Microfiltration of oil/water emulsions in industrial wastewaters. Oil/water emulsions vary greatly in their electrostatic properties, according to their sources and the nature of the surfactants that stabilize them; polymer filtration membranes that are post-processed to vary their electrostatic charge can be used for anti-fouling purposes. This invention takes advantage of the electrostatic interactions on electrospun fiber membranes to reduce fouling in the filtration process.
Unintentional release of large quantities of oily wastewater to the environment, without appropriate treatment, can cause negative impacts on the aquatic plants and animals. Conventional techniques to separate oil and water such as gravity-based or centrifugal separations become inefficient when the oil is present as an emulsion, with droplet sizes below 20 micrometers. While membrane separations have demonstrated high oil removal efficiency, low energy cost and compact design, fouling remains a primary challenge that can lead to flux decline, inefficient separation and increased material and energy cost. This invention provides a new strategy for membrane design to resist fouling based on the nature of the emulsion and the tuning of the electrostatic interactions.
Based on the electrostatic repulsion between the membrane and emulsion, a strategy was developed to demonstrate antifouling enhancement of electrospun fiber membranes in microfiltration of surfactant-stabilized oil in-water emulsions. Electrospun polyamide membranes are modified by plasma pre-treatment and layer-by-layer deposition of polyelectrolytes with polyanion or polycation top-layers. When testing as-spun and modified membranes against emulsions in dead-end and cross-flow filtration configurations under constant pressure, the results show that like charged membranes and emulsions result in higher permeate fluxes by 2-3 fold as compared to the as-spun membrane. The higher permeate flux is indicative of greater resistance to fouling.
- Provides fouling resistance against both cationic and anionic surfactant-stabilized oil/water emulsions
- Versatility of polyelectrolyte functionalization due to electrostatic interactions
- High permeate flux and improved robustness due to interconnected porosity of electrospun membranes
- Simple and controllable fabrication process through plasma treatment and LbL deposition