Abstract:

The radioactive waste water is generated in nuclear industry, nuclear research centers, medicine and other fields. It's harmful to living organisms, environment and natural resources. Thus, the radioactive waste water should be managed and treated well. Nanofiltration is a new kind separation technology with low-cost and high-efficiency, which ranges between ultrafiltration and reverse osmosis. In this work, TiO₂/ZrO₂ composite nanofiltration membranes with MWCO of about 500 and permeability of 270 L·m^-2·h^-1·MPa^-1 were used to remove the cobalt and strontium ions in the low-level radioactive wastewater without the addition of complexing agent. The effects of pH, transmembrane pressure and initial concentration on the permeability and retention property were investigated. It was demonstrated that the ion retention behaviors were enhanced with the increase of transmembrane pressure from 0.4 to 1.0 MPa, while the permeability changed slightly. The retention gradually increased along with the deviation from the isoelectric point(pH=7), where the retention was minimum value. Under the condition of pH=3, the retention of Co²⁺ and Sr²⁺ achieved the highest level, which was up to 99%. The ion retention and permeability decreased with the increase of initial concentration. With the operation time exceeding 2000 min, ions retention and permeability of ceramic nanofiltration membrane were almost stable. The ceramic nanofiltration membrane showed a good potential in the application of radioactive effluent treatment.

Key words: nanofiltration, ceramic membrane, radioactive wastewater, ions retention

摘要：

核工业、核研究及医疗等过程会产生大量的放射性废水，会对环境和生物体造成严重伤害，必须经过合适的处理后才能排放。采用高性能陶瓷纳滤膜处理模拟放射性废水，考察了跨膜压差、pH和离子浓度等操作参数对Co²⁺和Sr²⁺截留性能的影响，并对操作参数进行了优化。所用陶瓷纳滤膜材料为ZrO₂-TiO₂复合材料，截留分子量为500，纯水渗透率为270 L·m^-2·h^-1·MPa^-1。研究表明，陶瓷纳滤膜对Co²⁺和Sr²⁺两种离子的截留率随着跨膜压差的升高而增大，膜的渗透通量随着跨膜压差的增大呈线性增加。pH变化时，截留率在一定pH范围内先降低后升高，在等电点（pH=7）附近达到最小值；pH=3的情况下，两种离子的截留率均达到最高，Co²⁺和Sr²⁺的截留率均在99%以上，而纳滤膜渗透通量保持稳定。离子截留率和渗透通量均随进料浓度的增大而减小，在2000 min的连续循环操作过程中，陶瓷纳滤膜材料的渗透通量及其对Co²⁺和Sr²⁺的截留率均维持在较高水平。陶瓷纳滤膜在放射性废水处理方面展现出了良好的应用前景。

关键词: 纳滤, 陶瓷膜, 放射性废水, 离子截留