Application Of Membrane Separation Technology On Low-lelvel Radioactive Wastewater Treatment

In recent years,with the coal,oil and other non-renewable energy drying up,developping nuclear energy has become an effective way to actualize the sustainable development of energy in the world.Because China is in the efficient stage of developping nuclear power,it is bound to produce a lot of low-level waste water with more cobalt and strontium.Therefore,we should use appropriate techniques to remove the Co and Sr from low-level radioactive waste water in order to reduce the harm to human health and natural environment.This research focused on the removal of Co and Sr in simulated wastewater by complexation-ultrafiltration technology,and the significant factors affecting the removal effect were investigated.The water-soluble polyethyleneimine was used as the complexant,and the separation was achieved by polyether sulfone hollow fiber ultrafiltration membrane.The effects of pH,mass ratio of polymer/nuclide ions(P/M),transmembrane pressure(TMP),temperature on the retention of cobalt and strontium were determined by single factor test,orthogonal test and response surface test.The significant difference of the influencing factors and the best operating conditions were also analyzed.The experimental results show that the operating conditions with the highest rejection rate of cobalt ion were P/M=10,TMP=0.30 MPa,pH=7,the operating conditions for obtaining the maximum membrane flux were TMP=0.30 MPa,P/M=5,pH=7,and finally the actual operating conditions were TMP=0.30 MPa,P/M was 5~10,pH=7.The results showed that the cobalt and strontium ions in the mixed wastewater had the mutual interference effect,and the rejection rates of cobalt and strontium were lower than those of the single wastewater.When the experimental conditions were TMP=0.20 MPa,pH=7 and P/M=10,the rejection of cobalt in mixed wastewater decreased by 3% compared with that of single waste water,and the rejection of strontium in mixed wastewater was decreased 10%.For the removal of strontium in the wastewater,the theoretical operating conditions with the highest strontium ion rejection rate were TMP=0.20 MPa,P/M=15,pH=5by establishing the prediction model of strontium ion rejection rate.The theoretical operating conditions for the membrane flux were 0.29 MPa,P/M=10.29,pH=8.09 by establishing the prediction model of ultrafiltration membrane flux,and the actual operating conditions were TMP is between0.20 and 0.30 MPa,P/M was betwween 10 and 15,PH=8.The surface of the ultrafiltration membrane was observed by SEM and it was found that the polymer PEI and nuclide were formed on the surface of the membrane.The cleaning method of the ultrafiltration membrane was used to the water backwashing chemical washing andwater rinsing.The results of this study provide a reference for the application of the complexation-ultrafiltration technology in the practice of low-level radioactive waste water.