Foam fractionation for effective removal of Pseudomonas aeruginosa from water body: Strengthening foam drainage by artificially inducing foam evolution

Liquid foams: Properties, structures, prevailing phenomena and their applications in chemical/biochemical processes

Liquid foams are gas-liquid dispersions with flexible structures that provide high gas-liquid interfaces. This property nominates liquid foams as excellent gas-liquid contactors, systems that are widely used in the chemical and biochemical industries. However, challenges such as a lack of comprehensive understanding and foam instability have historically hindered their widespread industrial use in most applications. It was not until the recent development of nanofluidics, nanotechnology, surface science, and other related fields that the understanding, analysis, and control of foam phenomena improved. This led to the development of innovative stabilization techniques and foam-based unit operations in chemical and biochemical processes, each of which requires in-depth and exclusive reviews to fully comprehend their potential and limitations and to identify areas for further improvement and innovation. This paper reviews the foams, the common phenomena in them, the characteristics that make them suitable for chemical/biochemical engineering, reports on their current applications and recent developments in this field.

Improving rhamnolipids production using fermentation-foam fractionation coupling system: cell immobilization and waste frying oil emulsion

This work focused on the development of an inexpensive carbon source and the improvement of the fermentation-foam fractionation coupling system. The rhamnolipids production capacity of waste frying oil (WFO) was evaluated. The suitable bacterial cultivation of seed liquid and the addition amount of WFO was 16 h and 2% (v/v), respectively. A combined strategy of cell immobilization and oil emulsion avoid cell entrainment inside foam and improves the oil mass transfer rate. The immobilization conditions of bacterial cells into alginate-chitosan-alginate (ACA) microcapsules were optimized using the response surface method (RSM). Under the optimal conditions, rhamnolipids production using batch fermentation with immobilized strain reached 7.18 ± 0.23% g/L. WFO was emulsified into a fermentation medium using rhamnolipids as emulsifier (0.5 g/L). By monitoring dissolved oxygen, 30 mL/min was selected as a suitable air volumetric flow rate for fermentation-foam fractionation coupling operation. The total production and recovery percentage of rhamnolipids were 11.29 ± 0.36 g/L and 95.62 ± 0.38%, respectively.

Preferential Removal of Alkali Metal Using Dodecanoic Acid and Sodium Dodecyl Sulfate in Foam Separation System

The selectivity of adsorption between alkali metal ions (Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺) based on the ionic functional groups of the surfactants was studied using two types of surfactants, dodecanoic acid (DA) and sodium dodecyl sulfate (SDS), in the foam separation system. The results showed that Li⁺ was preferably removed by foam separation using DA. The removal rates of other alkali metal ions were relatively low, and there were no significant differences among other alkali metal ions (Na⁺, K⁺, Rb⁺, and Cs⁺). However, Cs⁺ exhibited the highest removal rate among the mixed alkali metals by foam separation using SDS. From these results, the selectivity of the alkali metal in foam separation was dependent on the type of surfactant.