The application of surfactant colloidal gas aphrons to remediate contaminated soil: A review

Surfactant solutions have been frequently studied for soil remediation. However, since they are expensive, massive consumption of surfactant solution can constrain their application. Surfactant microbubbles, or colloidal gas aphrons (CGAs), can serve as cost effective alternatives of surfactant solution because the use of CGAs reduce the amount of surfactant consumption. Moreover, CGAs can also improve the contact with the contaminated environment due to their unique surface properties, e.g. containing 40-70% of gas, small size, large interfacial areas, water-like flow properties and buoyant rise velocities. In this review paper, the properties and flow character of CGAs in soil matrix reviewed due to their relevance to soil remediation process. A comprehensive overview of the application of CGAs in flushing off organic pollutants and heavy metals, and carrying oxygen, bacteria and dissolved materials for soil remediation were provided. This paper also highlighted the limitation of CGAs application and important future research scopes.