Realizing the comprehensive utilization of fly ash is beneficial to reduce the environmental hazard. Herein, we propose a new route for synthesizing nano-scale kaolinite by a two-step hydrothermal method using fly ash as raw material. Above all, the feasibility of each step was determined by calculating the Gibbs free energy of the reaction. In 3 mol/kg sodium hydroxide solution at 240 °C, the glass sphere, quartz, and mullite in fly ash raw materials decomposed wholly and transformed to sodalite first and then hydroxycancrinite eventually. The intermediate product, hydroxycancrinite, dissolved in the HNO₃ solution quickly and precipitated to boehmite as a precursor, which combined with Si⁴⁺ from the solution and transformed to flaky kaolinite with a diameter of around 200 nm ultimately. This method has a potential in industrial-scale manufacturing of nano-size kaolinite and provides a new route for the green recycling of fly ash.

实现粉煤灰的综合利用，有利于减少环境危害。本文提出了一种以粉煤灰为原料的两步水热法合成纳米级高岭石的新途径。最重要的是，每个步骤的可行性是通过计算反应的吉布斯自由能来确定的。在240℃的3 mol / kg氢氧化钠溶液中，粉煤灰原料中的玻璃球，石英和莫来石会完全分解，先转化为方钠石，然后再转化为羟基钙锰矿。中间产物羟基钙锰矿快速溶解在HNO ₃溶液中并沉淀为勃姆石前体，并与Si ⁴⁺结合将其从溶液中转化为直径约200 nm的片状高岭石。这种方法在工业规模的纳米高岭石生产中具有潜力，并为粉煤灰的绿色回收提供了一条新途径。