磷石膏可溶性磷回收试验研究

Optimization of Process for Recovering Soluble Phosphorus from Phosphogypsum

湿法磷酸生产过程会产生固体废弃物磷石膏,其含有大量可溶性残磷,造成磷资源浪费和水污染等问题。通过添加低成本钙源,以磷酸钙沉淀的形式回收磷石膏中的可溶性磷,并考察不同工艺条件对磷回收效率的影响。结果表明:在室温条件下,以CaO为固磷剂,最佳反应时间为10 min;最佳反应pH值为7.5,pH值的增加导致更多杂质的沉淀;最佳钙磷比(Ca/P质量比)为1.7,钙源添加过多造成CaSO4沉淀;最佳初始磷质量浓度为700 mg/L,初始磷浓度会影响磷酸钙平衡常数。最佳反应条件下沉淀含磷量(以P2O5计)为33.5%,反应后磷回收率达到90.9%。扫描电镜和X射线衍射仪分析表明,以CaO为固磷剂时,回收的沉淀以羟基磷酸钙(HAP)为主,其他有害物质含量很低,产生的沉淀可直接作为磷矿资源回收再利用。

The production process of wet-process phosphoric acid produces solid waste phosphogypsum,which contains a large amount of soluble residual phosphorus,resulting in waste of phosphorus resources and water pollution.Soluble phosphorus in phosphogypsum was recovered by adding low-cost calcium source in the form of calcium phosphate precipitation,and the effects of different process conditions on phosphorus recovery efficiency were investigated.The experimental results show that at room temperature,CaO was used as phosphorus fixing agent,and the optimal reaction time was 10 min;The optimal reaction pH value is 7.5,and the increase of pH results in the precipitation of more impurities;The best calcium-phosphorus ratio(Ca/P mass ratio)is 1.7,excessive addition of calcium source causes CaSO4 precipitation;The optimal initial phosphorus concentration is 700 mg/L,and the initial phosphorus concentration will affect the calcium phosphate equilibrium constant.Under the best conditions,the phosphorus content in the precipitate(calculated as P2O5)was 33.5%,and the phosphorus recovery rate after the reaction also reached 90.9%.Analysis by scanning electron microscope and X-ray diffractometer shows that calcium hydroxy phosphate(HAP)is the main precipitate recovered when CaO is used as phosphorus fixing agent,and the content of other harmful substances is very low.The generated precipitate can be directly recycled as phosphate rock resources.