Study On Treatment Of Low-Level Uranium-Containing Wastewater By Flocculation Precipitation And Reverse Osmosis

Finding fossil alternative energy is the only way for the sustainable development of energy,and nuclear energy just meets this demand.During the development of the nuclear industry,the front and end of the nuclear power operation and the nuclear fuel cycle will produce uranium-containing wastewater with radioactive and chemical toxicity.It is necessary to reasonably and effectively treat these wastewater and reduce the emission of harmful substances.In this paper,three kinds of low radioactive uranium-containing wastewater treatment processes were studied,namely flocculation precipitation,reverse osmosis(RO),flocculation + reverse osmosis.The results show that:(1)For the flocculation and precipitation process,uranium can be effectively removed under alkaline conditions.In addition,the flocculation effect of uranium can be improved by increasing flocculant dosage and initial p H of wastewater at suitable temperature.p H is crucial for uranium removal.Under the optimal treatment conditions,the removal rate of uranium in wastewater by flocculation precipitation is more than 90%.(2)For RO process,although the rejection of uranium by seawater desalination(SW)membrane is higher than that of brackish water desalination(BW)membrane,the flux of SW membrane is low.Increasing uranium concentration and p H contributed to improving uranium removal,while transmembrane pressure had no significant effect on retention rate.Under most conditions,the rejection rate of uranium by SW membrane was above 90%.(3)Because the single flocculation-sedimentation or RO process is not sufficient to directly treat the nuclides in simulated wastewater to meet the discharge standard,the flocculation-sedimentation and RO process is combined into a combination process.The results show that the total removal of uranium,nickel and copper by the combined process of flocculation + SW membrane is more than99%,and the concentration of each nuclide in the permeate is lower than the national standard.(4)In order to increase the service life of reverse osmosis membrane and reduce the pollution of organic matter in waste liquid to reverse osmosis membrane during waste liquid treatment,dopamine was grafted with polyethyleneimine on BW membrane surface to modify the surface of membrane separation layer against organic pollution.The surface morphology,water contact angle,Zeta potential and functional groups of the separation layer before and after modification were analyzed by scanning electron microscopy,dynamic water contact angle meter,electric analyzer and Fourier transform infrared spectrometer.The results showed that dopamine and polyethyleneimine were successfully coated on the surface of the commercial membrane separation layer.By comparing and analyzing the experimental data before and after modification,it was found that the anti-organic pollution ability of the modified membrane was improved to some extent.After a long time of continuous treatment of simulated wastewater,the flux decline rate was 62.1% lower than that of commercial membrane,and the retention rate of uranium was 12.7% higher than that of commercial membrane.The modification was more successful.