Promoting the stability and adsorptive capacity of Fe3O4-embedded expanded graphite with an aminopropyltriethoxysilane-polydopamine coating for the removal of copper(ii) from water.

In this study, three magnetic graphites, namely, EGF, GAF, and GFA + KH550, were prepared, which were loaded either with Fe3O4 or with Fe3O4 and PDA or with Fe3O4, PDA, and KH550 onto expanded graphite. ATR-FTIR, XRD, XPS, SEM, TEM, and TGA characterization results showed that EGF, GAF, and GFA + KH550 were successfully prepared. Under the same initial copper concentration, the removal rates of copper ions by EGF, GFA, and GFA + KH550 were 86.2%, 96.9%, and 97.0%, respectively and the hazard index reductions of the three adsorbents were 2191 ± 71 (EGF), 1843 ± 68 (GFA), and 1664 ± 102 (GFA + KH550), respectively. Therefore GFA + KH550 exhibited better removal of Cu(ii) than EGF and GFA, for PDA and KH550 provided more adsorption-active sites like -OH and -NH. Here, the adsorption of GFA + KH550 fitted the pseudo-second-order kinetic and Langmuir models well within the testing range, which means that adsorption occurs on a monolayer surface between Cu(ii) and the adsorption sites. The intraparticle diffusion model and various thermodynamic parameters demonstrated that Cu(ii) was adsorbed on GFA + KH550 mainly via external surface diffusion and that the process was both endothermic and spontaneous. Recycling experiments show that GFA + KH550 has a satisfactory recyclability, and the way of direct recovery by magnets exhibits good magnetic induction. GFA + KH550 was applied in lake water and artificial seawater samples, and exhibited better removal of copper than that in DI water under the same environmental conditions for the existence of macromolecular organic matter. Furthermore, the adsorption capacity of copper ions was not relative to the salinity of water. The application of GFA + KH550 demonstrated the potential for application in water treatment procedures.

Numerical Research on the Flow Fields in the Power Generation Channel of a Liquid Metal Magnetohydrodynamic System.

The flow fields in the power generation channel of a magnetohydrodynamic system, which uses a mixture of liquid metal as the power generation medium and a low-boiling-point working medium as the carrying medium, were numerically investigated in the present paper. The influences of the magnetic field intensity, void fraction, and bubble diameter were examined, respectively. The results indicate that an increase in the magnetic field intensity will enhance the turbulence intensity and may reduce the stability of the flow fields, whereas increasing the void fraction will contribute to better flow stability in the power generation channel. The effect of the bubble diameter on the flow field stability is negligible in the range of the study. In addition, it is found that the volume fraction of the gas phase exhibits an M-shape distribution by studying the variation of the slip velocity over time. This paper presents our latest findings and will provide a fundamental theory for future design and operation of liquid metal magnetohydrodynamic systems.

Influences of the Geometry of the Scavenge Pipe on the Air-Oil Two-Phase Flow and Heat Transfer in an Aero-Engine Bearing Chamber.

In order to improve the characteristics of the air-oil two-phase flow and heat transfer in the scavenge pipe of an aero-engine bearing chamber, this paper presents several scavenge pipes with different cross-sectional geometries, by numerically investigating the processes of the air-oil two-phase flow and heat transfer, in comparison to a circular pipe. The findings indicate that the tripetal cross-section shows the best heat-transfer effect, while the four-petal cross-section has the lowest flow resistance. Under the same working condition and the equal wetted perimeter, the tripetal cross-section has an 8.8% higher heat-transfer effect than the circular section, while the four-petal cross-section has a 28.6% lower flow resistance than the circular; under the equal cross-sectional area, the tripetal cross-section has a 9.1% higher heat-transfer effect than the circular section, while the four-petal cross-section has a 23.6% lower flow resistance than the circular; under the equal hydraulic diameter, the tripetal cross-section has a 9.2% higher heat-transfer effect than the circular section, while the four-petal cross-section has a 21.9% lower flow resistance than the circular. Taking both the heat transfer and flow resistance into consideration, the four-petal cross-section exhibits the best comprehensive performance, with the comprehensive performance coefficient decreasing with the increase of oil inlet velocity and rising with the increase of air inlet velocity.