Effect of imposed electrical gradient on removal of toxic salt contaminants from alkali-saline low permeable soil during electrokinetic remediation

Abstract

Saline soils are one of the most hazardous environmental issues, retaining large and excessive amounts of noxious salt contaminants, thus damaging the ecosystem biodiversity, human health, as well as infrastructures and urban facilities. The low permeability and complex mineralogy of these soils make their remediation a very difficult task and an extreme challenge. While conventional techniques have been proven to be costly and mostly ineffective, electrokinetic remediation (EKR) can be an innovative, sustainable, and environmentally friendly alternative. This research investigates the effect of imposed electrical gradient (IEG) on the removal of harmful salts from highly alkaline saline soil during EKR. The samples obtained from Canakkale-Dardanos Campus area, northwest Turkey, exhibit severe alkalinity, extreme concentration of hazardous salts, high electrical conductivity, and salinity. Lab-scale electrokinetic runs were monitored for 5 days, with a set of three different IEG. The optimal results for salt contaminants removal were obtained during the highest IEG, reaching a remediation efficiency of 100% in the middle sections. Furthermore, harmful cationic salts, including sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+), were transported toward the cathode, owing to the electro-migration and electro-osmosis flow which were significantly accelerated with the increment of the (IEG). The toxic chloride (Cl−) and sulfate (SO42−) salts were transported with the electro-migration phenomenon. The results indicated that the IEG has a major effect on remediation of high alkaline, low permeable saline soils, and can be considered the driving vector and the key transport mechanism for the removal of hazardous salt contaminants.