粉煤灰提铝残渣碱浸过程中氧化硅的溶出行为

Dissolution behavior of silicon oxide during alkali leaching of aluminum residue from fly ash

为了提高粉煤灰的综合利用率,以循环流化床粉煤灰“一步酸溶法”提取氧化铝后高硅尾渣为原料,通过碱液浸出方式提高了氧化硅的回收率;考察了碱浓度、液固比、反应温度和反应时间对氧化硅溶出行为的影响,探究了碱浸脱硅动力学。结果表明:碱浓度、浸出温度对氧化硅溶出率的影响显著;当碱浓度为4.0 mol/L、浸出温度为70℃时,氧化硅溶出率达到64.70%;然而随反应温度继续上升,氧化硅溶出率降低,归因于硅酸根结合铝酸根形成方沸石;反应动力学表明:前10~40 min高硅尾渣中氧化硅碱浸反应的表观活化能为8.247 kJ/mol,遵循液体边界层扩散控制的核收缩模型。

In order to improve the comprehensive utilization of fly ash, the alkali leaching treatment of the high-silica tailings was carried out to improve the recovery rate of silicon oxide, the tailings were obtained by "one-step acid leaching process" of circulating fluidized bed fly ash to extract alumina. The effects of alkali concentration, liquid-to-solid ratio, reaction temperature and reaction time were studied on the dissolution behavior of silicon oxide, meanwhile, the alkali leaching desilication kinetics were explored. The results showed that the alkali concentration and leaching temperature could significantly affect the dissolution rate of silicon oxide. The dissolution rate of silicon oxide could reach 64.70% at the reaction temperature of 70℃ and with the alkali concentration of 4.0 mol/L. While along with the increase of reaction temperature, the dissolution rate of silicon oxide decreased, which was due to the formation of analcite between silicate and aluminate. The reaction kinetics result showed that in the first 10~40 min of the alkali leaching of silicon oxide in high-silica tailings, the apparent activity energy was 8.247 kJ/mol, which followed the shrinking core model with liquid boundary layer diffusion control.