Addition Of Surfactant Research Articles

Formulation, E-Beam Crosslinking, and Comprehensive Characterisation of Lavender Oil-Enriched Hydrogels

This study focused on the formulation, electron beam (e-beam) crosslinking, and characterisation of hydrogels enriched with lavender oil (LO) to enhance their structural and functional properties for biomedical applications. Stable hydrogels were synthesised using water-soluble polymers and suitable ratios of Tween 80 and Isopropyl alcohol (IPA) as surfactant and co-surfactant, respectively, via e-beam irradiation at doses up to 70 kGy. The most effective crosslinking was achieved with a radiation dose of 30 kGy, depending on the concentrations of surfactants and LO. LO-enriched hydrogels exhibited enhanced superabsorbent swelling (7700% to 18,000%) and faster equilibrium rates than the control hydrogel. Structural analysis revealed a flexible spongiform porous architecture with larger mesh sizes (156 nm to 246 nm) and adequate elastic moduli (130 to 308 Pa). Degradation tests aligned with swelling data, demonstrating a degradation rate of 12% after 35 days, indicating an appropriate balance of stability and degradation. These findings suggest that e-beam technology, in conjunction with LO and surfactant addition, can effectively tailor hydrogel properties for biomedical applications, making them promising candidates for further research in wound care, drug delivery systems, and other biological applications.

Surface Activity of Hydrophobized Modified Starch Hydrolysates in Mixed Systems

The manuscript presents research focusing on the adsorption and emulsion properties of starch hydrolysates modified through acetylation, oxidation, and cross-linking. The techniques used in this study included measurements of equilibrium surface tension (du Noüy ring) dynamic surface tension (drop shape analysis), and the preparation and evaluation of emulsion stability (TURBISCAN). The surface activity of the acetylated starch hydrolysates is affected by the degree of acetylation. The acetylated starch 0.02Ac-H exhibited higher surface activity than the more highly substituted derivative 0.1Ac-H. Furthermore, it was shown that the surface activity of the components increased as the acetylated oxidized starch underwent hydrolysis. The fractions collected after 180 min using a membrane with a low separation capability (8 kDa) revealed the highest capacity for reducing surface tension. In binary systems consisting of starch derivatives and surfactants, synergistic effects in reducing surface tension were particularly noticeable in systems containing ionic surfactants. The addition of a cationic surfactant to the modified starch hydrolysate solution (1:6 mol/mol) resulted in a significantly more efficient saturation of the air/water interface. This study demonstrated that emulsions stabilized with modified starch hydrolysates remained stable over time, even when these hydrolysates constituted up to 60% of the emulsifier mixture.

Transient transition from Stable to Dissipative Assemblies in Response to the Spatiotemporal Availability of a Chemical Fuel

AbstractThe transition from inactive to active matter implies a transition from thermodynamically stable to energy‐dissipating structures. Here, we show how the spatiotemporal availability of a chemical fuel causes a thermodynamically stable self‐assembled structure to transiently pass to an energy‐dissipating state. The system relies on the local injection of a weak affinity phosphodiester substrate into an agarose hydrogel containing surfactant‐based structures templated by ATP. Injection of substrate leads to the inclusion of additional surfactant molecules in the assemblies leading to the formation of catalytic hotspots for substrate conversion. After the local disappearance of the substrate as a result of chemical conversion and diffusion the assemblies spontaneously return to the stable state, which can be reactivated upon the injection of a new batch of fuel. The study illustrates how a dissipating self‐assembled system can cope with the intermittent availability of chemical energy without compromising long‐term structural stability.

Study on the synergism mechanism of composite surfactants for oily sludge treatment using microemulsion method

The nonionic surfactant was considered to be the most effective surfactant for the treatment of oily sludge. In this paper, Tween20 and Span80 (T/S) composite surfactant was chosen as emulsifier for the preparation of microemulsion, and their synergistic effect was explored. Clint equation and molecular dynamics simulation was used to interpret the formation of mixed micelles and the results showed that T/S composite surfactant with the mass ratio of 11:1 exhibited the good synergetic effect. Then, the microemulsion prepared using composite surfactants was applied for the treatment of oily sludge. Under the optimal conditions of solid-liquid ratio of 1:1(g: mL), stirring temperature of 40 °C, stirring time of 30 min and stirring speed of 400 rpm, the residual oil rate was reduced to 0.25%, which was much lower than other reported results using chemical methods. Interface tensiometer and quartz crystal microbalance measurement showed that the interfacial tension decreased significantly after the addition of composite surfactant. This work provides a feasible strategy for oily sludge treatment using microemulsion, which promoted the development of oily sludge treatment processes based on microemulsion in practical industry.

Deciphering the Influence of Zwitterionic Surfactants on Pluronic Co-assemblies: A Synergistic Odyssey through Spectroscopic, Microscopic, and Scattering Techniques.

Fundamental investigations into the photophysical properties and microenvironmental features of pluronic-zwitterionic surfactant mixed assemblies are essential for advancing our understanding of molecular interactions at the nanoscale, setting the stage for innovative solutions in drug delivery, diagnostics, and other applications of pluronic-zwitterionic surfactant assemblies. This investigation explores the intricate photophysics of pluronic-zwitterionic surfactant mixed assemblies, utilizing the twisted intramolecular charge transfer state forming styryl dye trans-2-[(4-dimethylamino) styryl] benzothiazole as a probe. By comparing the behaviors of two distinct poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) block copolymers with block composition of (PEO)132-(PPO)50-(PEO)132 [F108] and (PEO)100-(PPO)65-(PEO)100 [F127] at concentrations of 5 and 10 wt %, this study systematically examines the impact of the addition of zwitterionic surfactants. Through a comprehensive set of analytical techniques, including UV-visible absorption, steady-state emission, and time-resolved fluorescence emission studies, significant alterations in the emission spectra and quantum yields were observed upon the addition of zwitterionic surfactants. These modifications suggest a dynamic equilibrium for the transitioning of dye molecules between various microenvironments within the assemblies. Additionally, dynamic light scattering, zeta potential (ζ), nuclear Overhauser effect spectroscopy, small-angle neutron scattering, cryogenic transmission electron microscopy, field emission scanning electron microscopy, and fluorescence lifetime imaging microscopy analyses have shed light on the substantial impact of surfactant incorporation on the structural properties of assemblies.

Harnessing the Potential of Morphologically Tailored ZnSn(OH)6 Nanograss Photoanode for Solar‐Driven Water Splitting

AbstractHydrothermal growth of ZnSn(OH)6 nanograss on ZnO‐coated FTO substrates is demonstrated. Effect of surfactants addition (polyvinylpyrrolidone and polyethylene glycol), precursor concentration, and reaction temperature on surface morphology of ZnSn(OH)6 nanograss are investigated. Addition of surfactant in precursor solution results in growth of approximately 20–30 nm thick nanograss morphology with varying orientation. The nanograss grow longer by increasing the concentration of precursors solution. The grown ZnSn(OH)6, exhibits XRD peaks corresponding to cubic phase ZnSn(OH)6. Optical bandgap of the grown nanograss are calculated in the range from ∼3.0 to 3.5 eV. The nanograss photoanode grown with PEG surfactant (at 200 °C) has shown the highest photocurrent of 2.2 mA/cm2 at RHE 1.23VRHE and photoconversion efficiency of 1.4% at 0.46 VRHE. The longer nanograss has shown lower charge transfer resistance and higher charge carrier concentration, which is favorable for enhancing the PEC performance.

Removal and elimination of pharmaceuticals in water using zeolites in diverse adsorption processes and catalytic advanced oxidation technologies-a critical review.

Water pollution by pharmaceuticals is a current worrying environmental problem. Adsorption and catalytic processes using zeolites have been employed in several studies to remove/degrade pharmaceuticals from water. The interest of researchers in these two strategies based on the utilization of zeolites (i.e., adsorption and advanced oxidation technologies, AOT) is continuously growing. Then, this work presents a literature review, considering the origin of the zeolites (natural vs. synthetic) and the modifications of zeolites (e.g., the addition of surfactants) for the adsorption of diverse pharmaceuticals. The role of zeolites in catalytic ozonation, Fenton-based systems, and activation of peroxymonosulfate and peroxydisulfate is detailed. Also, the primary transformations of pharmaceuticals induced by these AOTs were examined. Moreover, the gaps regarding biodegradability and toxicity of the transformation products coming from the degradation of pharmaceuticals by the zeolites-based processes were discussed. To overcome the scarcity of information regarding the biodegradability and toxicity of the primary transformation products observed in the revised works, an initial approach to these topics, using a predictive tool, was made. Finally, from the present review, it was evidenced the need for future works involving zeolites that provide results about the simultaneous removal/elimination of multiple pharmaceuticals in complex matrices (e.g., hospital wastewater or municipal wastewater), new information about biodegradability and toxicity plus the development of combination or coupling of processes with other AOTs (e.g., sonochemistry) or classical systems (e.g., biological process).

Physicochemically modified polymer-based fluidic gates with tunable wetting properties for intelligent liquid manipulations

The creation of a selective flow path and the regulation of a flow rate are of critical importance for polymer-based devices that manipulate liquid at the microscale. The formation of a 3D interconnected network of voids (i.e., physical volumetric modification) and the addition of a nonionic surfactant, Silwet L-77, (i.e., chemical volumetric modification) are expected to affect the wetting properties of polymers, thereby achieving selective gating effect in the polymer-based devices as an appropriate technology. Here, a set of polydimethylsiloxane (PDMS)-based fluidic gates (F-gates) were developed to enable selectivity for liquids and flow-rate control of the liquids by tuning the wetting properties of PDMS with the physicochemical volumetric modifications. For water and oil with different surface tensions (STs), the effects of the physical and chemical volumetric modifications on the fluidic gating of PDMS were quantitatively characterized in terms of contact angle, mass flow rate, and liquid absorption speed. The applicability of PDMS-based F-gates to the selective separation of oil and water even from oil-in-water emulsion was demonstrated by fabricating Janus PDMS-based F-gates. Our physicochemical volumetric modifications were also extensively analyzed to examine whether they satisfy the technological, economic, and ecological requirements of appropriate technology. This is the first effort to tailor the wetting properties of PDMS through physicochemical volumetric modifications, thus configuring a set of PDMS-based F-gates that act both as a separator for liquids of different STs and as a switch for fluid flows.

Mesoscale modeling on the influence of surfactants on seepage law during water injection in coal

To investigate the mesoscopic influence of surfactants on seepage law during water injection in coal seam, this paper innovatively establishes a fluid transport lattice Boltzmann (LBM) model by incorporating the seepage resistance generated from the porous media and external forces, which embodies the impact of wettability degree resulted from cocamidopropyl betaine (CAB), sodium dodecyl sulfate (SDS), and coconutt diethanol amide (CDEA) reagents at a 0.1% concentration. The main conclusions derived from this investigation are as follows: Firstly, as the lattice number in the X direction increases, the average seepage velocities in coal samples treated by deionized water, 0.1% CAB, 0.1% SDS, and 0.1% CDEA reagents (Nos. 1, 2, 3, and 4) exhibit three distinct stages: rapid decline, slow decline, and steady decline; in comparison to raw coal sample, modified coal samples demonstrate decreases of 20.84%, 33.91%, and 61.70%, respectively. Secondly, the critical values of displacement pressure difference exist during the phenomenon that modified reagents spread out in the entire flow channel, which are 3.5 MPa, 3.5 MPa, and 5.2 MPa, respectively, for coal samples Nos. 2, 3, and 4; this signifies that surpassing these critical values help prevent issues such as blank belts within the wetting range and insufficient dust control. Finally, at a displacement pressure difference of 0.01 (lattice unit), the average velocity ratios for samples (Nos. 2, 3, and 4) are 0.78, 0.56, and 0.37(lattice unit), respectively; notably, the water flow velocities in modified coal samples are lower compared to that in raw coal sample, indicating that the addition of surfactants impede the seepage process of water injection in coal seam. Moreover, when the displacement pressure difference reaches 0.03 (lattice unit), the velocity ratio of CDEA-modified coal sample exceeds 100%; this means that when the displacement pressure difference surpasses 15.6 MPa, the water injection effect of CDEA-modified coal sample begins to be improved. These research findings offer a theoretical basis for enhancing water injection technology in coal mines.

Investigation of surfactant-laden bubble migration dynamics in self-rewetting fluids using lattice Boltzmann method

Self-rewetting fluids (SRFs), such as aqueous solutions of long-chain alcohols, show anomalous nonlinear (quadratic) variations of surface tension with temperature involving a positive gradient in certain ranges, leading to different thermocapillary convection compared to normal fluids (NFs). They have recently been used for enhancing thermal transport, especially in microfluidics and microgravity applications. Moreover, surface-active materials or surfactants can significantly alter interfacial dynamics by their adsorption on fluid interfaces. The coupled effects of temperature- and surfactant-induced Marangoni stresses, which arise due to surface tension gradients, on migration bubbles in SRFs remain unexplored. We use a robust lattice Boltzmann method based on central moments to simulate the two-fluid motions, capture interfaces, and compute the transport of energy and surfactant concentration fields, and systematically study the surfactant-laden bubble dynamics in SRFs. When compared to motion of bubbles in NFs, in which they continuously migrate without a stationary behavior, our results show that they exhibit dramatically different characteristics in SRFs in many different ways. Not only is the bubble motion directed toward the minimum temperature location in SRFs, but, more importantly, the bubble attains an equilibrium position. In the absence of surfactants, such an equilibrium position arises at the minimum reference temperature occurring at the center of the domain. The addition of surfactants moves the equilibrium location further upstream, which is controlled by the magnitude of the Gibbs elasticity parameter that determines the magnitude of the surface tension variation with surfactant concentration. The parabolic dependence of surface tension in SRF is parameterized by a quadratic sensitivity coefficient, which modulates this behavior. The lower this quantity, the greater is the role of surfactants modifying the equilibrium position of the bubble in SRF. Furthermore, the streamwise gradient in the surfactant concentration field influences the transient characteristics in approaching the terminal state of the bubble. These findings provide new means to potentially manipulate the bubble dynamics, and especially to tune its equilibrium states, in microchannels and other applications by exploiting the interplay between surfactants and SRFs.

Grafting of cinchonine onto rice husk nanosilica and its potential application in the synthesis of 2‐arylideneindan‐1,3‐diones and 2‐arylidene-5,5-dimethyl-1,3-cyclohexanedione

In this study, an eco-friendly and green procedure for Knoevenagel condensation reaction of aromatic aldehydes with indan-1,3-dione and dimedone was reported utilizing a rice husk silica‐anchored cinchonine nanocomposite as a heterogeneous catalyst in aqueous media. Without the need for an additional surfactant, rice husk was utilized as a raw material to create nanosilica. Through the grafting of 3-mercaptopropyl) trimethoxysilane, the rice husk nanosilica was modified. Next, azobisisobutylonitrile initiator was used to trigger the thiol-ene free radical interaction of the SH groups with the Cinchonine's alkene function. The morphology and structure of the nano SiO2-S-cinchonine were characterized using fourier transform infrared spectra, field emission scanning electron microscope, and energy-dispersive X-ray spectroscopy. The catalytic activity of the nanocomposite was investigated in the synthesis of 2-arylideneindan-1,3-diones and 2-arylidene-5,5-dimethyl-1,3-cyclohexanedione through an aqueous medium at 80 °C by the Knoevenagel condensation reaction. The advantages of this method are simple methodology, high yields, easy work-up, and green solvent.

Role of the Polymer in the Emulsion Stability of an Amphoteric Polyacrylamide in Different Flooding Systems.

Polymers with high viscosity and good viscosity-temperature property have attracted attention as chemical agents for enhanced oil recovery. The role of polymers in the emulsifying stability of an amphoteric polyacrylamide (TSPAM) with good viscosity-temperature property in different flooding systems was investigated by means of a new emulsion stability model and molecular simulations. The results indicated that TSPAM exhibited superior emulsion stability compared to hydrolyzed polyacrylamide (HPAM). The half-life of emulsions containing TSPAM was 1-7 min longer than that of emulsions containing HPAM. The results of molecular simulation revealed that the HPAM molecules adsorbed at the oil-water interface in a "point adsorption" mode, whereas the TSPAM molecules adsorbed in a "surface adsorption" mode, resulting in higher interfacial adsorption efficiency and more stable interfacial film. The polymer flooding systems containing TSPAM showed a larger interfacial thickness of 1.029 nm and higher emulsification efficiency compared to the polymer flooding systems containing HPAM. The addition of Na2CO3 or surfactants further improved the stability of emulsions in the binary systems containing TSPAM. The stability of emulsions containing all three oil displacement agents was the strongest, with the half-life extended by 3.8-13.6 min. Amphoteric polyacrylamide significantly enhanced the stability of the emulsions. Through the integration of experimental and molecular simulation techniques, the molecular structure of polyacrylamide can be optimized, facilitating the development of more efficient oil recovery formulations for enhanced oil recovery applications.

Distinct effects of dilute acid prehydrolysate inhibitors on enzymatic hydrolysis and yeast fermentation.

The effects of dilute acid prehydrolysate from poplar were investigated and compared in the enzymatic hydrolysis, fermentation, and simultaneous saccharification fermentation (SSF) in this study. The improvement of enzymatic hydrolysis and fermentation with resin adsorption and surfactant addition has also been represented. A total of 16 phenolic alcohols, aldehydes, acids and 3 furan derivatives in the prehydrolysates were identified and quantified by gas chromatography/mass spectrometry (GC/MS). The degree of inhibition from the phenolic compounds (26.55%) in prehydrolysate on the enzymatic hydrolysis was much higher than carbohydrates-derived inhibitors (0.52-4.64%). Around 40% degree of inhibition was eliminated in Avicel enzymatic hydrolysis when 75% of prehydrolysates phenolic compounds were removed by resin adsorption. This showed distinguishing inhibition degrees of various prehydrolysate phenolic compounds. Inhibition of prehydrolysate on enzymatic hydrolysis was more dosage-dependent, while their suppression on the fermentation showed a more complicated mode: fermentation could be terminated by the untreated prehydrolysate, while a small number of prehydrolysate inhibitors even improved the glucose consumption and ethanol production in the fermentation. Correlated with this distinct inhibition modes of prehydrolysate, the improvement of Tween 80 addition in SSF was around 7.10% for the final ethanol yield when the glucose accumulation was promoted by 76.6%.

Reductive pathways in molten inorganic salts enable colloidal synthesis of III-V semiconductor nanocrystals.

Colloidal quantum dots, with their size-tunable optoelectronic properties and scalable synthesis, enable applications in which inexpensive high-performance semiconductors are needed. Synthesis science breakthroughs have been key to the realization of quantum dot technologies, but important group III-group V semiconductors, including colloidal gallium arsenide (GaAs), still cannot be synthesized with existing approaches. The high-temperature molten salt colloidal synthesis introduced in this work enables the preparation of previously intractable colloidal materials. We directly nucleated and grew colloidal quantum dots in molten inorganic salts by harnessing molten salt redox chemistry and using surfactant additives for nanocrystal shape control. Synthesis temperatures above 425°C are critical for realizing photoluminescent GaAs quantum dots, which emphasizes the importance of high temperatures enabled by molten salt solvents. We generalize the methodology and demonstrate nearly a dozen III-V solid-solution nanocrystal compositions that have not been previously reported.

Effects of Pressure, Surfactant Concentration, and Heat Flux on Pool Boiling Using Expanding Microchanneled Surface for Two-Phase Immersion Cooling.

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant (Tween 20) and asymmetric structures (expanding microchannel) to enhance the boiling performances of deionized water under sub-atmospheric pressure. The research examines the effects of pressure (8.8~38.5 kPa), surfactant concentration (0.1~0.5 mL/L), and heat flux density (10~180 W/cm2) on the boiling heat transfer characteristics and analyzes the mechanism of unusual temperature oscillations induced by surfactants. It was found that the trade-off between the sub-atmospheric pressure, surface tension coefficient, and reduced static contact angle results in pronounced intermittent boiling on the heated surface. Even with the addition of surfactants, the improvement in heat transfer requires demanding conditions. Boiling enhancement throughout all heat flux conditions was achieved when the surfactant concentration was higher than 0.2 mL/L for the expanding microchanneled surface. The heat transfer coefficient reached 6.89 W·cm-2·K-1 under 8.8 kPa, which was 45% higher than without the surfactant. Under the same heat flux and sub-atmospheric pressure, as the concentration increased from 0.1 to 0.5 mL/L, the amplitudes of temperature fluctuation of the plane surface and expanding microchanneled surface decreased from 10 K to 2 K and 18 K to 1 K, respectively. The onset of nucleate boiling and wall superheat of the expanding microchanneled surface gradually decreased with the increase in surfactant concentration, where the onset of nucleate boiling decreased by 10.54 K. When the heat flux is 160 W/cm2, the wall superheat is reduced by 12.8 K.

Effect of water hardness and surfactant on the particle coverage and distribution of plant protection products granules

The paper presents a study done to determine how particles of different plant protection products (fungicides) are distributed onto treated surfaces when their solutions are prepared with water of different hardness and addition of surfactant. A total of fifteen plant protection products were studied, all in the same concentration of 0.3% with four type of solutions: only distilled water, distilled water plus a wetting agent – the organosilicone surfactant – Silwet L-77, very hard tap water (hardness = 196.9 ррm СаСО3, 11 °dH) and very hard tap water plus wetting agent. The observations and images were made via light microscope with magnification 200X and 3MP digital camera. The images were analyzed for a percent distribution, and spreading of particles by ImageJ software. The results showed that the distribution, and coverage of particles onto treated surfaces can be different even at application of similar plant protection products. The variations in the properties were observed when the solutions were made with waters with different hardness and a wetting agent was added to the solutions. Contrary to the common perception that hard water can reduce the effectiveness of pesticides towards pests, according to the distribution and coverage of particles onto treated surfaces, in some cases hard water can even enhance these properties of the pesticide solutions. Keywords: plant protection products, distribution, coverage, wetting agent, water hardness

Emulsification and interfacial characteristics of different surfactants enhances heavy oil recovery: experimental evaluation and molecular dynamics simulation study

The high viscosity and poor fluidity of heavy oil challenge its extraction, leading to the widespread use of surfactant emulsification to reduce viscosity and enhance recovery. This study evaluated three surfactants—sodium dodecyl sulfate (SDS), sodium oleate (SO), and APG0810—for their suitability and effectiveness in the X reservoir. The solution properties of these surfactants were analyzed and their micro-mechanisms investigated using MD calculations. The effects of surfactant concentration and additives on emulsification and viscosity reduction were elucidated. Ultimately, a system for emulsification and viscosity reduction was selected for physical simulation research. The experimental findings show that SO reduces interfacial tension from 52.4 mN/m to 0.0027 mN/m, transforming lipophilic surfaces into hydrophilic. MD analyses reveal SO’s optimal interfacial properties, with the lowest interfacial energy of −6423.4 kcal/mol, maximum interfacial thickness of 2.56 nm, and minimal diffusion coefficient of 0.4087 Å2/ps at the oil-water interface. These findings align with experimental results, confirming SO’s superior interfacial properties. Combining 0.3% SO with 0.5% n-pentanol results in a 98% viscosity reduction. The emulsion shows excellent stability, with no water separation in the first 30 min and only 8.3% after 2 h. Physical simulation results show that in high(low) permeability core displacement experiments, system flooding and subsequent water flooding can increase recovery rates by 15.39%(36.91%), indicating the system’s potential for enhancing oil recovery in Reservoir X. The findings suggest that the implementation of this system not only boosts the crude oil recovery rate but also carries economic significance in the industry.

Moringa Oil and Carbon Phases of Different Shapes as Additives for Lubrication

Vegetable oils in the lubricant field are largely studied. Their efficiency depends on their viscosity parameters and their fatty acid composition. The actions of moringa oil used as a lubricant base and as a lubricant additive have been shown in this work. Graphite, carbon nanofibers, and carbon nanodots are carbon phases of different shapes used as solid additives. The tribological performances of lubricant blends composed of between 0.5 and 1 wt.% of particles have been evaluated using a ball-on-plane tribometer under an ambient atmosphere. No additional surfactant was used. The positive and important actions of a small amount of moringa oil added in the lubricant formulas are demonstrated. The results obtained allow us to point out the influence of the type and shape of particles. Physicochemical investigations allow us to propose a synergistic effect between the particles and moringa oil as additives in dodecane.

Transient transition from stable to dissipative assemblies in response to the spatiotemporal availability of a chemical fuel.

The transition from inactive to active matter implies a transition from thermodynamically stable to energy-dissipating structures. Here, we show how the spatiotemporal availability of a chemical fuel causes a thermodynamically stable self-assembled structure to transiently pass to an energy-dissipating state. The system relies on the local injection of a weak affinity phosphodiester substrate into an agarose hydrogel containing surfactant-based structures templated by ATP. Injection of substrate leads to the inclusion of additional surfactant molecules in the assemblies leading to the formation of catalytic hotspots for substrate conversion. After the local disappearance of the substrate as a result of chemical conversion and diffusion the assemblies spontaneously return to the stable state, which can be reactivated upon the injection of a new batch of fuel. The study illustrates how a dissipating self-assembled system can cope with the intermittent availability of chemical energy without compromising long-term structural stability.

Enhancing the biodegradation of hydrophobic volatile organic compounds: A study on microbial consortia adaptation and the role of surfactants

The emission of hydrophobic Volatile Organic Compounds (VOCs) is a serious environmental issue. Typically, biofilters (BFs) are employed for their treatment, with the potential enhancement of mass transfer through the addition of surfactants. However, disparate results in previous studies have been observed, attributed to uncontrolled conditions during the introduction of surfactants to BFs. Additionally, there has been limited exploration of microbial consortium adaptation to surfactants. To address these gaps, this study followed two approaches. First, the long-term (247 days) removal of cyclohexane was studied in a stirred tank bioreactor (STBR) inoculated with Rhodococcus erythropolys E1 and using Tween 80 at three times the critical micelle concentration (CMC). Second, the short-term (9 days) impact of two (bio)surfactants [Tween 80 (1 × CMC) and Quillaja Saponin (QS, 1 × CMC)] on the removal of cyclohexane, hexane and toluene was investigated in batch tests using three types of inocula: a pure culture of Rhodococcus erythropolys E1 (X0), a microbial consortium adapted to cyclohexane (X1), and a microbial consortium adapted to cyclohexane with Tween 80 (X2). For long-term operation, the addition of Tween 80 at 3 × CMC improved cyclohexane removal efficiency (RE) to 87 ± 1% (elimination capacity, EC = 145 ± 25 mg m−3 h−1, gas residence time, GRT = 20 min, inlet concentration, Cin = 14.9 ± 2.5 ppmv), compared to a RE of 32 ± 9% (EC = 44 ± 8 mg m−3 h−1, GRT = 20 min, Cin = 15.1 ± 0.7 ppmv) under similar conditions without surfactants. For short-term operation, the addition of QS at 1 × CMC significantly increased biomass growth, resulting in lower maximum specific consumption rates for X1 and X2 compared to scenarios without surfactants or 1 × CMC Tween 80. The most abundant genera in X1 and X2 were Paludisphaera (26-23%), 67-14 genus (17–23%), and Rhodococcus (9–18%), respectively.