Papers by Author: Yong Nian Dai

Abstract: The extraction of aluminum by the AlCl disproportionation process in vacuum was researched using the furnace designed by ourselves. The features of aluminum products were characterized by X-ray diffraction, scanning electronic microscope and energy-dispersive X-ray spectroscopy. The results indicated that the purity of aluminum products increased with decreasing condensation temperature; aluminum products could be oxidized as their size was too small; the residues of the extraction of aluminum from alumina could be further treated with this process to generate metallic aluminum with a little carbon; aluminum products with high Al₄C₃, C and Al₂O₃ impurities could be purified by this process. The conclusions could provide bases for the industrial application of the process.

Abstract: 4-Bromo-1, 8-naphthalic anhydride and N, N-Dimethylethylenediamine covalently modified silica nanoparticles were synthesized. It can be utilized as an adsorbent for Pb (II), showing excellent adsorption capacity. According to the Langmiur fitting, the maximum adsorption capacity for lead ion is up to 293.26 mg/g. And the adsorption percentage is greater than 90 % when the initial concentration is lower than 100 mg/l.

Abstract: In this study, high-purity Li₂CO₃ was prepared by carbonation-decomposition and ion-exchange methods using the industrial-grade lithium carbonate, and the effect of cycles and ion-exchange of the mother liquor on purification was investigated. Results showed that the process of cycles can improve the purity and productivity of Li₂CO₃. The impurities (such as K, Na, Ca and Mg) could be removed in the process. The purity of product decreased and the impurity contents increased after 4 cycles. At the same time, the ion-exchange process by D412 resin was used to deeply remove the residual Ca and Mg after the simple carbonation-decomposition and cycle process. The comparison of different flowing speed of solution through the ion-exchange resin indicated that the low flowing speed was beneficial for the deep removal of the Ca and Mg. considering the problem of efficiency, the flowing speed of 10-20 ml/min was appropriate. The high purity and productivity of Li₂CO₃ indicated that the carbonation-decomposition method combining with the mother liquor cycles and ion-exchange method has a good perspective in the field of lithium carbonate purification.

Abstract: In this paper, removal of iron from metallurgical grade silicon with pressure leaching is carried out. We investigated the factors such as the concentration of hydrochloric, particle size of raw material ground, temperature, pressure and reaction time, which influenced on the removal of iron. The results show that the optimum operating conditions for pressure leaching in hydrochloride are: acid concentration 4 mol/L, diameter for raw material less than 50 μm, leaching temperature 160 0C，leaching pressure 2.0 MPa, leaching time 2.0 h. The content of iron residual in MG-Si powder was reduced to about 200 ppmw. The removal efficiency of iron is up to 90.90 %.

Abstract: Chemical modified silica fume by polyaniline was studied as a sorbent for removal of chromium (VI) determined by flame atomic absorption spectrometer. TEM analysis confirmed that the mean diameter of silica fume before and after treatment was of the order of 120 nm. The functionalized nanoparticles showed an extremely high efficiency towards chromium (VI) in the pH range of 4-5. Adsorption of chromium (VI) from water using functionalized silica fume was both a simple and efficient approach compared to the traditional adsorbents from the angle of integrated utilization of the secondary resources.

Abstract: The diffusion layer and melt of silicon-boron are respectively obtained after quenched in water at 1300 oC by using metallurgical grade silicon (MG-Si) powder and amorphous boron powder. The phase equilibria for boron in MG-Si have been investigated by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The back scattered electron (BSE) image of diffusion layer displays the intermediate phase SiB4 in silicon-boron phase band, and the XRD results also indicate that SiB4 exists in silicon-boron diffusion layer at 1300 oC. It is inferred that the intermediate phase SiB4 is formed by the reaction (Si) + SiB6 ↔ SiB4 according to the equilibrium composition of Si/B=4/1 as quantified by Energy Dispersive Spectroscopy.

Abstract: The carbothermal reduction of alumina in a vacuum was investigated by XRD and thermodynamic analysis. Experiments on mixtures of alumina and graphite in a vacuum furnace at 1743-1843K proved that the residues consisted of Al2O3and C, and the deposits formed on the upper wall of the crucible contained Al4O4C, C, Al4C3 and Al2O3. Thermodynamic analysis indicated that alumina should react with carbon to form gaseous Al2O and Al above 1671K and 1713K at 100Pa respectively, Al2O and Al react back with CO to form Al4O4C, C, Al4C3 and Al2O3, which constitute deposits.