Enhancing petroleum hydrocarbon removal efficiency in soil washing process by adding biosurfactant

Abstract

Soil contamination with petroleum hydrocarbons can cause environmental and health problems. This work aimed to combine Hydrophilic-Lipophilic Deviation (HLD) and microemulsion to formulate washing solution for petroleum removal from soil. When HLD value was fixed at zero, the composition of washing solution were calculated based on EACN and creates an optimum condition between oil and aqueous phases. The washing solutions contained lipopeptide biosurfactant produced from Bacillus sp. GY19, synthetic surfactant i.e. AMA or AOT, and NaCl. Hexane, decane, and hexadecane (EACN=6, 10, 16, respectively) were used to cover hydrocarbons found in the environment. Lipopeptide increased its purity by membrane filtration showed the potential in oil displacement, low CMC, and high hydrophobicity. It was mixed with hydrophilic surfactants to balance the system. The mixed surfactant systems formed microemulsion type III with various hydrocarbons and reduced IFT better than the single surfactant systems. The addition of lipopeptide in the formulations could enhance petroleum removal efficiency (70%-85%) from 5%-15% (w/w) petroleum hydrocarbon contaminated soil but around 60% came from the single synthetic surfactants. Consequently, microemulsion and HLD concept could create efficient soil washing solutions for different EACN hydrocarbons.