氧化钙对磷石膏中可溶磷和可溶氟固化性能的影响

Effect of Calcium Oxide on Solidification Properties of Soluble Phosphorus and Soluble Fluorine in Phosphogypsum

磷石膏是湿法磷酸过程产生的大宗固废(主要成分为CaSO_(4)·2H_(2)O),针对磷石膏堆场中可溶磷和可溶氟的迁移对周边环境造成一定程度污染的问题,采用氧化钙固化磷石膏中的可溶磷和氟,利用响应曲面优化可溶磷、氟固化工艺参数,通过溶液化学计算、SEM和XRD分析可溶磷和可溶氟固化机理及沉淀产物微观结构和物相组成。响应曲面分析表明,各因素对可溶磷和可溶氟的固化率存在一定交互作用,其中CaO用量影响最为显著,各因素对固化率的影响次序为:CaO用量>液固比>反应时间,经优化后的工艺条件为:CaO用量3.30%(质量分数),液固比1.90,反应时间110 min,可溶磷和可溶氟的固化率分别为98.6%和99.7%。溶液化学计算结果表明固化过程中可溶氟优先可溶磷生成沉淀。SEM及XRD分析结果表明可溶磷主要以CaHPO_(4)·2H_(2)O的形式析出,可溶氟则主要以CaF_(2)形式析出。

Phosphogypsum is a large-scale solid waste produced in wet-process production of phosphoric acid,which is mainly composed of CaSO_(4)·2H_(2)O.The migration of soluble phosphorus and fluorine in the phosphogypsum stack will cause environmental pollution.In this paper,calcium oxide was used to solidify soluble phosphorus and fluorine in phosphogypsum.Response surface analysis shows that the solidification efficiency of soluble phosphorus and soluble fluorine is positively correlated with CaO mass fraction and reaction time,the influence of various factors on the solidification efficiency is in the order of CaO mass fraction>liquid-solid ratio>reaction time.The optimized parameters are CaO mass fraction of 3.30%,liquidsolid ratio of 1.90 and reaction time of 110 min.And the solidification efficiencies of soluble phosphorus and soluble fluorine are 98.6%and 99.7%,respectively.The results of solution chemical calculation show that soluble fluorine is precipitated prior to soluble phosphorus in the solidification process.The results of X-ray diffraction and scanning electron microscopy show that soluble phosphorus is mainly precipitated in the form of CaHPO_(4)·2H_(2)O,while soluble fluorine in the form of amorphous CaF_(2).