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Effective separation of fusing agent from refined magnesium slag by supergravity technology
No full textSupergravity separation by high-temperature centrifugation is an effective and environmentally friendly method for separating and recycling waste refined magnesium slag. Based on the close density and greatly different wettability characteristics of fusing agent and inclusion in the refined magnesium slag, present work focused on the recovery of fusing agent from refined magnesium slag by supergravity separation. In a supergravity field, fusing agent and inclusions appeared obvious stratification phenomenon in the enrichment. The fusing agent with the purity of 97.9 wt% was obtained and filtered from waste refined magnesium slag by supergravity separation. The gravity coefficient (G) and reaction temperature (T) were favorable to the enrichment and separation of fusing agent. Under the optimal conditions of G = 400 and T = 500 degrees C, the fusing agent yield and recovery rate were 50.34% and 70.81%, respectively. The content of inclusion in the recovered fusing agent was less than 2.01 wt%, which meets the recycling demand of refined magnesium. The results indicated that supergravity technology provided a clean and efficient method for reclaiming valuable components from waste refined magnesium slag and creating significant economic and environmental benefits
Insight on the effect of Ni and Ni-N co-doping on SnO2 anode materials for lithium-ion batteries
No full textWith the increased demand for high-rate performance Li-ion batteries, it is necessary to find available methods to improve the rate properties of SnO2 electrodes. It is noteworthy that doping was considered to be a feasible means. The electronic structures and diffusion energy barriers of Ni-doped and Ni-N co-doped SnO2 were calculated based on density functional theory. The results estimated that the energy gaps of Ni-doped and Ni-N co-doped SnO2 are 1.07 eV and 0.94 eV, which both are smaller than the value of 2.08 eV of SnO2. These exhibit that the conduction properties of SnO2 can be enhanced by doping with the Ni or Ni-N atoms. Moreover, the diffusion properties of Li can also be improved by doping with Ni-N atoms due to the diffusion energy barrier of Li from the B to C point for Ni-N co-doped SnO2 being 0.12 eV smaller than the value of 0.24 eV for the pristine SnO2. Meanwhile, the diffusion energy barriers of Li along other pathways for Ni-N co-doped SnO2 are almost the same as 0.24 eV for SnO2. These results show that both the electronic and ionic conductivity of SnO2 can be enhanced by Ni-N co-doping, which provides a theoretical explanation to promote the rate properties of SnO2 by Ni-N co-doping as anode materials for Li-ion batteries
Revealing the Ca resistance enhancement mechanism for the NH3-SCR reaction over VTi catalyst by CuO modification
No full textCurrently, NOx emission control by the selective catalytic reduction of NOx with NH3 (NH3 SCR) technology for the cement industry has become urgent in China. The poisoning effect of Ca species from cement flue gas on V2O5/TiO2(V/Ti) catalysts still faces severe challenges. For the first time, CuO was investigated for the possibility of Ca resistance enhancement on V/Ti catalysts. The activity tests show that the Ca CuV/Ti catalyst maintains a good performance with an NO conversion above 80% between 260 330 degrees C, while the highest NO conversion of Ca V/Ti in the test temperature range is only 52.4%. According to the characterization results, CaO is easier to adsorb on CuO than V2O5, thus retaining the V active sites. Due to the cycles of 2Cu(2+) + V3+ 2Cu(+) + V5+, CuO modification can significantly improve the redox ability of the V/Ti catalyst. In situ DRIFTS results show that the effect of CaO poisoning on the adsorption rate and reactivity of NHx over Ca CuV/Ti is less than that of Ca V/ Ti. CaO even promotes the formation of the active nitrate species over CuV/Ti, which is the main reason for its strong Ca resistance. This study provides theoretical support for the industrial application of anti Ca poisoning SCR catalysts
<p>Stability of amorphous neodymium carbonate and morphology control of neodymium carbonate in non-hydrothermal synthesis</p>
No full textRare earth carbonates have shown great application value and potential in the process of preparing rare-earth materials. In this work, a non-hydrothermal method of uniform feeding was used to determine the nucleation kinetics of neodymium carbonate. On this basis, the crystallization process and evolution of amorphous phase were studied. For the first time, it is determined the macroscopic crystallization rate of neodymium carbonate follows a zero-order reaction. The primary nucleation activation energy is 36.98 kJ/mol, indicating that the formation of Nd2(CO3)3 is controlled by a mixture of diffusion and chemical reaction. In the initial stage of precipitation, spherical amorphous neodymium carbonate with diameter of 20 nm was formed, with the molecular formula being Nd-2(CO3)(3).1.87H(2)O, and subsequently crystallized into tengerite-(Nd) [Nd-2(CO3)(3).2.5H(2)O] and lanthanite-(Nd) [Nd-2(CO3)(3).8H(2)O]. The stability of the amorphous neodymium carbonate in anhydrous environment and aqueous solution was evaluated, and ion potential was used to judge the stability trend of the rare earth carbonates. During the transition from amorphous phase to crystal, it is found temperature and supersaturation play an important role in the morphology of the final product. The results provide a reference for evaluating the crystallization process and developing large-scale industrial production methods
