Effect of Increased Voltage and pH Adjustment to Improve the Efficiency of the Electrokinetic Method to Remove Kerosene from Contaminated Soil

Every year with the expansion and development of industrial and mining activities, millions of tonnes of toxic waste are produced throughout the world. Soil contamination by organic material as a result of various incidents and the leakage of organic compounds into the soil solid porous media will have an adverse effect on the environment. There are several methods for soil remediation contaminated with hydrocarbon compounds. Electrokinetic is one of the effective remediation which includes three main mechanisms for remediation, electroosmotic flow, ionic migration and electrophoresis. Electrokinetic is suitable in terms of cost and time for solid and porous fine-grained environment media that have high adsorption capacity of moisture and also organic pollutants. Kerosene is considered as one of the hydrophobic organic compounds with harmful physical and chemical properties to ecosystems and high adsorption onto the water and soil media. It has different hydrocarbons in its composition, each molecule having an average of 10 to 16 carbon atoms. It is so durable in the ecosystem, including the soil environment. The soil used in this study was fine-grained kaolinite due to the nature and effectiveness of the electrokinetic method for porous media. In this study, five series of experiments were carried out using electrokinetic method and its combination with improved techniques. The parameters including cumulative electroosmotic flow, electrical current intensity, reservoir and soil pH variation and residual kerosene concentrations in soil were studied. The highest electrical current devoted to increased voltage and pH control tests with 48 and 94 mA respectively for a time interval of 80 to 90 hours after the start of the tests were observed. The higher electric current intensity causes faster migration of ionic species to the opposite-electrode, resulting in greater electroosmotic flow transportation. In the present study, the removal percentage of kerosene from kaolinite soil through the different electrokinetic techniques including changing the electrolyte solution (nitrate potassium and tap water), increasing the-voltage (2 volts per cm of soil), and pH control over 5 and 7 days were investigated. Results revealed, using potassium nitrate as electrolyte solution, the the removal efficiency of kerosene was 47.24% and 50%, respectively, according to the remediation time of 5 and 7 days. With an increase of 2.9 times in the electroosmotic flow over a period of 48 hours from 5 to 7 days, the removal efficiency of the kerosene increased by 2.76%. Using distilled water as electrolyte solution despite the volume of 555 milliliters of electroosmotic flow, kerosene removal efficiency decreased to 33.02% in 7 days. The percentage of kerosene removal by pH control and increased voltage up to 2 v/cm, respectively with electroosmotic flow of 372 and 452 was 47.69 and 61.43%. Hence, a higher volume of electroosmotic flow represents a greater removal of kerosene in the soil. According to the obtained results, the best removal efficiency of kerosene (inspite of higher electroosmotic flow in tests with no enhancement technique) was due to the use of electrokinetic method by combining the higher voltage enhancement technique and the use of potassium nitrate electrolyte as solution over a period of 7 days.