Yi Ren,Mengqi Shi,Weiming Zhang,Dionysios D. Dionysiou,Junhe Lu,Chao Shan,Yanyang Zhang,Lu Lv,Bingcai Pan
A novel Fenton-like catalyst was synthesized by immobilizing nano-Fe2O3 (nFe2O3) on MIL-53(Cu). The pseudo-first-order rate constant of bisphenol A degradation in the nFe2O3/MIL-53(Cu)/H2O2 system reached 0.0123 min–1, while the values in MIL-53(Cu)/H2O2 and nFe2O3/H2O2 systems were only 0.0026 and 0.0040 min–1, respectively. The characterization of nFe2O3/MIL-53(Cu) reveals that the supreme catalytic activity of this material could be ascribed to iron–copper synergy, smaller size, and better dispersion of nFe2O3 particles. Moreover, a method of trapping Cu(I) by neocuproine was developed, which could shield Cu(I) from interacting with iron and H2O2, and thus allow quantitative differentiation of the contribution to the enhanced catalytic activity by each of the factors. Using this method, 19% of the enhancement was determined to be contributed by synergistic effect, while 24% of the enhancement was due to the smaller size and better dispersion of the nFe2O3 particles on MIL-53(Cu) support. In addition, the performance of nFe2O3/MIL-53(Cu) only dropped 10.7% after five treatment cycles in real wastewater, showing good potential in practical application. We believe this study sheds light on the tailored design of Fenton-like catalysts and elucidates the catalytic mechanisms of supported bimetallic catalysts.
Aluminum particles have the problems of difficult ignition, easy agglomeration, incomplete combustion, etc. Therefore, it is of great scientific significance and engineering value to find ways to improve the ignition and combustion performance of aluminum particles in order to promote the full release of energy of aluminum particles. In this paper, spherical nano-sized ferric oxide (nFe 2 O 3 ) and ammonium perchlorate (AP), a commonly used oxidizer in propellants, were used to synergistically improve the ignition and combustion performance of aluminum particles. AP modified the aluminum particles by both mixing and coating methods, respectively. On the basis of coating AP, nFe 2 O 3 was added in order to further enhance the ignition and combustion performance of the aluminum particles. Scanning electron microscope, laser particle size analyzer, thermal analysis system and laser ignition experiment system were used to test the physicochemical properties and ignition combustion performance of different samples. The results showed that AP and nFe 2 O 3 could be coated relatively uniformly on the surface of aluminum particles using the recrystallization method. The thermal reaction behavior of the samples showed that coating was beneficial to the decomposition of AP compared with mixing, and the addition of nFe 2 O 3 could further improve the decomposition efficiency of AP. Ignition and combustion experiments showed that coating AP was more conducive to improving the ignition and combustion performance of aluminum particles than mixing AP, and the addition of nFe 2 O 3 could further significantly enhance the combustion intensity and flame propagation speed of the sample. However, the addition of nFe 2 O 3 increased the ignition delay time of the sample, which may be related to the cold agglomeration phenomenon caused by the nanoparticles. The microscopic combustion flame morphology of different samples showed that coating AP and the introduction of nFe 2 O 3 could significantly reduce the agglomeration phenomenon of aluminum particles. Overall, coating AP reduces the distance between the aluminum particles and the oxidizer, thus significantly improving the ignition and combustion performance of the aluminum particles. The addition of nFe 2 O 3 can further improve the combustion performance of aluminum particles, but at the same time, it also increases the ignition delay time. Hence, the cold agglomeration problem caused by nanoparticles should be fully considered when nFe 2 O 3 is used to improve the ignition and combustion performance of aluminum particles.
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