粉煤灰基地质聚合物固化低放射性稀土酸溶渣

Immobilization of Low Radioactive Rare Earth Acid Soluble Slag by Fly Ash Based Geopolymer

离子型稀土酸溶渣是一种低放射性废渣,需要进行安全化处置。以稀土酸溶渣和粉煤灰为原材料,在碱激发剂的作用下制备地质聚合物,通过SEM、XRD、FTIR手段分析放射性核素在地质聚合物的固化机理。结果表明,当Si Al摩尔比为2.0,Na Al摩尔比为0.9,75℃固化24 h时,养护1 d所制得的地质聚合物抗压强度达45 MPa,制备的地质聚合物具有非晶态Si Al凝胶相,内部结构致密均匀,具有良好的力学性能。在酸溶渣添加量为25%时,地质聚合物固化体抗压强度可达12 MPa。对添加酸溶渣固化体进行浸出试验,渣添加量为25%时固化体中钍的7 d浸出率为3.47×10^(-5) cm d,7 d累计浸出分数为4.42×10^(-5)cm,实现了放射性核素的有效固化。钍、铀以沉淀及化学键结合两种方式存在于地质聚合物中。

Ionic rare earth acid soluble slag is a kind of low radioactive waste slag,which needs to be disposed safely.Applying ionic rare earth acid soluble slag and fly ash as raw materials,geopolymer was prepared in the presence of alkali exciter.The curing mechanism of radionuclides in geopolymer was analyzed by SEM,XRD and FTIR.The results show that the compressive strength of the geopolymer made by curing at 75℃for 24 h is 45 MPa when Si Al molar ratio is 2.0,Na Al molar ratio is 0.9,and curing at 75℃for 1 d.The prepared geopolymer has an amorphous Si Al gel phase with dense and uniform internal structure and good mechanical properties.The compressive strength of the geopolymer curing body is 12 MPa at 25%addition of acid-soluble slag,and 7 d leaching rate of thorium in curing body is 3.47×10^(-5) cm d at 25%slag addition,and the 7 d cumulative leaching fraction is 4.42×10^(-5) cm,which is effective for curing radionuclides.Thorium and uranium exist in geopolymers by precipitation and chemically bonded.