Oil Separation Research Articles

A TGA-FTIR study on the pyrolysis of oil-based drilling cuttings and the influence of its solids on pyrolysis characteristics

During the drilling process in oil and gas fields, rock cuttings and other solid impurities are returned to the wellhead along with oil-based drilling fluids, forming oil-based drill cuttings. Organic pollutants in oil-based drill cuttings can be removed through pyrolysis. Although there has been some research on the pyrolysis of oil-based drilling cuttings, there is little analysis of the impact of rock-solid impurities in oil-based drill cuttings on the pyrolysis of organic components. Therefore, in this study, thermogravimetry coupled with infrared spectroscopy was used to analyze the pyrolysis characteristics of oil-based drill cuttings, exploring the major volatile components at different pyrolysis temperatures. Meanwhile, the oil and solids in oil-based drilling cuttings were separated by Soxhlet extraction, and the influence of solids on pyrolysis characteristics was studied. The results showed that the average pyrolysis activation energy and pre-exponential factor of the main pyrolysis stage of oil-based drill cuttings obtained by the FWO method were 50.6 KJ/mol and 3.951×104 s−1, respectively, while those of the separated residual oil were 84.7 KJ/mol and 2.905×109 s−1, respectively. This indicates that solids in oil-based drilling cuttings is increasing the mass loss rate during pyrolysis. The difference in pyrolysis kinetics between oil-based drilling cuttings and residual oil indicates that the solid in oil-based rock cuttings provides a surface for the reaction, which provides a reaction site for the decomposition of hydrocarbons to produce lighter volatile hydrocarbons. Additionally, the results of infrared spectroscopy indicated that the volatile products of the pyrolysis of oil-based drilling cuttings include CH4, CO, CO2, H2O, aldehydes, organic acids, etc. CH4 is the main product of the first weight loss stage, mainly released between 150°C and 200°C. With the increase in temperature, the concentrations of H2O, CO2, aldehydes, and organic acids gradually increased. At 600°C, the maximum concentration of CO2 release occurred, and the release of CO2 was the main reason for the third-stage weight loss in the pyrolysis of oil-based drilling cuttings

Sandalwood Oils of Different Origins Are Active In Vitro against Madurella mycetomatis, the Major Fungal Pathogen Responsible for Eumycetoma.

In the search for new bioactive agents against the infectious pathogen responsible for the neglected tropical disease (NTD) mycetoma, we tested a collection of 27 essential oils (EOs) in vitro against Madurella mycetomatis, the primary pathogen responsible for the fungal form of mycetoma, termed eumycetoma. Among this series, the EO of Santalum album (Santalaceae), i.e., East Indian sandalwood oil, stood out prominently with the most potent inhibition in vitro. We, therefore, directed our research toward 15 EOs of Santalum species of different geographical origins, along with two samples of EOs from other plant species often commercialized as "sandalwood oils". Most of these EOs displayed similar strong activity against M. mycetomatis in vitro. All tested oils were thoroughly analyzed by GC-QTOF MS and most of their constituents were identified. Separation of the sandalwood oil into the fractions of sesquiterpene hydrocarbons and alcohols showed that its activity is associated with the sesquiterpene alcohols. The major constituents, the sesquiterpene alcohols (Z)-α- and (Z)-β-santalol were isolated from the S. album oil by column chromatography on AgNO3-coated silica. They were tested as isolated compounds against the fungus, and (Z)-α-santalol was about two times more active than the β-isomer.

Eco-friendly bacterial cellulose/MXene aerogel with excellent photothermal and electrothermal conversion capabilities for efficient separation of crude oil/seawater mixture

Developing novel absorbent materials targeting high-efficiency, low-energy-consumption, and environmental-friendly oil spill cleanup is still a global issue. Porous absorbents endowed with self-heating function are an attractive option because of that they are able to in-situ heat crude oil and dramatically reduce oil viscosity for efficient remediation. Herein, we facilely prepared an eco-friendly multifunctional bacterial cellulose/MXene aerogel (P-SBC/MXene aerogel) for rapid oil recovery. Thanks to excellent full solar spectrum absorption (average absorbance = 96.6 %), efficient photo-thermal conversion, and superior electrical conductivity (electrical resistance = 36 Ω), P-SBC/MXene aerogel exhibited outstanding photothermal and electrothermal capabilities. Its surface temperature could quickly reach 93 °C under 1.0 kW/m2 solar irradiation and 124 °C under 3.0 V voltage respectively, enabling effective heat transfer toward spilled oil. The produced heat significantly decreased crude oil viscosity, allowing P-SBC/MXene aerogel to rapidly absorb oil. By combining solar heating and Joule heating, P-SBC/MXene aerogel connected to a pump-assisted absorption device was capable of achieving all-weather crude oil removal from seawater (crude oil flux = 630 kg m−2 h−1). More notably, P-SBC/MXene aerogel showed splendid outdoor crude oil separation performance. Based on remarkable crude oil/seawater separation ability, the versatile aerogel provides a promising way to deal with large-area oil spills.

Research Progress in Structure Synthesis, Properties, and Applications of Small-Molecule Silicone Surfactants.

Silicone surfactants have garnered significant research attention owing to their superior properties, such as wettability, ductility, and permeability. Small-molecular silicone surfactants with simple molecular structures outperform polymeric silicone surfactants in terms of surface activity, emulsification, wetting, foaming, and other areas. Moreover, silicone surfactants with small molecules exhibit a diverse and rich molecular structure. This review discusses various synthetic routes for the synthesis of different classes of surfactants, including single-chain, "umbrella" structure, double chain, bolaform, Gemini, and stimulus-responsive surfactants. The fundamental surface/interface properties of the synthesized surfactants are also highlighted. Additionally, these surfactants have demonstrated enormous potential in agricultural synergism, drug delivery, mineral flotation, enhanced oil recovery, separation, and extraction, and foam fire-fighting.

Enhanced Photocatalytic and Filtration Performance of TiO2-Ag Composite-Coated Membrane Used for the Separation of Oil Emulsions

Polyvinylidene fluoride (PVDF) membranes were coated with TiO2 and TiO2-Ag to enhance their efficiency for oil-in-water emulsion separation. The photocatalytic activities of the two modified membranes and their filtration performances were compared in detail. The significantly enhanced photocatalytic activity of the TiO2-Ag composite was proved using a methyl orange (MO) solution (c = 10−5 M) and a crude oil emulsion (c = 50 mg·L−1). The TiO2-Ag-coated membrane reduced the MO concentration by 87%, whereas the TiO2-modified membrane reached only a 46% decomposition. The photocatalytic reduction in the chemical oxygen demand of the emulsion was also ~50% higher using the TiO2-Ag-coated membrane compared to that of the TiO2-coated membrane. The photoluminescence measurements demonstrated a reduced electron/hole recombination, achieved by the Ag nanoparticle addition (TiO2-Ag), which also explained the enhanced photocatalytic activity. A significant improvement in the oil separation performance with the TiO2-Ag-coated membrane was also demonstrated: a substantial increase in the flux and flux recovery ratio (up to 92.4%) was achieved, together with a notable reduction in the flux decay ratio and the irreversible filtration resistance. Furthermore, the purification efficiency was also enhanced (achieving 98.5% and 99.9% COD and turbidity reductions, respectively). Contact angle, zeta potential, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements were carried out to explain the results. SEM and AFM images revealed that on the TiO2-Ag-coated membrane, a less aggregated, more continuous, homogeneous, and smoother nanolayer was formed due to the ~50% more negative zeta potential of the TiO2-Ag nanocomposite compared to that of the TiO2. In summary, via Ag addition, a sufficiently hydrophilic, beneficially negatively charged, and homogeneous TiO2-Ag-coated PVDF membrane surface was achieved, which resulted in the presented advantageous filtration properties beyond the photocatalytic activity enhancement.

Novel superhydrophobic sponge with flower-like architecture for oily emulsion separation and organic pollutants photodegradation

Design functionalized absorbent materials that fulfillment complex requirements in sophisticated water-treatment fields remains challenging. In this paper, a novel superhydrophobic/superoleophilic sponge with flower-like channel structures and a photodegradation functionality was fabricated via in-situ chelation of zinc oxide (ZnO) and nano-Ag particles. After low surface energy modification with POTS, the as-prepared sponge displayed remarkable superwettability, with a water contact angle (WCA) of 158.8° ± 1.3°. This endowed it with the ultrafast, selective absorption of diverse oils that are 33.9–135.2 times of their own weight. The prepared sponge’s emulsified oil separation efficiency can reach 99.87%, owing to its superhydrophobic/superoleophilic properties and the electrostatic attraction demulsification, guiding effect of ZnO layer crystal plane. Furthermore, the construction of Schottky barrier at the ZnO@Ag interface reduced the recombination rate of photoexcited electrons and electron-holes. Thereby, the prepared sponge’s photodegradation efficiency reached up to 97.07% after 4 h sunlight irradiation. Notably, the stress attenuation of the prepared sponge was only 14.6% after 100 absorption cycles, indicating its excellent mechanical stability. Moreover, the prepared sponge showed excellent environmental tolerance under severe conditions with its WCA stably exceeding 150.0°. Thus, this durable superwetting sponge can be effectively used for oil/water emulsion separation and organic pollutant degradation.

Design of fluorine-free superhydrophobic silk fabrics with mechanical durability and self-cleaning properties for oil-water separation

The separation of oil and water can be effectively addressed through the application of superhydrophobic coatings. This method, known for enhancing the self-cleaning, anti-corrosive, and friction-reducing properties of materials, typically employs fluorine reagents to ensure the durability of the coating nanostructure. However, the use of fluorine reagents raises concerns related to health and the environment. We present a straightforward and efficient approach to fabricate a robust, fluorine-free superhydrophobic composite coating. The coating solution, comprised of hydrophobic silica nanoparticles and polydimethylsiloxane (PDMS), is formed through sonication. The resulting superhydrophobic coating is effortlessly applied to silk fabric through immersion and subsequent drying/curing. micrograph confirms the creation of porous micro/nanostructures on the silk fabric's surface. Exceptional superhydrophobicity is demonstrated with a water contact angle (WCA) of 161 °±1.5 ° and a small sliding angle (SA) of 5 °±0.5 °. The coating's firmness, durability, and UV resistance are assessed through 20 cycles of sandpaper friction (load 200 g) and repeated tape peeling tests. Furthermore, the modified silk fabrics exhibit excellent capabilities in oil-water separation. This fluorine-free superhydrophobic coating, characterized by its robustness, environmental friendliness, and ease of manufacture, holds promising applications in the textile industry.

Asymmetrically superwetting Janus membrane constructed by laser-induced graphene (LIG) for on-demand oil–water separation and electrothermal anti-/de-icing

Superwetting functional surfaces based on laser-induced graphene (LIG) have a wide range of applications in many fields. However, single wettability LIG films are difficult to respond to complex and changing environmental conditions. Despite the large number of experiments were carried out to demonstrate the formation of LIG, there is a lack of studies on the process and formation mechanisms of LIG. In this study, the conversion of PEI to graphene was systematically investigated by both experimental and molecular dynamics simulations. A new method for obtaining Janus membranes with both superhydrophobicity and superhydrophilicity by ethanol and plasma treatment of LIG is proposed. The asymmetrically superwetting Janus membrane are shown to realize the on-demand controllable separation of light oil–water and heavy oil–water. In addition, the superhydrophobic LIG is used as a coating material with excellent electrothermal properties, which provide the performance of anti-icing and electrothermal de-icing. The asymmetrically superwetting Janus membranes prepared by the proposed simple and environmentally friendly method are shown to have a variety of prospective applications.

Thin-film composite membranes with contorted monomer for high-flux isothermal refining

The development of isothermal refining processes is important because of the high energy demands of crude oil separation. Membrane technology provides separation efficiency and low carbon footprint. This efficiency can be fine-tuned and enhanced by modifying the chemistry of the membrane selective layer. Herein, we describe the fabrication of membranes by interfacial polymerization using a combination of contorted fluorinated monomer bearing six fluorine atoms and trimesoyl chloride in the organic phase. A fluorinated m-phenylene diamine was added to the aqueous phase. This approach produces membranes with high surface roughness, increases their hydrophobicity and promotes the transport of hydrocarbons with high selectivity and toluene permeance (15.6 L m−2 h−1 bar−1). Successful evaluations were conducted for the fractionation of crude oil, confirming the potential for application in the petrochemical industry.

Effect of jet cavitation on oil recovery from oily sludge

Jet cavitation method was proposed to treat oily sludge to improve oil recovery. The key components affecting the oil desorption efficiency were analyzed by TLC-FID (Thin-layer chromatography and flame ionization detection) method and FT-IR(Fourier-transform infrared spectroscopy), and the mechanism of oil recovery from oily sludge enhanced by jet cavitation was revealed. The results show that when the inlet pressure is 12 MPa, the temperature is 35 °C, the solid concentration is 25 %, and the hydraulic retention time for oily sludge is 4 s, the maximum oil recovery rate is 82.3 %, which is much higher than that after ultrasonic cavitation. After jet cavitation, the sedimentation performance of the oily sludge was improved, and the average particle size was reduced. Asphaltenes and resins are the main components affecting oil desorption. Heteroatoms such as N, S, and O form stable hydrogen bonds with the surface of solid particles, which impede the oil desorption process. The mechanical effect such as micro-jet shock waves and shear forces generated by jet cavitation could disrupt the hydrogen bonds, promoting the reformation of hydrogen bonds between water and solid particles, leading to the separation of oil from the surface of solid particles.

Design and Machine Learning Prediction of In Situ Grown PDA-Stabilized MOF (UiO-66-NH2) Membrane for Low-Pressure Separation of Emulsified Oily Wastewater.

Significant progress has been made in designing advanced membranes; however, persistent challenges remain due to their reduced permeation rates and a propensity for substantial fouling. These factors continue to pose significant barriers to the effective utilization of membranes in the separation of oil-in-water emulsions. Metal-organic frameworks (MOFs) are considered promising materials for such applications; however, they encounter three key challenges when applied to the separation of oil from water: (a) lack of water stability; (b) difficulty in producing defect-free membranes; and (c) unresolved issue of stabilizing the MOF separating layer on the ceramic membrane (CM) support. In this study, a defect-free hydrolytically stable zirconium-based MOF separating layer was formed through a two-step method: first, by in situ growth of UiO-66-NH2 MOF into the voids of polydopamine (PDA)-functionalized CM during the solvothermal process, and then by facilitating the self-assembly of UiO-66-NH2 with PDA using a pressurized dead-end assembly. A stable MOF separating layer was attained by enriching the ceramic support with amines and hydroxyl groups using PDA, which assisted in the assembly and stabilization of UiO-66-NH2. The PDA-s-UiO-66-NH2-CM membrane displayed air superhydrophilicity and underwater superoleophobicity, demonstrating its oil resistance and high antifouling behavior. The PDA-s-UiO-66-NH2-CM membrane has shown exceptionally high permeability and separation capacity for challenging oil-in-water emulsions. This is attributed to numerous nanochannels from the membrane and its high resistance to oil adhesion. The membranes showed excellent stability over 15 continuous test cycles, which indicates that the developed MOFs separating layers have a low tendency to be clogged by oil droplets during separation. Machine learning-based Gaussian process regression (GPR) models as nonparametric kernel-based probabilistic models were employed to predict the performance efficiency of the PDA-s-UiO-66-NH2-CM membrane in oil-in-water separation. The outcomes were compared with the support vector machine (SVM) and decision tree (DT) algorithm. This efficiency includes various metrics related to its separation accuracy, and the models were developed through feature engineering to identify and utilize the most significant factors affecting the membrane's performance. The results proved the reliability of GPR optimization with the highest prediction accuracy in the validation phase. The average percentage increase of the GPR model compared to the SVM and DT model was 6.11 and 42.94%, respectively.

Rheological Analysis on Hardening of Magnetorheological Grease with Kerosene

Magnetorheological grease (MRG) with dilution oils may suffer from reduced storage stability caused by oil separation. This phenomenon potentially causes a performance reduction of the material due to possible accelerated degradation of the grease medium. The long-term rheological behavior of MRG with kerosene (MRGK) was investigated in this study. MRGK was prepared with 10 wt% kerosene as the dilution oil, together with a sample of MRG without any kerosene as the control. A modular compact rheometer (MCR) was used to obtain rheological data from the MRG samples in an oscillatory strain sweep mode under the influence of magnetic fields, which ranged from 0A to 3A. After one year, the measurement was repeated to observe any changes to the rheology of MRG samples. Results showed a significant hardening of the sample diluted with kerosene, which mainly showed a drastic increase in off-state storage modulus at low strain. This was shown by the off-state storage modulus of MRGK, which after one year showed an increase of 15% in the initial storage modulus, and an increase of 2438% in the storage modulus at 10% strain. The MRG sample showed an increase of 50% and 47%, respectively. The on-state storage modulus did not appear to experience such a drastic change after one year. The study concluded that while dilution oil may be a promising candidate to reduce the initial viscosity of MRG, the resulting performance difference may compromise the long-term performance, and may even cause accelerated degradation when in use.

The effect of thickener structure degradation on tribological properties: Study on the decay mechanism of polyurea grease under mechanical-thermal aging conditions

The aging of lubricants is a primary factor contributing to rolling bearing failures. The rolling stability test simulated the aging behavior of grease under shear and high-temperature circumstances. An investigation was conducted on how mechanical-thermal aging impacts the chemical and physical structures of polyurea grease, as well as how changes in thickener microstructure affect rheological and tribological properties. The results show that under shear and high temperature, structural changes in urea lead to a transformation of the thickener morphologies from the growth of entangled ribbon fiber to a large-diameter rod structure, with a significant decrease in the degree of entanglement. When a certain proportion of fibrous and rod structures coexist, the grease has good oil separation capacity, the structural stabilities of grease become weak, and the deformation resistance decreases. During this phase, the polyurea grease has the best tribological performance.

Effects of Nanoparticle Wettability on the Meniscus Stability of Oil-Water Systems: A Coarse-Grained Modeling Approach.

A coarse-grained modeling approach is employed to probe the effect of nanoparticles and their wettability on the stability of the interface between two immiscible fluids. In this study, pure oil (dodecane) and water are placed side by side in a nanochannel, forming a meniscus. Homogeneous hydrophilic nanoparticles, Janus particles, and homogeneous hydrophobic nanoparticles are placed at the oil-water interface, and their dynamics are studied as they rearrange at the oil-water interface. The results show that when the water is set in motion, two instabilities occur: the formation of fingers and the detachment of water from the channel wall. It is observed that the formation of fingers is affected by the wettability of the nanoparticles. The second instability may lead to the formation of a drop that propagates through the channel. However, it is found that the wetting properties of the nanoparticles do not affect the critical flow rate for the detachment of the water from the wall. Therefore, detachment occurs at the same three-phase contact angle regardless of the nanoparticle wetting properties. These findings can be important for industrial applications such as enhanced oil recovery, separation technologies, and microfluidic and nanofluidic technologies.

Highly effective and reusable Ni–Al oxide/Zn0.4Co0.6Fe2O4 superparamagnetic aerogel for oil-water separation

Oily wastewater from the oil industry and oil spill accidents has become a serious environmental problem and has attracted worldwide attention. The present study reports on the successful preparation of a novel magnetic Ni–Al oxide/Zn0.4Co0.6F2O4 mesoporous aerogel (MNA) as a highly selective adsorbent for oil removal from water. Oleic acid (OA) and Triton X-100 (TX) were used as hydrophobic agents for MNA surface modification. It was found that the attached amount of OA on the mesoporous MNA aerogel is 3.5 times larger than that of TX, giving an advantage to MNA-OA in oil separation. The MNA-OA displayed superhydrophobicity (contact angle ∼150°) and superparamagnetism properties that allowed the adsorbent to be used selectively for oil removal. The MNA-OA was found to have a high oil removal efficiency of ∼97% with an adsorption capacity of ∼2 g/g. Furthermore, the produced magnetic adsorbent has high stability due to the strong chemical binding of OA, which is demonstrated by its good reusability performance. Throughout five separate runs, the MNA-OA was shown to be a very efficient and reusable adsorbent for oily wastewater.

Fluorine-Functionalized Covalent Organic Framework Superhydrophobic Modified Melamine Sponge for Efficient oil-water Separation.

Hydrophobic sponges have attracted significant interest in oil spills and water-oil separation as potential absorption materials due to their desirable absorptivity, selectivity, and elasticity. In this paper, a hydrophilic melamine sponge (MS) is transferred into a superhydrophobic sponge via polydimethylsiloxane (PDMS) modification followed by in situ growth of fluorine-functionalized covalent organic framework (denoted as TFA-COF) nanoparticles. Therefore, the PDMS@TFA-COF@MS sponge was successfully prepared for efficient oil-water separation. The resultant PDMS@TFA-COF@MS exhibits superhydrophobic properties with a water contact angle of 156.7°. The superhydrophobic sponge has selectivity adsorption for different organic solvents and oils from water as well as oil-water separation efficiency (96% after 30 cycles) and oil absorption capacity (12 646% after 30 cycles). Meanwhile, the PDMS@TFA-COF@MS sponge exhibits strong thermal stability and flame retardancy in addition to having exceptional resistance to chemical corrosion in acidic, alkaline, and salt solutions. Moreover, the surfactant-stabilized oil-in-water emulsion could be efficiently separated by the sponge. Therefore, the prepared superhydrophobic PDMS@TFA-COF@MS sponge demonstrates possible uses for long-life oil-water separation applications.

Sustainable superwetting membrane for effective separation of oil–water emulsion and dye removal

Water pollution from organic oily solvents and dyes is a major global problem. While some wettable materials exist for oily pollutants, few can effectively separate different oil–water emulsions and dyes. To address this problem, we developed a smart citric acid-crosslinked bamboo powder-coated membrane (CBM) with approprite surface roughness and switchable wettability. The CBM membrane is superhydrophobic in oil and superoleophobic in water, making it highly effective in separating oil–water emulsions and dyes. The membrane can efficiently separate various oil–water emulsions, including crude oil-in-water emulsions, with a separation efficiency of 99.76 % and a high flux of 1756 L/m2/h. It also adsorbs anionic (e.g. Congo red) and cationic (e.g. methylene blue) dyes in wastewater, with an adsorption rate of 99.45 % after multiple cycles. The membrane can simultaneously separate oil-in-water emulsions and remove dyes from water, facilitating high-value utilization of biomass waste and offering great promise for addressing global water pollution from oily organic solvents and dyes.

Separation of oil–water emulsions by electrocoagulation and electro-persulfate with sonication pretreatment: Determination of economical electrode configuration, optimization, and comparison

This study aimed to separate oil–water emulsions by electrocoagulation (EC), which is considered an effective and promising method for sustainable water management, and the electro-persulfate method (EPS) as an advanced EC process. Firstly, oil–water emulsions were treated with EC using three different electrode configurations and the most economical electrode pair (perforated and plate electrodes) was determined. Secondly, the Box-Behnken design (BBD) was applied to explore the influence of operational variables (pH, current density, and electrolysis time for EC; pH, current density, PS/COD, and electrolysis time for EPS) on the removal of COD (5800 mg/L) as a response with the identified electrodes. As a result, at neutral pH, the optimal operating conditions determined for maximum COD removal were 27 mA/cm2 and 37 min for EC and 27 mA/cm2, 25 min, and PS/COD = 0.5 for EPS. At the predicted optimal conditions, the predicted and tested COD removal was respectively 100 % and 97.15 % for EC, 88.18 % and 87.94 % for EPS. Moreover, the total cost was 2.39 $/m3 and 1.27 $/m3 for EC and EPS, respectively. Consequently, it was determined that perforated electrodes were more economical, and EC achieved higher wastewater treatment performance than EPS, however, from an economic point of view, the EPS process enabled the more efficient treatment of oil–water emulsions.

Parametric studies on fractionation column design for the separation of plastic waste pyrolysis oil into valuable fuels

The increased global consumption of plastics prompts concerns about disposal methods and management. The castoff plastics (of any kind) majorly end up in landfills or are incinerated or disposed of into the oceans. However, these methods are not sustainable in the long run and harm the ecosystem. A better approach to tackle these wastes is the need of the hour, as the climate change crisis negatively impacts the environment. In this work, a process is ideated and implemented in Aspen Plus® V12.0, which involves the simulation of a fractionation column with a feed that is obtained by the pyrolysis of the waste plastic to yield an array of distillate cuts consisting of different hydrocarbon mixtures. Analysis of the fractionation column performance with sieve and bubble-cap tray configurations and the effect of tray efficiency, temperature, pressure, and other factors on the composition of the hydrocarbon mixture in different product streams were studied and outlined with the equilibrium tray and rate-based calculation mode. A techno-economic analysis of the process was also performed, and the relevant comparative analyses were illustrated and outlined.

Stability of n‐hexadecane phase change material emulsions using sugar‐based surfactants and the HLD platform

AbstractStoring thermal energy and using renewable energy are some of the most important challenges humanity faces today. Using phase change materials (PCM) is a suitable solution to prevent heat loss. PCM emulsions (PCMEs) have several advantages and are specifically applied in heat exchangers. Here, the formulation of these emulsions, the type of surfactants, and their composition based on freeze–thaw cycle stability are investigated. The Hydrophilic–Lipophilic‐Deviation (HLD) platform is used for this purpose. Considering the importance of stability during temperature changes in PCMEs, three types of surfactants that have different behaviors with respect to temperature are used: ethoxylates, ionics, and sugar‐based surfactants. By performing freeze–thaw cycles on emulsions made by individual surfactants, after 10 freeze–thaw cycles it was observed that the oil separation in each of the samples containing polysorbate80, AOT, lauryl‐myristyl‐alcohol‐polyethylene‐glycol‐ether, SDS, sorbitan‐monooleate, and decylglucoside occurred at the 2nd, 4th, 6th, 7th, 8th, and 10th‐cycle, respectively. Therefore, the sorbitan‐monooleate and decylglucoside had better freeze–thaw cycle stability compared to the others because of their non‐sensitivity to temperature. We also applied the emulsion cycle stability with two combinations of surfactants: (1) polysorbate80 and sorbitan‐monooleate, (2) decylglucoside and sorbitan‐monooleate. The former, despite the effect of temperature, showed no oil phase separation in the nine freeze–thaw cycles, but in the latter, the oil phase separation occurred in the 5th‐cycle. This study shows that synergism of surfactants is the most important factor in the stability of emulsions. To better explore these emulsion systems, the storage stability, freeze–thaw stability, droplet morphology, and viscosity tests were performed on different samples at various HLD values.