A comparative study on effectiveness of soapnut, rhamnolipid and EDTA in cleaning diesel oil contaminated soil from a commercial site in Edinburgh

This study presents performances of soapnut, rhamnolipid and EDTA in washing soil contaminated with diesel oil. The soil was collected from a business park in Riccarton area of Edinburgh. The soil was contaminated with vehicle grade commercial diesel oil (BS EN590) available from a local gas station. While soapnut is derived from plant Sapindus mukorossi, rhamnolipid is a class of microbial surfactant produced by Pseudomonas aeruginosa and EDTA is an amino-polycarboxyilic acid, a synthetic chemical, widely used as a cleaning/chelating agent in industry.
The optimum operating conditions for all three cleaning agents were established by Box-Behnken method. When such operating conditions were used for column washing, EDTA had the highest cumulative removal efficiency of 43.3%, followed by rhamnolipid and soapnut, which recorded 40.7% and 39.3% respectively. The cumulative diesel oil removed by distilled water was 3.7%. However, considering the low cost of soapnut, it will be more economical to use soapnut than Rhamnolipid or EDTA.