Pumice-zno composite catalyst for photocatalytic water treatment

Abstract

A ZnO-pumice passive photocatalyst is fabricated by coating ZnO nanoparticles on a volcanic rock material called pumice, to form a strongly bonded composite substance that can be applied in solar- activated photocatalytic treatment of wastewaters. The composite is produced through an easily reproducible coating method that gives a solid long-lasting composite material.

Description

PUMICE-ZnO COMPOSITE CATALYST FOR PHOTOCATALYTIC WATER TREATMENTCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of United States Provisional Patent Application No. 63 / 676,792, filed on July 29, 2024, the entire contents of which are hereby incorporated by reference.FIELD

[0002] Disclosed examples generally relate to catalysts for wastewater treatment and remediation, and more particularly, to a pumice-ZnO composite catalyst for photocatalytic water treatment. The disclosed composite catalyst may be used for treating water contaminated with bitumen and / or bitumen byproducts, including oil sands process water (OSPW).BACKGROUND

[0003] In Canada’s oil industry, which relies heavily on crude oil production from oil sands, continuous advancement is being made in mining process optimization aimed at lessening the overall freshwater intake for crude oil extraction from the oil sands.

[0004] While much of the generated process by-product water is recycled, the unrecycled fraction has accumulated over the years to huge quantities of wastewater stored in tailings ponds in the oil sands deposits region. The tailings ponds are expected to eventually go through closure, with the contained process water reintegrated into the ecosystem. However, because of concerns about its potential adverse effects on human and aquatic life, this process wastewater - called oil sands process water (OSPW) - needs to be adequately treated for its safe release to the environment.

[0005] OSPW is a complex mixture comprising suspended particles and various classes of organic compounds and inorganic ions such as SO42-, Cl-, Na+, and HCO32-. Findings suggest it derives much of its studied toxicity from the organic constituents known as naphthenic acids (NAs). For instance, NAs (primarily cyclic and acyclic carboxylic acids) have been reported to pose potentialrisks such as acute toxicity, endocrine disruption, and narcosis to some fauna species. As such, studies on remediating OSPW have focused mainly on attenuating the NAs present.

[0006] Much research has been conducted on applying various water treatment technologies to degrade NAs in real and synthetic OSPW samples. However, because NAs are refractory to conventional water treatment methods, there has been an increase in studies investigating the application of various advanced oxidation processes (AOPs) for treating OSPW. For instance, oxidation processes such as semiconductor-based photocatalysis have been applied to degrade NAs in OSPW.

[0007] For large-volume wastewater remediation applications - such as the huge volumes of OSPW expected to be treated - scaling up semiconductor-based photocatalysis faces several challenges. These challenges include catalyst recoverability and reusability, low photocatalytic quantum yield, and high energy requirement.SUMMARY

[0008] Disclosed examples relate to a pumice-ZnO composite catalyst. The composite material can be applied for photocatalytic treatment and remediation of water contaminated with bitumen and / or bitumen byproducts, e.g., oil sands process water (OSPW). The composite material allows treatment for extended periods, as well as efficient catalyst recovery for reuse. When employed as a floating catalyst, it exhibits consistency in the degradation efficiency.

[0009] In both laboratory (simulated solar irradiation) and out-of-laboratory (real sun irradiation) applications, the prepared material exhibits considerable efficiencies in degrading organic compounds such as NAs and fluorophores in OSPW. Additionally, the toxicity and bioavailability assessment of the treated and untreated water samples indicate significant reductions in the acute toxic effect of OSPW and the bioavailable dissolved organics.

[0010] Furthermore, material stability and recovery evaluations show that the prepared photocatalyst is highly stable and has excellent recoverability and activity over repeated use in OSPW. The results suggest a positive potential of both the composite material for renewable-energy-driven and environmentally friendly remediation of OSPW.

[0011] In at least one broad aspect, there is provided a catalyst used for photocatalytic treatment of water contaminated with bitumen or a bitumen byproduct, comprising a pumice-ZnO composite.

[0012] In some examples, the composite comprises pumice particles coated with ZnO nanoparticles.

[0013] In some examples, the water is oil sand process water.

[0014] In another broad aspect, there is provided a process for photocatalytic treatment of water contaminated with bitumen or a bitumen byproduct, comprising: contacting the water with a pumice-ZnO composite catalyst; and exposing the composite to light.

[0015] In some examples, the catalyst is applied in suspended form and rises to float over the water surface.

[0016] In some examples, the light comprises solar radiation generated by a solar radiation source which is natural and / or artificial.

[0017] In some examples, the treatment is a passive photocatalytic treatment.

[0018] In some examples, the method further comprises measuring the concentration of an indicator to determine whether treatment is completed.

[0019] In some examples, the indicator is one or more of naphthenic acids and fluorophore organic compounds.

[0020] In some examples, the light is applied at an intensity to produce a water-surface fluence in the range of 1 MJ / m2to 5 MJ / m2.

[0021] In some examples, the catalyst is applied at a catalyst concentration of between 0.05 g / L and 1.0 g / L of water.

[0022] In some examples, the exposure time is between 0.5 hours to 10 hours per day, for one or more days.

[0023] In some examples, the process is applied as a batch or continuous process.

[0024] In some examples, the water is oil sand process water.

[0025] In some examples, the method further comprises initially allowing the water and composite catalyst to sit without light to attain an adsorption / desorption equilibrium during a dark phase reaction process.

[0026] In some examples, the method further comprises retrieving and reusing the catalyst for multiple reuse cycles.

[0027] In another broad aspect, there is provided a method of producing the catalyst, comprising: producing a suspension by mixing ZnO nanoparticles with water; mixing the suspension with pumice stone particles to form ZnO-coated pumice particles; and calcinating the ZnO-coated pumice particles.

[0028] In some examples, the pumice stone particles have a diameter between 0.5 mm to 5 mm.

[0029] In some examples, the pumice particles are not crushed or pulverized.

[0030] In some examples, the calcination occurs at 300°C to 600°C for approximately 2 to 5 hours, and more preferably, about 500°C for approximately 3 hours.

[0031] Other features and advantages of the present application will become apparent from the following detailed description taken together with the accompanying drawings. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the application, are given by way of illustration only, since various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0032] For a better understanding of the various embodiments described herein, and to show more clearly how these various embodiments may be carried into effect, reference will be made, by way of example, to the accompanying drawings which show at least one example embodiment, and which are now described. The drawings are not intended to limit the scope of the teachings described herein.

[0033] FIG. 1 is an example setup that includes ZnO-pumice floating photocatalyst in oil sands process water (OSPW).

[0034] FIG. 2 is an example process flow for a method for producing a ZnO-pumice photocatalyst.

[0035] FIGs. 3A - 3E include micrographs of (a) the ZnO particles (FIG. 3 A), (b) the pumice stone (FIG. 3B), (c) the composite pumice-ZnO photocatalyst (FIG. 3C), (d) an EDX (Energy- dispersive X-ray spectroscopy) spectra of the pumice stone (FIG. 3D), and (e) the composite pumice- ZnO photocatalyst (FIG. 3E).

[0036] FIGs. 4A - 4C show various plots of the percentage degradations of the various classes of naphthenic acids (NAs) in the oil sands process water (OSPW) after treatment with pure pumice and pumice-ZnO floating photocatalyst based on (a) oxygen number (FIG. 4A), (b) carbon number (FIG. 4B) and (c) double bond equivalent (DBE) (FIG. 4C). In these examples, the reaction time was 6 hours per day; and the radiation intensity is 115.74 W / m2.

[0037] FIG. 5 is a plot of solar photocatalytic degradation of fluorophore organics in the OSPW using the pumice-ZnO floating photocatalyst. In this example, the reaction time is 6 hours per day; and the radiation intensity is 115.74 W / m2.

[0038] FIGs. 6A - 6B are plots of photocatalytic degradation of fluorophore organic compounds in OSPW by using the pumice-ZnO floating photocatalyst in the sun on (a) day 1 (FIG. 6A), and (b) day 2 (FIG. 6B). In this example, the reaction time was 6 hours per day.

[0039] FIGs. 7A - 7D are plots showing the percentage degradations of (a) classical NAs (FIG. 7 A), (b) Os-NAs in the OSPW (FIG. 7B), (c) percentage degradations of classical NAs based on carbon number (FIG. 7C), and (d) percentage degradations of classical NAs based on DBE (FIG. 7D), after treatment with solar radiation and the pumice-ZnO floating photocatalyst in real solar radiation. In these examples, the reaction time was 6 hours per day.

[0040] FIGs. 8A - 8D show SEM (scanning electron microscope) images of freshly prepared pumice-ZnO (FIG. 8A), SEM images of used pumice-ZnO (FIG. 8B), an EDX spectra of freshly prepared pumice-ZnO (FIG. 8C), and an EDX spectra of used pumice-ZnO. (FIG. 8D)

[0041] FIGs. 9A - 9B show plots of a reusability assessment of the pumice-ZnO floating photocatalyst in solar-activated photocatalytic degradation of (a) fluorophore compounds (FIG. 9A), and (b) Ch-NAs in OSPW (FIG. 9B). In these examples, the reaction time was 6 hours per day; and the radiation intensity was 119.5 W / m2.

[0042] FIGs. 10A - 10B show plots of a toxicity assessment with (a) Microtox® assay (FIG. 10A), and (b) bioavailability assessment of treated and untreated OSPW samples (FIG. 10B).

[0043] FIGs. 11 A - 11C shows various plots of percentage degradations of (a) 04-NAs (FIG. 11 A), (b) Os-NAs (FIG. 11B), and (c) Oe-NAs (FIG. 11C) in the OSPW after treatment with the pumice-ZnO floating photocatalyst under sun’s radiation. The reaction time was about 6 hrs.

[0044] FIG. 12 shows X-ray diffraction patterns of (a) pumice and (b) pumice-ZnO, (c) XPS survey scan spectra of the pumice and pumice-ZnO (Inset shows the high-resolution spectrum of the Zn 2p states in the pumice-ZnO), and (d) high-resolution XPS spectra of O Is states in pumice and pumice-ZnO.

[0045] FIG. 13 shows the solar spectra of the simulated solar radiation and the real solar radiation.

[0046] FIG. 14 shows distribution of NAs in the raw OSPW based on (a) carbon number and (b) DBE.DETAILED DESCRIPTIONI. DEFINITIONS

[0047] Any term or expression not expressly defined herein shall have its commonly accepted definition understood by a person skilled in the art. As used herein, the following terms have the following meanings.

[0048] "Bitumen byproducts" include, by way of example, hydrocarbons, naphthenic acids, and / or fluorophore organic compounds.

[0049] "Floating catalyst" means a catalyst designed to remain suspended or float on the surface of a liquid, enhancing surface reactions, such as in photocatalysis.

[0050] "Fluorophore organic compounds" are aromatic, and are a class of organic compounds comprising benzene (fused and unfused) rings in their molecules.

[0051] "Naphthenic acids (NAs)" area group of acidic, water-soluble carboxylic acids. These are typically found in crude oil and bitumen, usually with cycloaliphatic structures.

[0052] "Nano-particles" means particles having at least one dimension, for example a diameter, in the nanometer range, which is less than 1000 nm, preferably less than 100 nm, and more preferably less than about 30 nm.

[0053] "Rod-shaped nano-sized particles" means particles having an elongated, cylindrical morphology with a length greater than their diameter, wherein at least one dimension is in the nanometer range . The particles may have a specific surface area in the range of about 1-10 m2 / g, such as between about 3.0 to 4.0 m2 / g.

[0054] "Oil sands process water (OSPW)" means water generated and affected during the extraction and processing of bitumen from oil sands, containing bitumen, salts, metals, and organic contaminants.

[0055] "Passive photocatalytic process" means a photocatalytic reaction driven by ambient or natural light without active mixing, pumping, or external energy input beyond the light source.

[0056] "Photocatalytic treatment" means a water purification process that uses light-activated catalysts to break down organic pollutants.

[0057] "Pumice" is a porous, lightweight volcanic rock. It is an amorphous volcanic glass, primarily composed of silicon dioxide (SiCh), aluminum oxide (AI2O3), and other oxides (e.g., Na?O, K2O, Fe2O3).II. GENERAL OVERVIEW

[0058] Disclosed examples provided for a pumice-ZnO composite catalyst for photocatalytic water treatment.

[0059] In at least one example, the catalyst is applied as a "floating" or "floatable" catalyst. This allows effective harnessing of solar radiation at the water surface, and further allows for easy recovery of the catalyst from the water surface and subsequent reusability.

[0060] More generally, ZnO is a preferred photocatalyst due to its low cost and high chemical stability, as well as thermal stability. ZnO is efficient in degrading naphthenic acids (NAs) and fluorophore organic compounds typically found in water contaminated with bitumen and / or bitumen byproducts, e.g., OSPW. The ZnO is preferably used in nano-particular form, and more preferably as rod-shaped nano-particles.

[0061] Pumice is used as a preferred substrate or catalyst support for the ZnO. Pumice is a natural rock material with potential for green applications to environmental remediation. As opposed to other substrates (e.g., perlite), pumice - as a catalyst support - is more useful as a chemically inert material due to its good mechanical strength and high thermal stability, as well as its ability to float in water to produce a floatable or floating catalyst.

[0062] More specifically, and without limitation to particular theory, pure pumice is a noncrystalline material with an irregularly formed surface having tubular macrovesicles and an extensive surface for the deposition of the ZnO rod-shaped nano-sized particles. The vesicles of pumice are of advantage as they can serve as pockets, holding the water and helping achieve good contact between the pollutants and the photocatalyst for enhanced oxidation to take place.

[0063] The composite photocatalyst comprises a formation of a composite material of a large base (the pumice) with numerous relatively very small particles (i.e., the ZnO particles) discretely deposited and firmly attached on it. The ZnO particles are attached both on the external surface and within the vesicles of the pumice, but without completely blocking the tubular macrovesicles (i.e., tubes) in the pumice. The unblocked channels of the composite facilitate transport of dissolved solutes in water and enhance contact between the organics and photocatalyst active site.

[0064] The composite catalyst is easily recoverable and retains its photocatalytic efficiency over multiple cycles, indicating stability and reusability. These features make it highly suitable for scale-up and field application in passive water treatment systems. The ability to treat OSPW without mechanical energy input, using only sunlight, offers a promising, sustainable, and cost-effective solution for industrial wastewater remediation with low operational energy input costs. This representsa meaningful advancement in applying solar-driven photocatalysis for the environmentally friendly treatment of OSPW.III. EXAMPLE PROCESS FOR PRODUCING THE PUMICE-ZnO COMPOSITE PHOTOCATALYST

[0065] FIG. 2 shows an example process flow 200 for producing the pumice-ZnO composite photocatalyst.

[0066] In at least one example, the pumice particles are initially soaked and washed in deionized (DI) water to clean them, and remove any loose particles. The cleaned pumice particles are collected through floatation, dried in air, and stored for future use. The pumice particles may be screened to a desirable size, or measured using known particle size measurement techniques, such as by dynamic light scattering.

[0067] At 202, a ZnO suspension is prepared by adding and mixing an appropriate quantity of ZnO nanoparticles in a water mixture, e.g., 2-propanol / DI water mixture. For example, the ZnO suspension may comprise about 0.05 to 1.0 grams per liter of liquid. The mixture may be sufficiently agitated, for example by sonication, to disperse the nanoparticles in the liquid medium.

[0068] At 204, the ZnO suspension is mixed with the pumice particles to form ZnO-coated pumice stone particles. In at least one example, the pumice particles used have a diameter of between about 0.5 mm and 5 mm. In other examples, the pumice particles have a diameter of between about 1.5 mm and 3.5 mm. Once the mixing is completed, the ZnO-coated pumice particles may be collected and dried in air.

[0069] At 206, the dried solids are subsequently heated, e.g., calcinated. In some examples, the solids are calcinated at above 300°C to 600°C for approximately 2 to 5 hours, and more preferably, about 500°C in a furnace for 3 hours.

[0070] The calcinated particles may then be soaked in DI water to remove unbound ZnO particles and recover only floating particles. The as-prepared pumice-ZnO composite may be further dried at room temperature and stored ready for use.

[0071] Accordingly, the ZnO-pumice photocatalyst is produced by coating ZnO nanoparticles on pumice, to form a strongly bonded composite substance. To this end, the disclosed process for forming the composite catalyst has a number of appreciated advantages:

[0072] First, proposed method uses a slurry-mixing method that starts with ZnO. Thus the method allows for the flexibility of synthesizing ZnO of desired properties using suitable synthesis methods before its subsequent immobilization on the pumice.

[0073] Second, the method requires a low calcination temperature (500°C), which makes it require less heating energy during the calcination stage.

[0074] Third, the composite is produced through a reproducible coating method that is believed to provide an enduring composite material.

[0075] Fourth, the pumice substrate is used as it is in its macro sizes without grinding it into powder. The general practice is to crush or pulverize such a substrate before composite formation with target catalysts. The disclosed process avoids that step while still producing a durable composite catalyst. The material is recovered and dried easily without caking (forming of lumps). By this, the as-fabricated photocatalyst makes efficient catalyst recovery significantly practical and helps to minimize the impact of its potential field application on the environment. The as-produced photocatalyst also facilitates easy drying and reuse.IV. TREATMENT OF CONTAMINATED WATER WITH COMPOSITE CATALYST

[0076] The pumice-ZnO composite photocatalyst may be applied for treating water contaminated with bitumen and / or bitumen byproducts (e.g., OSPW).

[0077] In use, the catalyst is applied to contaminated water and exposed to light or solar radiation for a treatment time. Any form or source of solar radiation may be used, including both natural sunlight and artificial sources that simulate solar radiation, such as solar simulators or high- intensity light lamps. Alternatively, the light / solar radiation source may be filtered or produced in a specific band of wavelengths determined to be effective for the desired photocatalysis.

[0078] The treatment can be carried out as either a batch process or a continuous process. In some cases, where applied as a batch process, the catalyst may be applied at a concentration of between0.1 g / L to 10 g / L of water per batch, and in some cases, between about 3.0 g / L to about 5.0 g / L, such as 4.0 g / L. Further, the treatment time of each batch can extend between 0.5 hours to 10 hours per day, and in some cases, 6.0 hours per day. The treatment time can further extend for a duration of time that extends one or more days. The applied solar radiation can be adjusted to produce a water-surface fluence in the range of 1 MJ / m2to 5 MJ / m2, and in some cases approximately 2.5 MJ / m2

[0079] It is noted that the method of producing the composite catalyst allows a low concentration to be used, while providing a high surface area for absorbing strong solar radiation by the catalyst.

[0080] The composite catalyst can also be applied in any manner to the water requiring treatment. In some examples, the catalyst is applied in suspended form, as shown in FIG. 1 (catalyst 106), such that it floats to the surface by virtue of the pumice substrate. This exposes the catalyst to solar radiation positioned above, and assists in ease of recovery after treatment. In these cases, the light or solar radiation source may be positioned directly above the water being treated, such as to expose the catalyst to light.

[0081] In other examples, the catalyst may be deployed in a fixed bed configuration, where the process water fluid passes through a stationary catalyst bed comprising the catalyst. In these cases, the light source may be directed towards the catalyst bed. In other examples, a fluidized bed may be used, wherein the catalyst particles are suspended by the upward flow of gas or liquid. The catalyst may also be introduced via bubbling.

[0082] The catalyst may be used as part of a passive photocatalytic process, or a photocatalytic process that involves active energy input, such as mechanical mixing (agitation), pumping, or concentrated light sources.

[0083] In some examples, method of treating wastewater further comprises measuring an indicator to determine whether treatment is completed.

[0084] In at least one example, the concentration of naphthenic acids (NAs) in the treated water is used as an indicator to test the efficacy of applying the composite material. This is because NAs are considered a primary constituent of water contaminated with bitumen and / or bitumen byproducts. The method may therefore involve testing the water before applying the composite catalyst to determinethe initial concentration of NAs. The treatment is then applied until the tested concentration of NAs is degraded by greater than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or greater than 90%.

[0085] In some cases, the selected NAs used as indicators are classified based on their oxygen number. For example, the contaminated water is tested to determine the concentration of one or more of 02-NAS, OS-NAS and C -NAs.

[0086] In other cases, the NAs selected as an indicator are based on carbon number. For example, the wastewater is tested to determine the concentration of NAs with a carbon number of greater than 10, or between 10 and 20. In still other cases, the NAs selected as an indicator are classified based on their double bond equivalent (DBE) number, e.g. ranging between 3 to 10.

[0087] In still other examples, the concentration of fluorophore organic compounds are used as an indicator to test the efficacy of applying the composite material. The method may involve testing the contaminated water before applying the composite catalyst to determine the initial concentration of fluorophore organic compounds. The treatment is then applied until the tested concentration of fluorophore organic compounds is degraded by greater than 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or greater than 90%.

[0088] In some examples, after treatment is completed, the composite catalyst is retrieved from the water. For example, the composite catalyst may be collected from the water surface when applied in suspended form. It may then be reapplied or reused for subsequent treatment owing to its reusability properties.V. EXAMPLE RESULTS

[0089] The following examples are intended solely to illustrate aspects or features associated with the described invention, and not to limit any claimed invention.(i) Example 1 - Production of Composite Pumice-ZnO Catalyst.

[0090] A composite pumice-ZnO catalyst was produced and manufactured according to process flow 200 (FIG. 2). The zinc oxide (3.34 m2 / g) was obtained from Fisher Chemical™ (Canada), while pumice stone (1.5 mm < size < 3.5 mm) were obtained from Sigma-Aldrich™ (Canada). All chemicals used were of analytical grade and used as received.

[0091] With reference to FIG. 2, at 202, a ZnO suspension was made by adding an appropriate quantity of ZnO nanoparticles in a 2-propanol / DI water mixture (2-propanol / water = 1 / 3), also obtained from Fisher Chemical™ (Canada). The mixture was sonicated for at least 30 minutes.

[0092] At 204, the ZnO suspension was mixed with the pumice stone particles to form ZnO- coated pumice stone particles. The suspension was emptied into a wide beaker containing the wet (freshly taken out of DI water) pumice (typically 20 g) and the mixture in the beaker was sonicated for 1 h. The ZnO-coated pumice particles were then collected and dried in the air (typically for more than 24 h).

[0093] At 206, the dried solids were subsequently calcinated at 500°C in a muffle furnace for 3 hours. The calcinated particles were soaked in DI water to remove unbound ZnO particles and recover only floating particles. The as-prepared pumice-ZnO composite was then further dried at room temperature and stored in closed plastic containers ready for use.

[0094] The pumice-ZnO composite was structurally and chemically examined and the pure constituent substances were compared through SEM and EDX analyses. Scanning electron microscopy (SEM) images were taken with a Zeiss™ EVO™ MAIO, while chemical compositions of the solid samples were determined through energy-dispersive X-ray spectroscopy (EDX).

[0095] The SEM images and the EDX spectra of the substances are depicted in FIGs. 3 A - 3E. As seen from the micrographs, the pure pumice (FIG. 3B) is an irregularly formed surface with tubular macrovesicles and an extensive surface for the deposition of the ZnO particles. The vesicles are of advantage as they can serve as pockets, holding the water and helping achieve good contact between the pollutants and the photocatalyst for enhanced oxidation to take place. The micrograph of the ZnO (FIG. 3 A) shows that it primarily consists of rod-shaped nano-sized particles.

[0096] An examination of the micrograph for the fabricated floating photocatalyst (FIG. 3C) indicates a formation of a composite material of a large base (the pumice) with numerous relatively very small particles (i.e., the ZnO particles) discretely deposited and firmly attached on it. The attachment of the ZnO particles onto the pumice expectedly impacted a much rougher texture to the surface of the pumice.

[0097] The SEM images also indicate that the ZnO particles are attached both on the external surface and the vesicles, but without completely blocking the tubular macrovesicles (i.e., tubes) in thepumice. This is imperative because the unblocked channels of the composite allow mass transport of substance and ensure maximum contact between the organics and photocatalyst active site.

[0098] In addition, the EDX spectra of the pure pumice (FIG. 3D) and the fabricated composite(FIG. 3E) indicate a concrete formation of pumice-ZnO with Zn element peaks displayed in the composite material compared to none found in the pristine pumice. Pumice is an aluminosilicate earth material commonly reported to contain elements such as aluminum, silicon, oxygen, and calcium. The results of the EDX analysis indicate that the pristine pumice used consisted mainly of Si, O, Al, Na, and K, while having trace amounts of Cl, Fe, Ca, and Ti. Therefore, the zinc element peaks found in the composite material came from the deposited ZnO particles.

[0099] Furthermore, X-ray diffraction (XRD) analyses were conducted on the pristine pumice and the composite catalyst. As shown in FIG. 12, the results indicate the presence of ZnO particles in the composite material (FIG. 12(b)) with the characteristic peaks a

[0100] , b

[0002] , c

[0101] , d

[0102] , e

[0110] , f

[0103] and g

[0200] of ZnO identified. Also, the XRD patterns (FIG. 12(a)) indicate a highly amorphous material in the pristine pumice with no diffraction peaks detected, in strong agreement with the results of the SEM analysis. The crystallinity of the pristine pumice was calculated to be zero, while that of the composite material was 10.34%.

[0100] Further examination of the composition of the pristine pumice and pumice-ZnO materials by using XPS analysis revealed elemental compositions similar to what the results of EDX indicated. The XPS results (FIG. 12(c) - (d)) indicate the prominence of O, Si, and Al in the pumice with no Zn present. The results also confirm the successful formation of pumice-ZnO, with the peaks of 2p states of Zn found in the spectrum of the fabricated composite catalyst.(ii) Example 2 - OSPW Used in Experimental Runs.

[0101] The OSPW used was obtained from an oil sands tailings pond in the northern region of Alberta and stored in polyvinyl chloride containers at a temperature of 4°C. Table 1 shows the water parameters of the OSPW and the concentrations of the various classes of NAs based on their oxygen numbers per molecule._ Parameter _ Value _Conductivity (mS / cm) 2.90 ± 0.05Alkalinity (mg / L as 932.918 ± 5CaCO3)pH 8.96 ± 0.02Absorbance; UV250 1.106 ± 0.002Turbidity (NTU) 1.05 ± 0.02Hardness (mg / L as CaCO3) 62.595 ± 0.5B (mg / L) 2.814 ± 0.005Ba (mg / L) 0.269 ± 0.002Ca (mg / L) 10.843 ± 0.02Mg (mg / L) 8.638 ± 0.005K (mg / L) 14.653 ± 0.02Na (mg / L) 728.793 ± 5.5Si (mg / L) 2.767 ± 002Cl’ (mg / L) 767.163 ± 2.5SO42’-S (mg / L) 214.824 ± 0.52N03’-N (mg / L) 4.978 ± 0.002O2-NAS; Classical NAs 18.178 ± 0.02(mg / L)O3-NAs (mg / L) 13.284 ± 0.02O4-NAs (mg / L) 9.362 ± 0.05Os-NAs (mg / L) 1.755 ± 0.002O6-NAs (mg / L) 0.559 ± 002Table 1 - Water Quality of Raw OSPW

[0102] NAs were determined by ultra-high performance with time-of-flight mass spectrometry, UPLC-TOF-MS in high-resolution mode (mass resolution = 40000 FWHM at 1431 m / z) at a mass range of 100-600 m / z. A detailed description of the method has been previously reported L. Meng, Z.T. How, P. Chelme-Ayala, C. Benally, M. Gamal El-Din, Z-scheme plasmonic Ag decorated Bi2WO6 / NiO hybrids for enhanced photocatalytic treatment of naphthenic acids in real oil sands process water under simulated solar irradiation, Journal of Hazardous Materials. 454 (2023) 131441. https: / / doi.Org / 10.1016 / j.jhazmat.2023.131441, the entire contents which are incorporated herein by reference.

[0103] Testing of the OSPW indicates that 02-NAs (classical NAs) were of the highest quantity followed by Os-NAs. These two groups of NAs together accounted for -73% of the total NAs. Oe-NAs were the least abundant accounting for -1.3% of the NAs, and these were closely followed by Os-NAs, which accounted for 4.1% of the NAs. This has been the commonly reportedorder of abundance of NAs in OSPW, although the actual concentrations vary widely across different OSPW streams.

[0104] According to the carbon-number-based abundance, compounds with carbon numbers 11 to 20 in their molecules were those that had considerable concentrations. NAs with carbon numbers 13 to 18 made 82 % of the total NAs.

[0105] When considering the distribution based on DBE (double bonded equivalents), NAs with DBEs of 1 to 10 were present, in the OSPW but those with DBEs of 3 to 10 together were the dominant group. Information on these distributions can help guide the focus of treated water sample analysis and assess treatment efficiency.

[0106] Fluorophore organic compounds in the OSPW were assessed through synchronous fluorescence spectroscopy (Agilent Cary Eclipse™ Fluorescence Spectrophotometer).

[0107] By using SFS analysis, the aromatics can be detected and delineated into fused and unfused-ring compounds. The SFS spectra normally return three (3) distinct peaks (see FIG. 5 - Untreated OSPW). Peak I, which appears around 274 nm, depicts those compounds consisting of unfused aromatic rings while the remaining two peaks represent compounds containing fused rings in their molecules.

[0108] Without limitation to theory, the compounds with fused rings are typically the more easily degraded compounds because of high electron-rich sites that can be easily attacked by the generated reactive species, while the ones with unfused rings are generally the more recalcitrant. Peaks II and III which appear around 312 nm and 322 nm respectively represent compounds(iii) Example 2 - Treatment of OSPW under Simulated Solar Radiation Conditions.

[0109] The prepared composite material (Example 1) was applied in treating real OSPW (Example 2) under simulated solar light with the reacting mixture left undisturbed during the photocatalysis to simulate a passive water treatment mode where no mechanical energy input is required to provide water mixing. Thus, natural diffusion molecules in solution and occasional draughts from nature dictate the mixing of target compounds with the photocatalyst.

[0110] (a.) Experimental Setup.

[0111] FIG. 1 shows the experimental reactor setup 100 for testing the pumice-ZnO composite to treat OSPW under simulated solar radiation conditions. In the reactor setup 100, pumice-ZnO composite 106 of Example 1 was applied to treat oil sands process water (OSPW) in Example 2.

[0112] As shown, the water was received in a batch reactor 102 for batch treatment. In these conditions, the pumice-ZnO floats owing to the floatability of the pumice stone. The composite 106 is then exposed to light radiation 110 from a light source 108 to activate the photocatalyst function.

[0113] The batch reactor 102 used was a rectangular transparent plastic container (11 cm x 7.5 cm x 4.2 cm). The floating composite photocatalyst 106 was applied at 4g (estimated 0.05 g ZnO) per liter to treat 100 mL of OSPW. Radiation 108 was provided by a solar simulator (Photo Emission Technology Inc.™, USA) with the solar radiation intensity measured as 115.740 W / m2(FIG. 13).

[0114] (b.) Conditions for Experimental Test Runs.

[0115] For each experimental run, the reactor 102 with the OSPW 104 and composite photocatalyst 106 were initially covered in the dark for 1 hour to attain adsorption / desorption equilibrium. Subsequently, the reactor 102 and its contents were placed directly under the radiation 108 for the solar photocatalytic treatment. The solar photocatalytic treatment was conducted for 6 h with no agitation to simulate the same conditions that could be encountered when the floating catalyst is applied on a field scaled-up test. The OSPW was sampled at the start and end of the 6 h irradiation.

[0116] (c.) Evaluating Degradation of Naphthenic Acids (NAs).

[0117] The changes in the concentrations of the NAs was used as indicator to determine the effectiveness of each treatment.

[0118] As noted previously, the concentration of NAs was determined by ultra-high performance with time-of-flight mass spectrometry, UPLC-TOF-MS in high-resolution mode (mass resolution = 40000 FWHM at 1431 m / z) at a mass range of 100-600 m / z.

[0119] FIGs. 4A - 4C show the degradation efficiencies for the different classes of NAs present in the OSPW after the treatments.

[0120] As indicated in FIG. 4A, the percentage degradation of the total NAs after the solar photocatalytic treatment for 6 h (water-surface fluence = 2.484 MJ / m2) by using the pumice-ZnOfloating catalyst was -78%. The irradiation with pumice alone achieved a 3.4 % degradation of the NAs which suggests possible photocatalytic activity in the pumice, although the value is too small to be conclusive.

[0121] Pumice is normally an amorphous rock material that contains chiefly silicon dioxide, although the actual chemical composition varies across deposits. The atomic composition of the pumice used (Table 2, below) indicates silicon and oxygen as the primary constituent elements. Therefore, an exhibition of some photocatalytic activity by pumice is consistent with its chemical constituents.ELEMENT Atomic %O 69.68Na 2.27Al 4.73 Si 21.22 Cl 0.05 K 1.54 Ca 0.23 Ti 0.02 Fe 0.21 Pd 0.07Total 100Table 2 - Elemental Composition of the Pure Pumice

[0122] A closer evaluation of the degradation of the NAs indicated that various classes of NAs exhibited different degradation efficiencies. For the photocatalytic degradation of the NAs with pumice-ZnO as the photocatalyst, Ch-NAs showed the highest degradation efficiency, achieving 91.5%, followed by Ch-NAs and CU-NAs in that order with degradation efficiencies of 61.1% and59.6% respectively.

[0123] Both Os-NAs and Oe-NAs showed increases in their concentration, thereby giving negative percentage degradations, however, it is believed without restriction to a theory that some Os-NAs and Oe-NAs had been formed from the oxidative conversion of the NAs with lower oxygen numbers (especially Ch-NAs and C -NAs).

[0124] These results appear to agree with previously reported observations in oxidative degradation NAs in OSPW. It was reported that NAs with higher oxygen numbers could be less susceptible to oxidative degradation and that they could be produced because of advanced oxidative degradation of Ch-NAs.

[0125] It should be noted that, although the concentrations of Os-NAs and Oe-NAs increased by 30% and 95.4%, respectively after the treatment, their respective concentrations were 2.28 and 1.09 mg / L. Therefore, the production of these classes of NAs did not significantly impact the degradation percentage of the total NAs. Similar results were observed for the irradiation with pure pumice as the catalyst, indicating that the observed 3.4% reduction in total NAs was mainly due primarily to photocatalytic degradation, since the increment in oxy-NAs could only result from the photocatalytic reactions.

[0126] It is noted that dark reactions resulted in positive removal efficiencies for all the classes of NAs and that photocatalytic treatment experiments were started after the dark reaction phase.

[0127] The changes in the concentrations of the NAs based on the carbon number per molecule and the DBE were also assessed. With the composite floating catalyst under solar radiation, there was high degradation across the various groups of NAs based on DBE except for compounds with a DBE value of 8, which had less than 50% degradation. Based on the carbon number per molecule, and moving from carbon numbers 10 to 20, compounds with 10 carbon atoms were degraded the least, and the degradation generally increased as the carbon number increased. Thus, it appears there was a degradation pattern based on carbon number.

[0128] (d.) Evaluating Degradation of Fluorophore Organics.

[0129] Fluorophore organic compounds in the OSPW were also assessed using synchronous fluorescence spectroscopy (SFS) (Agilent Cary Eclipse™ Fluorescence Spectrophotometer).

[0130] As shown in FIG. 5, after dark reaction (adsorption phase), no noticeable changes were observed in the peaks generated by the SFS (e.g., Peaks I, II and III). Solar irradiation treatment showed some changes in peaks. With the pure pumice irradiated for 6 h in the OSPW, both peaks IIand III showed some reductions suggesting that they were partly degraded during the process. However, peak I increased in intensity.

[0131] The results indicate some fused-ring compounds are converted to compounds with unfused rings as part of their degradation pathways, and that the compounds with unfused rings could be comparatively less susceptible to the oxidation process.

[0132] The results are consistent with previously observed results and elucidated reaction mechanisms for the advanced oxidation of fluorophore compounds. The results also confirm that the pumice exhibited some photocatalytic activity in degrading some fluorophore organics. The results, however, indicate that the photocatalytic activity exhibited in OSPW by pumice is considerably weak. There is about 17.4% degradation of the aromatic compounds. It should be noted that direct photolysis can help degrade the aromatic organics to some extent, especially in the absence of a catalyst of considerable photocatalytic activity.

[0133] The percentage degradation of the fluorophore organics, when compared with the corresponding 3.5% degradation of NAs, indicate that the aromatics are more susceptible to oxidative degradation. On the other hand, the pumice-ZnO material exhibited significant photocatalytic activity in degrading the fluorophore compounds. Peaks II and III were effectively attenuated after the 6 h of photocatalysis, while only ~ 19% of peak I remained. Overall, -90% of aromatic organics in the OSPW were degraded during the photocatalysis with the composite floating catalyst.

[0134] (e.) Evaluating Impact of the Solar Photocatalytic Treatment on Water Quality.

[0135] To assess the impact of the solar-activated photocatalytic treatment on water being treated, the water quality parameters of raw and treated OSPW samples were evaluated. Both anions and cations in the water samples were determined along with water hardness and alkalinity.

[0136] Dissolved anions were determined with a colorimetric autoanalyzer, Gallery Plus Beermaster Autoanalyzer™ (Thermo Fisher Scientific™, Finland). Dissolved target analytes, including SO4-S, NO3-N, NO2-N, CF, PO4-P, and NH4-N, were measured via well-known color reactions. Samples and method reagents were injected into reaction cuvettes, generating colored complexes after the reaction. A separate analysis method was run in each cuvette. The intensity of color change in the solution was dependent on the concentration of analyte in the sample and wasmeasured by light absorbance at a specific wavelength. The amount of light absorbed by the solution follows the Beer-Lambert law:Ax = xlc where: Ax is the absorbance of light at the target wavelength, e is the extinction coefficient of the colour complex at that wavelength, I is the path length of the cuvette in cm, and c is the concentration of the analyte in solution.

[0137] Dissolved metal ions, S, and P, were determined through inductively coupled plasma- optical emission spectroscopy, ICP-OES, by using the iCAP6300™ Duo ICP-OES Spectrometer (Thermo Fisher Corp. ™, UK). This method is appropriate for total dissolved solids (TDS) concentrations <2000 mg / L. Samples were aspirated by a nebulizer into an argon plasma, where they were atomized at temperatures of approximately 5500 - 8000 K. Analyte atoms were excited, producing characteristic emission patterns unique to each element. These emission lines were detected by a spectrometer, permitting the simultaneous analysis of several elements at once. An internal standard solution containing yttrium (Y) was used during analysis to correct for matrix effects. Analyte emission lines, viewing positions (radial vs. axial), and sample dilution factors were chosen to minimize inter-element interferences. Elements like Li, Na, K, Mg, and Ca are typically viewed radially to minimize Easily-Ionizable-Element (EIE) interferences.

[0138] Table 3 (below) and Table 4 (below) show the results obtained.Sample Untreated OSPW Pumice-ZnO + solar-treated* TON-N = NO3— N + NO2’-N.Table 3 - Water Quality Parameters of Treated and Untreated OSPW SamplesMetal ion (mg / L) Untreated OSPW Treated OSPWAl 0.434 0.013As 0.024 0.032B 2.814 3.42Ba 0.269 0.302Ca 10.843 13.821Cu 0.006 0.012Fe 0.085 0.002K 14.653 20.541Li 0.202 0.253Mg 8.638 10.483Mo 0.127 0.16Na 728.793 761.906Ni 0.006 0.007Si 2.767 3.091Sr 0.574 0.7Zn <LOD 0.034LOD = limit of detection. Table 4 - Metal and Metalloids in Untreated and Treated OSPW Samples

[0139] As shown in these tables, were no significant changes in the concentrations of elements of environmental concern such as As, Zn, and Ba after the treatment application. This can help allay any concerns about potential leaching as a result of applying the composite material for OSPW treatment.

[0140] Considering other water parameters, there were increases in the hardness and alkalinity. Without limitation to theory, these increases may be ascribed to the production of carbonates (carbon dioxide dissolved in water) during oxidation and degradation of the organic compounds. It should be noted that the composite catalyst or the pure pumice did not contain carbon or carbonates. However, considering the initial values of these parameters, the changes would not be expected to have significantly affected the water quality.

[0141] Looking at the anions, the concentrations of CT, SC>42', and PC>42' increased in the treated water. This can be explained as resulting from oxidation of the reduced forms of S and P (sulfite and phosphite ions) by the photocatalysis to form more phosphate and sulfate ions.

[0142] The ions can also partly come from the oxidation of heterogeneous organic compounds containing these elements, especially sulfur. The elemental analysis of the pumice indicated that the materials did not contain P and S (Table 4).

[0143] The increase in CT can be attributed to the leaching of some chlorides from the pumice stone, more especially because its results indicate that some Na, Mg, and K could have also leached from the stone (Table 4).

[0144] Considering the results as a whole, there was no significant adverse impact of the treatment on the water.(iv) Example 4 - Passive Treatment of OSPW under Real Solar Radiation (Sunlight).

[0145] The prepared pumice-ZnO composite material in Example 1 was applied in passive photocatalytic treatment of scaled-up volume of OSPW (Example 2) under natural solar radiation, away from laboratory conditions.

[0146] (a.) Experimental Setup.

[0147] To assess the practical application of the fabricated floating photocatalyst in field outside laboratory environments, a similar experimental setup as shown in FIG. 1 was used. The light source 108 was however removed and replaced with natural solar radiation (FIG. 13).

[0148] The pumice-ZnO composite was again applied at 4g per L to treat real OSPW in solar- activated photocatalysis under natural solar radiation. A scaled-up volume (200 mL) of OSPW was used in the same reactors as were used for the laboratory experiments in Example 3. The OSPW in batch reactors was exposed to the sun undisturbed for the duration of treatment while the reactors were covered in a clear, solar-transparent polyvinyl material to minimize water loss to evaporation.

[0149] As a control, photolysis experiment was also simultaneously conducted where 200 mL of OSPW was put in an identical batch reactor and exposed to sunlight without the floating photocatalyst.

[0150] The experiments were conducted at a location on the north campus of the University of Alberta (53.5262°N, 113.5279°W) between 11 a.m. and 5 p.m. on two different days in August. The solar radiation intensity was monitored at intervals with a spectrometer (StellarNet Inc.™, USA).

[0151] (b.) Conditions for Experimental Test Runs.

[0152] Before the start of the photocatalysis by exposure to natural sunlight, dark experiment was conducted for 1 h to allow adsorption / desorption equilibrium. The sample was then exposed to natural solar radiation for 6 h.

[0153] Samples were taken at the start and end of treatment to assess the degradation of the fluorophore organic compounds and NAs in the OSPW. The content of the reactor was mixed before sampling to ensure homogeneity. For control, direct photolysis of OSPW was also conducted and samples were analyzed for NAs and fluorophore organic compounds.

[0154] (c.) Evaluating Degradation of Naphthenic Acids (NAs).

[0155] The effectiveness of the treatment in degrading NAs in real solar radiation was also assessed. NAs were again determined by ultra-high performance with time-of-flight mass spectrometry, UPLC-TOF-MS in high-resolution mode (mass resolution = 40000 FWHM at 1431 m / z) at a mass range of 100-600 m / z.

[0156] The degradation efficiencies were analyzed based on the classes of NAs and the results are as depicted in FIGs. 7A - 7D and 11 A - 11C.

[0157] On day 1, after solar photocatalysis with the composite material, 70.72%, 52.95%, and 31.12% degradations were recorded, while the degradations recorded on day 2 were 72.69%, 42.19%, and 32.05%, for 02-NAs, Os-NAs and 04-NAs, respectively.

[0158] The results for both days indicate increases in the concentrations of Os-NAs and Oe- NAs (FIGs. 11A - 11C), consistent with the results obtained from the laboratory experiments in Example 3. Considering the percentage degradation of total NAs, there was 50.5% on day 1 and 48.7% on day 2 in the total NAs.

[0159] These are significant reductions when the actual concentration of the active photocatalyst (ZnO) is factored in along with the no-mechanical-mixing condition. The closeness in the overall degradation efficiencies was expected as the total fluence values determined for both days did not differ considerably.

[0160] Additionally, the average solar spectra for both days were similar. Some degradation of the NAs was recorded from the irradiation of OSPW in the absence of the catalyst. As a result of the solar radiation alone, 5.80% and 11.41% reductions in total NAs were recorded for day 1 and day 2, respectively. It is understood that NAs in OSPW are negligibly degradable in direct photolysis. Without restriction to theory, this is attributed to the low molar absorption coefficient of NAs within the solar spectrum (300 nm and above), which makes direct photolysis ineffective for their degradation.

[0161] As shown in the radiation spectra, there were some high intensities of UV radiation around 200 nm on both days which likely explains the observed reductions due to the photolysis.Furthermore, degradation of the Ch-NAs based on carbon number (molecular weight) and DBE was examined.

[0162] In general, as shown in FIGs. 7C - 7D, Ch-NAs with higher molecular weights showed higher degradation efficiencies, consistent with the results of the laboratory experiments on the degradation of NAs. Without restriction to particular theory, this degradation pattern is attributed to the availability of more carbon sites for oxidative attacks on compounds with higher carbon numbers and the presence of more hydrogen atoms which can be involved in hydrogen abstraction reactions. This is positive for this treatment method, since the more hydrophobic tendency of NAs with higher molecular weights (due to higher carbon numbers) can make them more toxic.

[0163] Thus, the toxic effects can be expected to be reduced by the treatment technology, which eliminates high carbon numbers of NAs. Similarly, NAs having higher DBEs showed higher degradation percentages than others with lower DBEs. Without limitation to theory, this may be partly attributed to the availability of more electron-rich sites resulting from higher hydrogen deficiencies (more DBEs). NAs with lower DBEs may also be generated as intermediates from the oxidative degradation of NAs with higher DBEs. Oxidative ring opening has been reported as a possible degradation pathway for NAs with saturated carbon rings in their molecules.

[0164] (d.) Evaluating Degradation of Fluorophore Organic Compounds.

[0165] Fluorophore organic compounds in the OSPW were again assessed through synchronous fluorescence spectroscopy (SFS) (Agilent Cary Eclipse™ Fluorescence Spectrophotometer).

[0166] The changes in the concentrations of the fluorophore compounds assessed through SFS analysis are shown in FIGS. 6A - 6B.

[0167] At the end of 6 h (-250 MJ / m2) treatment on day 1, about 72.5% degradation of the initial fluorophore compounds in the OSPW was recorded as a result of the photocatalysis by using the pumice-ZnO catalyst, while -75% degradation was recorded on day 2 (fluence - 2.42 MJ / m2) ascalculated from the relative intensities of the peaks. It should be noted that no mechanical mixing was applied in these experiments.

[0168] Thus, the results highlight the positive potential of the fabricated floating photocatalyst for field applications in the effective solar photocatalytic treatment of industrial wastewater such as OSPW using natural sunlight as the radiation source. Photolysis accounted for -24.1% and -25.6% for day 1 and day 2, respectively.(v) Example 4 - Recovery and Reusability of the Composite Floating Photocatalyst

[0169] Easy recoverability and high reuse are among the necessary properties that a heterogeneous photocatalyst should have to be a good candidate for scaled-up water treatment applications. Therefore, the fabricated pumice-ZnO floating catalyst in Example 1 was tested and analyzed to evaluate its recoverability and reusability for repeated use in the photocatalytic treatment of OSPW. This was conducted by examining the physical and chemical stability of the material through SEM and EDX analyses. The material was also taken through several runs of solar photocatalytic treatment and the observed efficiencies were compared.

[0170] For photocatalyst reusability experiments, the composite catalyst was additionally collected at the end of each experiment run, rinsed appropriately with DI water, dried at room temperature, and stored for the next application. The OSPW samples were analyzed to assess the degradation of the fluorophore organics and NAs in the OSPW.

[0171] Scanning electron microscopy (SEM) images were taken with a Zeiss™ EVOTM MAIO, while chemical compositions of the solid samples were determined through energy-dispersive X-ray spectroscopy (EDX).

[0172] The results of the EDX and SEM analyses are depicted in FIGs. 8A - 8D. From the examination of the SEM images of fresh and used (and then recovered) pumice-ZnO material, there was no noticeable change in the physical structure of the material even after it had been applied for the treatment. Similarly, the recorded EDX spectra indicate that the composition of the material was not affected by the application in OSPW treatment even at the microstructural level.

[0173] This suggests that there was negligible leaching of the catalyst material, consistent with the results obtained above from analysis of the impact of the treatment on water quality. The resultsindicated that a strongly bonded and highly stable composite material was formed from the fabrication method employed.

[0174] Additionally, as indicated in FIGs. 9A - 9B, there was no steep decline in the treatment efficiency of the material in degrading both the organic compounds as it was repeatedly recovered and reused. These results suggest that the fabricated floating catalyst is an easily recoverable and highly reusable material with the potential for cost-effective and environmentally friendly scale-up treatment applications.(vi) Example 5 - Impact of the Treatment on Toxicity and Bioavailability.

[0175] To assess the implications of the application of the prepared material on the treated OSPW, the change in toxicity analysis of the raw and treated OSPW samples was conducted.

[0176] Acute toxicity assessment was conducted by using Microtox® bioassay. This was used as a surrogate to determine acute toxicity of water samples. The Microtox® bioassay used a 96-well microplate with Vibrio fischeri™ as the bioluminescent bacteria.

[0177] Bioavailability analysis was conducted by using biomimetic extraction through solid phase micro-extraction (BE-SPME) where the bioavailable organics were adsorbed onto poly dimethyl siloxane-coated fibers, and the quantification of the extracted organics was conducted by using a gas chromatograph equipped with a flame ionization detector (GC-FID).

[0178] More particularly for the bioavailability analysis, OSPW samples were collected in ~20 mL glass vials with Teflon caps. The samples were acidified with 50 pL of phosphoric acid, bringing the sample pH to approximately 2.4. Acidified samples were then transferred to the SPME autosampler. Acidified OSPW samples were equilibrated with the 30 pm PDMS (polydimethylsiloxane) SPME fibers for 100 minutes with orbital agitation (250 rpm) at 30°C in the autosampler’s sample incubation module. After completion of sample equilibration / extraction, the autosampler automatically retracted the fiber and injected it into the GC injection port. The fiber was thermally desorbed in the injection port for three minutes to fully desorb the organic components that had partitioned into the PDMS. The use of an SPME autosampler permits a single fiber to be used for multiple, successive sample extractions. The carrier gas used was helium at a constant flow rate of 17 mL / min. The GC oven was temperature programmed from 40°C for three minutes up to 300°C at arate of 45°C / minute. The FID temperature is 300°C and the inlet temperature is 280°C. The detector signal attenuation was -3 (Perkin Elmer Autosystem GC).

[0179] As shown in FIG. 10A, there were reductions in the observed inhibition effects of OSPW on the marine bacteria after the photocatalytic treatment with the floating catalyst. For instance, based on 15 -minute exposure of the bacteria, the inhibition effect decreased from 65.29% recorded in untreated OSPW to 40.87%, 52.21%, and 32.71% recorded in treated OSPW samples from the photocatalysis conducted in the laboratory, real solar photocatalysis (day 1), and real solar photocatalysis (day 2), respectively. These results are consistent with the reductions in the organics in the OSPW especially NAs which have been reported to be primary contributors to the acute toxic effects of OSPW.

[0180] However, compared to the percentage degradation of NAs in these treated OSPW samples, the toxicity did not decrease proportionally with the reduction in concentration of the NAs, suggesting a complex multifactor cause of the observed acute toxic effects.

[0181] Also, the impact of the photocatalytic treatment on the bioavailability effect in the OSPW was evaluated by using BE-SPME (Biomimetic Extraction-Solid Phase Microextraction). As shown in FIG. 10B, there were considerable reductions in the bioavailability recorded in the treated samples compared to the raw OSPW. Comparing the results with the corresponding reductions in the fluorophore aromatics and NAs could indicate that these groups of organics are major contributors to the bioavailability recorded in the untreated OSPW. It should be noted that the BE-SPME results account for the bioavailable acid-extractable organic compounds.VI. INTERPRETATION

[0182] Various systems or methods have been described to provide an example of an embodiment of the claimed subject matter. No embodiment described limits any claimed subject matter and any claimed subject matter may cover methods or systems that differ from those described below. The claimed subject matter is not limited to systems or methods having all of the features of any one system or method described below or to features common to multiple or all of the apparatuses or methods described below. It is possible that a system or method described is not an embodiment that is recited in any claimed subject matter. Any subject matter disclosed in a system or methoddescribed that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such subject matter by its disclosure in this document.

[0183] Furthermore, it will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[0184] It should also be noted that the terms “coupled” or “coupling” as used herein can have several different meanings depending in the context in which these terms are used. For example, the terms coupled or coupling may be used to indicate that an element or device can electrically, optically, or wirelessly send data to another element or device as well as receive data from another element or device. As used herein, two or more components are said to be “coupled”, or “connected” where the parts are joined or operate together either directly or indirectly (i.e., through one or more intermediate components), so long as a link occurs. As used herein and in the claims, two or more parts are said to be “directly coupled”, or “directly connected”, where the parts are joined or operate together without intervening intermediate components.

[0185] It should be noted that terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree may also be construed as including a deviation of the modified term if this deviation would not negate the meaning of the term it modifies.

[0186] Furthermore, any recitation of numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified bythe term "about" which means a variation of up to a certain amount of the number to which reference is being made if the end result is not significantly changed.

[0187] The present invention has been described here by way of example only, while numerous specific details are set forth herein in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that these embodiments may, in some cases, be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the description of the embodiments. Various modification and variations may be made to these exemplary embodiments without departing from the spirit and scope of the invention, which is limited only by the appended claims.

Claims

CLAIMS:

1. A catalyst used for photocatalytic treatment of water contaminated with bitumen or a bitumen byproduct, comprising a pumice-ZnO composite.

2. The catalyst of claim 1, wherein the composite comprises pumice particles coated with ZnO nanoparticles.

3. The catalyst of any one of claims 1 to 4, wherein the water is oil sand process water.

4. A process for photocatalytic treatment of water contaminated with bitumen or a bitumen byproduct, comprising: contacting the water with a pumice-ZnO composite catalyst; and exposing the composite to light.

5. The process of claim 5, wherein the catalyst is applied in suspended form and rises to float over the water surface.

6. The process of any one of claims 5 or 6, wherein the light comprises solar radiation generated by a solar radiation source which is natural and / or artificial.

7. The process of any one of claims 5 to 7, wherein the treatment is a passive photocatalytic treatment.

8. The process of any one of claims 5 to 8, further comprising measuring the concentration of an indicator to determine whether treatment is completed.

9. The process of claim 9, wherein the indicator is one or more of naphthenic acids and fluorophore organic compounds.

10. The process of any one of claims 5 to 10, wherein the light is applied at an intensity to produce a water-surface fluence in the range of 1 MJ / m2to 5 MJ / m2.

11. The process of any one of claims 5 to 11, wherein the catalyst is applied at a catalyst concentration of between 0.05 g / L and 1.0 g / L of water.

12. The process of any one of claims 5 to 12, wherein the exposure time is between 0.5 hours to 10 hours per day, for one or more days.

13. The process of any one of claims 5 to 13, wherein the process is applied as a batch or continuous process.

14. The process of any one of claims 5 to 14, wherein the water is oil sand process water.

15. The process of any one of claims 5 to 14, further comprising initially allowing the water and composite catalyst to sit without light to attain an adsorption / desorption equilibrium during a dark phase reaction process.

16. The process of any one of claims 5 to 16, further comprising retrieving and reusing the catalyst for multiple reuse cycles.

17. A method of producing the catalyst of any one of claims 1 to 4, comprising: producing a suspension by mixing ZnO nanoparticles with water; mixing the suspension with pumice stone particles to form ZnO-coated pumice particles; and calcinating the ZnO-coated pumice particles.

18. The method of claim 18, wherein the pumice stone particles have a diameter between 0.5 mm to 5 mm.

19. The method of any one of claims 18 or 19, wherein the pumice particles are not crushed or pulverized.

20. The method of any one of claims 18 to 20, wherein the calcination occurs at 300°C to 600°C for approximately 2 to 5 hours, and more preferably, about 500°C for approximately 3 hours.

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