Evaluation of sodium adsorption in clay soil in the presence of crude oil

Abstract

Throughout the productive life of an oil field there is usually a simultaneous production of gas, oil, water, and impurities. This formation water which composes the crude oil presents high levels of dissolved salts, being on average three times superior to those of seawater, whose salinity is 35 g L−1. In this perspective, crude oil contaminated soil presents great influence of the salinity requiring studies to determine its comportment, bringing clarity to the interaction between the soil, oil, and salt and the process involved in soil remediation. The soil was sampled in an area of oil extraction on land in the state of Sergipe, northeast of Brazil. For this purpose, stable oil-in-water emulsions were prepared from a heavy oil sample and a light oil sample. The aqueous phase of the emulsions was distributed with different salinities: 0 L−1 to 150 g L−1 sodium chloride. All the emulsions were prepared at 80 °C and rotation speed (Turrax) of 16,000 or 22,000 rpm for 15–20 min. The batch test was used for the determination of soil-contaminant interaction parameters. The assay was performed during the 24 h period in Erlenmeyers of 250 ml containing a 1:10 ratio of soil:emulsions. Chloride, sodium, and electrical conductivity were measured. As a result, it was observed that high contents of NaCl results in desorption of Chloride for sorption tests with saline solution and emulsions. Sorption Tests appointed to higher sorption of sodium on Emulsion Tests (light oil > heavy oil). Tree isotherm models were tested therefore none of them could fit the sorption process observed.