Abstract:

The treatment of radioactive wastewater by chemical precipitation method has the advantages of being simple, wide application and large amount of water treatment. Membrane separation technology can improve the effectiveness of solid liquid separation. In this paper, precipitation and membrane separation technology were combined to treat the simulated wastewater containing radioactive iodide on a laboratory scale. The initial iodide concentration was approximately 5 mg·L^-1. The concentration of added Na₂SO₃ used for removing oxygen from the influent was 40 mg·L^-1 and the dosage of CuCl used as a precipitant was 260 mg·L^-1. The entire system was under the protection of nitrogen gas that was recycled after drying. The whole process was operated continuously, which was controlled by programmable logic controller (PLC). The I^- removal mechanism was the formation of sparingly soluble CuI. Besides that, Cu₂O and Cu(II) ion were produced in this reaction system, which were demonstrated by solid phase analysis. This study investigated I^- removal efficiency and other water quality parameters under different temperatures and the effects of two membrane flux 4.17×10^-6 m·s^-1 and 8.33×10^-6 m·s^-1 on membrane fouling. The operation time was 168 h and the volumes of treated wastewater were 1540 L. In two tests, the average I^- removal efficiency was 94.8% with stable effluent water qualities. However, the Cu(II) ion concentrations in the effluent were higher and it was required for the subsequent removal. Under the conditions that the membrane fluxes were 4.17×10^-6 m·s^-1 and 8.33×10^-6 m·s^-1, the final membrane specific flux decreased to 65.0% and 55.0% of the initial one, respectively, and the membrane specific flux values of the membrane modules were recovered to 90.0% and 79.0% of the initial one, respectively after physical and chemical cleaning. Furthermore, the average concentration factor value was 2.02×10³, and the volume of the sludge produced in the experiment was small.

Key words: radioactive wastewater, iodide, microfiltration, chemical precipitation, combined process, membrane fouling

摘要：

采用实验室规模的沉淀与膜分离组合工艺处理模拟含放射性I-废水，初始I-浓度约为5 mg·L^-1，Na₂SO₃投加量为40 mg·L^-1，CuCl投加量为260 mg·L^-1。分析考察了不同水温条件下的除碘效果及其他水质参数变化情况和两个膜通量4.17×10^-6 m·s^-1和8.33×10^-6 m·s^-1运行条件下的膜污染情况。运行时间均为168 h，处理含碘离子的废水水量为1540 L。两个膜通量在各自运行期间，平均去除率为94.8%，出水水质较稳定，但是出水的Cu（Ⅱ）离子含量较高，需要增加后续除铜工艺；最终膜比通量分别降至初始膜比通量的65.0%和55.0%，膜组件经物理和化学清洗后SF值分别恢复至初始SF值的90.0%和79.0%。反应结束后两次试验的CF（浓缩倍数）平均值为2.02×10³，试验产生的污泥体积较小。

关键词: 放射性废水, 碘离子, 微滤, 化学沉淀, 组合工艺, 膜污染