A method to prepare amorphous silica particles from zircon has been developed using the fluorination method through a three-step process: the fluorination of zircon using ammonium bifluoride at 230 ℃, the sublimation of (NH₄)₂SiF₆ at 300 ℃ and the hydrolysis of (NH₄)₂SiF₆. During above progress, the composition and phases of materials produced during fluorination of zircon were analyzed; the chemical reaction of silica with ammonium bifluoride, the sublimation behavior of (NH₄)₂SiF₆ and its composition were determined; the effect of hydrolysis temperature (30 ℃, 45 ℃ and 60 ℃) on the hydrolysis ratio of Si and the size of silica particles were investigated. The results indicated that (NH₄)₃ZrF₇ and (NH₄)₂SiF₆ formed after the fluorination of zircon at 230 ℃ for 5 hr. (NH₄)₂SiF₆ started to sublimate at 175 ℃, but the sublimation dominated at 280 ℃ and ended at 300 ℃. The hydrolysis results indicated that uni-modal silica particles in micrometer size range were produced at 45 ℃, while bi-modal particles in a variety of sizes ranging from nanometer to micrometer were produced at 30 ℃ and 60 ℃. The amorphous silica particles obtained at 45 ℃ exhibited high purity above 99.96 wt.%, narrow size distribution (average: 254 ± 17 nm), high specific surface (136.8 m²/g), high dibutyl phthalate (DBP)-absorption (2.7 cm³/g), low density (0.532 g/cm²) and pH (5.7). Therefore, the amorphous silica obtained has potential application as filler in plastic and rubber compounding. After the hydrolysis process, ammonium bifluoride can be recycled through the evaporation of NH4F solution. Thus, this work provides a novel strategy for processing zircon by ammonium bifluoride to produce amorphous silica particles and recycle of ammonium bifluoride.

已经开发出一种通过氟化方法通过三步法从锆石制备无定形二氧化硅颗粒的方法：在230℃下使用氟化氢铵对锆石进行氟化，在300℃下将（NH ₄）₂ SiF ₆升华和水解（NH ₄）₂ SiF _6的摩尔数。在上述进展过程中，分析了锆石氟化过程中产生的材料的成分和相。二氧化硅与氟化氢铵的化学反应，（NH ₄）₂ SiF ₆的升华行为确定其组成；研究了水解温度（30℃，45℃和60℃）对硅水解率和二氧化硅颗粒尺寸的影响。结果表明，锆石在230℃氟化5 hr后，生成（NH ₄）₃ ZrF ₇和（NH ₄）₂ SiF ₆。（NH ₄）₂ SiF ₆在175℃开始升华，但在280℃升华占主导，在300℃结束升华。水解结果表明，在45℃时产生了微米级的单峰二氧化硅颗粒，而在30℃和60℃时产生了从纳米级到微米级的各种尺寸的双峰二氧化硅颗粒。在45℃下获得的无定形二氧化硅颗粒具有高于99.96 wt。％的高纯度，窄尺寸分布（平均：254±17 nm），高比表面积（136.8 m ² / g），邻苯二甲酸二丁酯（DBP）吸收率高（2.7） cm ³ / g），低密度（0.532 g / cm ²）和pH（5.7）。因此，所获得的无定形二氧化硅在塑料和橡胶混炼中具有作为填料的潜在应用。水解过程后，可以通过蒸发NH4F溶液来回收氟化氢铵。因此，这项工作提供了一种通过氟化氢铵处理锆石以生产无定形二氧化硅颗粒和回收氟化氢铵的新策略。