Surface heating membrane distillation overcomes several limitations inherent in conventional membrane distillation technology. Here we report a successful effort to grow in situ a hexagonal boron ...nitride (hBN) nanocoating on a stainless-steel wire cloth (hBN-SSWC), and its application as a scalable electrothermal heating material in surface heating membrane distillation. The novel hBN-SSWC provides superior vapour permeability, thermal conductivity, electrical insulation and anticorrosion properties, all of which are critical for the long-term surface heating membrane distillation performance, particularly with hypersaline solutions. By simply attaching hBN-SSWC to a commercial membrane and providing power with an a.c. supply at household frequency, we demonstrate that hBN-SSWC is able to support an ultrahigh power intensity (50 kW m
) to desalinate hypersaline solutions with exceptionally high water flux (and throughput), single-pass water recovery and heat utilization efficiency while maintaining excellent material stability. We also demonstrate the exceptional performance of hBN-SSWC in a scalable and compact spiral-wound electrothermal membrane distillation module.
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Membrane separation has enjoyed tremendous advances in relevant material and engineering sciences, making it the fastest growing technology in water treatment. Although membranes as a ...broad-spectrum physical barrier have great advantages over conventional treatment processes in a myriad of applications, the need for higher selectivity and specificity in membrane separation is rising as we move to target contaminants at trace concentrations and to recover valuable chemicals from wastewater with low energy consumption. In this review, we discuss the drivers, fundamental science, and potential enabling materials for high selectivity membranes, as well as their applications in different water treatment processes. Membrane materials and processes that show promise to achieve high selectivity for water, ions, and small molecules—as well as the mechanisms involved—are highlighted. We further identify practical needs, knowledge gaps, and technological barriers in both material development and process design for high selectivity membrane processes. Finally, we discuss research priorities in the context of existing and future water supply paradigms.
Efficient use of solar energy for desalination is one strategy to solve the world's water scarcity issues. In this work, a dual functional, omniphobic−photothermal nanocomposite membrane was ...developed to achieve wetting resistance and low energy consumption in desalination by direct solar membrane distillation (DSMD). The membrane was prepared by forming a hierarchical structure of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS17) modified carbon black (CB) nanoparticles (NPs) on a polyvinylidene fluoride (PVDF) membrane surface. The fluorinated CB NPs absorbed sun light to provide localized heating for DSMD, which increased membrane flux by 25% upon simulated solar irradiation at one sun unit. The utilization efficiency of solar energy in the DSMD process, 75.4%, is more than one order of magnitude higher than the energy efficiency of the conventional direct contact membrane distillation process. Furthermore, the re-entrant structure formed by the CB NPs together with the hydrophobic FAS17 coating led to low surface energy and hence omniphobicity, increasing the contact angle of the 80 vol% ethanol-in-water from 0 to 94.2°. As a result, the dual functional membrane exhibited much higher resistance to wetting by surfactants. Whereas the pristine PVDF membrane was wetted by 0.2 mM SDS, SDS had no effect on the dual function membrane over the whole SDS concentration range tested (0.1–0.4 mM). The photothermal activity, improved thermal efficiency, and strong wetting resistance make the dual functional omniphobic−photothermal membrane an excellent membrane material for the DSMD process.
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•First membrane distillation membrane with omniphobic and photothermal properties.•The membrane achieves wetting-resistance and photothermal heating simultaneously.•Photothermal carbon black provides re-entrant structure for omniphobicity.
Nusselt correlations originally developed for estimating heat transfer rates in heat exchangers poorly describe heat transfer in membrane distillation (MD) processes. In this work, we assess the ...impact of module design in bench-scale experiments, simplified treatment of heat transfer rates in MD models, and the effect of permeate flux on temperature polarization as sources of error in Nusselt correlation estimates of heat transfer rates. To test these effects, we systematically vary membrane structure, module sizes, temperatures, and Reynolds numbers to generate a large dataset (n = 240) of MD experiments. We apply this dataset to estimate the heat transfer rate for each unique membrane/module combination and compare our predictions to the classical Sieder-Tate Nusselt correlation (Nus-t). Our results show that heat transfer rates in small modules can be up to five times higher than predicted by Nus-t. The heat transfer rate decreases with increasing module size, with heat transfer in large modules adequately described by the Sieder-Tate correlation. We demonstrate that this high heat transfer rate in small modules is a result of an entrance effect, which increases fluid mixing over the membrane area. These results validate the use of Nu correlation in large membrane modules while highlighting issues with their application in small scale systems. This work also emphasizes the importance of bench-scale module design in materials evaluation and process characterization. Finally, it highlights the need for direct measurement techniques that better characterize interfacial processes in membrane systems with modeled driving forces.
•Study relates module design and mass transfer rate to heat transfer rate.•Nusselt correlations underestimate heat transfer in small modules by up to 5x.•Entrance effects induce mixing and increase the heat transfer rate.•Mass transfer does not increase the heat transfer rate in bench-scale modules.•Nusselt correlations more accurately describe heat transfer in large modules.
Fresh and clean water is highly demanded throughout the world. To effectively address the need, nanomaterials enabled nanotechnology has been explored as a means of more efficient, reliable, and ...environmentally friendly approach towards water treatment practices. One concern in adopting nanomaterials is how to retrieve them from water body to avoid secondary contamination. In this work, the earth abundant and sustainable wood, e.g., basswood, was selected and carbonized into porous carbon as host skeleton, and metal-organic frameworks (MOFs), e.g., MOF-199 with extremely high surface area, were grown throughout all channels in the porous basswood carbon. Targeting the traditional organic pollutant, methyl orange (MO), the combination of MOFs and basswood carbon (MOFs@carbon) demonstrates a remarkable adsorption capacity, which is 243% and 454% higher than basswood carbon and MOF-199, respectively. Such an outstanding adsorption performance originates from that the positively charged carbon pulls MO molecules close to carbon surface, leading to a high MO molecule concentration, and then the concentration gradient drives the MO molecules to be stored inside MOFs, functioning like pockets. These findings highlight the potential application of coupled MOFs and biomass carbon in addressing water remediation.
The COVID-19 pandemic has accounted for millions of infections and hundreds of thousand deaths worldwide in a short-time period. The patients demonstrate a great diversity in clinical and laboratory ...manifestations and disease severity. Nonetheless, little is known about the host genetic contribution to the observed interindividual phenotypic variability. Here, we report the first host genetic study in the Chinese population by deeply sequencing and analyzing 332 COVID-19 patients categorized by varying levels of severity from the Shenzhen Third People's Hospital. Upon a total of 22.2 million genetic variants, we conducted both single-variant and gene-based association tests among five severity groups including asymptomatic, mild, moderate, severe, and critical ill patients after the correction of potential confounding factors. Pedigree analysis suggested a potential monogenic effect of loss of function variants in GOLGA3 and DPP7 for critically ill and asymptomatic disease demonstration. Genome-wide association study suggests the most significant gene locus associated with severity were located in TMEM189-UBE2V1 that involved in the IL-1 signaling pathway. The p.Val197Met missense variant that affects the stability of the TMPRSS2 protein displays a decreasing allele frequency among the severe patients compared to the mild and the general population. We identified that the HLA-A*11:01, B*51:01, and C*14:02 alleles significantly predispose the worst outcome of the patients. This initial genomic study of Chinese patients provides genetic insights into the phenotypic difference among the COVID-19 patient groups and highlighted genes and variants that may help guide targeted efforts in containing the outbreak. Limitations and advantages of the study were also reviewed to guide future international efforts on elucidating the genetic architecture of host-pathogen interaction for COVID-19 and other infectious and complex diseases.
Preventing condensation frosting is crucial for air conditioning units, refrigeration systems, and other cryogenic equipment. Coalescence-induced self-propelled jumping of condensed microdroplets on ...superhydrophobic surfaces serves as a favorable strategy against condensation frosting. In previous reports, efforts were dedicated to enhance the efficiency of self-propelled jumping by constructing appropriate surface structures on superhydrophobic surfaces. However, the incorporation of surface structures results in larger area available for condensation to occur, leading to an increase in total amount of condensed water on the surface and partially counteracts the effect of promoted jumping on removing condensed water from the surface. In this paper, we focus on the competing effects between condensing and self-propelled jumping on promoting and preventing water accumulation, respectively. A series of micro- and nanostructured superhydrophobic surfaces are designed and prepared. The condensation process and self-propelled jumping behavior of microdroplets on the surfaces are investigated. Thousands of jumping events are statistically analyzed to acquire a comprehensive understanding of antifrosting potential of superhydrophobic surfaces with self-propelled jumping of condensed microdroplets. Further frosting experiments shows that the surface with the lowest amount of accumulated water exhibits the best antifrosting performance, which validates our design strategy. This work offers new insights into the rational design and fabrication of antifrosting materials.
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