Treatment of Simulated Radioactive Wastewater Using Reverse Osmosis and Membrane Distillation

Abstract

With the rapid development of nuclear power, increasing attention has been paid to the treatment of low-level radioactive wastewater (LLRW). In this study, reverse osmosis (RO) and membrane distillation (MD) are used to treat LLRW containing Ce(III), U(VI), and Co(II). RO was used for the purification of LLRW. MD was used for further concentration of RO concentrate. The effect of the operating parameters, including operating pressure (0.6 to 1.4 MPa), feed pH (7 to 9), feed concentration (2 to 10 mg/L), feed temperature (50°C to 90°C), and feed flow rate (80 to 160 L/h) on the permeate flux and the rejection rate of the RO process and MD process was studied. The results demonstrate that it is very effective to use the RO process to treat LLRW containing Ce(III), U(VI), and Co(II), with the rejection rates of Ce(III), U(VI), and Co(II) higher than 99.97%, 99.98%, and 99.35%, respectively. The operating pressure has a significant effect on the permeate flux in the RO process. The permeate flux increases from 9.84 to 23.03 L/m2·h when the operating pressure increases from 0.6 to 1.4 MPa. The feed pH has an apparent influence on nuclide rejection. At the feed pH = 9, the rejection rates of Ce(III), U(VI), and Co(II) by the RO process can reach 99.99%, 99.99%, and 99.79%, respectively. MD can reject almost all the nuclides in the RO concentrate, with rejection rates consistently higher than 99.98%. Increasing the feed temperature and feed flow rate can result in a significant increase in the permeate flux, but has almost no effect on nuclide rejection in the MD process.