赤泥-磷石膏复合材料中重金属浸出研究

为实现赤泥和磷石膏两大工业固废的资源化利用，采用未经改性处理的赤泥与磷石膏为原料，通过复合助剂的改性固化作用制备达到充填要求的复合材料。当赤泥用量为总原料质量的85%、磷石膏为5%时，复合材料养护28 d的抗压强度为4.34 MPa，达到了矿山充填力学性能要求。参照《固体废物浸出毒性浸出方法水平振荡法》（HJ 557—2010）和《块状废物或建材中无机组分扩散浸出行为测试容器实验》（EA NEN 7375—2004）对颗粒状和块状样品对比进行浸出实验，研究了赤泥-磷石膏复合材料中重金属元素（镉、铬、镍、钡）的浸出行为。结果表明，重金属浸出浓度由大到小依次为铬、钡、镍、镉；磷石膏掺量在5%以内时重金属元素浸出浓度及扩散系数变化较小，超过5%后重金属元素浸出率增加。对两种浸出方法复合材料中重金属元素的浸出行为进行动力学分析，发现重金属元素的浸出行为主要受扩散作用控制，在长期浸出过程中还受到耗竭作用和延滞作用控制。

Study on leaching of heavy metals from red mud-phosphogypsum composite materials

In order to realize the resource utilization of two major industrial solid wastes of red mud and phosphogypsum,the unmodified red mud and phosphogypsum were used as raw materials to prepare composite materials meeting requirements of mine filling through the modification and solidification of composite additives.When the mass fraction of red mud was 85% of the total raw materials and phosphogypsum was 5%,the compressive strength of the composite cured for 28 d was 4.34 MPa,which met the requirements of mechanical properties of mine filling.According to the“Horizontal oscillation method of solid waste leaching method”（HJ 557—2010） and the Dutch standard“container experiment for testing the diffusion leaching behavior of inorganic components in block waste or building materials”（EA NEN 7375—2004）,the leaching experiment was carried out on the comparison of granular and block samples.The leaching behavior of heavy metals（Cd,Cr,Ni,Ba） in red mud phosphogypsum composite materials was studied.The results showed that the leaching concentrations of heavy metals from large to small was Cr,Ba,Ni and Cd.When the content of phosphogypsum was less than 5%,the leaching concentration and diffusion coefficient of heavy metals were changed slightly,and the leaching rate of heavy metals was increased when it was above 5%.The leaching behavior of heavy metals in composites by two leaching methods was analyzed dynamically.It was found that the leaching behavior of heavy metals was mainly controlled by diffusion,and also by depletion and retardation in the long-term leaching process.