Microwave treatment of naphthenic acids in water

Abstract

Naphthenic acids (NAs) are natural constituents of bitumen and crude oil. These compounds are concentrated as part of the oil sands process water (OSPW) during petroleum refining and separation from oil sands. NAs are considered among the major water contaminants in OSPW due to their toxicity and environmental recalcitrance. A laboratory scale microwave system was developed and experiments were conducted to determine the efficiency of NA degradation during microwave treatment. The effects of water source and quality (deionized lab water and river water) and of TiO2 catalyst in the degradation process were also investigated. Degradation kinetic parameters for both total NAs and individual z-family were calculated. The microwave system degraded OSPW NAs and commercial Fluka NAs in river water in the presence of TiO2 rapidly, producing half-life values of 3.32 and 3.61 hours, respectively. Toxicity assessments of the NA samples pre-and post-treatment indicated that the microwave system reduced overall toxicity of water containing Fluka NAs from high (5 min. IC50 v/v = 15.85%) to moderate (5 min. IC50 v/v = 36.45%) toxicity levels. However, a slight increase in toxicity was noted post-treatment in OSPW NAs.