Bauxite reaction residue (BRR) produced from the poly-aluminum chloride (PAC) coagulant industry is a solid acidic waste that is harmful to environment. A low temperature synthesis route to convert the waste into water glass was reported. Silica dissolution process was systematically studied, including the thermodynamic analysis and the influence of calcium and aluminum on the leaching of amorphous silica. Simulation studies have shown that calcium and aluminum combine with silicon to form hydrated calcium silicate, silica–alumina gel, and zeolite, respectively, thereby hindering the leaching of silica. Maximizing the removal of calcium, aluminum, and chlorine can effectively improve the leaching of silicon in the subsequent process, and corresponding element removal rates are 42.81%, 44.15%, and 96.94%, respectively. The removed material is not randomly discarded and is reused to prepare PAC. The silica extraction rate reached 81.45% under optimal conditions (NaOH; 3 mol L −1 , L S −1 ; 5/1, 75°C, 2 h), and sodium silicate modulus ( n SiO 2 : n Na 2 O) is 1.11. The results indicated that a large amount of silica was existed in amorphous form. Precipitated silica was obtained by acidifying sodium silicate solution at optimal pH 7.0. Moreover, sodium silicate (1.11) further synthesizes sodium silicate (modulus 3.27) by adding precipitated silica at 75°C.

中文翻译：

---

从铝土矿反应残留物中提取二氧化硅和水玻璃的合成

聚氯化铝（PAC）混凝剂工业产生的铝土矿反应残留物（BRR）是一种酸性固体废物，对环境有害。据报道，有一种低温合成路线可将废物转化为水玻璃。系统地研究了二氧化硅的溶解过程，包括热力学分析以及钙和铝对无定形二氧化硅浸出的影响。模拟研究表明，钙和铝与硅结合形成水合硅酸钙，二氧化硅-氧化铝凝胶和沸石，从而阻碍了二氧化硅的浸出。最大限度地去除钙，铝和氯可有效改善后续工艺中硅的浸出，相应的元素去除率分别为42.81％，44.15％和96.94％。去除的材料不会随机丢弃，可重新用于制备PAC。在最佳条件下（NaOH; 3 mol L -1，LS -1; 5/1，75°C，2 h），二氧化硅的萃取率达到81.45％，硅酸钠模量（n SiO 2：n Na 2 O）为1.11。结果表明，大量存在的非晶态二氧化硅，通过在最适pH 7.0下酸化硅酸钠溶液得到沉淀二氧化硅。而且，硅酸钠（1.11）通过在75℃下添加沉淀的二氧化硅来进一步合成硅酸钠（模量3.27）。通过在最佳pH 7.0下酸化硅酸钠溶液，可获得沉淀二氧化硅。而且，硅酸钠（1.11）通过在75℃下添加沉淀的二氧化硅来进一步合成硅酸钠（模量3.27）。通过在最佳pH 7.0下酸化硅酸钠溶液，可获得沉淀二氧化硅。而且，硅酸钠（1.11）通过在75℃下添加沉淀的二氧化硅来进一步合成硅酸钠（模量3.27）。