Efficient Removal of Pollutants in Wastewater by Continuous Admicelle-Flotation System

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Surfactant molecules in water are adsorbed on solid surfaces to form admicelles by electrostatic or hydrophobic interactions. In the present study, admicelles were examined as novel separation and concentration media for the wastewater treatment and the assessment of water quality. Since admicelles are capable of incorporating water-insoluble compounds into their hydrocarbon cores by the hydrophobic interaction, attempts were made to collect organic and inorganic pollutants by using these admicelles or hydrophobic ligand-impregnated admicelles. For a comparison, surfactant aggregates formed on liquid-liquid interfaces (i.e., water-in-oil emulsion) were also investigated in detail.Optimized admicelles were designed using several kinds of anionic, cationic, and nonionic surfactants and solid materials (including alumina, silica gel, cross-linked dextran gel, and polystyrene beads). The resulting admicelles provided the quantitative collection of some hydrophobic organic pollutants, e.g., polyaromatic hydrocarbons and chlorophenols, and toxic heavy metals (after the conversion into hydrophobic chelates) in batch and column operations. The admicelles were also effective to collect valuable substances, such as enzymes and precious metals. In addition, the admicelles incorporating desired substances were easily floated onto the water surface with numerous tiny bubbles. This phenomenon owes to the tendency of the long alkyl chains of the admicelles to readily adhere to the gas-water interfaces. Compared with the batch and column operations, the admicelle-flotation scheme allowed to perform the separation and preconcentration of pollutants in water more efficiently. Because we have considerable experience of the flotation technique, further studies on the admicelle-flotation will open the highly efficient methodology for the wastewater treatment.