Sodium Alpha-olefin Sulfonate Research Articles

Effect of ionic liquid-surfactant compound solutions on the wettability and functional groups of coal

In order to investigate the feasibility of ionic liquid-surfactant compound solutions for coal dust suppression, three ionic liquids and sodium alpha-olefin sulfonate (AOS) were selected to be compounded respectively. The compound solutions were optimized by surface tension tests and coal dust settling experiments, and FTIR and SEM tests were carried out on coal samples treated with the optimum wetting agent. The results show that when the concentration is 0.3 wt%, and the ratio of [Bmim][Cl]/AOS is 4:6, the wetting rate of compound solution is the maximum. The content of hydrophilic functional groups OH…O and C-O in the coal samples increases significantly, and the degree of benzene ring substitutions is elevated; while hydrophobic functional groups –CH, aromatic ring C = C, and benzene ring 3 substitutions (3H) are destroyed by dissolution. The micromorphology of the coal surface changes with the appearance of many cracks and pores and an increase in surface roughness. [Bmim]+ can adsorb on the drain absorption points on the coal surface by electrostatic effect, turning them into water absorption sites and attracting the surrounding AOS molecules to arrange the composite adsorption layer more closely. These results can contribute to the development of novel wetting agents with specific structures and provide theoretical guidance for the reduction of coal dust concentrations.

Synergistic effect of surfactants and nanoparticles on the wettability of coal: An experimental and simulation study

Injecting surfactants into coal seams is an effective means to improve coal wettability. Previous studies have shown that nanofluids provided excellent drag reduction and wetting. Therefore, this manuscript investigates the synergies of AOS (Sodium alpha-olefin sulfonate)-modified SiO2 nanofluid on the wettability of coal. Contact angle experiments were performed to examine the effects of deionized water on the wettability of coal treated with different solutions. The results demonstrated that 0.01 wt% nanofluid containing with 0.2 wt% AOS as the significantly increased the wettability. At the micro level, molecular dynamics simulations were employed to analyze the relative concentration distribution and MSD (mean square displacement) of water molecules in different systems. The simulation outcomes revealed that water molecules formed the thickest adsorption layer, and the diffusion range was more expansive, in the H2O/AOS-modified SiO2/Coal system. This was attributed to the amphiphilic structure of AOS-modified SiO2, which bent and folded on the coal surface, where hydrophobic sites were masked and hydrophilic sites were increased. Therefore, water molecules were attracted to the coal, the potential for collision was increased, and the wettability of the coal was enhanced. These findings provide a crucial foundation for modifying nanoparticles with surfactants and using them in coal seam water injection.

Enhanced solubility of methyl ester sulfonates below their Krafft points in mixed micellar solutions

HypothesisMethyl ester sulfonates (MES) show limited water solubility at lower temperatures (Krafft point). One way to increase their solubility below their Krafft points is to incorporate them in anionic surfactant micelles. The electrostatic interactions between the ionic surfactant molecules and charged micelles play an important role for the degree of MES solubility. ExperimentsThe solubility and electrolytic conductivity for binary and ternary surfactant mixtures of MES with anionic sodium alpha olefin sulfonate (AOS) and sodium lauryl ether sulfate with two ethylene oxide groups (SLES-2EO) at 5 °C during long-term storage were measured. Phase diagrams were established; a general phase separation theoretical model for their explanation was developed and checked experimentally. FindingsThe binary and ternary phase diagrams for studied surfactant mixtures include phase domains: mixed micelles; micelles + crystallites; crystallites, and molecular solution. The proposed general phase separation model for ionic surfactant mixtures is convenient for construction of such complex phase diagrams and provides information on the concentrations of all components of the complex solution and on the micellar electrostatic potential. The obtained maximal MES mole fraction of transparent micellar solutions could be of interest to increase the range of applicability of MES–surfactants.

Polymer surfactants as viscosity reducers for ultra-heavy oil: Synthesis and viscosity reduction mechanism

Polymeric surfactants have poor viscosity-reducing effect and little adaptability on ultra-heavy oils. We synthesized a novel polymeric surfactant, named PAMOs, by introducing 2-acrylanmido-2-methylpropanesulfonic acid (AMPS) and sodium alpha-olefin sulfonate (AOS) into the acrylamide (AM) backbone for viscosity reduction in ultra-heavy oil. The PAMOs with high surface and interfacial activity, strong emulsification, good molecular efficiency and viscoelasticity, which emulsified ultra-heavy oil effectively. The formed oil in water (O/W) emulsions with small droplet size and high stability. PAMOs also reduced the oil-water mobility ratio. At a concentration of 3 mg/mL, PAMOs reduced viscosity by more than 90% for different ultra-heavy oils (>15000 mPa·s), showing a broad range of suitability. Combining experimental and molecular dynamics simulation results, polymeric surfactants penetrate into the asphaltene molecular layers to form a “sandwich” structure, weakening the interaction forces between asphaltenes. The structure obtained via the ion-pair dipolar coupling between the polar groups, such as amide and sulphonic acid, and the asphaltene molecules. By strong hydrogen bonding between PAMOs and asphaltene, the supramolecular structure of asphaltene is destroyed and transformed into a low molecular structure. At the meantime, re-agglomeration is prevented by the steric hinerance of hydrophobic long chains, thus achieving viscosity reduction of ultra-heavy oil. It shown that polymeric surfactants have unique advantages in the field of viscosity reduction for ultra-heavy oil.

Research and Evaluation of Foam-Drainage Corrosion-Inhibition Hydrate Anti-Aggregation Integrated Agent

In natural gas exploitation, foam drainage, corrosion inhibition and hydrate inhibition of wellbore fluid are conventional operations. However, there is often a problem where multiple chemical agents cannot be effectively used together and can only be used separately, resulting in complex production processes. In this study, the final integrated formulation was determined: 0.1% sodium alpha-olefin sulfonate (AOST) + 0.3% dodecyl dimethyl betaine (BS-12) + 0.3% sodium lignosulfonate + 0.5% hydrazine hydrate. The minimum tension of the integrated agent could be reduced to 23.5 mN/m. The initial foaming height of the integrated agent was 21.5 cm at 65 °C, the liquid-carrying capacity was 143 mL, and the liquid-carrying rate reached 71.5%. The maximum corrosion depth also decreased from 11.52 µm without the addition of hydrazine hydrate, gradually decreasing to 5.24 µm as the concentration of hydrazine hydrate increased. After adding an integrated agent, the growth rate of hydrates was slow and aggregation did not easily occur, and the formation temperature was also more demanding. Therefore, the integrated agent has a inhibitory effect on the formation of hydrates and has a good anti-aggregation effect. From the observation of the microstructure, the emulsion is an oil-in-water type, and the integrated agent adsorbs at the oil–water interface, preventing the dispersed water droplets in the oil phase from coalescing in one place. The oil-in-water type emulsion is more likely to improve the performance of the natural gas hydrate anti-aggregation agent.

Multistep cascade continuous flow synthesis of AOS based on microreactor

Sodium alpha-olefin sulfonate (AOS) is highly esteemed for its exceptional properties and widespread utility in diverse industrial applications. This study introduces a pioneering investigation into the sulfonation of olefins, employing an innovative microchannel continuous sulfonation setup. The primary focus lies in process intensification through a multistage continuous flow synthesis approach, exploring the fundamental laws governing the influence of various process conditions on the generation process. Key process parameters, including sulfonation temperature, molar ratio of raw materials, sulfonating agent concentration, material flow rate, residence time, hydrolysis temperature, and hydrolysis time, are systematically examined to elevate the final product's quality. By leveraging 1-tetradecene as the primary feedstock and successfully implementing the microreaction minipilot platform, we achieve continuous synthesis of olefin sulfonate. Notably, post-hydrolysis, we attain an outstanding content of active substances exceeding 90%. This research showcasing the successful application of microchemical technology. By focusing on process enhancement and exploring influential factors, our research results highlight the transformative potential of microchemical technology for process intensification. The developed multistep cascade continuous flow synthesis of AOS demonstrates promising prospects for process intensification in the production of valuable sulfonated compounds.

Effect of welan gum and carbomer on foam and wetting properties of sodium alpha-olefin sulfonate for coal dust control

Using foam to reduce coal dust is one of the effective means to control coal dust pollution. In this work, the solution and foam properties of foaming agents consisting of sodium alpha-olefin sulfonate (AOS), welan gum (WL) and carbomer (CBM) were investigated, the wetting ability of the composite system on coal dust was compared, and the adsorption mechanism among AOS, WL and CBM was analyzed. The results show that with the increase of AOS concentration, the viscosity of AOS/WL solutions decreases gradually and then becomes stable, while the viscosity of AOS/CBM solutions displays an opposite trend. The addition of WL and CBM promotes foam production at low AOS concentrations but inhibits it at high concentrations. Both WL and CBM can improve the liquid volume and half-life time of foam drainage of AOS solutions. The WL molecules spontaneously form a zipper network structure, making the foam liquid film significantly thicker and slightly enlarging the bubble size. The addition of CBM can form a viscoelastic surface layer on the Plateau borders, making foam less permeable and delaying the bubble Ostwald ripening. The wetting time of coal dust is extended after adding WL and CBM. These results can provide theoretical guidance for the formula study of foaming agents for coal dust suppression.

Preparation of fluorine-free foam extinguishing agent based on silicone and hydrocarbon surfactants for markedly suppressing the pool fire

To solve the serious environmental hazard of fluorinated aqueous film-forming foam (AFFF), it is urgently to develop environmental-friendly fluorine-free foam extinguishing agents. In this study, a highly effective phosphate betaine silicone surfactant (PPSS) was prepared successfully, and then combined with various hydrocarbon surfactants to prepare the fluoride-free foam extinguishing agents. The effect of PPSS on the surface tension, foaming ability, foam stability and fire-extinguishing efficiency of fluoride-free foam extinguishing agents were investigated. The results show that the surface tension of PPSS is as slow as 20.68 mN/m, which imparts a lower surface tension to the mixed systems of PPSS and hydrocarbon surfactants. Especially, the mixture of PPSS and sodium alpha-olefin sulfonate (AOS) possess the lowest surface tension of 22.95 mN/m compared to the CTAB/PPSS and LAD-30/PPSS mixed systems. Moreover, AOS/PPSS mixture presents the excellent comprehensive performance with the critical micelle concentration (CMC) of 0.165 g/L, the surface tension at CMC value of 22.95 mN/m, the initial foam height of 111.9 mm, and the foam stability of 83.45%. Fire-extinguishing tests show that the foam obtained from AOS and PPSS exerts a wonderful fire-extinguishing efficiency compared to two commercial fire-fighting foams. In addition, the fire-extinguishing efficiency of foam extinguishing agents is closely related to the gas–liquid ratio. When the gas–liquid ratio is 17, the foam shows the maximum temperature reduction rate of 6.05 °C/s as well as the minimum extinguishing time of 38.9 s.

Experimental Study on Water-Rock Interaction Characteristics of Unconsolidated Sandstone during CO2 Multicomponent Thermal Fluid Injection

According to the reservoir characteristics and the current situation of CO2 utilization during thermal recovery in an unconsolidated sandstone heavy oil reservoir, the mechanism and law of porosity and permeability change in an unconsolidated sandstone heavy oil reservoir during CO2+steam and CO2+steam+ sodium alpha-olefin sulfonate (AOS) injection were studied by combining a static monomineral water-rock reaction and a dynamic polymineral sand pack displacement experiment. In the static water-rock reaction between CO2 and monomineral of reservoir rock, the dissolution degree of monomineral at 200°C is greater than that at 100°C and 300°C, and the order of mineral dissolution is illite, montmorillonite, kaolinite, and quartz. Besides, the dissolution rate of single rock minerals decreased significantly in the system of CO2 with AOS. In the polymineral sand pack displacement experiment, the porosity gradually decreases by CO2 multicomponent thermal fluid, and the permeability first decreases and then increases by CO2 multicomponent thermal fluid, but the permeability change is only about 0.5% by CO2+steam+ AOS, which is mainly attributed to the adsorption of AOS on the rock surface, and it is confirmed in the infrared spectrum of unconsolidated sand after displacement. This also shows that CO2+steam+AOS can stabilize the rock skeleton structure of the reservoir and prevent the deterioration of heterogeneity in the subsequent development of thermal recovery of heavy oil reservoirs; therefore, the CO2 multicomponent thermal fluid with chemical agents can improve the damage of a single CO2 thermal fluid to the reservoir.

Suppression of anthracite dust by a composite of oppositely-charged ionic surfactants with ultra-high surface activity: Theoretical calculation and experiments

In this study, we developed composite anionic–cationic (AC) surfactants with ultra-high surface activity using sodium alpha olefin sulfonate and octadecyltrimethylammonium chloride to improve the wettability and dust suppression efficiency of coal dust. Moreover, we investigated the synergistic suppression mechanisms of AC surfactant compounds at a molecular level. The thermodynamics of the self-assembly suggested that the surfactant molecules in the composite solution form a flexible alternating anion–cation bilayer. The analysis of the critical micelle concentration (CMC), surface tension (24.121 mN·m−1), contact angle (35.14°) and settling time (18 s) of the composite surfactant solution proved the superior performance of our composite surfactants compared to the monomeric alternatives, resulting in enhanced wettability owing to an ultra-high surface activity. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) experiments revealed an increased number of hydrophilic groups on the surface of the composite surfactant-treated anthracite, explaining the microscopic mechanism behind the high wettability induced by the composite surfactant. The specific surface area and pore size distribution of anthracite before and after dust suppressant treatment were calculated, and it was concluded that the dust suppressant was adsorbed on the surface and in the pores of the anthracite. In addition, the microscopic external morphology of the anthracite was shown by scanning electron microscopy (SEM), and it was found that the dust suppressant showed filling and aggregation behavior. Wind erosion and evaporation resistance experimental results show that dust suppressant-treated coal dust has enhanced water retention and wind resistance. Our findings indicate that ionic surfactants with oppositely charged compounds are promising high-efficiency dust suppressants, laying the foundation for safe coal mining and providing a theoretical background for a broad range of applications, such as haze control.

Development of a High Efficient Compound Surfactant for Foam Drainage in Gas Wells

In this study, the foaming properties of a compound surfactant formula containing cetyltrimethylammonium chloride (CTAC), cocamidopropyl betaine (CDAB), fatty alcohol polyoxyethylene ether-7 (AEO7) and sodium alpha-olefin sulfonate (AOST) were evaluated to meet the application requirements for foam generation and foam drainage in gas wells. The results exhibited that the foaming volume and the half-life of the compound surfactant solution (0.05 wt % CTAC + 0.7 wt % CDAB + 0.6 wt % AEO7 + 0.05 wt % AOST) can reach the values of 550 mL and 23 min, respectively, which suggested that the foaming ability and stability were improved in comparison with each solution containing a single surfactant. It showed that the surface tension can be lowered to 22.4 mN/m with the presence of the compound surfactants. Simultaneously, the microstructure of the foam was observed using a polarizing microscope, and it was found that there were almost no polyhedron structures in the foam within a certain range of formula concentrations. The results of the experiments also clarify that the formula has well properties of temperature resistance and salt resistance (measured using a high-speed agitator).

Study of D-limonene as novel green hydraulic fracturing surfactant in shale gas reservoir

This study focuses on rock-fluid interaction during hydraulic fracturing in shale gas reservoir. Hydraulic fracturing is a well stimulation technique used to create fracture network in reservoirs by connecting the main planar hydraulic fracture with the pre-existing natural fracture. Hydraulic fracturing fluid additives such as surfactants are added into the hydraulic fracturing fluid system to enhance oil and gas productivity by assisting fluid recovery after fracturing. The main objective of this study is to evaluate the effectiveness and formation damage parameters of the proposed novel green surfactant as hydraulic fracturing fluid additive where commercial-chemical based surfactant was studied for comparison purpose. The green surfactant used was D-limonene whereas Sodium Alpha Olefin Sulfonate (AOS) was used as commercial-chemical based surfactant. Thermogravimetric analysis (TGA) was done to ensure the D-limonene can withstand the high reservoir temperature in which the D-limonene had inflection point and onset temperature of 410 °C and 380 °C respectively. Soaking test was then conducted where the shale samples were soaked in hydraulic fracturing fluid for seven days. The outcome of the soaking test was then studied in Scanning Electron Microscopy (SEM) and wettability analysis. The SEM test showed that the average pore size of the soaked shale samples were similar to the original shale sample which indicated minimal to no formation damage caused by the hydraulic fracturing fluid. Besides that, the contact angle test resulted in the distilled water and D-limonene forming a contact angle of 90° and 0° respectively on the shale samples. The AOS formed contact angles between 65° and 75° for the tested concentrations. From the results, the shale sample was found to be oil wet and showed a high affinity towards the D-limonene followed by AOS and distilled water. Higher affinity of the surfactants promoted the desorption of the hydraulic fracturing fluid from the shale surface.

An Environmentally Friendly Antioxidant Foamed Gel for Inhibiting Spontaneous Combustion of Coal

ABSTRACT Coal spontaneous combustion can cause serious coal mine fire and gas explosion. In order to overcome the problem that the effect of existing materials to inhibit coal spontaneous combustion is reduced at high temperature and some environmental protection problems of materials, this study developed an effective, green and environmental protection antioxidant foamed gel (AFG). Modified sodium polyacrylate, konjac glucomannan, sodium dodecyl sulfate, sodium alpha-olefin sulfonate, modified silicone polyether microemulsion, montmorillonite, and tert-butyl hydroquinone were selected as raw materials. A single factor experiment was conducted to determine the appropriate adding proportions for each component. Then, the optimal proportion for the five components were fitted and verified by response surface analysis. The structures of the samples were characterized, and their properties were compared and tested. The fluidity, water loss, and thermogravimetry experiments demonstrated that the effect of AFG was excellent. In the experiment of in situ diffuse reflectance Fourier transform infrared spectroscopy, the AFG inhibition reaction was verified. Finally, combined with the structural characteristics of the AFG, the following inhibiting mechanisms were confirmed: AFG adhered to the coal surface and blocked the coal–oxygen contact; the antioxidant component slowed down chemisorption and the chemical reactions; AFG interrupted the free radical chain reaction.

The stability and decontamination of surface radioactive contamination of biomass-based antifreeze foam

Conventional water-based foam decontaminants used for the removal of radionuclides lose their efficacy in winter at temperatures below 0 °C. To address this problem, an antifreeze foam, with characteristics of good stability, high decontamination efficiency, less liquid waste generation, and excellent biodegradability, was developed using a biomass-based surfactant, a polysaccharide foam stabilizer, and an antifreeze agent. Furthermore, the surface tension, solution viscosity, foam stability, and decontamination of simulated radionuclides on different plates of a xanthan gum (XG)-stabilized antifreeze foam at temperatures ranging from −10 °C to 10 °C were investigated. Especially, the bulk-phase performance and stabilizing mechanism of the antifreeze foam were analyzed. Compared with the antifreeze foam without stabilizer, the half-life of the XG-stabilizing foam increases from 30.5 min to 2785 min, and the initial drainage time increases from 5 min to 383.5 min at −10 °C, which considerably extends the decontamination time and is conducive to improving the decontamination efficiency. Furthermore, the foam stability and bulk viscosity of the foam solution at a low shear rate exhibited a significant positive correlation. As a result, with decreasing the temperature, the viscosity of the XG-stabilized antifreeze foam solution increased leading to a better stability of foam at a lower temperature. The stabilizing mechanism of the XG stabilizer would possibly be the rigid chain structure of the XG molecule, which could lightly resist the contraction and bending of the molecular chain caused by Na+ originated from the surfactant sodium alpha-olefin sulfonate (AOS) and H+ originated from acidic chelator citric acid (CA) in the decontamination foam. Another probable stabilizing mechanism would be that the electrostatic repulsion generated by the negatively charged groups on the XG molecular chains could prevent the molecular aggregation and precipitation. Moreover, surface decontamination results revealed that the XG-stabilized antifreeze foam can remove >90% of the radionuclide contamination physically attached to surfaces of glass, stainless steel, white paint, green paint, and tile plate below 0 °C. Therefore, the antifreeze foam detergent exhibits good application potential for the decontamination of surface radioactive contamination in winter due to its excellent stability, high decontamination efficiency, and biodegradability.

High-temperature high-pressure microfluidic system for rapid screening of supercritical CO2 foaming agents

CO2 foam helps to increase the viscosity of CO2 flood fluid and thus improve the process efficiency of the anthropogenic greenhouse gas’s subsurface utilization and sequestration. Successful CO2 foam formation mandates the development of high-performance chemicals at close to reservoir conditions, which in turn requires extensive laboratory tests and evaluations. This work demonstrates the utilization of a microfluidic reservoir analogue for rapid evaluation and screening of commercial surfactants (i.e., Cocamidopropyl Hydroxysultaine, Lauramidopropyl Betaine, Tallow Amine Ethoxylate, N,N,N′ Trimethyl-N′-Tallow-1,3-diaminopropane, and Sodium Alpha Olefin Sulfonate) based on their performance to produce supercritical CO2 foam at high salinity, temperature, and pressure conditions. The microfluidic analogue was designed to represent the pore sizes of the geologic reservoir rock and to operate at 100 °C and 13.8 MPa. Values of the pressure drop across the microfluidic analogue during flow of the CO2 foam through its pore network was used to evaluate the strength of the generated foam and utilized only milliliters of liquid. The transparent microfluidic pore network allows in-situ quantitative visualization of CO2 foam to calculate its half-life under static conditions while observing if there is any damage to the pore network due to precipitation and blockage. The microfluidic mobility reduction results agree with those of foam loop rheometer measurements, however, the microfluidic approach provided more accurate foam stability data to differentiate the foaming agent as compared with conventional balk testing. The results obtained here supports the utility of microfluidic systems for rapid screening of chemicals for carbon sequestration or enhanced oil recovery operations.

Effect of Air-entraining and Water-repellent Admixtures and of Their Dosage on the Performance of Lime Mortars

ABSTRACT This work explores the short- and long-term effects of admixtures typically used to improve durability on air lime mortars. With that purpose, two air-entraining admixtures (AEA), based on sodium alpha olefin sulfonate (AOS) and sodium dodecyl sulfate (SDS), and a water-repellent admixture (WRA) based on alkylsilicone resin were studied. The AEAs proved not to be detrimental to mechanical strength both in the short- and long-term, when used in an appropriate dosage, and reduced water intake, while improving water vapour permeability, allowing a faster drying. Comparing the AEAs, SDS led to less entrained air and, thus, to higher mechanical strength and lower porosity and pore size than AOS. In turn, the WRA substantially increased mechanical strength in the short- and long-term, despite delaying carbonation, but also increased stiffness. Water intake was reduced, as well as the mortar’s drying kinetics, which can hamper its compatibility with old masonries. With increasing dosage, both types of admixtures increased the air content, but different implications in the short-term mechanical strength of the mortars were observed: WRA led to an increase, whereas the AEAs led to a decrease in this property.

Investigation of Countercurrent Imbibition in Oil-Wet Tight Cores Using NMR Technology

Summary Countercurrent spontaneous imbibition is one of the most significant mechanisms for the mass transfer between fractures and matrixes in tight reservoirs. Adding surfactants and pressurization are two common methods to enhance the imbibition. In this study, we used the low-field nuclear magnetic resonance (NMR) instrument to monitor the dynamic imbibition processes with surfactants added and fluid pressure applied. The T2 relaxation distribution and corresponding water saturation profiles during the imbibition process were obtained by analyzing NMR responses. We found that sodium alpha-olefin sulfonate (AOS) could improve the oil recoveries of laboratory-scale cores to 22.31 and 29.59% with different concentrations (0.1 and 0.5 wt%). The surfactant addition not only expands the imbibition area, but also reduces the residual oil saturation in the imbibition profile. However, the actual maximum imbibition distances are only approximately a centimeter long (0.9412 and 1.1372 cm), which is insignificant for field scale. Due to the minimal imbibition distance, high-quality hydraulic fracturing is required to generate a large number of fractures for imbibition to ensure considerable oil recovery at the field scale. In addition, surfactant is consumed during spontaneous imbibition of oil-wet rocks and increasing surfactant concentration facilitates the imbibition process. However, arbitrarily increasing the concentration does not achieve the expected oil recovery because of the high adsorption capacity resulting from the high concentration. We need to consider economic efficiency to optimize a reasonable surfactant concentration. It was found that traditional dimensionless scaling models are not applicable in the complicated surfactant-enhanced imbibition. Hence, we proposed a new scaling group for scaling laboratory date to the field in fractured oil-wet formations. Moreover, we compared the imbibition process under different pressure conditions (7.5 and 15 MPa) and found that the effect of fluid pressure on countercurrent imbibition is not obvious.

Synergistic Effects of Nano-Montmorillonite and Polyethylene Microfiber in Foamed Paste with High Volume Fly Ash Binder.

Foamed cement-based materials have attracted much attention as a new type of thermal insulation materials (TIMs) that may offer a sustainable solution to the built environments. This laboratory study explores the combined use of nano-montmorillonite and polyethylene microfiber in foamed paste with high volume fly ash (HVFA) binder. A total of 16 foamed HVFA paste mixtures were fabricated which consisted of 70% Class F fly ash, 30% Portland cement, 2% sodium alpha-olefin sulfonate, 0.38% Na₃PO₄, and 2% nano-montmorillonite. The dosage and type of polyethylene microfibers (90 μm in diameter) were explored in the present study, with six dosages (0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% by volume) and three lengths (3 mm, 6 mm, and 9 mm) tested. Based on the experimental results, the highest 28-day rupture strength (1.51 MPa) was achieved with the use of 3-mm long PE microfibers at 0.4 vol.%. Synergistic utilization of nMMT and microfibers exhibited a great influence on the dry density and water absorption of the foamed paste. The SEM micrographs illustrated the multiple mechanisms by which the microfibers serve to reduce shrinkage-induced cracking of the foamed paste. Energy-dispersive X-ray spectroscopy was employed to obtain the contents of Ca, Si, Al, S and mole ratios of Ca/Si, Ca/(Si + Al), S/Ca, and Al/Si in the hardened pastes, which reveal the difference in hydration products near or away from the nMMT-pretreated polyethylene microfibers. The results of microhardness test were also used to elucidate such nano-/micro-synergistic effects, which improved the bonding between microfibers and foamed paste matrix. A mechanism was proposed to explain the role of various admixtures and the balanced performance of such inorganic TIMs.

Experimental investigation of surfactant-stabilized foam stability in the presence of light oil

The foam plays an important role in EOR application, while crude oil properties significantly affect foam behavior. In this study we compare the performance of foam generated by two types of surfactant, which in the presence of two light oils. The foaming properties and foam stability, film thickness and emulsified oil effect were fully studied. The final results show that light oil has a positive impact on foam ability of sodium alpha-olefin sulfonate (AOS). However, the alkyl glycosides (APG) did not have the same effect. As the oil saturation increases from 0 to 80%, the light oil has a significant impact on foam stability of APG than AOS. Furthermore, the half-life change degree k is introduced to characterize the change of bulk foam half-life and foam drainage half-life. According to the calculation results, the positive effect of light oil on AOS was reconfirmed. The AOS is more effective in reducing the coalescence of foam and increasing the foam uniformity compared with APG. Moreover, the formation of emulsion has a positive effect on the foam stability. According to the micrograph of foam, the light oil in AOS is emulsified into quite small oil droplets, filling the plateau borders and lamellas. Furthermore, unlike APG, light oil (oil B and C) performed well in thickening the foam film of AOS.

Experimental investigation of the wetting ability of surfactants to coals dust based on physical chemistry characteristics of the different coal samples

To select suitable surfactant as water-spray additive to improve dust suppression efficiency, six types of coal sample (lignite, long flame coal, non-caking coal, gas coal, coking coal, and anthracite) were selected from some typical mining areas in China, the influence of the physical chemistry characteristics of coal samples on the wetting ability of surfactants to the coals dust was investigated. Their proximate composition, ultimate content, chemical structure, surface morphology, pore structure parameters, and contact angle were determined. Three kinds of anionic surfactants – Sodium Alcohol Ether Sulphate (AES), Sodium Alpha-Olefin Sulfonate (AOS), Fatty Acid Methyl Esters Ethoxylate Sulfonate (FMES) – and one kind of nonionic surfactant – Coco Diethanolamide (CDEA) – were selected to carry out sedimentation experiments on the coal samples dust, to explore the main factors influencing the wettability of the coal samples dust. Among these factors, pore size is the main factor determining the wettability of coal dust, the contact angle decreases linearly (R2 = 0.96) with pore size increase. The experimental results demonstrate that the following factors produce correspondingly increased wettability: higher moisture content, lower carbon content, higher oxygen content, more oxygen-containing functional groups, and increased pore size. In addition, the wettability of the six types of the coal samples dust shows a high-low-high trend with metamorphic degree increase, lignite has the strongest wettability, and the coking coal with the highest degree of metamorphism in the selected bituminous coal sample has the weakest wettability. Moreover, compared with nonionic surfactants, anionic surfactants have stronger wetting ability, but the same anionic surfactants have different wetting abilities to coal dust with different metamorphic degrees. AOS has stronger wetting ability to the dust of long flame coal, non-caking coal, and anthracite; AES has stronger wetting ability to the dust of lignite and coking coal; and FMES has stronger wetting ability to the dust of gas coal. The research results provide a theoretical basis for different coal mines to select suitable surfactants as water-spray additives to improve dust suppression efficiency.