Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada; Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Water Science and Technology Directorate, Environment and Climate Change Canada, Saskatoon, Saskatchewan S7N 3H5, Canada.
Chemosphere. 2018 Jun;200:180-190. doi: 10.1016/j.chemosphere.2018.02.049. Epub 2018 Feb 12.
Bitumen extraction in Canada's oil sands generates oil sands process-affected water (OSPW) as a toxic by-product. Naphthenic acids (NAs) contribute to the water's toxicity, and treatment methods may need to be implemented to enable safe discharge. Heterogeneous photocatalysis is a promising advanced oxidation process (AOP) for OSPW remediation, however, its successful implementation requires understanding of the complicated relationship between structure and reactivity of NAs. This work aimed to study the effect of various structural properties of model compounds on the photocatalytic degradation kinetics via high resolution mass spectrometry (HRMS), including diamondoid structures, heteroatomic species, and degree of unsaturation. The rate of photocatalytic treatment increased significantly with greater structural complexity, namely with carbon number, aromaticity and degree of cyclicity, properties that render particular NAs recalcitrant to biodegradation. It is hypothesized that a superoxide radical-mediated pathway explains these observations and offers additional benefits over traditional hydroxyl radical-based AOPs. Detailed structure-reactivity investigations of NAs in photocatalysis have not previously been undertaken, and the results described herein illustrate the potential benefit of combining photocatalysis and biodegradation as a complete OSPW remediation technology.
在加拿大的油砂中提取沥青会产生油砂加工影响水（OSPW），这是一种有毒的副产品。环烷酸（NAs）是导致水毒性的原因之一，可能需要采取处理方法来实现安全排放。多相光催化是一种很有前途的高级氧化工艺（AOP），可用于修复 OSPW，但要成功实施该工艺，需要了解 NAs 的结构和反应性之间复杂的关系。本工作旨在通过高分辨率质谱（HRMS）研究模型化合物的各种结构特性对光催化降解动力学的影响，包括金刚烷结构、杂原子种类和不饱和程度。光催化处理的速度随着结构复杂性的增加而显著提高，即随着碳原子数、芳香性和环状程度的增加，这些特性使得某些 NAs 难以生物降解。据推测，超氧自由基介导的途径可以解释这些观察结果，并为传统的基于羟基自由基的 AOP 提供额外的好处。此前，人们尚未对光催化中的 NAs 进行详细的结构-反应性研究，本文所述的结果说明了将光催化和生物降解相结合作为一种完整的 OSPW 修复技术的潜在好处。
