Foam Separation of Dyes Using Anionic, Cationic, and Amphoteric Surfactants

Foam Fractionation as an Efficient Method for the Separation and Recovery of Surfactants and Surface-Inactive Agents: State of the Art

Surface-active agents are widely used in industrial processes and products for daily use. Surfactants are essential in consumer products, although they are environmentally harmful. Consequently, new technologies are being sought to address the surfactant waste problem effectively. Foam fractionation is a multifunctional method of removing or purifying surface-active and inactive agents. This environmentally friendly technology enables foam separation of many compounds based on adsorption at the gas-liquid interface. The technology has been employed in wastewater treatment, remediation, metallurgy, biotechnology, pharmacy, and the cosmetics and food industries. This review highlights process handling and equipment design in terms of the enrichment and recovery of many proteins, surfactants, metal ions, and pollutants. Furthermore, the mode of action, basic laws, and mechanisms of the technology are explained, and relevant examples of the application of foam fractionation will be provided.

A review of foam fractionation for the removal of per- and polyfluoroalkyl substances (PFAS) from aqueous matrices

The detection of per- and polyfluoroalkyl substances (PFAS) in aqueous matrices is an emerging environmental concern due to their persistent, bioaccumulative and toxic properties. Foam fractionation has emerged as a viable method for removing and concentrating PFAS from aqueous matrices. The method exploits the surface-active nature of the PFAS to adsorb at the air-liquid interfaces of rising air bubbles, resulting in foam formation at the top of a foam fractionator. The removal of PFAS is then achieved through foam harvesting. Foam fractionation has gained increasing attention owing to its inherent advantages, including simplicity and low operational costs. The coupling of foam fractionation with destructive technologies could potentially serve as a comprehensive treatment train for future PFAS management in aqueous matrices. The PFAS-enriched foam, which has a smaller volume, can be directed to subsequent destructive treatment technologies. In this review, we delve into previous experiences with foam fractionation for PFAS removal from various aqueous matrices and critically analyse their key findings. Then, the recent industry advancements and commercial projects that utilise this technology are identified. Finally, future research needs are suggested based on the current challenges.

Exploring the Versatility of Microemulsions in Cutaneous Drug Delivery: Opportunities and Challenges

Microemulsions are novel drug delivery systems that have garnered significant attention in the pharmaceutical research field. These systems possess several desirable characteristics, such as transparency and thermodynamic stability, which make them suitable for delivering both hydrophilic and hydrophobic drugs. In this comprehensive review, we aim to explore different aspects related to the formulation, characterization, and applications of microemulsions, with a particular emphasis on their potential for cutaneous drug delivery. Microemulsions have shown great promise in overcoming bioavailability concerns and enabling sustained drug delivery. Thus, it is crucial to have a thorough understanding of their formulation and characterization in order to optimize their effectiveness and safety. This review will delve into the different types of microemulsions, their composition, and the factors that affect their stability. Furthermore, the potential of microemulsions as drug delivery systems for skin applications will be discussed. Overall, this review will provide valuable insights into the advantages of microemulsions as drug delivery systems and their potential for improving cutaneous drug delivery.

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.

Separation of Some Anionic Dyes Using Reverse Micelles of CTAB and SDS as Efficient Surfactants Adsorbents from Aqueous Medium

Extractive removal of anionic dyes, namely, Color Index (CI) Reactive Blue 222 and Reactive Yellow 145, using reverse micelles based on liquid-liquid extraction (LLE) was carried out from aqueous solutions using different anionic and cationic surfactants (e.g., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), resp.), which dissolved in ethyl acetate as solvent. The reverse micelle principal acts on the dye encapsulated in the solvent in an aqueous micropool. The experiments were carried out by mixing in a simple mixer a given amount of dyes and surfactants dissolved in a solvent in an aqueous process. Due to gravity, the dye is separated from water after the solvent phase is separated from the aqueous phase, including dye encapsulated in reverse micelles. Under various experimental conditions, extraction efficiency was studied, including solution pH, extraction time, initial dye concentration, extractant concentration, temperature, stripping agent, and solvent reusability. Dyes extracted were stripped quantitatively with NaOH solution. Recovery of the solvent and the reuse of dyes and surfactants after extraction of dye molecules from reverse micelles surfactant core considered are very important from an economic point of view. The optimized conditions were 7 ± 0.2 solution pH, 9 × 10−2 mol/L extractant concentration, 1M NaOH stripping agent concentration, 60 min extraction time, 6 × 10−5 mol/L dye concentration, and 1 : 1 aqueous to organic (A/O) ratio. 87–93% of dyes were extracted at experimental optimum conditions.