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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.
Sci Total Environ ; 646: 1126-1139, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30235599

RESUMO

Environmental applications of carbon nanotubes (CNTs) have grabbed worldwide attentions due to their excellent adsorption capacities and promising physical, chemical and mechanical properties. The functionalization of CNTs, which involves chemical/physical modification of pristine CNTs with different types of functional groups, improves the capabilities of CNT for desalination and/or removals of waterborne contaminants. This paper intends to provide a comprehensive review of functional CNT materials (f-CNT) and their existing and potential applications in membrane-based water treatment and desalination processes, with focuses on critical evaluation of advances, knowledge gaps and future research directions. CNT nanocomposite membranes have been studied at bench scale to efficiently remove a variety of waterborne contaminants and salts, while future improvement is under way with development in CNT functionalization techniques. The CNT-based membrane applications are found to possess a variety of advantages, including improve water permeability, high selectivity and antifouling capability. However, their applications at full scale are still limited by their high cost. Finally, we highlight that f-CNT membranes with promising removal efficiencies for respective contaminants be considered for commercialization and to achieve holistic performance for the purpose of water treatment and desalination.

3.
J Hazard Mater ; 365: 64-73, 2019 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-30408688

RESUMO

In this work, a bench scale study was designed to investigate the removal of zinc (Zn2+) and regeneration efficiencies of functionalized-MWCNT (f-MWCNT) membranes. The f-MWCNTs were incorporated into polyvinylchloride (PVC) hollow fiber membranes (HFMs), which acted as a substrate and a barrier for MWCNTs leaching to water. The results revealed that the removal capacity of Zn2+ through f-CNT membranes were above 98% for the synthetic water and over 70% for real wastewater effluents; predominantly involved surface complexation reaction. The acquired removal efficiency of CNT membrane is attributed to high absolute zeta potential followed by the hydrophilicity of the nanotubes coated the inside surface of HFMs and high concentration of oxygen functional groups on CNT surfaces. Later on, different regenerating solutions were used to desorb Zn2+ ions repeatedly from the inner surface of membranes and to recycle the CNT membranes for continuous removal of Zn2+ from water. The XPS analysis revealed that, Zn2+ ions were completely recovered owing to the ion exchange interactions. The results further confirmed that f-CNT membranes retained their original removal capacity after several successive cycles. Therefore, we recommend that, f-CNTs-based membranes have the potential to be used for large-scale removal and recovery of heavy metal ions from water or wastewater.

4.
Nanoscale ; 10(9): 4475-4487, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29459912

RESUMO

While the cytotoxicity of graphene oxide (GO) has been well established, its bactericidal mechanism, however, has yet to be elucidated to advance GO-based biomedical and environmental applications. In an attempt to better understand the bactericidal action of GO, herein we studied the interactions of GO with Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus cells using physical techniques and chemical probes, respectively. In particular, a novel laser-induced breakdown spectroscopy (LIBS) based elemental fingerprint analysis revealed notable differences between viable and non-viable cells based on the difference in the concentration of trace inorganic elements in complex bacterial systems, which reflect cellular membrane integrity. Lower emission intensities from essential inorganic ions in the GO-treated cells offered explicit evidence on the efflux of intracellular molecules from the bacteria through damaged cell membranes. Furthermore, a detailed structural and morphological investigation of bacterial membrane integrity confirmed GO-induced membrane stress upon direct contact interactions with bacterial cells, resulting in the disruption of cellular membranes. Moreover, the generation of intracellular reactive oxygen species (ROS) in the presence of an added antioxidant underlined the role of GO-mediated oxidative stress in bacterial cell inactivation. Thus, by correlating the changes in the bacterial elemental compositions with the severe morphological alterations and the high ROS production witnessed herein, we propose that the bactericidal mechanism of GO is likely to be the synergy between membrane and oxidative stress towards both tested species. Our findings offer useful guidelines for the future development of GO-based antibacterial surfaces and coatings.


Assuntos
Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Grafite/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Lasers , Estresse Oxidativo , Óxidos , Espécies Reativas de Oxigênio/metabolismo , Análise Espectral
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