Solubility of petroleum hydrocarbons in oil/water systems

To elucidate mechanisms, two laboratory-scale experiments were correlated t o understand and quantify how oil partitions into the aqueous phase. In the two experiments, free-phase petroleum was exposed to water in an effort to determine aqueous concentrations of various oil components. In the first i nvestigation, an oil/water system was allowed to equilibrate for 16 days. T he water column in the system was periodically sampled, and sample analysis was performed by GC-MS. After analyzing for naphthalene and various alkyl- substituted naphthalene compounds, the data was modeled and rate coefficien ts and the saturation concentrations were predicted. For naphthalene, the m odeled saturation concentration was 1.4 x 10(-6) mol/l, the rate coefficien t was 0.239 h(-1) and the predicted time to reach equilibrium was 19.3 h. F or the alkyl-substituted compounds, there was an inverse correlation betwee n both the rate coefficients and saturation concentrations and the degree o f alkyl-substitution. In the second investigation, oil/water systems were a llowed to equilibrate for 36 h. Various oil loadings (mass of oil/volume of water) were investigated. The mixing energy was twice that of the first ex periment. After the 36 h, the water column was sampled and analyzed by GC-M S. There was a direct correlation between the measured total petroleum hydr ocarbon (TPH) concentrations in the water and the oil loading. However, the re was no such correlation between the naphthalenes and oil loading. It was concluded that the first experiment was a solubility phenomenon while the second experiment also included a colloidal phenomenon. (C) 2000 Elsevier S cience B.V. All rights reserved.