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1.
Water Res ; 174: 115600, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32088385

RESUMO

A hierarchically assembled superomniphobic membrane with three levels of reentrant structure was designed and fabricated to enable effective treatment of low surface tension, hypersaline oily wastewaters using direct contact membrane distillation (DCMD). The overall structure is a combination of macro corrugations obtained by surface imprinting, with the micro spherulites morphology achieved through the applied phase inversion method and nano patterns obtained by fluorinated Silica nanoparticles (SiNPs) coating. This resulted in a superomniphobic membrane surface with remarkable anti-wetting properties repelling both high surface tension water and low surface tension oils. Measurements of contact angle (CA) with DI water, an anionic surfactant, oil, and ethanol demonstrated a robust wetting resistance against low surface tension liquids showing both superhydrophobicity and superoleophobicity. CA values of 160.8 ± 2.3° and 154.3 ± 1.9° for water and oil were obtained, respectively. Calculations revealed a high liquid-vapor interface for the fabricated membrane with more than 89% of the water droplet contact area being with air pockets entrapped between adjacent SiNPs and only 11% come into contact with the solid membrane surface. Moreover, the high liquid-vapor interface imparts the membrane with high liquid repellency, self-cleaning and slippery effects, characterized by a minimum droplet-membrane interaction and complete water droplet bouncing on the surface within only 18 ms. When tested in DCMD with synthetic hypersaline oily wastewaters, the fabricated superomniphobic membrane demonstrated stable, non-wetting MD operation over 24 h, even at high concentrations of low surface tension 1.0 mM Sodium dodecyl sulfate and 400 ppm oil, potentially offering a sustainable option for treatment of low surface tension oily industrial wastewater.


Assuntos
Destilação , Purificação da Água , Membranas Artificiais , Óleos , Tensão Superficial , Águas Residuárias
2.
Water Res ; 165: 114982, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31473356

RESUMO

In this study, an omniphobic membrane was fabricated by electrospraying fluorinated zinc oxide (ZnO) nanoparticles (NPs) mixed with polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) on the surface of an organosilane functionalized polyvinylidene difluoride (PVDF) membrane. Our results revealed that the functionalized ZnO NPs membrane exhibited a rough hierarchical re-entrant morphology with low surface energy which allowed it to achieve high omniphobic characteristics. It was observed that the addition of 30% ZnO (w/w of PVDF-HFP) was found to be optimal and imparted a high repulsive characteristic. The optimized PVDF/ZnO(30)/FAS/PVDF-HFP referred as cPFP-30Z membrane exhibited a high contact angle values of 159.0 ±â€¯3.1°, 129.6 ±â€¯2.2°, 130.4 ±â€¯4.1° and 126.1 ±â€¯1.2° for water, sodium dodecyl sulfate (SDS) saline solution (0.3 mM SDS in 3.5% NaCl), ethanol, and vegetable oil, respectively. The low surface energy and high surface roughness (Ra) of optimised membrane was assessed as 0.78 ±â€¯0.14 mN m-1 and 1.37 µm, respectively. Additionally, in contrast with the commercial PVDF membrane, the cPFP-30Z membrane exhibited superior anti-wetting/anti-fouling characteristics and high salt rejection performance (>99%) when operated with a saline oil solution (0.015 v/v) and SDS (0.4 mM) feed solutions.


Assuntos
Nanopartículas , Purificação da Água , Óxido de Zinco , Destilação , Membranas Artificiais , Polivinil , Água do Mar , Tensão Superficial
3.
Environ Sci Technol ; 53(9): 4948-4958, 2019 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-30978006

RESUMO

Electrospun nanofiber membranes (ENMs) have garnered increasing interest due to their controllable nanofiber structure and high void volume fraction properties in membrane distillation (MD). However, MD technology still faces limitations mainly due to low permeate flux and membrane wetting for feeds containing low surface tension compounds. Perfluorinated superhydrophobic membranes could be an alternative, but it has negative environmental impacts. Therefore, other low surface energy materials such as silica aerogel and polydimethylsiloxane (PDMS) have great relevancy in ENMs fabrication. Herein, we have reported the high flux and nonwettability of ENMs fabricated by electrospraying aerogel/polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) over electrospinning polyvinylidene fluoride- co-hexafluoropropylene (PVDF-HFP) membrane (E-PH). Among various concentrations of aerogel, the 30% aerogel (E-M3-A30) dual layer membrane achieved highest superhydrophobicity (∼170° water contact angle), liquid entry pressure (LEP) of 129.5 ± 3.4 kPa, short water droplet bouncing performance (11.6 ms), low surface energy (4.18 ± 0.27 mN m-1) and high surface roughness ( Ra: 5.04 µm) with re-entrant structure. It also demonstrated nonwetting MD performance over a continuous 7 days operation of saline water (3.5% of NaCl), high antiwetting with harsh saline water containing 0.5 mM sodium dodecyl sulfate (SDS, 28.9 mN m-1), synthetic algal organic matter (AOM).


Assuntos
Nanofibras , Purificação da Água , Dimetilpolisiloxanos , Destilação , Interações Hidrofóbicas e Hidrofílicas , Membranas Artificiais
4.
Chemosphere ; 206: 718-726, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29787973

RESUMO

This study demonstrates the application of in situ ferrate (Fe(VI)) for the efficient removal of dissolved algal organic matter (AOM) from seawater. Sodium hypochlorite (NaOCl) and ferric (Fe(III)) were used to produce in situ Fe(VI) by wet chemical oxidation. First, the removal efficiencies of two model AOM compounds, humic acid (HA) and sodium alginate (SA), were evaluated in the presence of sodium chloride with an initial influent dissolved organic carbon (DOC) concentration of 5.0 mg C L-1 at different pH levels to establish the optimal doses for in situ Fe(VI) generation. The concentration of Fe(VI) was determined by the 2,2-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) ultraviolet-visible spectrophotometry method. In the case of HA, 72% DOC removal was recorded when applied with 1.5 mg L-1 of Fe(III) and 1.5 mg L-1 of NaOCl (in situ Fe(VI) concentration of 1.46 mg L-1) while 42% DOC removal was observed for SA. Subsequently, the removal of AOM extracted from two bloom-forming algal species, Chaetoceros affinis (CA) and Hymenomonas (Hym), cultivated in seawater from the Red Sea, were tested with in situ generated Fe(VI) at the established optimum condition. In situ Fe(VI) recorded superior performance in removing AOM extracted from CA and Hym, showing 83% and 92% DOC removal when the influent DOC concentrations were 2.48 and 2.63 mg L-1, respectively. A detailed AOM characterization was conducted using liquid chromatography-organic carbon detection.


Assuntos
Ferro/química , Compostos Orgânicos/química , Oxirredução
5.
Environ Sci Technol ; 51(17): 10117-10126, 2017 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-28753303

RESUMO

To consolidate the position of membrane distillation (MD) as an emerging membrane technology that meets global water challenges, it is crucial to develop membranes with ideal material properties. This study reports a facile approach for a polyvinylidene fluoride (PVDF) membrane surface modification that is achieved through the coating of the surface with poly(dimethylsiloxane) (PDMS) polymeric microspheres to lower the membrane surface energy. The hierarchical surface of the microspheres was built without any assistance of a nano/microcomposite by combining the rapid evaporation of tetrahydrofuran (THF) and the phase separation from condensed water vapor. The fabricated membrane exhibited superhydrophobicity-a high contact angle of 156.9° and a low contact-angle hysteresis of 11.3°-and a high wetting resistance to seawater containing sodium dodecyl sulfate (SDS). Compared with the control PVDF-hexafluoropropylene (HFP) single-layer nanofiber membrane, the proposed fabricated membrane with the polymeric microsphere layer showed a smaller pore size and higher liquid entry pressure (LEP). When it was tested for the direct-contact MD (DCMD) in terms of the desalination of seawater (3.5% of NaCl) containing SDS of a progressively increased concentration, the fabricated membrane showed stable desalination and partial wetting for the 0.1 and 0.2 mM SDS, respectively.


Assuntos
Membranas Artificiais , Microesferas , Polivinil , Purificação da Água , Destilação
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