Membrane-based separation technologies are attractive to remediating unconventional water sources, including brackish, industrial, and municipal wastewater, due to their versatility and relatively high energy efficiency. However, membrane fouling by dissolved or suspended organic substances remains a primary challenge which can result in an irreversible decline of the permeate flux. To overcome this, membranes have been incorporated with photocatalytic materials that can degrade these organic substances deposited on the surface upon light illumination. While such photocatalytic membranes have demonstrated that they can recover their inherent permeability, less information is known about the effect of photocatalysis on the kinetics of the permeate flux. In this work, a photocatalytic mesh that can selectively permeate water while repelling oil was fabricated by coating a mixture of nitrogen-doped TiO2(N-TiO2) and perfluorosilane-grafted SiO2(F-SiO2) nanoparticles on a stainless steel mesh. Utilizing the photocatalytic mesh, the time-dependent evolution of the water-rich permeate flux as a result of photocatalytic degradation of the oil was studied under the visible light illumination. A mathematical model was developed that can relate the photocatalytic degradation of the organic substances deposited on a mesh surface to the evolution of the permeate flux. This model was established by integrating the Langmuir–Hinshelwood kinetics for photocatalysis and the Cassie–Baxter wettability analysis on a chemically heterogeneous mesh surface into a permeate flux relation. Consequently, the time-dependent water-rich permeate flux values are compared with those predicted by using the model. It is found that the model can predict the evolution of the water-rich permeate flux with a goodness of fit of 0.92.
- Award ID(s):
- 1846628
- PAR ID:
- 10094656
- Date Published:
- Journal Name:
- MRS Advances
- Volume:
- 4
- Issue:
- 07
- ISSN:
- 2059-8521
- Page Range / eLocation ID:
- 359 to 367
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract A facile, one‐step, and single‐component fabrication of superhydrophobic and superoleophilic coating by electropolymerization of polythiophene on a stainless steel mesh is presented. The resulting coating has low surface energy and shows surface morphology bearing both micro‐ and nano‐features without the need to add nanofillers, or pretreatment of the substrate to make it rough. The polythiophene coating also shows reversible wetting property (superhydrophobic to superhydrophilic, and vice versa) by electrochemical doping and dedoping. The coated mesh is shown to repel water of different pH (1, 7, and 14) and salt content. On the other hand, oil such as dichloromethane, gasoline, kerosene, dodecane, and crude oil can easily pass through the mesh. Therefore, the coated mesh is an excellent material for the separation of oil and water.
-
null (Ed.)Initiated chemical vapor deposition (iCVD) was used to coat two porous substrates (i.e., hydrophilic cellulose acetate (CA) and hydrophobic polytetrafluoroethylene (PTFE)) with a crosslinked fluoropolymer to improve membrane wetting resistance. The coated CA membrane was superhydrophobic and symmetric. The coated PTFE membrane was hydrophobic and asymmetric, with smaller pore size and lower porosity on the top surface than on the bottom surface. Membrane performance was tested in membrane distillation experiments with (1) a high-salinity feed solution and (2) a surfactant-containing feed solution. In both cases, the coated membranes had higher wetting resistance than the uncoated membranes. Notably, wetting resistances were better predicted by LEP distributions than by minimum LEP values. When LEP distributions were skewed towards high LEP values (i.e., when small pores with high LEP were greater in number), significant (measurable) salt passage did not occur. For the high-salinity feed solution, the coated PTFE membrane had greater wetting resistance than the coated CA membrane; thus, reduced surface pore size/porosity (which may reduce intrapore scaling) was more effective than increased surface hydrophobicity (which may reduce surface nucleation) in preventing scaling-induced wetting. Reduced pore size/porosity was equally as effective as increased hydrophobicity in resisting surfactant-induced wetting. However, reduced porosity can negatively impact water flux; this represents a permeability/wetting resistance tradeoff in membrane distillation – especially for high-salinity applications. Membrane and/or membrane coating properties must be optimized to overcome this permeability/wetting resistance tradeoff and make MD viable for the treatment of challenging streams. Then, increasing hydrophobicity may not be necessary to impart high wetting resistance to porous membranes. These results are important for future membrane design, especially as manufacturers seek to replace perfluorinated materials with environmentally friendly alternatives.more » « less
-
The goal of this stydy was to explore the potential of the enhanced corrosion resistance of Ti(N,O) cathodic arc evaporation-coated 304L stainless steel using oxide nano-layers deposited by atomic layer deposition (ALD). In this study, we deposited Al2O3, ZrO2, and HfO2 nanolayers of two different thicknesses by ALD onto Ti(N,O)-coated 304L stainless steel surfaces. XRD, EDS, SEM, surface profilometry, and voltammetry investigations of the anticorrosion properties of the coated samples are reported. The amorphous oxide nanolayers homogeneously deposited on the sample surfaces exhibited lower roughness after corrosion attack compared to the Ti(N,O)-coated stainless steel. The best corrosion resistance was obtained for the thickest oxide layers. All samples coated with thicker oxide nanolayers augmented the corrosion resistance of the Ti(N,O)-coated stainless steel in a saline, acidic, and oxidising environment (0.9% NaCl + 6% H2O2, pH = 4), which is of interest for building corrosion-resistant housings for advanced oxidation systems such as cavitation and plasma-related electrochemical dielectric barrier discharge for breaking down persistent organic pollutants in water.more » « less
-
more » « less
Abstract In this study, a facile method is presented to fabricate superamphiphobic surfaces with controllable adhesion on polytetrafluoroethylene (PTFE), for the first time, using femtosecond laser Bessel beam. Compared to previous structures mostly based on 1D microstructure produced by Gaussian beam, the surfaces are characterized by highly uniform 2D periodic hill‐groove structures covered with extensive porous‐mesh nanostructures. Most significantly, the 2D hill‐groove structures have a very high‐aspect‐ratio since the energy distribution of the Bessel beam is more uniform over a longer focusing range. Moreover, the profile of the obtained microstructures is a nearly perfect semi‐spherical shape. As a result, the processed surfaces become superamphiphobic, exhibiting a contact angle of 166° for water and 160° for oil, respectively. Furthermore, the surface adhesion can be controlled from ultralow to ultrahigh by adjusting the period of the hill‐groove 2D‐patterned structures. It is demonstrated that the ultralow adhesion surfaces show excellent antifog and anti‐icing properties, while the ultrahigh adhesion surfaces can be used for water and oil collection. Both surfaces have a good mechanical stability and are stable over a wide range of temperatures. The superamphiphobic PTFE surfaces with tunable adhesion can be used for self‐cleaning, microfluidic systems, and harsh environments.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1557/adv.2018.604
