Search

Previous simulations of three-phase fluidization systems based on the Euler-Lagrange approach have made progress in the studies of bubble and suspension dynamics. However, for guiding the operation and design of reactors, it is obviously more practical to obtain the phase holdup characteristics under the steady state. In this study, the hydrodynamic simulations on the gas–liquid-solid mini-fluidized beds (GLS-mFBs) were performed from the initial introduction of bubbling flow to the steady three-phase fluidization using the coupling model of volume of fluid (VOF) and discrete element method (DEM). After the initial process of bubbling flow accompanied by redistribution of phase holdups, i.e., the contraction of fluidized bed, the steady state of the GLS-mFB was achieved and maintained by the interactions between bubbles and fluidized bed. The axial and radial profiles of phase holdups in the steady GLS-mFBs, which is difficult to measure through experiments, are obtained and discussed. It is found that the suspension resistance against the rising bubbles is strengthened by the wall confining effect arising from the shrinkage of bubble-wall gap under smaller column diameter, and the phase holdup characteristics and bubble dynamics are investigated and explained by this effect. The bubble wake, which plays an important role in the momentum exchange between bubbles and suspension, is analyzed in terms of formation mechanism and size changes. It is proved that the VOF-DEM simulation is an effective method to predict the phase holdups of the GLS-mFBs and explain the underlying hydrodynamic mechanism.

In this paper, a novel ion-selective and ultra-strong poly-m-phenyleneisophthalamide (PMIA)-based gel polymer electrolyte (GPE) containing fluorinated emulsion and octa(aminophenyl)silsesquioxane (OAPS) nanoparticles is rationally designed for lithium-sulfur batteries by electrospinning. Under the significant effect of OAPS, the PMIA-based GPE acts as a multi-functional separator with exceedingly high electrolyte uptake, exceptional thermal stability and robust mechanical strength. Particularly, the -NH2 groups of OAPS provide an electronegative environment, which facilitate the lithium ions migration while inhibit the negative polysulfide anions transfer. Thus, the PMIA-based GPE exhibits an effective electrostatic shielding effect to restrain lithium polysulfide on cathode side, while vigorously stimulating the transmission of lithium ions. As a great result, the lithium ions migration, the interface impedance and the reversible rate capacity of the assembled lithium-sulfur battery obtain a marked improvement. Meantime, the cell with the PMIA-based separator, adopting conventional sulfur-carbon black as cathode materials, delivers a high initial capacity of 851.1 mAh·g−1 with capacity retention of 458.3 mAh·g−1 after 800 cycles at 0.5 C rate, accompanied by a low capacity decay of 0.057% per cycle. Therefore, the prepared PMIA separator imbedding with OAPS can be deemed as an extraordinary potential candidate for the application in high-performance lithium-sulfur cells.

The bimetallic Fe–Cu/O 2 process exhibited significantly higher reactivity than did the Fe/O 2 process for the degradation of ethylenediaminetetraacetic acid (EDTA). With the analysis of the soluble Cu 2+ in the solution and decomposition of H 2 O 2 catalyzed by Cu 0 , possible enhanced-pathways at different pHs were suggested. The degradation efficiency of EDTA increased with decreasing initial pH ranging 3–9, however, the reactions proceeded at a weakly-basic to basic condition in most of the reaction time. POD inhibition test showed that in situ generation of H 2 O 2 played a pivotal role in the EDTA degradation, however, the instant concentration analyzed by DPD–POD method was less than 4.5 μM due to rapid subsequent Fenton reaction. Furthermore, DMPO–ESR spectroscopy and BA-trapping experiments detected the in situ generation of OH. The mechanism of EDTA oxidative degraded by the bimetallic Fe–Cu/O 2 process was verified using control experiments of absorption, stripping, and coagulation sedimentation of EDTA in the system, analysis of solid residue, oxidation of O 2 and H 2 O 2 , as well as detection of H 2 O 2 and OH.