Abstract

The study investigates the effectiveness of electrokinetic remediation (EKR) using three different electrolytes: citric acid (C₆H₈O₇), ethylenediamine tetraacetic acid (EDTA), and sodium nitrate (NaNO3) for the remediation of crude oil-contaminated medium sand (typically has particle size ranging from 0.25mm to 0.5mm). The study evaluates the removal efficiency of these electrolytes (at 0.1mole concentrations) by determining concentrations of the crude after remediation and examining changes in soil properties (gradation, specific gravity, liquid limit, plastic limit, soil compaction parameters and moisture content). Electrolytes were applied in the EKR process, which involves applying direct current at a steady voltage of 1.0V/cm across the contaminated soil to facilitate pollutant transmission. The results indicated that sodium nitrate achieved the highest removal efficiency with 67%, citric acid (45.97%) and EDTA (35.0%). Sodium nitrate was found to increase the solubility of hydrocarbons making it easier to remove them from the soil, it was also found to improve the electroosmotic flow which help to transport the contaminant towards the cathode (cell containing the electrolytes) and increase the ionic strength of the solution. Sodium nitrate helps to reduce the attraction between soil particles and the contaminant. The contaminated soil has the highest fines with 54% passing the 75micron BS sieve, Sodium Nitrate treatment reducing this value the most by 14.8%. The specific gravity of Sodium Nitrate-treated soil also returned the highest, 2.68 indicating the soil became denser compared to others, thereby making the soil coarser and potentially improving its load-bearing capacity. All the three electrolytes reduced the plasticity index. Similarly, the reduction in plastic limit in Sodium Nitrate-treated soil coupled with reduced liquid limit (39%) suggests improved soil workability and reduced shrink-swell behavior. There is also a general improvement in the compaction parameters, maximum dry density increased by 3.4% reducing the requirement for water by 13.9%.

Key words: Electrolytes, Electrokinetic remediation, Hydrocarbons, removal efficiency, voltage, direct current, crude oil, contamination