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Many well-established models can be applied to calculate the filtration efficiencies. In these models the filtration velocity and challenging particle size are assumed to be known accurately. However, in realistic filtration tests, the filtration velocity has profiles dependent on the filter holder geometry and experimental conditions; the challenging particles have size distributions dependent on the instruments and operation conditions. These factors can potentially affect the measured filtration efficiency and lead to discrepancies with the models. This study aims to develop an integrative model to predict the filtration efficiencies in realistic tests by incorporating the effects of the filtration velocity profile and challenging particle size distribution classified by a differential mobility analyzer (DMA) into the existing filtration models. Face velocity profile is modeled with fluid mechanics simulations; the initial generated particle size distribution, the particle charging status and the DMA transfer function are modeled to obtain the challenging particle size distribution. These results are then fed into the filtration models. Simulated results are compared with experimental ones to verify the model accuracy. This model can be used to reduce filtration test artifacts and to improve the experimental procedure. The results reveal that the face velocity upstream the filter exhibits high degree of homogeneity not affecting the filtration efficiency if the filter pressure drop is not very low. The generated particle size distribution and the DMA selection size window could influence the challenging particle size distribution and therefore the measured filtration efficiency. Copyright © 2017 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

MnO 2 - and Ag- based micromotors were developed recently as new types of micromotors with the advantage of low costs and have been utilized to treat environmental pollutants. However, knowledge about the effects of ambient conditions on the performance of them is still lacking. In this article, the influences of pH, electrolytes and surfactant on the treatment of organic dye (with methylene blue as the representative) by the commercial MnO 2 and Ag micromotors with H 2 O 2 as the fuel were studied. In the motion visualization experiments, besides the routine types of trajectories, the circular motion of micromotors around the already formed bubbles was observed for the first time. In the pollutant removal experiments, two abatement mechanisms (catalytic degradation and adsorptive bubble separation) were studied. The decolorization efficiency for MnO 2 due to catalytic degradation increased with the increasing pH, which disagreed with previous studies in which no H 2 O 2 was added. The inhibitory effects of the tested electrolytes were in the order: CaCl 2 >NaNO 3 >NaCl. Surfactant can increase the decolorization efficiency only under highly alkaline conditions. For Ag, decolorization only occurs with the existence of surfactant at high pH values (pH = 11.4) indicating that the dominant mechanism is adsorptive bubble separation., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Material flow studies have shown that a large fraction of the engineered nanoparticles used in products end up in municipal waste. In many countries, this municipal waste is incinerated before landfilling. However, the behavior of engineered nanoparticles (ENPs) in the leachates of incinerated wastes has not been investigated so far. In this study, TiO 2 ENPs were spiked into synthetic landfill leachates made from different types of fly ash from three waste incineration plants. The synthetic leachates were prepared by standard protocols and two types of modified procedures with much higher dilution ratios that resulted in reduced ionic strength. The pH of the synthetic leachates was adjusted in a wide range (i.e. pH 3 to 11) to understand the effects of pH on agglomeration. The experimental results indicated that agglomeration of TiO 2 in the synthetic landfill leachate simultaneously depend on ionic strength, ionic composition and pH. However, when the ionic strength was high, the effects of the other two factors were masked. The zeta potential of the particles was directly related to the size of the TiO 2 agglomerates formed. The samples with an absolute zeta potential value < 10 mV were less stable, with the size of TiO 2 agglomerates in excess of 1500 nm. It can be deduced from this study that TiO 2 ENPs deposited in the landfill may be favored to form agglomerates and ultimately settle from the water percolating through the landfill and thus remain in the landfill., (Copyright © 2017 Elsevier Ltd. All rights reserved.)