Degradation of Naphthenic Acids in Athabasca Oil Sands Process-Affected Water Using Ozone

摘要

Naphthenic acids (NAs) are natural low molecular weight surfactants released from bitumen during caustic hot water digestion of oil sands ore. As a result, NAs are released into the oil sands process-affected waters (OSPW) at concentrations ranging from 40 to 120 mg/L. NAs are closely related alicyclic carboxylic acids (C_nH_(2n-z)O_2), and have been shown to contribute to most of the acute toxicity of OSPW. The treatment of OSPW to reduce or remove NAs is critical for their reclamation and potential discharge options. As a part of an ongoing study, a series of experiments were undertaken where OSPW samples from an Athabasca oil sands tailings pond was treated with an advanced oxidation approach. Using a simple non-optimized treatment, in which ozone was bubbled through an OSPW sample for different periods of time (1 to 30 min), up to 99% reductions of NAs were achieved. In the same samples, the maximum reductions in dissolved organic carbon and chemical oxygen demand were 32% and 53%, respectively. This indicates that ozonation produced smaller organic by-products. This preliminary data shows that ozone offers a promising treatment for the removal of NAs in OSPW within water management options. Further research will focus on optimizing ozone treatment efficiency, assessing of the dose-relationship, and understanding the mechanisms of NAs degradation pathways and the effects on toxicity of OSPW.