Lignin@Fe 3 O 4 nanoparticles adsorb at oil–water interfaces, form Pickering emulsions, induce on-demand magnetic responses to break emulsions, and can sequester oil from water. Lignin@Fe 3 O 4 nanoparticles were prepared using a pH-induced precipitation method and were fully characterized. These were used to prepare Pickering emulsions with castor oil/Sudan red G dye and water at various oil/water volume ratios and nanoparticle concentrations. The stability and demulsification of the emulsions under different magnetic fields generated with permanent magnets (0–540 mT) were investigated using microscopy images and by visual inspection over time. The results showed that the Pickering emulsions were more stable at the castor oil/water ratio of 50/50 and above. Increasing the concentration of lignin@Fe 3 O 4 improved the emulsion stability and demulsification rates with 540 mT applied magnetic field strength. The adsorption of lignin@Fe 3 O 4 nanoparticles at the oil/water interface using 1-pentanol evaporation through Marangoni effects was demonstrated, and magnetic manipulation of a lignin@Fe 3 O 4 stabilized castor oil spill in water was shown. Nanoparticle concentration and applied magnetic field strengths were analyzed for the recovery of spilled oil from water; it was observed that increasing the magnetic strength increased oil spill motion for a lignin@Fe 3 O 4 concentration of up to 0.8 mg mL −1 at 540 mT. Overall, this study demonstrates the potential of lignin-magnetite nanocomposites for rapid on-demand magnetic responses to externally induced stimuli.
more »
« less
Novel castor oil/water/ethanol Pickering emulsions stabilized by magnetic nanoparticles and magnetically controllable demulsification
A novel castor oil/water/ethanol Pickering emulsion, stabilized by magnetic nanoparticles (NPs), was developed to allow on-demand demulsification by an external magnetic field for the extraction of ethanol from aqueous solution using the castor oil. The emulsion was stabilized by Fe3O4-coated cellulose nanocrystals (CNC@Fe3O4) and lignin-coated Fe3O4 NPs (lignin@Fe3O4). The stability of the emulsions was investigated at various castor oil to ethanol-water ratios (50/50 and 70/30), various NP concentrations, and ethanol concentrations in the aqueous phase. The magnetically controlled demulsification ability of the emulsions was investigated by using a permanent magnet. The results showed that the 70/30 emulsions were more stable than the 50/50 emulsions for all the ethanol concentrations. Moreover, increasing the NP concentration increased the emulsion stability and hence, 1 w/v% NPs concentration provided the more stable systems. However, all the emulsions were successfully broken by the permanent magnet. Yet, the presence of ethanol improves the ability of the external magnetic field to demulsify these dispersions. Furthermore, the used hybrid NPs were recovered and recycled for three cycles. The recycled NPs were characterized with X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) indicating that they retained their saturation magnetization and crystalline structure, demonstrating their lack of degradation over multiple recycling cycles. This study facilitates the exploration of innovative two-phase Pickering emulsions comprising three distinct liquid components and their utilization in liquid-liquid extraction processes.
more »
« less
- PAR ID:
- 10470627
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Colloids and Surfaces A: Physicochemical and Engineering Aspects
- Volume:
- 677
- Issue:
- PB
- ISSN:
- 0927-7757
- Page Range / eLocation ID:
- 132424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Nanoparticle additives increase the thermal conductivity of conventional heat transfer fluids at low concentrations, which leads to improved heat transfer fluids and processes. This study investigates lignin-coated magnetic nanocomposites (lignin@Fe3O4) as a novel bio-based magnetic nanoparticle additive to enhance the thermal conductivity of aqueous-based fluids. Kraft lignin was used to encapsulate the Fe3O4 nanoparticles to prevent agglomeration and oxidation of the magnetic nanoparticles. Lignin@Fe3O4 nanoparticles were prepared using a pH-driven co-precipitation method with a 3:1 lignin to magnetite ratio and characterized by X-ray diffraction, FT-IR, thermogravimetric analysis, and transmission electron microscopy. The magnetic properties were characterized using a vibrating sample magnetometer. Once fully characterized, lignin@Fe3O4 nanoparticles were dispersed in aqueous 0.1% w/v agar–water solutions at five different concentrations, from 0.001% w/v to 0.005% w/v. Thermal conductivity measurements were performed using the transient line heat source method at various temperatures. A maximum enhancement of 10% in thermal conductivity was achieved after adding 0.005% w/v lignin@Fe3O4 to the agar-based aqueous suspension at 45 °C. At room temperature (25 °C), the thermal conductivity of lignin@Fe3O4 and uncoated Fe3O4 agar-based suspensions was characterized at varying magnetic fields from 0 to 0.04 T, which were generated using a permanent magnet. For this analysis, the thermal conductivity of lignin magnetic nanosuspensions initially increased, showing a 5% maximum peak increase after applying a 0.02 T magnetic field, followed by a decreasing thermal conductivity at higher magnetic fields up to 0.04 T. This result is attributed to induced magnetic nanoparticle aggregation under external applied magnetic fields. Overall, this work demonstrates that lignin-coated Fe3O4 nanosuspension at low concentrations slightly increases the thermal conductivity of agar aqueous-based solutions, using a simple permanent magnet at room temperature or by adjusting temperature without any externally applied magnetic field.
-
more » « less
Abstract Oil‐in‐water droplets stabilized with polymer zwitterions (PZWs) exhibit salt‐responsive aggregation–disaggregation behavior. Here, a method to shape these droplets is described, starting from their aggregated state, into supracolloidal fibers by simply extruding them into aqueous media. The effect of salt concentration, in both the initial emulsion and the aqueous medium, on the ability of the emulsions to form fibers is examined. After fiber formation, a transition from well‐defined macroscopic structures to noninteracting droplet dispersions can be triggered, simply by increasing the salt concentration of the aqueous environment. The interdroplet energy of adhesion and emulsion rheology correlate qualitatively with salt concentration and thus impact the ability of the emulsions to be shaped by extrusion. The interdroplet adhesion is dependent on both salt concentration and polymer composition, which allows tailoring of conditions to trigger fiber disaggregation. Finally, fibers with variable compositions along their length are prepared by sequential loading and extrusion of emulsions containing oil phases of differing densities.
-
Graphene oxide/polymer composite water filtration membranes were developed via coalescence of graphene oxide (GO) stabilized Pickering emulsions around a porosity-generating polymer. Triptycene poly(ether ether sulfone)-CH2NH2:HCl polymer interacts with the GO at the water−oil interface, resulting in stable Pickering emulsions. When they are deposited and dried on polytetrafluoroethylene substrate, the emulsions fuse to form a continuous GO/polymer composite membrane. X-ray diffraction and scanning electron microscopy demonstrate that the intersheet spacing and thickness of the membranes increased with increasing polymer concentration, confirming the polymer as the spacer between the GO sheets. The water filtration capability of the composite membranes was tested by removing Rose Bengal from water, mimicking separations of weak black liquor waste. The composite membrane achieved 65% rejection and 2500 g m−2 h−1 bar−1. With high polymer and GO loading, composite membranes give superior rejection and permeance performance when compared with a GO membrane. This methodology for fabrication membranes via GO/polymer Pickering emulsions produces membranes with a homogeneous morphology and robust chemical separation strength.more » « less
-
We report a microfluidic droplet generator which can produce single and compound droplets using a 3D axisymmetric co-flow structure. The design considered for the fabrication of the device integrated a user-friendly and cost-effective 3D printing process. To verify the performance of the device, single and compound emulsions of deionized water and mineral oil were generated and their features such as size, generation frequency, and emulsion structures were successfully characterized. In addition, the generation of bio emulsions such as alginate and collagen aqueous droplets in mineral oil was demonstrated in this study. Overall, the monolithic 3D printed axisymmetric droplet generator could offer any user an accessible and easy-to-utilize device for the generation of single and compound emulsions.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.colsurfa.2023.132424
