time to UV/H₂O₂. Carbonyl compounds were detected as products of the UV photolysis of nonadienal. These carbonyls were not removed by further UV irradiation, which was thought to be partially related with production of new odors. The results indicate that the UV/H₂O₂ is effective to control both odorous compounds and brominated DBPs. This process can be seasonally applied to control both contaminants especially, in the warm summer when both odorants and DBPs have their higher concentrations. Removal of brominated DBPs can be a significant addition to water utilities that have difficulty in meeting regulatory levels for these highly toxic compounds. The result on the removal of odorous aldehydes indicate that new types of odors were produced from the oxidation of odorous aldehydes suggesting sensory test coupled with chemical analysis should be considered in designing oxidation process to control recalcitrant odorants.