In this work, a two-step wet carbonation process was developed to synthesize amorphous nano-silica by extracting the silicon phase from recycled cement fines (RCF), aiming to convert RCF into value-added products and sequester CO₂. The phases evolution and their microstructure during carbonation were investigated. The results indicated that the RCF was carbonated rapidly to form a mixture of calcite and amorphous silica gel, followed by the formation of silica bearing gel containing aluminosilicate gel and silica gel after two-step wet carbonation. An amorphous silica with a purity of 98.8% and in the form of aggregated nanoparticles (<10 nm) was successfully prepared, and another calcium carbonate-rich material was produced as a by-product. The proposed approach tackled several issues such as sequestration of CO₂ (0.27 g CO₂ per 1 g RCF), converting RCF into value-added nano-silica and promoting the recycling of RCF, which has good potential to be industrialized.

在这项工作中，开发了一种两步湿式碳酸化工艺，通过从回收水泥细粉 (RCF) 中提取硅相来合成无定形纳米二氧化硅，旨在将 RCF 转化为增值产品并封存 CO ₂. 研究了碳化过程中的相演变及其微观结构。结果表明，RCF迅速碳酸化，形成方解石和无定形硅胶的混合物，然后经过两步湿法碳酸化后形成含硅铝凝胶和硅胶。成功制备了纯度为 98.8% 且呈聚集纳米粒子形式 (<10 nm) 的无定形二氧化硅，并产生了另一种富含碳酸钙的副产物。所提出的方法解决了多个问题，例如固存 CO ₂（每 1 g RCF 0.27 g CO ₂）、将 RCF 转化为具有附加值的纳米二氧化硅以及促进 RCF 的回收利用，具有良好的工业化潜力。