Formation of fatty acid methyl ester based microemulsion and removal mechanism of PAHs from contaminated soils

Performance of ethanol transformable microemulsions and remediation of salinized oil - contaminated soils

The effective and efficient separation of oil pollutants solubilized in microemulsions (MEs) represents a significant challenge in the remediation of oil-contaminated soils (OS). In this study, phase-transformable W/O microemulsions (W/O-MEs) were configured for efficient elution of salinized OS. Meanwhile, the phase transformation mechanism was demonstrated by investigating of the effect of ethanol concentration on microemulsions phase behavior. Firstly, W/O-MEs with an oil removal efficiency (Re) of 90.2 wt% were formulated through an analysis of the phase distribution and elution effect. Furthermore, the impact of ethanol concentration on microemulsion phase behavior was investigated in depth using dynamic light scattering (DLS), interfacial tension (IFT), and UV-visible spectroscopy. The findings substantiated that ethanol can facilitate the transformation of W/O-MEs (Winsor II) to O/W-MEs (Winsor I), thereby enhancing oil Re and separation capability. Moreover, a microemulsion elution route for salinized OS was devised on the basis of the principles of continuity and recycling in industrial cleaning processes. The results demonstrated that the ethanol and water facilitated the desorption of residues, including residual oils, surfactants, salts and alkalis, achieving an oil Re of 97.2 wt%. In particular, the recovered ethanol and water can be recycled for microemulsion preparation. Finally, the efficiency and feasibility of the microemulsion elution process is evaluated using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), fluorescence imaging, and contact angle (CA) analysis. This study provides theoretical guidance for the application of microemulsion elution in the remediation of industrial OS.

Multi spectroscopic investigation of maisine-based microemulsions as convenient carriers for co-delivery of anticancer and anti-inflammatory drugs

Lipid-based drug delivery systems are very promising in addressing critical medical needs associated with cancer because they are able to enhance the efficacy of the therapeutic agents loaded in. Yet, their transferability from bench to bedside is still a challenge as it hits many barriers. Among them, the absence of a clear design made on the deeper understanding of the intermolecular forces underlying the formation of the drug-carrier system and the controlled release of the drug is relevant. In this contribution, we rationally designed and prepared lipid-based formulations of an anticancer drug, fluorouracil (FU - hydrophilic) and an anti-inflammatory drug, ibuprofen (IBU - hydrophobic) to thoroughly characterize the specific intermolecular interactions between drugs and components of the carrier matrix. Microemulsions (ME) were selected as the main carriers for this study, but a comparison with liposomes was performed to observe if different organization of the lipophilic and hydrophilic compartments influences the loading capacity and controlled release of these two drugs. Using Maisine CC, a biocompatible oil, and Tween 20 as the surfactant, normal oil-in-water ME loaded with FU and IBU (1:1, 1:3, 1:6, wt:wt) were prepared by the water titration method. MEs were characterized by DLS, Zeta potential, and DOSY spectroscopies to assess their droplet size, surface charge, structure and type of emulsion. Intermolecular interactions between drugs and components of the ME's matrix were investigated by FT-IR, RAMAN and 1H-NMR spectroscopies. The experimental results of DOSY revealed that all components of MEs are gathered in normal oil-in-water ME. Due to their different affinities for the main components of the ME, FU, and IBU were mainly distributed in the aqueous and oily phases, respectively, as supported by the droplet size measured by DLS. It was observed that co-loading the two drugs impacted the release behavior, assessed by the dialysis bag method, as compared with the mono-drug formulations. Based on the findings of this work, a release mechanism for FU and IBU was proposed, as well. Overall, the ME proved to be more suitable nanocarriers since the drugs, which were loaded in higher amounts as compared to liposomes, followed a controlled and sustained release of at least 96 h.

Low-carbon treatment and remediation of oil sludge in mid-to-high latitude regions: A coupled approach of freeze-thaw and supercritical CO2 extraction

The oil sludge produced while extracting large oil and gas fields in the middle and high latitude regions has caused serious pollution to the surrounding soil. The key to solving this problem in the future is to unify the remediation of soil and the treatment of oil sludge. This study uses supercritical carbon dioxide(scCO2) technology to construct a low-carbon method, providing a new approach to achieve this goal. The study determines the optimal extraction conditions for black calcareous soil with 15% oil content to be 55 °C, 25 MPa, and 90 min through single factor and response surface experiments. Experiments on the scCO2 extraction coupled with freeze-thaw cycles show that oil sludge with a water content of 10% can improve the extraction efficiency of scCO2 by about 2.69% after less than five freeze-thaw cycles. The study also compares the extraction efficiency of the four soils, with a difference of 6.03% observed under the same conditions. Additionally, we analyze the impact of the extraction process on changes in the properties of the oil and soil in the oil sludge. Comprehensive tests, including scanning electron microscope (SEM), nutrient detection, X-ray powder diffractometer (XRD), fourier transform infrared spectroscopy (FTIR), and Gas Chromatography (GC), have been conducted. Results show that standalone scCO2 extraction can remove up to 98.2% of petroleum hydrocarbons from the oil sludge, while simultaneously causing small changes to the soil microstructure and the crystal structure of the oil sludge. Furthermore, this process does not lead to a significant depletion of key nutrients or the generation of new pollutants.

Retrieval and Reuse of Surfactants From Microemulsions Enabled by a pH-Triggered Precipitation-Dissolution Strategy

How to retrieve and reuse surfactants efficiently from surfactant-based microemulsions (MEs) has long been a problem, which is full of challenges and needs to be solved urgently. To this end, a pH-triggered precipitation-dissolution (PTPD) strategy is developed. The surfactant sodium 3-(laurylamino)propane-1-sulfonate (LMPS) transforms into an insoluble precipitate (the inner salt of LMPS, LMP) after reaction with HCl, by which the monophasic LMPS-based MEs demulsified entirely, giving a separable mixture of oil, water and LMP. LMP can be retrieved efficiently (~95.3 %) regardless of the ME type, and can then be conveniently restored to LMPS via reactions with NaOH. Conceptually, the retrieval of LMPS (~96.6 %), toxic benzo[a]pyrene (BaP, ~99.5 %) and a mixture of co-surfactant n-butanol and the oil phase n-heptane (~97.1 %) from the sufficiently emulsified soil eluents is achievable by respectively using the PTPD strategy and distillation, wherein the soil eluents were generated from the remediation of BaP-contaminated soil using an oil-in-water LMPS-based ME as washing agent. It reveals a promising future for the PTPD strategy in the post-processing of soil eluents containing toxic hydrophobic organic contaminants and excessive surfactants.

Acai Oil-Based Organogel Containing Hyaluronic Acid for Topical Cosmetic: In Vitro and Ex Vivo Assessment

Organogels are semi-solid pharmaceutical forms whose dispersing phase is an organic liquid, for example, an oil, such as acai oil, immobilized by a three-dimensional network formed by the gelling agent. Organogels are being highlighted as innovative release systems for cosmetic active ingredients such as hyaluronic acid for topical applications. Acai oil was evaluated for its physicochemical parameters, fatty acid composition, lipid quality index, spectroscopic pattern (Attenuated total reflectance Fourier Transform Infrared Spectroscopy), thermal behavior, total phenolic, total flavonoids, and total carotenoids and β-carotene content. The effectiveness of the organogel incorporated with hyaluronic acid (OG + HA) was evaluated through ex vivo permeation and skin retention tests, in vitro tests by Attenuated total reflectance Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry. The physicochemical analyses highlighted that the acai oil exhibited quality standards in agreement with the regulatory bodies. Acai oil also showed high antioxidant capacity, which was correlated with the identified bioactive compounds. The cytotoxicity tests demonstrated that the formulation OG + HA does not release toxic substances into the biological environment that could impede cell growth, adhesion, and efficacy. In vitro and ex vivo analyses demonstrated that after 6 h of application, OG + HA presented a high level of hydration, thermal protection and release of HA. Thus, it can be concluded that the OG + HA formulation has the potential for physical-chemical applications, antioxidant quality, and potentially promising efficacy for application in the cosmetic areas.

Enhanced removal of antibiotics and heavy metals in aquatic systems using spent mushroom substrate-derived biochar integrated with Herbaspirillum huttiense

A novel integrated removal strategy was developed to enhance the concurrent elimination of copper (Cu), zinc (Zn), oxytetracycline (OTC), and enrofloxacin (ENR) from the aqueous environments. The underlying adsorption mechanisms of spent mushroom substrate (SMSB) and the Herbaspirillum huttiense strain (HHS1), and their efficacy in removing Cu, Zn, OTC, and ENR was also examined. Results showed that the SMSB-HHS1 composite stabilized 29.86% of Cu and 49.75% of Zn and achieved removal rates of 97.95% for OTC and 59.35% for ENR through a combination of chemisorption and biodegradation. Zinc did not affect Cu adsorption, and ENR did not impact the adsorption of OTC on SMSB. However, the co-presence of OTC and ENR modified the adsorption behaviors of both Cu and Zn. Copper and Zn enhanced the adsorption of OTC and ENR by serving as bridging agents, facilitating the interaction between the contaminants and SMSB. Conversely, OTC and ENR inhibited the adsorption process of Cu by obstructing its interaction with the SMSB and occupying the oxygen-containing functional groups. The ‒OH (3415 cm-1) and C-O-C (1059 cm-1) functional groups were identified as the principal active sites to form hydrogen bonds and interact with Cu and Zn, leading to the formation of CuP4O11 and Zn4CO3(OH)6H2O. HHS1 also enhanced antibiotic removal through biodegradation, as evidenced by the decrease of ‒C‒O and increase of ‒C = O groups. This study underscores the innovative potential of the SMSB-HHS1 composite, offering a sustainable approach to addressing multifaceted pollution challenges in the aquatic environments.

Advancements in Characterization Techniques for Microemulsions: From Molecular Insights to Macroscopic Phenomena

Microemulsions are thermodynamically stable, optically isotropic, transparent, or semi-transparent mixed solutions composed of two immiscible solvents stabilized by amphiphilic solutes. This comprehensive review explores state-of-the-art techniques for characterizing microemulsions, which are versatile solutions essential across various industries, such as pharmaceuticals, food, and petroleum. This article delves into spectroscopic methods, nuclear magnetic resonance, small-angle scattering, dynamic light scattering, conductometry, zeta potential analysis, cryo-electron microscopy, refractive index measurement, and differential scanning calorimetry, examining each technique's strengths, limitations, and potential applications. Emphasizing the necessity of a multi-technique approach for a thorough understanding, it underscores the importance of integrating diverse analytical methods to unravel microemulsion structures from molecular to macroscopic scales. This synthesis provides a roadmap for researchers and practitioners, fostering advancements in microemulsion science and its wide-ranging industrial applications.

Microstructure-dependent CO2-responsive microemulsions for deep-cleaning of oil-contaminated soils

CO2-responsive microemulsion (ME) is considered a promising candidate for deep-cleaning and oil recovery from oil-contaminated soils. Understanding the responsive nature of different microstructures (i.e., oil-in-water (O/W), bicontinuous (B.C.) and water-in-oil (W/O)) is essential for unlocking the potential and mechanisms of CO2-responsive emulsions in complex multiphase systems and providing comprehensive guidance for remediation of oil-contaminated soils. Herein, the responsiveness of microstructures of ME to CO2 trigger was investigated using experimental designs and coarse-grained molecular dynamic simulations. MEs were formed for the first time by a weakly associated pseudo-Gemini surfactant of indigenous organic acids (naphthenic acids, NAs are a class of natural surface-active molecules in crude oil) and tetraethylenepentamine (TEPA) through fine tuning of co-solvent of dodecyl benzene sulfonic acid (DBSA) and butanol. The O/W ME exhibited an optimal CO2-responsive character due to easier proton migration in the continuous aqueous phase and more pronounced dependence of configuration on deprotonated NA ions. Conversely, the ME with W/O microstructure exhibited a weak to none responsive characteristic, most likely attributed to its high viscosity and strong oil-NA interactions. The O/W ME also showed superior cleaning efficiency and oil recovery from oil-contaminated soils. The results from this study provide insights for the design of CO2-responsive MEs with desired performance and guidance for choosing the favorable operating conditions in various industrial applications, such as oily solid waste treatment, enhanced oil recovery (EOR), and pipeline transportation. The insights from this work allow more efficient and tailored design of switchable MEs for manufacturing advanced responsive materials in various industrial sectors and formulation of household products.

Sustainable Utilization of Surfactant-Free Microemulsion Regulated by CO2 for Treating Oily Wastes: A Interpretation of the Response Mechanism

Surfactant-free microemulsions (SFMEs) have been explored extensively to avoid the residual surfactant problem caused by traditional surfactant microemulsions. Many researchers focused on the SFMEs with tertiary amine, which exhibited the typical CO2 response behavior. In this study, the phase diagram of the SFMEs consisting of tripropylamine (TPA), ethanol, and water was readily prepared via the measurements of electrical conductivity. The CO2 response behavior of SFME was confirmed by determination of conductivity and measurement of the average diameter of SFME, which was mainly dependent on the protonation of TPA induced by the additional CO2. The transition of protonated TPA to a more hydrophilic nature from lipophilicity to hydrophilicity should be responsible for the variation of SFME average diameter. In addition, the SFMEs exhibited remarkable solubilizing capacity of crude oil, and three types of SFMEs achieved more than 80% oil removal rate in the washing process of oil sands. It was noted that both oil-in-water and bicontinuous SFMEs could be circularly utilized at least three times with a relatively high oil removal rate (%). Our work provided the insight perspective on the mechanism of SFMEs with a CO2 response behavior.

Preparation, characteristics, and performance of the microemulsion system in the removal of oil from beach sand

Oil deposited on shoreline substrates has serious adverse effects on the coastal environment and can persist for a long time. In this study, a green and effective microemulsion (ME) derived from vegetable oil was developed as a washing fluid to remove stranded oil from beach sand. The pseudo-ternary phase diagrams of the castor oil/water (without or without NaCl)/Triton X-100/ethanol were constructed to determine ME regions, and they also demonstrated that the phase behaviors of ME systems were almost independent of salinity. ME-A and ME-B exhibited high oil removal performance, low surfactant residues, and economic benefits, which were determined to be the W/O microstructure. Under optimal operation conditions, the oil removal efficiencies for both ME systems were 84.3 % and 86.8 %, respectively. Moreover, the reusability evaluation showed that the ME system still had over 70 % oil removal rates, even though it was used six times, implying its sustainability and reliability.

New insight into desorption behavior and mechanism of oil from aged oil-contaminated soil in microemulsion

The intractable nature of oil-contaminated soil (OS) constitutes the chief limiting factor for its remediation. Herein, the aging effect (i.e., oil-soil interactions and pore-scale effect) was investigated by analyzing the properties of aged OS and further demonstrated by investigating the desorption behavior of the oil from the OS. XPS was performed to detect the chemical environment of N, O, and Al, indicating the coordination adsorption of carbonyl groups (oil) on the soil surface. Alterations in the functional groups of the OS were detected using FT-IR, indicating that the oil-soil interactions were enhanced via wind-thermal aging. SEM and BET were used to analyze the structural morphology and pore-scale of the OS. The analysis revealed that aging promoted the development of the pore-scale effect in the OS. Moreover, the desorption behavior of oil molecules from the aged OS was investigated via desorption thermodynamics and kinetics. The desorption mechanism of the OS was elucidated via intraparticle diffusion kinetics. The desorption process of oil molecules underwent three stages: film diffusion, intraparticle diffusion, and surface desorption. Owing to the aging effect, the latter two stages constituted the major steps for controlling oil desorption. This mechanism provided theoretical guidance to apply microemulsion elution for remedying industrial OS.

Review of the application of surfactants in microemulsion systems for remediation of petroleum contaminated soil and sediments

Microemulsions are important for soil and sediment remediation technology. The characteristics of the surfactants that make up these microemulsions include low sorption into soil or sediments, low surface and interfacial tension, the ability to penetrate tiny pores, and good solubilization of contaminants. This review revealed that microemulsions formulated with nonionic and anionic surfactants have higher recovery efficiencies for hydrophobic contaminants than cationic ones, as evidenced by the surveyed studies reporting effective remediation of soils and sediments using on microemulsions. These microemulsified systems have been found to remove petroleum and its derivatives from soil or sediments at percentages ranging from 40 to 100%. As such, this review can aid with the choice of surfactants used in microemulsions for remediation, such as those with plant-based components, which are promising solutions for the remediation of contaminated soils due to their contaminant extraction efficiency and biodegradability.

Joint effects of bacterium and biochar in remediation of antibiotic-heavy metal contaminated soil and responses of resistance gene and microbial community

Soils containing both veterinary antibiotics (VAs) and heavy metals necessitate effective remediation approaches, and microbial and molecular levels of the results should be further examined. Here, a novel material combining waste fungus chaff-based biochar (WFCB) and Herbaspirillum huttiense (HHS1) was established to immobilize copper (Cu) and zinc (Zn) and degrade oxytetracycline (OTC) and enrofloxacin (ENR). Results showed that the combined material exhibited high immobilization of Cu (85.5%) and Zn (64.4%) and great removals of OTC (41.9%) and ENR (40.7%). Resistance genes including tet(PB), tetH, tetR, tetS, tetT, tetM, aacA/aphD, aacC, aadA9, and czcA were reduced. Abundances of potential hosts of antibiotic resistance genes (ARGs) including phylum Proteobacteria and genera Brevundimonas and Rhodanobacter were altered. Total phosphorus and pH were the factors driving the VA degrading microorganisms and potential hosts of ARGs. The combination of WFCB and HHS1 can serve as an important bioresource for immobilizing heavy metals and removing VAs in the contaminated soil.