Various surface-active agents used in flotation technology for the removal of noxious pollutants from wastewater: a critical review

Abstract

Treating emerging pollutants from industrial effluent that cause inevitable damage to human wellness and the environment is paramount. In this regard, the flotation process is one of the unique and effective separation processes among the traditional treatment methods available for the treatment of noxious pollutants. Surface-active agents are used as flotation reagents that could remarkably improve the variations in surface possession of contaminants, thereby enhancing the separation efficiency. For a flotation process to be effective and successful, it is mandated to understand the importance, role, and selection of a suitable type of surfactant/collector regime along with the specific adsorption mechanism, and molecular chemistry. In this review article, different types of surface-active agents used in the flotation treatment are discussed. This paper expounds on the versatility of each type of surfactant's interaction mechanism concerning contaminants' surface characteristics. From several literature studies, it can be denoted that cost-efficient and environmentally friendly surfactants can be produced by infusing new functional groups and molecular modelling of surfactants (flotation reagents). The virtue of biosurfactants is better when compared to chemical surfactants as they possess good biodegradability, lower toxicity, high selectivity, and biocompatibility. So, the application of biosurfactants can be improved further that can make the flotation technology green, paving the way for environmental sustainability. Further, the integration of surfactants could increase the synergetic effect which enhances the process's effectiveness. On that account, the selection of the appropriate type of surfactant is required to instigate the most ideal result that could help in the remediation of contaminants effectively as well for successful flotation performance.