Enhanced foamability and foam stability of polyoxyethylene cholesteryl ether in occurrence of ionic surfactants

An experimental study of foam-oil interactions for nonionic-based binary surfactant systems under high salinity conditions

A key factor affecting foam stability is the interaction of foam with oil in the reservoir. This work investigates how different types of oil influence the stability of foams generated with binary surfactant systems under a high salinity condition. Foam was generated with binary surfactant systems, one composed of a zwitterionic and a nonionic surfactant, and the other composed of an anionic and a nonionic surfactant. Our results showed that the binary surfactant foams investigated are more tolerant under high salinity conditions and in the presence of oil. This was visually observed in our microscopic analysis and was further attributed to an increase in apparent viscosity achieved with binary surfactant systems, compared to single surfactant foams. To understand the influence of oil on foam stability, we performed a mechanistic study to investigate how these oils interact with foams generated with binary surfactants, focusing on their applicability under high salinity conditions. The generation and stability of foam are linked to the ability of the surfactant system to solubilize oil molecules. Oil droplets that solubilize in the micelles appear to destabilize the foam. However, oils with higher molecular weights are too large to be solubilized in the micelles, hence the molecules will have less ability to be transported out of the foam, so oil seems to stabilize the foam. Finally, we conducted a multivariate analysis to identify the parameters that influenced foam stability in different oil types, using the experimental data from our work. The results showed that the oil molecular weight, interfacial tension between the foaming liquid and the oil, and the spreading coefficient are the most important variables for explaining the variation in the data. By performing a partial least square regression, a linear model was developed based on these most important variables, which can be used to predict foam stability for subsequent experiments under the same conditions as our work.

Preparation and Application of Foaming Agent Based on the Compound System of Short-Chain Fluorocarbon and Soybean Residue Protein

This study provides a new idea for the design of an advanced foaming agent with soybean residue protein (SRP) as a potential protein source. In order to achieve the most effective foaming performance, we employed the novel approach of response surface methodology (RSM) to improve important process parameters in a hot-alkali experiment. The experimental results showed that the optimum reaction parameters of pH and temperature were pH 10.2 and 50.5 °C, respectively, which, when continued for 3 h, led to the highest foaming property of the SRP foaming agent (486 mL). Based on the scheme, we also designed an experiment whereby we incorporated 1.0g/L FS-50 into the SRP foaming agent (SRP-50) to achieve higher foaming capacity compared with the commercial foaming agent. This foaming agent was cheaper than commercial vegetable protein foaming agents (12 USD/L) at 0.258 USD/L. Meanwhile, the properties of foam concrete prepared using SRP-50 were studied in comparison with a commercial vegetable protein foaming agent (PS). The results demonstrated that the foam prepared using SRP-50 had better stability, and the displacement of the foam decreased by 10% after 10 min. During the curing period, the foam concrete possesseda compressive strength of 5.72 MPa after 28 days, which was an increase from 2.95 MPa before. The aperture of the foam ranged from 100 to 500 μm with the percentage increasing up to 71.5%, which indicated narrower pore-size distribution and finer pore size. In addition, the shrinkage of the foam concrete was also improved. These findings not only achieve the utilization of waste but also provide a new source for protein foaming agents.

An overview on surfactants as pollutants of concern: Occurrence, impacts and persulfate-based remediation technologies

Surfactants are molecules that reduce interfacial energy and increase solubility of other pollutants in water. These properties make them suitable for various domestic and industrial applications, soil remediation, pesticide formulation, among others. The increase in their use and the lack of strict regulations regarding their disposal and management is a matter of concern and requires more attention since the release and distribution of these compounds into the environment can modify important water quality parameters. As a result of these changes, different toxicological effects to aquatic organisms are discussed and exposed herein. On this basis, we provide an overview of the classes of surfactants, as well as their occurrence in different aqueous matrices. In addition, existing regulations around the world regarding their concentration limit for different environments are discussed. Current research focuses on the application of conventional treatments, such as biological treatments; notwithstanding, more toxic and bioaccumulative products can be generated. Advanced Oxidation Processes are promising alternatives and have also been widely applied for the removal of surfactants. This study provides, for the first time, an overview of the application of persulfate-based processes for surfactants degradation based on recent literature findings, as well as the various factors related to the activation of the persulfate anions. This review also highlights the challenges and opportunities for future research to overcome the obstacles to the practical application of this process.

The Garbage Enzyme with Chinese Hoenylocust Fruits Showed Better Properties and Application than When Using the Garbage Enzyme Alone

Garbage enzyme (GE) is a vinegar or alcohol product derived from fermenting fresh kitchen waste, such as vegetable and fruit residues (peels, cuttings and bits), sugar (brown sugar, jaggery or molasses sugar) and water. Chinese honeylocust fruits (Gleditsia sinensis) have been used in China for at least 2000 years as a detergent. The aim of the study was to investigate the properties and application of Chinese honeylocust garbage enzyme (CHGE), which is produced when equal amounts of Chinese honeylocust fruits and fresh wastes are mixed. The results showed that CHGE had lesser microbial communities and lower surface tension than GE. CHGE also had higher viscosity, foam stability and emulsion stability than GE. Compared with GE, CHGE induced higher enzymatic amylase, cellulase, lipase and protease activities. CHGE had stronger detergency than GE and a 100× dilution of CHGE could significantly remove pesticide residues after a 30 min soaking treatment. The study showed that as a biological detergent, CHGE is safer and more environmentally friendly than GE and has remarkable washing and cleaning power. The preparation method of the detergent is simple: it can be prepared at home using fruit and vegetable waste, which is beneficial to the secondary utilization of waste and the reduction of pollution to the environment and damage to human health.

Highly wet aqueous foams stabilized by an amphiphilic bio-based hydrogelator derived from dehydroabietic acid

Exploration of novel molecular aggregates that stabilize foam systems is helpful to optimize foam properties. Herein, solutions of a rosin-based low-molecular-weight hydrogelator, abbreviated as R-6-AO, were used to generate foams above the critical gelation temperature (Tgel). The foams with R-6-AO concentrations above the critical gelation concentration were very stable below Tgel. The high stability of the foams under such conditions was attributed to the self-assembly of nanoscale fibers of R-6-AO in the liquid films of the foams, leading to extremely slow drainage of water. The foams showed strong water retention and were classified as very wet foams. For example, the foams generated from 10 mM (0.44 wt%) R-6-AO solution subjected to a fast cooling process contained about 45 vol% trapped water after 2000 min. In comparison, the water volume fraction of a 10 mM sodium dodecyl sulfate (SDS) foam decreased from 20 vol% to 1 vol% within 18 min. Because the growth, elongation, and cross-linking of the assembled nanofibers in the liquid films were affected by the cooling process, the stability of these foams also depended on the initial preparation temperature. The present system reveals the importance of microstructures in regulating foam behavior and serves as a new type of condition-sensitive intelligent foam.

Comparison of coagulative colloidal microbubbles with monomeric and polymeric inorganic coagulants for tertiary treatment of distillery wastewater

The flotation using coagulative colloidal gas aphrons (CCGAs) is of great potential in effectively removing the recalcitrant dissolved organic matter (DOM) and colorants from the bio-chemically treated cassava distillery wastewater. As bubble modifier, the monomeric and polymeric inorganic coagulants need to be studied considering their distinct influence on the surfactant/coagulant complex, the properties of colloidal aphrons as well as the process performance and mechanisms. Such studies help to create robust CCGAs with high flotation potential. In this work, the commonly-used monomeric and polymeric Al(III)- and Fe(III)-coagulants were combined with the cationic surfactant - cetyl trimethylammonium bromide (CTAB) to generate CCGAs. The CCGAs functionalized with Al(III)-coagulants (both monomeric and polymeric ones) were featured as small bubble size, strong stability and high air content. Particularly, the monomeric Al(III)-coagulant (AlCl₃ in this work) resulted in low surface tension and high foamability when being mixed with CTAB in the bubble generation solution. Those CCGAs achieved high removal efficiencies of DOM and colorants at low coagulant concentrations. The molecular weight of DOM in effluent was well controlled below 1 kDa by CCGAs. For the flocs obtained from CCGA-flotation, the characteristic Raman band of DOM and colorants showed the layer-by-layer variation of Raman intensity which decreased from the outer layer to the center. In contrast with the conventional coagulation-flotation, the reduction of coagulant dosage by CCGAs was 67% (AlCl₃), 25% (polyaluminum chloride), 60% (Fe₂(SO₄)₃) and 40% (polyferric sulfate). The sludge production could then be largely reduced, and meanwhile, the retention time was shortened by 9.5 min.

Investigation of Physiological Properties of Transglycosylated Stevia with Cationic Surfactant and Its Application To Enhance the Solubility of Rebamipide

The poor water solubility of rebamipide was enhanced by the mixed micelles of transglycosylated stevia (Stevia-G) and trimethylammonium chloride with varying carbon chain length (C _nTAC, n = 14, 16, and 18). Fluorometry, isothermal titration calorimetry (ITC) and dynamic light scattering techniques examined the aggregation properties of Stevia-G and C _nTAC. Synergism was found between Stevia-G and C _nTAC using the approaches of Clint and Rubingh. The negative interaction parameter (average β_m = -4.17, -5.47, and -7.07) and excess free energy (average ΔG°_ex = -2.47, -3.06, and -3.88 kJ mol^-1) increased with increasing chain length of C _nTAC. The negative B₁ values by the Maeda approach suggested that chain-chain interactions contribute to the formation of a mixed micelle. The solubilization of rebamipide in the mixed micelle was evaluated in the term of the molar solubilization ratio (MSR) and partition coefficient ( K_m). The K_m from the Stevia-G/C₁₆TAC system was highest at a low mole fraction of C _nTAC (0.2-0.6). In conclusion, the solubilization of rebamipide was more favorable between Stevia-G and C₁₆TAC, although the stability of the mixed micelle was enhanced by an increase in hydrophobicity of the longer chain lengths used in C _nTAC.