Effective recovery of oil slick using the prepared high hydrophobic and oleophilic Fe3O4 magnetorheological fluid

Vortex-assisted dispersive liquid-liquid microextraction based on the hydrophobic deep eutectic solvent-based ferrofluid for extraction and detection of myclobutanil

A vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) procedure using hydrophobic deep eutectic solvent-based ferrofluid (HDES-FF) as an extractant was established. The developed sample preparation method coupled with high-performance liquid chromatography-diode array detector (HPLC-DAD) was applied to the pretreatment and determination of myclobutanil (MYC) in fruit juice. Hydrophobic deep eutectic solvent, synthesized by n-decanoic acid and DL-menthol, was as a carrier and combined with magnetic nanoparticles (Fe3O4@OA) to form HDES-FF as an extractant with high extraction capacity. The synthesized materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Parameters affecting extraction efficiency were optimized using single-factor experiments and Box-Behnken design via response surface methodology (BBD-RSM). Parallel tests were performed three times under the optimal conditions predicted by the model, yielding an actual mean recovery of 94.77% with RSD of 2.7% (n = 3) and an enrichment factor of 41.8 ± 0.98 (mean value ± SD, n = 3). Under the optimal conditions, the linear range was 1.0-100.0 µg·mL-1; the limit of detection (LOD) and limit of quantification (LOQ) were 0.25 and 0.80 µg·mL-1, respectively. The average spiked recoveries in the samples ranged from 98.2 to 100.5% with intra-day relative standard deviations (RSDs) of 1.2-3.5% (n = 3) and inter-day RSDs of 1.1-3.8% (n = 3). Finally, the method was successfully applied to the determination of MYC antimicrobial agent in different fruit juice samples. The proposed HDES-FF-VA-DLLME/HPLC-DAD method was verified to widely apply to the extraction of triazole fungicides.

High positively charged Fe3O4 nanocomposites for efficient and recyclable demulsification of hexadecane-water micro-emulsion

Oily wastewater not only causes major environmental issues, but also threatens human health. Magnetic nanoparticles (MNPs) are an attractively alternative commercial demulsifiers for their recyclability and high surface area. The wettability and surface charge of magnetic materials are significant factors in oily wastewater treatment. However, the specific influence of surface charge on the demulsification performance has not been rigorously investigated. Herein, a series of MNPs coated by dimethyl-diallyl-ammonium chloride (PDDA) and fulvic acid (FA) (Fe₃O₄/FA/PDDA) with different surface positive charges were synthesized by adjusting the PDDA concentrations and applied in demulsification of hexadecane-water micro-emulsion. The oil-water separation efficiency (Es) was enhanced gradually with increasing the surface positive charge of demulsifiers. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory confirmed that with increasing surface positive potential, the electrostatic attraction between demulsifiers and oil droplets increased, and thus, Es increased. In addition, the superior Es of Fe₃O₄/FA MNPs for hexadecyl trimethyl ammonium bromide (CTAB)-stabilized micro-emulsions and Fe₃O₄/FA/PDDA MNPs for sodium dodecyl sulfate (SDS)-stabilized micro-emulsions further confirmed that electrostatic force was critical in demulsification. The high positively charged Fe₃O₄/FA/PDDA MNPs can be used as an efficient and recyclable demulsifier for hexadecane-water micro-emulsion. This study provides a theoretical basis for designing demulsifiers.

Superhydrophobic Fe3O4/OA Magnetorheological Fluid for Removing Oil Slick from Water Surfaces Effectively and Quickly

Considering the severe impacts on the economic losses caused by oil spills, it is of great significance to develop an oil-absorbent material for removing the oil slick from the water surface effectively. As a new oil-absorbent material, magnetorheological fluid (MRF) has unsinkability, hydrophobicity, and lipophilicity, which could effectively remove the oil slick on the water surface while repelling water. Particularly, the prepared MRF shows a good response to external magnetic field. MRFs show high oil removal capacity in fresh water, deionized water, and salt water with efficiencies up to 94.39, 93.65, and 92.71%, respectively. Besides, Fe₃O₄/OA magnetic nanoparticles (MPs) could be reprepared into MRF by simple treatments. After the fifth cycle, the MRF prepared by the recovered Fe₃O₄/OA MPs still has high oil removal efficiency, and that means the Fe₃O₄/OA MPs has excellent reusability and stability. The method for preparing MRFs provided in this work is simple and effective, and the MRFs have a promising potential for cleaning oil slick.