Search

The hydroxyl radical ( • OH) scavenging capacity is a useful parameter for the design and operation of an advanced oxidation process (AOP) in water treatment. The scavenging capacity may change with time, and it would be useful to continuously measure this change to be able to optimize AOP doses. In this study, we first reviewed current methods for scavenging capacity measurement to identify strengths and weaknesses of each method. This information helped guide the design of an external calibration method to allow straightforward laboratory and field measurement of • OH scavenging capacity. The method used low-pressure UV/H 2 O 2 as the • OH generation system, methylene blue (MB) as the probe compound, and isopropyl alcohol (IPA) as the standard. By monitoring, offline, the color decay of MB in a series of IPA solutions with different scavenging capacity, a calibration curve was established between the color decay rate and the scavenging capacity. The measured color decay in real water samples can then be used with this external calibration to estimate their scavenging capacity. Work was undertaken to ensure that the process would be robust under a wide range of water quality conditions. Parallel tests using this method compared with the benchmark methods confirmed its robustness and accuracy.

This paper investigates the oxidation of oil sands process-affected water (OSPW) by potassium ferrate(VI). Due to the selectivity of ferrate(VI) oxidation, two-ring and three-ring fluorescing aromatics were preferentially removed at doses <100 mg/L Fe(VI), and one-ring aromatics were removed only at doses ≥100 mg/L Fe(VI). Ferrate(VI) oxidation achieved 64.0% and 78.4% removal of naphthenic acids (NAs) at the dose of 200 mg/L and 400 mg/L Fe(VI) respectively, and NAs with high carbon number and ring number were removed preferentially. (1)H nuclear magnetic resonance ((1)H NMR) spectra indicated that the oxidation of fluorescing aromatics resulted in the opening of some aromatic rings. Electron paramagnetic resonance (EPR) analysis detected signals of organic radical intermediates, indicating that one-electron transfer is one of the probable mechanisms in the oxidation of NAs. The inhibition effect of OSPW on Vibrio fischeri and the toxicity effect on goldfish primary kidney macrophages (PKMs) were both reduced after ferrate(VI) oxidation. The fluorescing aromatics in OSPW were proposed to be an important contributor to this acute toxicity. Degradation of model compounds with ferrate(VI) was also investigated and the results confirmed our findings in OSPW study.

A simple metal-free method for the synthesis of 3-aryloxindoles via Brønsted acid catalyzed aromatic C-H functionalization of electron-rich arenes with 3-diazooxindoles is developed. In the presence of a catalytic amount of TfOH, a series of 3-aryloxindoles are synthesized as single regioisomers in good to excellent yields. This transformation is proposed to proceed through acid-catalyzed protonation of 3-diazooxindoles into diazonium ions followed by Friedel-Crafts-type alkylation of arenes.

Efficient Rh(II)-catalyzed three-component reactions of 3-diazooxindoles and formaldehyde with either anilines or water were developed to give a series of substituted 3-amino-3-hydroxymethyloxindoles or 3-hydroxy-3-hydroxymethyloxindoles in good to excellent yields. In this atom- and step-economic transformation, Rh2(OAc)4-catalyzed decomposition of 3-diazooxindoles with anilines or water forms the corresponding active ammonium or oxonium ylides. Electrophilic trapping of the resulting ammonium ylides or oxonium ylides by formaldehyde in the form of formalin efficiently produces the title compounds in one step.