1. Preparation of sodium manganate from low-grade pyrolusite by alkaline predesilication-fluidised roasting technique.
- Author
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Deng Xiang-yi, Du Zhu-wei, Feng Ya-li, Guo Cheng-lin., Kang Jin-xing, Li Hao-ran, Deng Xiang-yi, Du Zhu-wei, Feng Ya-li, Guo Cheng-lin., Kang Jin-xing, and Li Hao-ran
- Abstract
Low concentration alkaline leaching was used for predesilication treatment of low-grade pyrolusite. The effects of initial NaOH concentration, liquid-to-solid ratio, leaching temperature, leaching time and stirring speed on the silica leaching rate were investigated and the kinetics of the alkaline leaching process was studied. Results show that the silica leaching rate reached 91.2% under the conditions of initial NaOH concentration of 20%, liquid-to-solid ratio of 4:1, leaching temperature of 180 degrees C, leaching time of 4 h and stirring speed of 300 r/min. The shrinking-core model showed that the leaching process was controlled by the chemical surface reaction with activation energy Ea of 53.31 kJ/mol. The fluidised roasting conditions for preparation of sodium manganate were optimised by orthogonal experiments using the desiliconised residue. The conversion rate of sodium manganate was obtained to be 89.7% under the conditions of silica leaching rate of 91.2%, NaOH/MnO2 mass ratio of 3:1, roasting temperature of 500 degrees C and roasting time of 4 h, and it increased with the increase of silicon leaching rate., Low concentration alkaline leaching was used for predesilication treatment of low-grade pyrolusite. The effects of initial NaOH concentration, liquid-to-solid ratio, leaching temperature, leaching time and stirring speed on the silica leaching rate were investigated and the kinetics of the alkaline leaching process was studied. Results show that the silica leaching rate reached 91.2% under the conditions of initial NaOH concentration of 20%, liquid-to-solid ratio of 4:1, leaching temperature of 180 degrees C, leaching time of 4 h and stirring speed of 300 r/min. The shrinking-core model showed that the leaching process was controlled by the chemical surface reaction with activation energy Ea of 53.31 kJ/mol. The fluidised roasting conditions for preparation of sodium manganate were optimised by orthogonal experiments using the desiliconised residue. The conversion rate of sodium manganate was obtained to be 89.7% under the conditions of silica leaching rate of 91.2%, NaOH/MnO2 mass ratio of 3:1, roasting temperature of 500 degrees C and roasting time of 4 h, and it increased with the increase of silicon leaching rate.