Photocatalytic treatment of organoselenium in synthetic mine-impacted effluents.

Biological selenium reduction processes are commonly employed as the best available technology (BAT) for selenium removal; however, as a by-product they produce trace amounts of organoselenium compounds with orders of magnitude greater bioaccumulation potential and toxicity. Here, we assessed buoyant photocatalysts (BPCs) as a potential passive advanced oxidation process (P-AOP) for organoselenium treatment. Using a synthetic mine-impacted water solution, spiked with selenomethionine (96 µg/L) as a representative organoselenium compound, photocatalysis with BPCs fully eliminated selenomethionine to <0.01 µg/L with conversion to selenite and selenate. A theoretical reaction pathway was inferred, and a kinetics model developed to describe the treatment trends and intermediates. Given the known toxic responses of Lepomis macrochirus and Daphnia magna to organoselenium, it was estimated that photocatalysis could effectively eliminate organoselenium acute toxicity within a UV dose of 8 kJ/L (1-2 days solar equivalent exposure), by transformation of selenomethionine to less hazardous oxidized Se species. Solar photocatalysis may therefore be a promising passive treatment technology for selenium-impacted mine water management.

Photocatalytic treatment of diverse contaminants of potential concern in oil sands process-affected water.

Oil sands process-affected water (OSPW), generated by surface mining in Canada's oil sands, require treatment of environmentally persistent dissolved organic compounds before release to the watershed. Conventional chemical and mechanical treatments have not proved suitable for treating the large quantities of stored OSPW, and the biological recalcitrance of some dissolved organics may not be adequately addressed by conventional passive treatment systems. Previous work has evaluated photocatalytic treatment as a passive advanced oxidation process (P-AOP) for OSPW remediation. This work expands upon this prior research to further characterize the effects of water chemistry on the treatment rate and detoxification threshold. Under artificial sunlight, buoyant photocatalysts (BPCs) detoxified all OSPW samples within 1 week of treatment time with simultaneous treatment of polycyclic aromatic hydrocarbons, naphthenic acid fraction components (NAFCs), and un-ionized ammonia. Overall, these results further demonstrate passive photocatalysis as an effective method for treatment of OSPW contaminants of potential concern (COPCs).

A multi-step approach: Coupling of biodegradation and UV photocatalytic oxidation TiO2 for the treatment of naphthenic acid fraction compounds in oil sands process-affected water.

Bitumen extraction in Alberta's oil sands region uses large volumes of water, leading to an abundance of oil sands process-affected water (OSPW). OSPW contains naphthenic acid fraction compounds (NAFCs) which have been found to contribute to OSPW toxicity. This study utilized a multistep treatment, coupling biological degradation with UV photocatalytic oxidation, and nutrient addition to boost the native microbial community's degradation capacity. OSPW initially contained 40-42 mg/L NAFCs with a toxicity of 3.8-3.9 TU. Initial biodegradation (Step 1) was used to remove the easily biodegradable NAFCs (11-25% removal), followed by a light or heavy dose of oxidation (Step 2) to breakdown the recalcitrant NAFCs (66-82% removal). Lastly, post-oxidation biodegradation with nutrients (Step 3) removed the residual bioavailable NAFCs (16-31% removal). By the end of the multistep treatment, the final NAFC concentrations and toxicity ranged from 5.3 to 6.8 mg/L and 1.1-1.2 TU. Analysis showed that OPSW was limited in phosphorus (below detection limit), and the addition of nutrients improved the degradation of NAFCs. Two treatments throughout the multistep treatment never received nutrients and showed minimal NAFC degradation post-oxidation. The native microbial community survived the stress from UV photocatalytic oxidation as seen by the post-oxidation NAFC biodegradation. Microbial community diversity was reduced considerably following oxidation, but increased with nutrient addition. The microbial community consisted predominately of Proteobacteria (Gammaproteobacteria and Alphaproteobacteria), and the composition shifted depending on the level of oxidation received. Possible NAFC-degrading microbes identified after a light oxidation dose included Pseudomonas, Acinetobacter and Xanthomonadales, while Xanthobacteracea and Rhodococcus were the dominant microbes after heavy oxidation. This experiment confirms that the microbial community is capable of degrading NAFCs and withstanding oxidative stress, and that degradation is further enhanced with the addition of nutrients.

A Light Touch: Solar Photocatalysis Detoxifies Oil Sands Process-Affected Waters Prior to Significant Treatment of Naphthenic Acids.

Environmental reclamation of Canada's oil sands tailings ponds is among the single largest water treatment challenges globally. The toxicity of oil sands process-affected water (OSPW) has been associated with its dissolved organics, a complex mixture of naphthenic acid fraction components (NAFCs). Here, we evaluated solar treatment with buoyant photocatalysts (BPCs) as a passive advanced oxidation process (P-AOP) for OSPW remediation. Photocatalysis fully degraded naphthenic acids (NAs) and acid extractable organics (AEO) in 3 different OSPW samples. However, classical NAs and AEO, traditionally considered among the principal toxicants in OSPW, were not correlated with OSPW toxicity herein. Instead, nontarget petroleomic analysis revealed that low-polarity organosulfur compounds, composing <10% of the total AEO, apparently accounted for the majority of waters' toxicity to fish, as described by a model of tissue partitioning. These findings have implications for OSPW release, for which a less extensive but more selective treatment may be required than previously expected.

Targeted nanoparticle binding & detection in petroleum hydrocarbon impacted porous media.

Targeted nanoparticle binding has become a core feature of experimental pharmaceutical product design which enables more efficient payload delivery and enhances medical imaging by accumulating nanoparticles in specific tissues. Environmental remediation and geophysical monitoring encounter similar challenges which may be addressed in part by the adoption of targeted nanoparticle binding strategies. This study illustrates that engineered nanoparticles can bind to crude oil-impacted silica sand, a selective adsorption driven by active targeting based on an amphiphilic polymer coating. This coating strategy resulted in 2 mg/kg attachment to clean silica sand compared to 8 mg/kg attachment to oil-impacted silica sand. It was also shown that modifying the surface coating influenced the binding behaviour of the engineered nanoparticles - more hydrophobic polymers resulted in increased binding. Successful targeting of Pluronic-coated iron oxide nanoparticles to a crude oil and silica sand mixture was demonstrated through a combined quantitative Orbital Emission Spectroscopy mass analysis supported by Vibrating Scanning Magnetometer magnetometry, and a qualitative X-ray micro-computed tomography (CT) visualization approach. These non-destructive characterization techniques facilitated efficient analysis of nanoparticles in porous medium samples with minimal sample preparation, and in the case of X-Ray CT, illustrated how targeted nanoparticle binding may be used to produce 3-D images of contaminated porous media. This work demonstrated successful implementation of nanoparticle targeted binding toward viscous LNAPL such as crude oil in the presence of a porous medium, a step which opens the door to successful application of targeted delivery technology in environmental remediation and monitoring.

Size-Tunable Fe3O4 Spherical Nanoclusters Through a One-Pot Hydrothermal Synthesis.

A new method is presented for the synthesis of monodisperse, size-tunable Fe3O4 spherical nanocluster particles through a simple, one-step hydrothermal reaction, according to a kinetics-controlled self-assembly process of smaller nanocrystals into hierarchical mesoporous aggregates. The mean diameter of the particles can be controlled over a broad range up to ~230 nm by simply varying the concentration of the precipitating reagent (urea or ammonia). The particles can be easily dispersed in water with excellent colloidal stability, exhibit a high surface area of ~ 60 m2 g(-1), and demonstrate size-dependent magnetic separation kinetics, where the larger nanoclusters exhibit rapid magnetophoresis, and the smaller nanoclusters remain inseparable. Thus particle size control is essential for improving magnetic separation processes.

Synthesis of magnetic rattle-type nanostructures for use in water treatment.

A hydrothermal technique to simultaneously remove a SiO2 template and crystallize a TiO2 outer layer was used to create magnetically separable, hollow rattle-type nanoparticles consisting of a magnetic Fe3O4 core contained within a hollow TiO2 shell. Fe3O4 cores approximately 240 nm in diameter were synthesized, subsequently coated by SiO2 and finally coated with TiO2. This was followed by a hydrothermal treatment to selectively etch the silica, resulting in rattle-type particles with a final outer shell diameter of approximately 390 nm. The product of hydrothermal treatment were rattle-type particles with increased crystallinity and a 68% increase in surface area. Characterization confirmed the ability to etch a hard SiO2 template through use of a simple and benign thermal treatment with pure water, while simultaneously introducing a crystalline phase into the TiO2 active layer. The potential of the particles to be employed as a catalyst in UV induced advanced water treatment for removal of organic contaminants was evaluated through a colorimetric photocatalytic degradation assay using methylene blue as a model contaminant. The ability of the particles to be magnetically separated from solution after treatment and recycled for consecutive treatment cycles was then demonstrated. This technique for selectively removing a hard SiO2 template while simultaneously crystallizing a TiO2 shell avoids the use of hazardous chemical etchants or complex processing, rendering the synthesis of hierarchical, multimaterial, hollow, porous rattle-type particles a simple, attractive, and environmentally friendly "one-pot" technique for potential industrial application.

Silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biocompatible contrast agent in biomedical photoacoustics.

In this study, we report for the first time the use of silica-coated superparamagnetic iron oxide nanoparticles (SPION) as contrast agents in biomedical photoacoustic imaging. Using frequency-domain photoacoustic correlation (the photoacoustic radar), we investigated the effects of nanoparticle size, concentration and biological media (e.g. serum, sheep blood) on the photoacoustic response in turbid media. Maximum detection depth and the minimum measurable SPION concentration were determined experimentally. The nanoparticle-induced optical contrast ex vivo in dense muscular tissues (avian pectus and murine quadricept) was evaluated and the strong potential of silica-coated SPION as a possible photoacoustic contrast agents was demonstrated.