Composition and Analysis of Mineral Oils and Other Organic Compounds in Metalworking and Hydraulic Fluids

Abstract

Metalworking fluids (MWFs) are the primary source of organic contaminants in oily wastewater at many manufacturing facilities. Such facilities, including those in the automotive industry, face the continuing challenge of improving wastewater treatment for organics. Hydraulic fluids (HFs), chemically similar to MWFs, have been a major source of costly soil contamination at industrial and commercial facilities.A better understanding of these organics is essential to the treatment of oily wastewater and HF decontamination. Therefore, two aspects were reviewed: (1) current and historical organic chemical compositions of MWFs and HFs and (2) existing and emerging analytical methods. Base mineral oils were emphasized, as they are the primary ingredient of these fluids and the main contaminant in oily wastewater and HF-contaminated soil. Hydrocarbon compositions of “naphthenic” (cycloalkanes) and “paraffinic” (straight and branched noncyclic alkanes) mineral oils were described, as were the chemical nature of the various MWF and HF additives.Analytical methods for gross organic measurements, individual organics, and structure- and sizebased fractions and distributions were reviewed. Most promising for characterizing the base oil fraction were gas chromatography (GC) coupled with two soft ionization mass spectrometry detection methods and comprehensive 2-dimensional GC. These methods can provide complete distributions of hydrocarbon structures and sizes and are potentially useful to monitor hydrocarbon fate in wastewater treatment, soil/sediment remediation, or other applications involving complex hydrocarbon mixtures.