Experimental and theoretical study on extraction and recovery of naphthenic acid using dicyanamide-based ionic liquids

Transcriptome reveals the toxicity and genetic response of zebrafish to naphthenic acids and benzo[a]pyrene at ambient concentrations

Naphthenic acids (NAs) are typical contaminants in heavily crude oil. Benzo[a]pyrene (B[a]P) is also a component of crude oil, but their combined effects have not been systematically explored. In this study, zebrafish (Danio rerio) were used as the test organisms, and behavioral indicators and enzyme activities were used as toxicity indicators. Combined with the effects of environmental concentrations, the toxic effects of low concentrations of commercially available NAs (0.5 mg/LNA) and benzo[a]pyrene (0.8 μg/LBaP) at single and compound exposures (0.5 mg/LNA and 0.8 μg/LBaP) were assayed in zebrafish, and transcriptome sequencing technology was used to explore the molecular mechanism of the two compounds affecting zebrafish from the molecular biology level. Sensitive molecular markers that could indicate the presence of contaminants were screened. The results showed that (1) zebrafish in the NA and BaP exposure groups exhibited increased locomotor behavior, and the mixed exposure group exhibited inhibition of locomotor behavior. Oxidative stress biomarkers showed increased activity under single exposure and decreased activity under the mixed exposure. (2) NA stress led to changes in the activity of transporters and the intensity of energy metabolism; BaP directly stimulates the pathway of actin production. When the two compounds are combined, the excitability of neurons in the central nervous system is decreased, and the actin-related genes are down-regulated. (3) After BaP and Mix treatments, genes were enriched in the cytokine-receptor interaction and actin signal pathway, while NA increased the toxic effect on the mixed treatment group. In general, the interaction between NA and BaP has a synergistic effect on the transcription of zebrafish nerve and motor behavior-related genes, resulting in increased toxicity under combined exposure. The changes in expression of various zebrafish genes are manifested in the changes in the normal movement behavior of zebrafish and the intensification of oxidative stress in the apparent behavior and physiological indicators. CAPSULE ABSTRACT: We investigated the toxicity and genetic alterations caused by NA, B[a]P, and their mixtures in zebrafish in an aquatic environment using transcriptome sequencing technology and comprehensive behavioral analysis. These changes involved energy metabolism, the generation of muscle cells, and the nervous system.

Ultrasound-assisted deep eutectic solvents extraction of glabridin and isoliquiritigenin from Glycyrrhiza glabra: Optimization, extraction mechanism and in vitro bioactivities

Licorice (Glycyrrhiza glabra) is extensively used owing to the superior pharmacological effects. However, its maximum application potential has not been fully exploited due to the limitation of currently available extraction solvent and methods. In this study, an eco-friendly deep eutectic solvent (NADESs) based ultrasound-assisted extraction (DES-UAE) method was applied to prepare licorice extracts. The DES-UAE using choline chloride and lactic acid as solvent was optimized and modeled by using response surface methodology to maximize the extraction yields of glabridin (GLA) and isoliquiritigenin (ISL). The optimized extracts possessed higher contents of GLA and ISL than available extraction methods, and the enriched products showed superior pharmacological activities in vitro. Furthermore, scanning electron microscopy (SEM) and molecular dynamic simulation analyses were performed to deeply investigate the interaction between solvent and targeted compounds. This study not only provides an eco-friendly method for high-efficient extraction of GLA and ISL from licorice but also illustrates the mechanism of the increased extraction efficacy, which may contribute to the application of licorice and deep insight into extraction mechanism using DES.

Ultrasonic-Assisted Technique as a Novel Method for Removal of Naphthenic Acid from Model Oil Using Piperidinium-Based Ionic Liquids

In this study, piperidinium-based ionic liquids (IL) containing trifluoromethanesulfonate, phenolate, and dicyanamide anions were synthesized. Using the ILs, extraction of naphthenic acid from highly acidic oil with a total acid number (TAN) of 1.44 was studied. Two agitation techniques have been implemented for the extraction process, which were mechanical stirring and ultrasonic-assisted irradiation. 1-Butyl-1-methylpiperidinium phenolate [BMPi][Phe] showed the best potential in extracting naphthenic acid from oil, with complete removal of naphthenic acid with IL-to-oil ratios of 0.010 and 0.0025 for the mechanical stirring method and the ultrasonic-assisted method, respectively. Ultrasonic-assisted extraction process shows very good potential in enhancing the extraction efficiency of naphthenic acid. Optimization and study on the effects of ultrasonic parameters, namely, IL-to-oil ratio, ultrasonic amplitude, and time, were studied through response surface methodology (RSM). Using [BMPi][Phe], the optimum conditions obtained are IL-to-oil ratio of 0.03, 53.91% of amplitude, and 4.29 min of extraction time. Under these optimum conditions, 100% removal of naphthenic acid was achieved.

Separation of m-Cresol from Coal Tar Model Oil Using Propylamine-Based Ionic Liquids: Extraction and Interaction Mechanism Exploration

m-Cresol is an important chemical material, which is mainly derived from low-temperature coal tar. In this work, for separating m-cresol from coal tar model oil, two propylamine-based ionic liquids (ILs) propylamine formate ([PA][FA]) and propylamine acetate ([PA][Ac]) were selected as extractants. The selected ILs were synthesized and characterized by Fourier transform infrared (FT-IR) and ¹H nuclear magnetic resonance (NMR) spectroscopy. The effects of temperature, mass ratio of IL to model oil, and separation time on the separation efficiency of m-cresol were explored. The separation efficiency (SE) and distribution coefficient (D) were calculated from the experimental data to assess the separation performance of [PA][FA] and [PA][Ac]. The results showed that propylamine formate was a promising extractant with the separation efficiency of 97.8% and distribution coefficient of 27.59 at 298.15 K and m _IL/m _oil = 0.2. In the meantime, molecular dynamics (MD) simulations were employed to comprehend the interaction mechanism, from which the noncovalent interaction energy (IE), radial distribution function (RDF), spatial distribution function (SDF), and averaged noncovalent interaction (aNCI) were calculated. The results showed that both cation and anion formed hydrogen bonds with m-cresol and the anions played a leading role with electrostatic interaction energy in separating m-cresol. In addition, the regeneration and reuse of the ionic liquids were explored.