Anionic Surfactant Sodium Dodecylbenzenesulfonate Research Articles

Formation and survival of clay-mediated protocell membranes composed of single-chain amphiphiles in aqueous solutions

Protocell compartments composed of simple amphiphilic molecules could have survived on the clay mineral surfaces which can serve well as plausible sites for prebiotic chemistry on the early Earth. Herein we chose four common single-chain amphiphiles (SCAs), including the anionic surfactant sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS), the cationic surfactant dodecyltrimethylammonium bromide (DTAB) and the zwitterionic lauryl sulfobetaine (LSB)), as model constituents of early membranes to establish a tentative model for protocell compartment. Positively charged Mg2Al-/Mg2Fe-layered double hydroxides (LDHs) and FeS2 are viewed as models of clay minerals. We demonstrate by comprehensively experimental study that unconventional vesicles can be easily promoted in a SCA aqueous micellar solution in the presence of model particles. Morphology evolutions are traced by collecting samples from mixtures of LDHs and SCA aqueous solutions and then recording at different incubation times via negative-staining or cryo-transmission electron microscopy (NS-TEM or cryo-TEM) and dynamic light scattering (DLS). Additionally, the stability of SCA bilayer membranes under possible prebiotic environment are tentatively studied. This work not only offers a robust yet versatile approach for the fabrication of novel vesicles but also provides new insights into the origin of cellular life.

An artificial liquid–liquid phase separation-driven silk fibroin-based adhesive for rapid hemostasis and wound sealing

The powerful adhesion systems of marine organisms have inspired the development of artificial protein-based bioadhesives. However, achieving robust wet adhesion using artificial bioadhesives remains technically challenging because the key element of liquid–liquid phase separation (LLPS)-driven complex coacervation in natural adhesion systems is often ignored. In this study, mimicking the complex coacervation phenomenon of marine organisms, an artificial protein-based adhesive hydrogel (SFG hydrogel) was developed by adopting the LLPS-mediated coacervation of the natural protein silk fibroin (SF) and the anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SF/SDBS complex coacervate enabled precise spatial positioning and easy self-adjustable deposition on irregular substrate surfaces, allowing for tight contact. Spontaneous liquid-to-solid maturation promoted the phase transition of the SF/SDBS complex coacervate to form the SFG hydrogel in situ, enhancing its bulk cohesiveness and interfacial adhesion. The formed SFG hydrogel exhibited intrinsic advantages as a new type of artificial protein-based adhesive, including good biocompatibility, robust wet adhesion, rapid blood-clotting capacity, and easy operation. In vitro and in vivo experiments demonstrated that the SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, thus advancing its clinical applications. Statement of significanceMarine mussels utilize the liquid–liquid phase separation (LLPS) strategy to induce the supramolecular assembly of mussel foot proteins, which plays a critical role in strong underwater adhesion of mussel foot proteins. Herein, an artificial protein-based adhesive hydrogel (named SFG hydrogel) was reported by adopting the LLPS-mediated coacervation of natural protein silk fibroin (SF) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SFG hydrogel enabled the precise spatial positioning and easy self-adjustable deposition on substrate surfaces with irregularities, allowing tight interfacial adhesion and cohesiveness. The SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, exhibiting intrinsic advantages as a new type of artificial protein-based bioadhesives.

Effects of sodium dodecylbenzene sulfonate (SDBS) on zebrafish (Danio rerio) gills and blood

ABSTRACT Sodium dodecylbenzene sulfonate (SDBS) is an important surfactant used as a cleaning agent and industrial additive to remove unwanted chemicals which have been detected in the aquatic environment. The aim of this study was to examine the toxicological potential of SDBS on the gills of adult male zebrafish (Danio rerio) exposed to this chemical. For the 96 hr acute exposure, fish were divided into three groups: control, 0.25 mg/L, and 0.5 mg/L of SDBS. After the experiment, morphophysiological analyses (gill histopathology and histochemistry), oxidative stress (determination of gill activities of superoxide dismutase (SOD) and catalase (CAT)), and hematological analyses (leukocyte differentiation) were conducted. Data demonstrated that SDBS at both tested concentrations altered the histopathological index and initiated circulatory disturbances, as well as adverse, progressive, and immunological changes in the gills. In the 0.5 mg/L group, SOD activity decreased significantly, but CAT activity was not altered. Prominent blood changes observed in this group were neutrophilia and lymphocytosis. The number of mucous and chloride cells increased significantly in both groups. Taken together, our findings demonstrated that exposure of D. rerio to SDBS, even for 96 hr, produced adverse morphological and hematological effects associated with a reduction in SOD activity. Our findings indicate that exposure of aquatic species to the anionic surfactant SDBS may lead to adverse consequences associated with oxidative stress. Therefore, this study highlights the risks that this substance may pose to aquatic ecosystems and emphasizes the need for further investigations and strict regulations on its disposal.

Molecular dynamics models to investigate the diffusion behavior of emulsified asphalt

The utilization of emulsified asphalt is widespread in the recycling of asphalt pavement due to its eco-friendliness and energy efficiency. While numerous research studies have been conducted on the mixture design and strength assessment of emulsified asphalt, the mechanism by which it diffuses and adheres to the aggregate surface remains inadequately comprehended. This study developed molecular dynamics models to investigate the diffusion behavior of emulsified asphalt on the aggregate surface to clarify the role of emulsifier, water, and asphalt in the adsorption process from a molecular perspective. Interface models are established according to the diffusion state for interfacial adhesion evaluation. The results show that the movement of water molecules is the driving force for the entire emulsified asphalt to adsorb to the aggregate surface, whether the aggregate is silica or reclaimed asphalt pavement (RAP). Compared with anionic surfactant Sodium Dodecylbenzene Sulfonate (SDBS), cationic emulsifier Cetyltrimethylammonium Chloride (CTAC) has a better affinity, stronger adsorption, and higher interfacial adhesion energy with silica. Compared with RAP, emulsified asphalt is more readily adsorbed to the surface of silica. It is concluded that emulsifiers have two distribution conformations during the adsorption process, delamination, and aggregation, with delamination exhibiting stronger interface strength with silica than aggregation. When the emulsified asphalt spreads on the RAP surface, the penetration of water molecules into the aged asphalt layer in the RAP structure reduces the structure's water resistance. These results can provide a molecular perspective for understanding the internal structure of emulsified cold recycle mixture (ECRM) and link the adsorption behavior of emulsified asphalt on aggregate surfaces with the internal interface strength of ECRM.

Molecular dynamics simulation of surfactant induced wettability alteration of shale reservoirs

Shale oil has recently received considerable attention as a promising energy source due to its substantial reserves. However, the recovery of shale oil presents numerous challenges due to the low-porosity and low-permeability characteristics of shale reservoirs. To tackle this challenge, the introduction of surfactants capable of modifying wettability has been employed to enhance shale oil recovery. In this study, we perform molecular dynamics simulations to investigate the influence of surfactants on the alteration of wettability in shale reservoirs. Firstly, surfaces of kaolinite, graphene, and kerogen are constructed to represent the inorganic and organic constituents of shale reservoirs. The impact and underlying mechanisms of two types of ionic surfactants, namely, the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and cationic surfactant dodecyltrimethylammonium bromide (DTAB), on the wettability between oil droplets and surfaces are investigated. The wettability are analyzed from different aspects, including contact angle, centroid ordinates, and self-diffusion coefficient. Simulation results show that the presence of surfactants can modify the wetting characteristics of crude oil within shale reservoirs. Notably, a reversal of wettability has been observed for oil-wet kaolinite surfaces. As for kerogen surfaces, it is found that an optimal surfactant concentration exists, beyond which the further addition of surfactant may not enhance the efficiency of wettability alteration.

Complexes of an Anionic Surfactant with Chitosan and Its Hydrophobic Derivatives As Disinfectants against SARS-CoV-2

This work is aimed at the preparation of complexes of chitosan and hydrophobically modified (HM) chitosan with an anionic surfactant sodium dodecylbenzene sulfonate (SDBS), and at the study of the virucidal activity of the complexes and their components against SARS-CoV-2. It is shown that the introduction of a sufficient amount (4 mol%) of hydrophobic n-dodecyl side groups provides the activity of HM chitosan against SARS-CoV-2 at moderate concentrations, at which unmodified chitosan and chitosan containing a lower amount of hydrophobic groups do not show any activity. Complexes of HM chitosan with SDBS are prepared, which is proven by fluorescence spectroscopy and isothermal titration calorimetry. It is discovered that HM chitosan/SDBS complex is more active than the polymer without surfactant, and an increase of the amount of hydrophobic groups enhances the activity

A novel PVA/MWCNTs hydrogel with high toughness and electromagnetic shielding properties

AbstractCarbon nanotubes (CNTs) are widely utilized as conductive fillers due to their high conductivity, lightweight, and ease of modification. However, their poor dispersion limits their otherwise excellent performance. In this study, we successfully prepared a high toughness, strong electromagnetic interference (EMI) shielding hydrogel by blending polyvinyl alcohol (PVA) hydrogel with multi‐walled carbon nanotubes (MWCNTs) modified by anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and (3‐aminopropyl) triethoxysilane (KH550). We found that the modifiers can not only promote the uniform dispersion of MWCNTs but also improve the mechanical properties of the hydrogel. The results demonstrate that the stress (≈14.86 MPA), elongation at break (233.9%), and compressive strength (≈2.89 MPA) of PVA/MWCNTs composite hydrogel with 1 wt% MWCNTs and 5 wt% PVA were increased by 533.6%, 241.4%, and 206.5%, respectively. Encouragingly, the total electromagnetic shielding effectiveness (SET) is 123.6 dB at a thickness of 5 mm. In summary, this work provides a general approach to functionalizing MWCNTs, which has great potential for developing EMI shielding materials with high toughness.

Designing an Efficient Surfactant–Polymer–Oil–Electrolyte System: A Multi-Objective Optimization Study

This research aimed to study the effects of individual components on the physicochemical properties of systems composed of surfactants, polymers, oils, and electrolytes in order to maximize the recovery efficiency of kerosene while minimizing the impact on the environment and human health. Four independent factors, namely anionic surfactant sodium dodecylbenzene sulfonate (X1) (SDBS), oil (X2) (kerosene), water-soluble polymer poly(ethylene glycol) (X3) (PEG), and sodium chloride (X4) (NaCl), were studied using the full factorial design (FFD) model. Four output variables, namely conductivity (Y1), turbidity (Y2), viscosity (Y3), and interfacial tension (IFT) (Y4), were taken as the response variables. All four FFD models have high coefficients of determination and low errors. The developed models were used in a multi-objective optimization (MOO) framework to determine the optimal conditions. The obtained optimal conditions are X1 = 0.01, X2 = 50, X3 = 5, and X4 = 0.1, with an error of 0.9414 between the predicted and experimental objective function values. This result shows the efficiency of the model developed and the system used for the recovery of kerosene, while also having a positive effect on the protection of the environment.

Generation of Fermat’s spiral patterns by solutal Marangoni-driven coiling in an aqueous two-phase system

The solutal Marangoni effect is attracting increasing interest because of its fundamental role in many isothermal directional transport processes in fluids, including the Marangoni-driven spreading on liquid surfaces or Marangoni convection within a liquid. Here we report a type of continuous Marangoni transport process resulting from Marangoni-driven spreading and Marangoni convection in an aqueous two-phase system. The interaction between a salt (CaCl2) and an anionic surfactant (sodium dodecylbenzenesulfonate) generates surface tension gradients, which drive the transport process. This Marangoni transport consists of the upward transfer of a filament from a droplet located at the bottom of a bulk solution, coiling of the filament near the surface, and formation of Fermat’s spiral patterns on the surface. The bottom-up coiling of the filament, driven by Marangoni convection, may inspire automatic fiber fabrication.

A sensitive photoluminescent sensor based on highly charged monoruthenium(II) complexes for dopamine detection

A sensitive and selective photoluminescent sensor based on the highly charged monoruthenium(II) complex was designed to detect dopamine (DA) in aqueous samples. Two novel highly charged cationic ruthenium(II) complexes [Ru(bpy)2(bpy-N)]X4 (bpy = 2,2′-bipyridine, bpy-N = 4,4′-bis[N,N,N-triethyl-(methylamino)]-2,2′-bipyridine, X− = [PF6]− (1a) or Cl− (1b) and [Ru(bpy)(bpy-N)2]X6 (X− = [PF6]− (2a) or Cl−(2b)) can be assembled with anionic surfactant sodium dodecylbenzene sulfonate (SDBS), leading to an enhancement of photoluminescence intensity. Upon addition of DA to the system, the photoluminescence intensity of the assembled system was quenched due to the energy transfer effect. It exhibited a wide linear range (0.1–50 μM) and low detection limit (10 nM). The sensor demonstrated a high selectivity toward DA, especially in the presence of adrenaline (Adr) and norepinephrine (NE), whose structures are similar to DA in biological systems. With the merits of simple operation, obvious phenomenon and fast response speed, the sensor had a potential application prospect in human urine sample.

Preparation and characterization of self-crosslinking acrylic emulsion with different fluorocarbon chain lengths

PurposeFluorine materials have received the keen attention of many researchers because of their water repellency and low surface free energy. The purpose of this paper is to prepare self-crosslinking fluorocarbon polyacrylate latexes containing different fluorocarbon chain lengths by semi-continuous seeded emulsion polymerization technology.Design/methodology/approachMethyl methacrylate (MMA), butyl acrylate (BA), hydroxypropyl methacrylate (HPMA) and fluorine-containing monomers were used as main monomers. The fluorine-containing monomers included hexafluorobutyl methacrylate (HFMA), dodecafluoroheptyl methacrylate (DFMA) and trifluorooctyl methacrylate (TFMA). Potassium persulfate (KPS) was used as thermal decomposition initiator, non-ionic surfactant alkyl alcohol polyoxyethylene (25) ether (DNS-2500) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS) as mixed emulsifier.FindingsThrough optimizing the reaction conditions, the uniform and stable latex is gained. The polymer of structure was characterized by Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA) were tested on latex films. The particle size and distribution range of emulsion were tested with nano particle size analyzer. After comprehensively comparing the latexes and films prepared by HFMA, DFMA and TFMA, the performance of DFMA monomer modified is better.Originality/valueThe self-crosslinking acrylic emulsion is prepared via semi-continuous seeded emulsion polymerization, which methyl methacrylate (MMA), butyl acrylate (BA), hydroxypropyl methacrylate (HPMA) and fluorine-containing monomers were used as main monomers. The fluorine-containing monomers were composed of hexafluorobutyl methacrylate (HFMA), dodecafluoroheptyl methacrylate (DFMA) and trifluorooctyl methacrylate (TFMA). Potassium persulfate (KPS) was used as thermal decomposition initiator, non-ionic surfactant alkyl alcohol polyoxyethylene (25) ether (DNS-2500) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS) as mixed emulsifier. There are two main innovations. One is that the self-crosslinking acrylic emulsion is prepared successfully. The other is that the effects of monomers containing different fluorocarbon chain lengths on polyacrylate, such as monomer conversion rate, coagulation rate, mechanical stability, chemical stability, emulsion particle size and storage stability, are studied in detail.

Effect of solution pH on removal of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) from model wastewater using nanoscale zero-valent iron (nZVI)

Batch experiments for removal of anionic surfactant sodium dodecylbenzenesulfonate (SDBS) from model wastewater using nanoscale zero-valent iron (nZVI) were conducted to elucidate mechanisms of SDBS removal by nZVI. To clarify the effects of solution pH on removal of SDBS by nZVI, the concentration profiles of Fe ions and dissolved oxygen (DO) were measured besides the concentrations of SDBS and total organic carbon (TOC) at pH of 3, 5, 7 and 9. The SDBS concentration rapidly decreased to less than 4% of the SDBS loadings within 40 min at pH 3, 7 and 9. However, TOC decreases were rather slow and the maximum TOC removal of 62% after 240 min was obtained at pH 7. The XRD patterns confirmed that the main corrosion product was lepidocrocite at pH 5 and 7 while magnetite was dominant at pH 9. The maximum removal of SDBS by nZVI at pH 7 was attributed mainly to the ionic adsorption of anionic SDBS onto the positively charged nZVI surface. The novel kinetic model for dynamic linkage of SDBS removal with concentrations of total eluted iron ions and DO via the formation of iron oxide/hydroxide layer on nZVI surface could simulate the experimental results with the average correlation coefficient of 0.952. The mechanisms of SDBS removal by nZVI at different pH values were clarified and quantified by the proposed kinetic model.

Effect of surfactants on the transport of polyethylene and polypropylene microplastics in porous media

The transport of microplastics in porous media is attracting increasing attention. However, to date, research is limited to polystyrene microplastics. Meanwhile, surfactants can promote solid dispersion to form a stable suspension, possibly allowing microplastics to migrate when attached to a surfactant, which would increase the scope and degree of microplastic pollution, further endangering human health and the stability of the ecological environment. Therefore, in this study, the transport behavior of microplastics in porous media was explored in the presence of surfactants. Herein, polyethylene (PE) and polypropylene (PP) were evaluated while dispersed by two ionic surfactants: cationic surfactant-cetyltrimethylammonium bromide (CTAB) and anionic surfactant-sodium dodecylbenzenesulfonate (SDBS). The influence of different factors (surfactant concentration, ionic strength, pH, flow rate, and multivalent cations) on the transport of microplastics in porous media was explored via quartz sand packed-column experiments. Our experimental results show that the transport abilities of PE and PP increased with increasing surfactant concentration when the surfactant concentration was less than the critical micelle concentration (CMC). In the presence of CTAB and SDBS, physicochemical factors had different effects on the transport of microplastics mainly by controlling Zeta potential, advection diffusion and CMC. The mobility of PE and PP decreased with increasing ionic strength, cation valence and pH, and decreasing flow rate. However, the mobility of PE and PP under CTAB is much greater than that of PE and PP under SDBS, because quartz sand can absorb more CTAB molecules through electrostatic attraction to weaken the collision between microplastics and quartz sand. Further, the transport ability of PP was greater than that of PE under all conditions considered. Notably, the Extended-Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory formed by adding osmotic, elastic, and hydrophobic force could well described the migration behavior of microplastics in CTAB and SDBS well. This research highlights that surfactant has a significant impact on the transport ability of microplastics, and provides a comprehensive understanding of the migration and fate behaviors of microplastics affected by surfactants, which is necessary to prevent and reduce the environmental hazards of microplastics.

Migration behavior of Cr(VI) during the transformation of ferrihydrite-Cr(VI) co-precipitates: The interaction between surfactants and co-precipitates

Redistribution of Cr(VI) in ferrihydrite-Cr(VI) co-precipitates (Fh-Cr) was affected by co-precipitates transformation and coexisting substances. These effects were crucial for predicting the migration path of Cr(VI) in ferrihydrite-Cr(VI) co-precipitates. This work investigated the effects of the extensively used surfactants of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and cationic surfactant cetyltrimethylammonium bromide (CTAB) on the Fh-Cr transformation and redistribution of Cr(VI) for 10 days at different pH values (5.0, 7.5 and 9.0) and concentration of surfactants (0.5, 2.0 and 5.0 mM). The results showed that SDBS hindered the transformation of Fh-Cr to hematite and tended to transform into goethite. SDBS inhibited hematite formation by inhibiting the aggregation of Fh-Cr particles, and it enhanced the dissolution of Fh-Cr to facilitate the formation of goethite. Affected by the inhibition of Fh-Cr transformation, the process of Cr(VI) redistribution was delayed. CTAB did not affect the transformation of Fh-Cr, but allowed more Cr(VI) to enter the interior of iron minerals. When the surfactants were adsorbed on the Fh-Cr, SDBS decreased the adsorption of Cr(VI) by Fh-Cr, while CTAB increased the Cr(VI) adsorption. The findings of this study contribute to understand the effects of surfactants on the transformation of Fh-Cr and the behaviors of Cr(VI) during this process.

Optimization of synthesis of geopolymer adsorbent for the effective removal of anionic surfactant from aqueous solution

This paper describes the optimization of synthesis of fly ash based geopolymer (FAGP) for removing the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) using response surface methodology (RSM) by varying the synthesis parameters of silica to alumina (Si/Al), sodium to alumina (Na/Al) and water to solid (W/S) ratios with the adsorption capacity as the response. The geopolymer samples were designed, synthesized, characterized, used for removing SDBS surfactant, and regenerated. Surface area and pore size analysis, Fourier Transform Infrared Spectroscopy (FTIR) analysis, phase analysis, and microstructural analysis confirmed the synthesis of mesoporous and amorphous geopolymers with the presence of pores, cavities and rods in the geopolymer structure. Geopolymer sample synthesized with the composition of Si/Al-2.87, Na/Al-1.0 and W/S-0.35 (FAGP-2) achieved maximum surface area of 59.512 m2/g and displayed the highest adsorption capacity of 743.706 mg/g and removal efficiency of 84.5%. The ANOVA analysis showed a correlation coefficient (R2) of 0.952, F-value of 22.27, and p value of 0.05 which indicated the significance of the model and lack of fit was non-significant which showed good fitting of the experimental data to the quadratic model with 95% confidence level. The proposed geopolymer composition of Si/Al-2.353, Na/Al-1.056, and W/S-0.339 achieved adsorption capacity of 730.212 mg/g which is 99% similar to the predicted adsorption capacity. Thermal method successfully regenerated SDBS adsorbed geopolymer with only 13.8% loss of adsorption capacity after five cycles of regeneration. The adsorption capacity of optimized geopolymer is higher than other adsorbents such as cross-linked chitosan films, commercial activated carbon, surface functionalized mesoporous silica nanoparticles, multi-walled carbon nanotubes (MWCNTs), and others used for removing SDBS surfactant and only amino crosslinked chitosan microspheres (ACCMs) has higher adsorption capacity than geopolymer. This shows that geopolymer can also be effectively used to adsorb SDBS surfactant from wastewater.

Dynamics of interfacial layers for sodium dodecylbenzene sulfonate solutions at different salinities

This study investigates the adsorption mechanisms and the dilational surface rheology of the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) at the air–liquid interface, in the presence and absence of NaCl over a wide range of SDBS concentrations. We also evaluate the Langmuir and Frumkin models in order to predict the dynamic adsorption of SDBS solutions. Our results reveal that the equilibrium surface tension of SDBS solutions is a monotonically decreasing function of NaCl concentration. However, the dilational viscoelastic properties of SDBS solutions are found to be a non-monotonic function of NaCl concentration. NaCl manifests opposing effects on the dilational viscoelastic moduli of the gas–liquid interface, depending on the frequency of surface oscillation and surfactant bulk concentration. Our measured dilational surface elasticity and viscosity data show a shift in the surfactant transition concentration, at which the viscoelastic moduli reach their maximum values, towards smaller surfactant bulk concentrations with increasing salt concentration. It is attributed to suppressing the electrostatic repulsion between the hydrophilic head groups of surfactant molecules in the presence of electrolytes. The maximum viscoelastic moduli at different NaCl concentrations is found to be the reflection of the relative impact of enhanced adsorption and increased diffusion exchange between bulk and interface.

Defoaming of industrial lean methyldiethanolamine solution using ultrasonic waves and their kinetic studies

Amine foaming is a well-known incident in the natural gas sweetening unit. In this study, anionic surfactant sodium dodecylbenzenesulfonate (SDBS) and cationic surfactant hexadecyltrimethylammonium bromide (HTAB) were used as model foam creators in industrial lean methyldiethanolamine (MDEA) solution. The surfactant concentrations of 300, 500, 1000, and 3000 mg/L were prepared in lean MDEA solution and stirred to create foam. The final foam volume was found to increase with the increase in both the surfactant concentration and the stirring speed. However, SDBS showed higher foam volume (35 and 55 mL) than HTAB (20 and 25 mL) at low surfactant concentrations (300 and 500 mg/L). Ultrasonic waves were effective in defoaming all tested solutions. The rate of defoaming increased with temperature rise. At a fixed temperature and stirring, foam formation and defoaming obeyed the exponential function. The differences in physical properties, including density, dynamic viscosity, and surface tension before and after sonication, were insignificant. Interestingly, the content of organic acids, known as primary degraded products, remained almost constant. This work demonstrated the promising potential of ultrasonic waves for defoaming amine solutions in the natural gas industry.

Improve the energy efficiency: Effects of additives on longtime zinc electrowinning

In this paper, the theoretical energy consumption required in the zinc electrowinning process was analyzed. The theoretical energy consumption is only a half of the energy consumption in industrial production. To save energy of the production process, we studied five kinds of additives with the industrial electrolyte in the longtime zinc electrowinning process. The results indicated that the presence of non-ionic compound (thiourea) or anionic surfactant (sodium dodecyl sulfonate or sodium dodecylbenzene sulfonate) adversely affected the energy consumption and current efficiency. However, an improvement in energy consumption was observed with the addition of cetyltrimethylammonium bromide. Our results should be helpful for the production of zinc electrowinning.

Ecotoxicity and micellization behavior of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and its mixtures with nonionic surfactant fatty alcohol-polyoxyethylene ether (AEO)

Surfactant mixtures have extensive industrial applications due to their ideal properties and low ecotoxicity. However, the ecotoxicity of surfactant mixtures with different proportions and their correlation with surface properties have remained poorly investigated. In this study, the ecotoxicity and surface activity of the composites of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) and nonionic surfactant fatty alcohol-polyoxyethylene ether (AEO) in various mass ratios were assessed, and the correlation between ideal application properties and safe ecological perspective of the composites was explored. The ecotoxicity of individual SDBS, AEO, and SDBS/AEO mixtures was determined using the bioluminescence inhibition assay with Photobacterium phosphoreum, and the critical micelle concentrations (CMC) were measured by surface tension method and steady-state fluorescence spectroscopy. Sodium dodecylbenzene sulfonate (SDBS) showed a considerably higher toxicity than individual AEO and SDBS/AEO mixtures. Scanning electron microscope images illustrated the rupture of bacteria membrane induced by SDBS, and the addition of AEO alleviated the damage. According to the dose–response relationship on luminous bacteria, SDBS/AEO mixtures were divided into three groups (group I with a high proportion of SDBS, SDBS:AEO = 4:1 and 3:2; group II, SDBS:AEO = 1:1; group III with a high proportion of AEO, SDBS:AEO = 2:3 and 1:4). The sequence of toxicity of the SDBS/AEO mixtures was group II > group III > group I, demonstrating that the toxicity of the composites was related to the mixture proportion instead of the amount of AEO added. The CMC order of SDBS/AEO mixtures was group II > group I > group III, and it was proportion dependent. Furthermore, ΔCM was defined as the difference of the experimental (CM) and ideal CMC (CMideal) of the mixed system, indicating the interaction between the two kinds of surfactants. The order of the ΔCM was group II > group III > group I, which was consistent with the sequence of the toxicity. Therefore, ΔCM can be a potential indicator for the hazardous assessment of surfactant mixtures involving high ionic strength.

Removal of anionic surfactants from aqueous solutions using Fe-aluminosilicate sorbents

Fe-aluminosilicate sorbents were obtained by modifying bentonite clay with iron polyoxocations and heat treatment at 400°C and 500°C. The specific surface of the sorbents determined by the method of low-temperature nitrogen adsorption was 118-136 m2 · g–1. The iron content in sorbents was equal 7.8 %. The adsorption properties of the obtained sorbents were studied with respect to anionic surfactants (sodium dodecyl sulfate and sodium dodecylbenzenesulfonate) in aqueous solutions. It was shown that the modification of clay leads to a significant increase in anion-exchange capacity. The value of the adsorption capacity was in good agreement with the increase in the number of the basic groups of Fe – OH and the value of the specific surface of the sorbents. Adsorption isotherms of sodium dodecyl sulfate on bentonite clay and on Fe –aluminosilicate sorbents are described by the Langmuir adsorption isotherm equation which describes monolayer adsorption on a homogeneous surface with a correlation coefficient of 1.000 at initial surfactant concentrations of 10-1000 mg · l–1. The adsorption capacity of Fe-aluminosilicate sorbents was more than 3 times higher than the capacity of the original clay in the adsorption of sodium dodecyl sulfate and was about 5 times higher in the adsorption of sodium dodecylbenzenesulfonate. The results of the study suggest that the Fe-aluminosilicate sorbents can be effective for removing anionic surfactants from wastewater.