This article looks into process of supercritical-CO₂ phosphogypsum (PG) conversion, which is production residue after making mineral fertilizers by "Kasphosphate" LLC. Nowadays, over 30 million tons of PG have been accumulated in Kazakhstan; its background radiation is low enough to recycle it into valuables such as construction materials, rare earth elements and strontium salts. Complete factorial experiment method was used to describe conversion process; conversion of PG into CaCO₃ was optimized using simplex method. Conversion optimization outcomes show possibility of using fewer reagents and shortening conversion process compared to existing technologies. Conversion degree is 87% after 10 min at 33 °С. Conversion was carried out at semi-industrial supercritical equipment with maximum CO₂ flow rate up to 5000 g/min and integrated CO₂ recirculation system. Characteristics of initial PG samples and conversion products/semi-products were done using X-ray phase analysis, scanning electron microscopy, atomic absorption spectroscopy, ICP-MS, and gravimetric procedure. In order to obtain purer CaCO₃ PG was cleared of water-soluble impurities beforehand. As conversion result, finely dispersed CaCO₃ and Ca(HCO₃)₂ as well as Na₂SO₄ solution were obtained.

本文研究了超临界-CO ₂磷石膏（PG）转化过程，这是“Kasphosphate”有限责任公司生产矿物肥料后的生产残渣。目前，哈萨克斯坦已经积累了超过3000万吨的PG；它的背景辐射足够低，可以将其回收成有价值的物品，例如建筑材料、稀土元素和锶盐。采用完全析因实验法描述转化过程；PG转化为CaCO ₃采用单纯形法进行优化。转化优化结果表明，与现有技术相比，可以使用更少的试剂并缩短转化过程。在 33°С 下 10 分钟后转化度为 87%。_{在最大CO 2}流速高达5000 g/min和集成CO ₂再循环系统的半工业超临界设备上进行转换。使用 X 射线物相分析、扫描电子显微镜、原子吸收光谱、ICP-MS 和重量分析程序对初始 PG 样品和转化产物/半产物进行了表征。为了获得更纯的CaCO ₃ PG，预先清除了水溶性杂质。作为转化结果，精细分散的 CaCO ₃和 Ca(HCO₃ ) ₂以及Na ₂ SO ₄溶液得到。