粉煤灰提铝渣碱浸提硅动力学

摘要

Kinetics of SiO2 leaching from Al2O3 extracted slag of fly ash with sodium hydroxide solution was studied. The effect of leaching temperature, mass ratio of NaOH to SiO2 and stirring speed on SiO2 leaching rate was investigated. The results show that increasing leaching temperature, mass ratio of NaOH to SiO2 and stirring speed increases SiO2 leaching rate. The SiO2 leaching rate is 95.66%under the optimized conditions. There are two stages for the SiO2 leaching process, and the leaching reaction is very rapid in the first stage but quite slow in the second stage. The whole leaching process follows the shrinking core model, and the outer diffusion of no product layer is the rate-controlling step. The activation energies of the first and second stages are calculated to be 8.492 kJ/mol and 8.668 kJ/mol, respectively. The kinetic equations of the first and the second stages were obtained, respectively.%对粉煤灰提铝渣碱浸提硅过程的动力学进行研究。实验考察碱浸温度、碱硅比(NaOH与SiO2质量比)及搅拌速度对二氧化硅浸出率的影响。实验结果表明，升高碱浸温度、加大碱硅比及加强搅拌速度对浸出过程有利，在最优条件下，二氧化硅浸出率为95.66%。该浸出过程分为两个阶段，在第一阶段二氧化硅的浸出速率快，在第二阶段二氧化硅的浸出速率慢，两阶段均符合收缩核模型且受不生成固体产物层的外扩散控制。碱浸提硅过程第一阶段和第二阶段的反应活化能分别为8.492 kJ/mol和8.668 kJ/mol，分别求得这两个阶段的动力学方程。