烧结活化-酸浸法浸出粉煤灰中铝元素

为实现粉煤灰的高效资源化，并控制资源化过程中的能耗，采用NaOH为烧结助剂，利用烧结活化-酸浸法浸出粉煤灰中的铝元素；在探究最佳工艺条件的同时，通过分析烧结产物矿物组成及官能团的变化来探究粉煤灰烧结活化的机理。结果表明，当烧结温度为550 °C、NaOH/CFA 质量比=1.40、硫酸浓度为30%、烧结时间为10 min的条件下，铝元素浸出率可达95.00%以上。在粉煤灰烧结活化过程中，莫来石及非晶态硅铝化合物与NaOH反应，其中的铝氧八面体结构转变为铝氧四面体结构，铝氧四面体与硅氧四面体结构相结合形成以四元环和六元环为基本结构的铝硅酸盐，即八面沸石和霞石。在酸浸过程中，八面沸石和霞石与硫酸发生反应使铝元素以离子形式存在于酸浸液中，其中霞石相更有利于烧结产物的酸浸过程。该研究结果可为烧结活化-酸浸法浸出粉煤灰中铝元素提供参考。

Extraction of aluminum from coal fly ash by sintering-acid leaching process

In order to utilize coal fly ash efficiently and control the energy consumption during the utilization process, the NaOH sintering-acid leaching method was used to extract Al from coal fly ash in this study. The optimal conditions of the aluminum extraction process were explored, and the sintering activation mechanisms were discussed according to the changes of composition and functional groups of the sintered products. When the sintering temperature was 550 °C, the NaOH/CFA mass ratio was 1.40, the sulfuric acid concentration was 30%, and the sintering time was 10 min, the aluminum leaching efficiency was more than 95.00%. Mullite and amorphous aluminosilicate react with NaOH, and their alumina octahedron transform into alumina tetrahedron during the sintering activation process of coal fly ash. Meanwhile, alumina tetrahedron combine with the silicate tetrahedron to form aluminosilicates with 4-number ring and 6-number ring units, such as faujasite and nepheline. During the acid leaching process, faujasite and nepheline react with sulfuric acid. Aluminum element exists in the acid leaching solution in the form of ions after the acid leaching process, and the nepheline phase is more conducive to the acid leaching process of the sintered product. This study can provide certain supports for further researches on fly ash sintering-acid leaching aluminum extraction.