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.
Air pollution, especially fine particulate matter (PM2.5), may impair cognitive performance1–3, but its short-term impact is poorly understood. We investigated the short-term association of PM2.5 with the cognitive performances of 954 white males measured as global cognitive function and Mini-Mental State Examination (MMSE) scores and further explored whether taking nonsteroidal anti-inflammatory drugs (NSAIDs) could modify their relationships. Higher short-term exposure to PM2.5 demonstrated nonlinear negative associations with cognitive function. Compared with the lowest quartile of the 28-d average PM2.5 concentration, the 2nd, 3rd and 4th quartiles were associated with 0.378, 0.376 and 0.499 unit decreases in global cognitive function score, 0.484, 0.315 and 0.414 unit decreases in MMSE score and 69, 45 and 63% greater odds of low MMSE scores (≤25), respectively. Such adverse effects were attenuated in users of NSAIDs compared to nonusers. This study elucidates the short-term impacts of air pollution on cognition and warrants further investigations on the modifying effects of NSAIDs.
There is little evidence on the short-term impact of fine particulate matter (PM2.5) on renal health, and the potential interactions and various influences of PM2.5 components on renal health have not been examined. We investigated whether short-term (≤28 days) ambient PM2.5 and 15 PM2.5 components were associated with serum uric acid (SUA), blood urea nitrogen (BUN), estimated glomerular filtration rate (eGFR), and odds of incident chronic kidney disease (CKD) using both mixed-effect and Bayesian kernel machine regression (BKMR) models in the Normative Aging Study. This analysis included 2466 study visits from 808 older males enrolled during 1998–2016 with available data. BKMR showed positive relationships of PM2.5 mixture with SUA and odds of CKD, and an inverse relationship with eGFR. In the 28-day exposure window, an interquartile range (IQR) increase in vanadium was associated with a 0.244-mg/dL higher SUA. IQR increases in sulfur and lead were associated with a 1.281- and 1.008-mL/min/1.73m2 decrease in eGFR, respectively. The same change in sulfur was also associated with a 39% higher odds of CKD. Our findings provide solid evidence supporting short-term adverse effects of PM2.5 on renal health and further highlight that components from oil combustion and regional pollution may be major contributors.
Herein, a silicate-enhanced flow-through electro-Fenton system with a nanoconfined catalyst was rationally designed and demonstrated for the highly efficient, rapid, and selective degradation of antibiotic tetracycline. The key active component of this system is the Fe2O3 nanoparticle filled carbon nanotube (Fe2O3-in-CNT) filter. Under an electric field, this composite filter enabled in situ H2O2 generation, which was converted to reactive oxygen species accompanied by the redox cycling of Fe3+/Fe2+. The presence of the silicate electrolyte significantly boosted the H2O2 yield by preventing the O–O bond dissociation of the adsorbed OOH*. Compared with the surface coated Fe2O3 on the CNT (Fe2O3-out-CNT) filter, the Fe2O3-in-CNT filter demonstrated 1.65 times higher kL value toward the degradation of the antibiotic tetracycline. Electron paramagnetic resonance and radical quenching tests synergistically verified that the dominant radical species was the 1O2 or HO· in the confined Fe2O3-in-CNT or unconfined Fe2O3-out-CNT system, respectively. The flow-through configuration offered improved tetracycline degradation kinetics, which was 5.1 times higher (at flow rate of 1.5 mL min–1) than that of a conventional batch reactor. Liquid chromatography–mass spectrometry measurements and theoretical calculations suggested reduced toxicity of fragments of tetracycline formed. This study provides a novel strategy by integrating state-of-the-art material science, Fenton chemistry, and microfiltration technology for environmental remediation.
Mixtures of U(VI) and chlorinated compounds have been detected at many radionuclides-contaminated sites. Yet, simultaneous removal of the two classes of contaminants is still challenging. Herein, we prepared a new type of composite material (TNTs/ACF) based on commercial TiO2 and activated carbon fiber (ACF) through a hydrothermal approach and tested it for simultaneous removal of U(VI) and 2-Chlorophenol (2-CP). The hydrothermal treatment converted TiO2 into titanate nanotubes (TNTs), a cation exchanger, which are not only supported by bulk ACF, but also modified by carbon nanoparticles. TNTs/ACF exhibited fast sorption kinetics and high adsorption capacities for both U(VI) (Langmuir Qmax = 188.0 mg/g) and 2-CP (Qmax = 122.1 mg/g). Moreover, higher adsorption was observed when both solutes are co-present than in the single-solute systems. An extended dual-mode model, which considers adsorption and other specific mechanisms well interpreted the adsorption isotherms. The optimal working pH for U(VI) ranged from 6.0 to 8.0, while the sorption of 2-CP remained high over a broader pH range. The presence of 1.0–10.0 mg/L humic acid as TOC increased the adsorption of both chemicals. The key adsorption mechanism for U(VI) is ion-exchange at the –O− functional sites in the interlayers of TNTs, while 2-CP was taken up via hydrophobic interactions with ACF and capillary condensation. The adsorption synergy of U(VI) and 2-CP in the binary systems resulted from the complexation between U(VI) ions and phenolic groups of 2-CP and the cation–π interactions. TNTs/ACF appears promising for simultaneous removal of radionuclides and chlorinated chemicals from contaminated water.
Agrobacterium sp. LAD9 capable of heterotrophic-aerobic nitrogen removal was applied into a single biological aerated filter (BAF) for bioaugmented treatment of municipal wastewater. The achievement of simultaneous nitrogen and carbon removal in the bioaugmented system was systematically evaluated by ratios of COD to nitrogen (COD/N), ranging from 1 to 20. The results showed that at an appropriate COD/N ratio of 10, the BAF exhibited excellent carbon and nutrients removal, the averaged removal efficiencies for COD, NH4+-N and TN were 92.3%, 100% and 80.0%, respectively. Long-term operation of the bioaugmented system also confirmed the stability of the treatment efficiency. Further comparisons of SOUR and PCR-DGGE profiles between the bioaugmented and the control system revealed that the introduction of strain LAD9 greatly changed the structure of original microbial community and facilitated their capabilities of aerobic nutrients removal. The proposed bioaugmentation strategy is of particular importance to upgrading or retrofitting concurrent municipal wastewater treatment systems. [GRAPHICS] .