Abstract:

Phosphogypsum (PG) was used as raw material, Ca²⁺ was leached from PG by sodium D-gluconate, and then CO₂ was captured by the leaching solution to prepare calcium carbonate powder. The effects of liquid-solid mass ratio and reaction temperature on leaching rate of Ca²⁺, as well as the effects of ammonia addition and carbonization time on the conversion rate of Ca²⁺ were studied. The morphological characteristics and formation mechanism of carbonized products under different ammonia additions and carbonization times were analyzed by scanning electron microscope, X-ray diffraction and particle size analysis. The results showed that the Ca²⁺ leaching rate increased with the increase of liquid-solid mass ratio and the Ca²⁺ leaching rate of PG increased from 91% to 100% when the reaction temperature decreased from 85℃ to 25℃. Under the reaction temperature of 20℃ and CO₂ concentration of 20%, the calcium carbonate particle size distribution interval showed a decreasing trend with the increase of ammonia addition and carbonization time, and the Ca²⁺ conversion rate was increasing. When the amount of ammonia added was 20mL and the carbonization time was 150min, the conversion rate of CaCO₃ was up to 92.7% and the carbonization product was rounded rhombic calcite with the peak particle size as well as the median particle size of 1.5μm and 5μm, respectively. The increase of ammonia addition in the reaction solution was more conducive to the formation of calcite, and the increase of carbonation time promoted the formation of spherulite aragonite. However, the number of carbonization products decreased abruptly with the decrease of Ca²⁺ in the reaction solution. Due to the poor stability of the generated spherical chalcocite and the role of the organic solvent D-gluconate sodium solution, the reaction products would undergo dissolution and recrystallization, and form rounded rhombic calcite with a small and uniform particle size. This study provided a new process method for the comprehensive utilization of PG as well as the capture of CO₂ and preparation of calcium carbonate powder.

Key words: phosphogypsum, carbonization, sodium D-gluconate, calcium carbonate powder

摘要：

以磷石膏为原料，采用D-葡萄糖酸钠浸取磷石膏中Ca²⁺，再以该浸出液固定CO₂制备碳酸钙微粉。研究了液固质量比、反应温度对Ca²⁺浸出率的影响，以及氨水添加量、碳化时间对Ca²⁺转化率的影响。通过扫描电子显微镜、X射线衍射仪、粒度分析等方法分析了不同氨水添加量、碳化时间下碳化产物的形态特征及生成机理。结果表明，随着液固质量比增大，Ca²⁺浸出率增加；反应温度由85℃降到25℃时，磷石膏Ca²⁺浸出率由91%增至100%。在反应温度20℃、CO₂体积分数为20%下，随氨水添加量、碳化时间增加，碳酸钙粒径分布区间呈减小趋势，且Ca²⁺转化率不断增加。氨水添加量为20mL、碳化时间为150min时，碳酸钙的转化率可达92.7%，碳化产物为圆角菱形方解石，峰值粒径以及中值粒径分别为1.5μm和5μm。反应溶液中氨水添加量增加更有利于方解石的形成，而碳化时间增加会促进球霰石的形成，但随着反应溶液中Ca²⁺减少，碳化产物数量骤减，由于已生成的球霰石稳定性较差以及有机溶剂D-葡萄糖酸钠溶液作用，反应产物会发生溶解重结晶，形成粒径小且均匀的圆角菱形方解石。本研究为磷石膏综合利用以及CO₂的捕集并制备碳酸钙微粉提供了一种新的工艺方法。

关键词: 磷石膏, 碳化, D-葡萄糖酸钠, 碳酸钙微粉