Russian Journal of Non-Ferrous Metals | 2021
Effects of Diffusion with Electrode Spacing and Concentration Difference on Al2O3 Preparation from AlCl3 Solution by Electrotransformation
Abstract
With China’s bauxite resources depleting year by year, high-alumina fly ash has been regarded as a potential secondary aluminum resource, with alumina content as high as 40–60%. In view of recognized problems, such as large amounts of circulating acid and environmental pollution in the process of extracting alumina from high-alumina fly ash, Northeastern University has proposed a new electrotransformation method. This method has the main advantages of slag reduction, no waste acid, no waste alkali, and recycling. In this study, the effects of diffusion were examined during electrotransformation, in terms of electrode spacing and concentration difference on solution pH and temperature. In addition, the phase, FT-IR results, roasting weight loss rate of products, D(50), D(90), isothermal adsorption and desorption curves, BET surface area, pore volume, impurity chlorine content of roasted products, and Al recovery rate were investigated. The results showed that pH and temperature increased with prolonged electrotransformation time. And that these products were all amorphous containing-carbon aluminum salt precipitation. Roasted products were all alumina (Al2O3) with a steep broad X-ray diffraction peak. The effects of electrode spacing and concentration difference on isothermal adsorption and desorption curves, BET surface area, and pore volume were not clear. With decreased electrode spacing, the Al recovery rate increased and impurity chlorine content decreased. With increased concentration difference, the Al recovery rate tended to first decrease and then increase, while the impurity chlorine content increased. In other words, small electrode spacing and high concentration difference were beneficial for improving the Al recovery rate.