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Iron recovery from a lead slag in Henan province was carried out with the technique of coal-based direct reduction followed by magnetic separation. Scanning electron microscopy (SEM) was used to investigate the transformation of iron-containing minerals and the particle size of metallic iron generated by coal reduction. The results showed that technique is feasible for iron recovery from the lead slag. Under the conditions of weight ratio of slag: coal: CaO as 50:15:5, the roasted temperature of 1250 °C for 45 min, and then two stage of grinding and twice magnetic separation, the metallic iron powder was obtained with the iron grade of 92.85% and iron recovery of 92.85%. The iron-containing minerals in the forms of hercynite, fayalite and maghemite were mianly transformed into metallic iron and the particle size of metallic iron was more than 50μm. Therefore, the metallic iron in roasted product can be dissociated by coarse grinding and further was separated by magnetic separation to recover the metallic iron.

Graphene oxide (GO) is a promising two‐dimensional building block for fabricating high‐performance gas separation membranes. Whereas the tortuous transport pathway may increase the transport distance and lead to a low gas permeation rate, introducing spacers into GO laminates is an effective strategy to enlarge the interlayer channel for enhanced gas permeance. Herein, we propose to intercalate CO2‐philic MIL‐101(Cr) metal‐organic framework nanocrystals into the GO laminates to construct a 2D/3D hybrid structure for gas separation. The interlayer channels were partially opened up to accelerate gas permeation. Meanwhile, the intrinsic pores of MIL‐101 provided additional transport pathways, and the affinity of MIL‐101 to CO2 molecules resulted in higher H2/CO2 diffusion selectivity, leading to a simultaneous enhancement in gas permeance and separation selectivity. The MIL‐101(Cr)/GO membrane with optimal structures exhibited outstanding and stable mixed‐gas separation performance with H2 permeance of 67.5 GPU and H2/CO2 selectivity of 30.3 during the 120‐h continuous test, demonstrating its potential in H2 purification application.

Contact erosion during arcing is one of the main causes of electrical ageing of vacuum circuit breakers. The degree of contact erosion is controlled by the behaviours of cathode spots. Therefore, modification of cathode material and consequentially adjusting the cathode spot characteristics is of interest to mitigate contact erosion. In this paper, a simulation model of Molecular Dynamics (MD) is built to investigate the process of single cathode spot formation induced by the assumed leftover plasma ions. The heating factors of leftover plasma ions, back ions, and Joule heating, as well as the cooling effects of heat conduction, evaporation, and surface electron emission, are considered to achieve a self-consistent model. Based on simulation results, the influences of contact material characteristics on the process of cathode spot formation are discussed, such as the material type (copper, chromium and tungsten) and the crystal type (monocrystal and polycrystal). This work provides foundations for further analysis of cathode spot formation and studying of cathode spot dynamics for a complex alloy cathode.

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