Mass Recovery for BTEX Stripping from Organic and Sandy Soil Using Soil Vapor Extraction Process

The soil vapor extraction (SVE) process is a well-recognized method for removing BTEX (benzene, toluene, ethylbenzene and xylene) compounds from gasoline-contaminated sites. Though primarily used for large scale contaminated sites, recent concern has shifted towards smaller sites where its effectiveness is still in question. The understanding of mass recovery of BTEX compounds in a lab scale experiments can justify the use of the process in small, contaminated sites. In order to understand the BTEX extraction ability in sandy and organic soil, SVE process columns were replicated in the laboratory. Three air flow rates, 1.5, 3.0 and 6.0 L/h, were used for each of nine sets of experiments. These nine sets represented each BTEX compounds for sandy and organic soil and another with mixture of all for sandy soil only. The mass fraction removed for each experiment was determined from cumulative mass removed and estimated total mass added in the column. In sandy soil, at higher airflow rates, contaminant was removed at a faster rate and resulted in lower residual concentration. The organic soil columns showed higher removal fraction compared to sandy soil. Mass fraction recovery rate for benzene, toluene, xylene and ethylbenzene was 98%, 90%, 90% and 84%, respectively. More than 95% of BTEX contaminated mass fraction was removed within 24 h for sandy soil and within 20 h for organic soil. However, higher porosity and moisture content in organic soil caused a higher recovery rate compared to sandy soil.