Removal of organic compounds and trace metals from oil sands process-affected water using zero valent iron enhanced by petroleum coke.

The oil production generates large volumes of oil sands process-affected water (OSPW), referring to the water that has been in contact with oil sands or released from tailings deposits. There are concerns about the environmental impacts of the release of OSPW because of its toxicity. Zero valent iron alone (ZVI) and in combination with petroleum coke (CZVI) were investigated as environmentally friendly treatment processes for the removal of naphthenic acids (NAs), acid-extractable fraction (AEF), fluorophore organic compounds, and trace metals from OSPW. While the application of 25 g/L ZVI to OSPW resulted in 58.4% removal of NAs in the presence of oxygen, the addition of 25 g petroleum coke (PC) as an electron conductor enhanced the NAs removal up to 90.9%. The increase in ZVI concentration enhanced the removals of NAs, AEF, and fluorophore compounds from OSPW. It was suggested that the electrons generated from the oxidation of ZVI were transferred to oxygen, resulting in the production of hydroxyl radicals and oxidation of NAs. When OSPW was de-oxygenated, the NAs removal decreased to 17.5% and 65.4% during treatment with ZVI and CZVI, respectively. The removal of metals in ZVI samples was similar to that obtained during CZVI treatment. Although an increase in ZVI concentration did not enhance the removal of metals, their concentrations effectively decreased at all ZVI loadings. The Microtox(®) bioassay with Vibrio fischeri showed a decrease in the toxicity of ZVI- and CZVI-treated OSPW. The results obtained in this study showed that the application of ZVI in combination with PC is a promising technology for OSPW treatment.

Detection and characterization of silver nanoparticles in aqueous matrices using asymmetric-flow field flow fractionation with inductively coupled plasma mass spectrometry.

Engineered nanomaterials (EN) may be released into the environment as a result of their use in various consumer products. Silver nanoparticles (nAg) are widely used as an antimicrobial agent in personal care and household products, and in textiles. Since there is high potential for nAg to be released into municipal wastewater and then discharged into the aquatic environment, there is a need to develop methods for the analysis of these materials in aqueous matrices. Asymmetric-flow field flow fractionation (AF4) with on-line detection by ultra violet-visible (UV-Vis) spectroscopy or inductively coupled plasma mass spectrometry (ICP-MS) was used to detect and characterize nAg in aqueous matrices. Analysis of a mixture of 20, 40 and 60 nm nAg standards suspended in water resulted in a well resolved fractogram. Retention times of nAg separated by AF4 were correlated with the particle sizes of the standards. The limit of detection (LOD) for analysis of nAg using the on-line AF4/ICP-MS method was 0.80 ng mL(-1). Two calibration approaches (i.e., external calibration and standard addition) were used to quantify nAg concentrations, and both methods gave similar results. Using the on-line AF4/ICP-MS analytical method, nano-sized Ag was detected and quantified in untreated wastewater (i.e., influent) collected from a wastewater treatment plant. The concentration and the modal size of nAg in the influent were 1.90 ng mL(-1) and 9.3 nm respectively.

A novel approach for determining total titanium from titanium dioxide nanoparticles suspended in water and biosolids by digestion with ammonium persulfate.

Titanium dioxide (i.e. TiO(2)) in nano-form is a constituent of many nanomaterials that are used in sunscreens, cosmetics, industrial products and in biomedical applications. Quantification of TiO(2) nanoparticles in various matrixes is a topic of great interest for researchers studying the potential health and environmental impacts of nanoparticles. However, analysis of TiO(2) as Ti(4+) is difficult because current digestion techniques require use of strong acids that may be a health and safety risk in the laboratory. To overcome this problem, we developed a new method to digest TiO(2) nanoparticles using ammonium persulfate as a fusing reagent. The digestion technique requires short times to completion and optimally requires only 1 g of fusing reagent. The fusion method showed >95% recovery of Ti(4+) from 6 µg mL(-1) aqueous suspensions prepared from 10 µg mL(-1) suspension of different forms of TiO(2,) including anatase, rutile and mixed nanosized crystals, and amorphous particles. These recoveries were greater than open hot-plate digestion with a tri-acid solution and comparable to microwave digestion with a tri-acid solution. Cations and anions commonly found in natural waters showed no significant interferences when added to samples in amounts of 10 ng to 110 mg, which is a much broader range of these ions than expected in environmental samples. Using ICP-MS for analysis, the method detection limit (MDL) was determined to be 0.06 ng mL(-1), and the limit of quantification (LOQ) was 0.20 ng mL(-1). Analysis of samples of untreated and treated wastewater and biosolids collected from wastewater treatment plants yielded concentrations of TiO(2) of 1.8 and 1.6 ng mL(-1) for the wastewater samples, respectively, and 317.4 ng mg(-1) dry weights for the biosolids. The reactions between persulfate ions and TiO(2) were evaluated using stoichiometric methods and FTIR and XRD analysis. A formula for the fusing reaction is proposed that involves the formation of sulfate radicals.