稀土氧化物及黏土负载La2O3除磷性能的实验研究

地表水体富营养化现象与磷的积累有密切关系,去除水体中溶解态磷是降低富营养化风险的技术关键。近十余年来,稀土元素被用于污水除磷剂的开发,并获得了良好的应用成效。本文实验比较了8种结晶态稀土氧化物(Y_2O_3、La_2O_3、CeO_2、Pr6O11、Nd_2O_3、Sm_2O_3、Eu_2O_3和Dy_2O_3)的除磷性能,结果表明La_2O_3的除磷性能最好,Pr6O11、Y_2O_3、Eu_2O_3、Nd_2O_3次之,Sm_2O_3和Dy_2O_3效果微弱,CeO_2完全没有除磷能力;研究表明稀土氧化物表面磷吸附的动力学行为更符合准一级反应模型,吸附等温线符合Langmuir模型。实验表征了除磷后的稀土氧化物和除磷过程中溶液p H值的变化,认为稀土氧化物除磷是一个表面吸附占主导,氧化物溶解出来的离子辅助沉淀的吸附过程。为了避免稀土氧化物颗粒在水体中发生团聚并降低表面吸附能力,将稀土氧化物La_2O_3微纳米颗粒负载在不同黏土矿物上,发现负载于黏土矿物表面的稀土氧化物除磷能力有较好提升,磷吸附量均提高25%左右。负载等量La_2O_3的3种黏土矿物的除磷性能差异不显著,黏土矿物提高稀土氧化物颗粒分散度可能是后者除磷能力提升的主要原因。

An experimental study of phosphorus removal performance of rare earth oxides and La2O3 supported on clay minerals

The eutrophication is closely related to the accumulation of phosphorus in surface water. Therefore, the removal of dissolved phosphorus in water is the key to reducing the risk of eutrophication. In the past 10 years, the utilization of rare earth elements as an agent for sewage dephosphorization has achieved good results. In this study, the capability of eight crystalline rare earth oxides (Y₂O₃, La₂O₃, CeO₂, Pr₆O₁₁, Nd₂O₃, Sm₂O₃, Eu₂O₃ and Dy₂O₃) for removing phosphorus was detected. The results show that La₂O₃ has the best phosphorus removal performance, followed by Pr₆O₁₁, Y₂O₃, Eu₂O₃, Nd₂O₃. Sm₂O₃ and Dy₂O₃ have weak effects. CeO₂ has no phosphorus removal capability at all. The kinetic behavior of phosphorus adsorption on the surface of rare earth oxides is more in line with the quasi-first-order reaction model. The adsorption isotherm is consistent with the Langmuir model. The experiment reflects the alteration of rare earth oxides after phosphorus removal and the variance of pH value in the liquid during the process of phosphorus removal. It is believed that the dephosphorization of using the rare earth oxide to remove phosphorus is mainly by adsorption. The precipitation induced by the dissolution of oxides also plays a role. In order to avoid the declining of the surface adsorption capacity caused by agglomerate of the rare earth oxides in the water, the authors loaded the micro-nano particles of the La₂O₃ on the surface of different clay minerals. This design has significantly improved the phosphorus removal capability of the rare earth oxides. The amount of absorbed phosphorus was increased by approximately 25%. The phosphorus removal performance of the three clay minerals with the same amount of La₂O₃ was not significant. The improvement of rare earth oxide particle dispersion by clay minerals might be the main reason for increasing the phosphorus removal capability.