Study On The Treatment Of Simulated Radioactive Wastewater By Forward Osmosis

Forward osmosis(FO)is a novel membrane process driven by osmosis pressure.Compared with reverse osmosis(RO),it featured equally high effluent quality,lower energy consumption,easy equipment and low fouling,etc.In this work,FO was applied for simulated radioactive wastewater treatment.Retention of the simulated radionuclides by FO was investigated in the single-nuclide,multi-nuclides and boron contained feeds.The effects membrane properties,simulated wastewater properties,draw solution(DS)concentration and cross-flow rate were studied on FO performance.Membrane fouling was eventually analyzed.The results indicated that CTA-ES membrane featured higher nuclide retention than CTA-NW and TFC-ES in both the single-nuclides and multi-nuclides systems.AL-FS mode performanced better than AL-DS mode.The optimal DS concentration was 1.0 mol·L-1 NaCl.The optimal cross-flow rate of the radioactive wastewater was 11 cm·s-1.Under the optimal operating condition,the water flux,Co(II)retention and the reverse NaCl flux reached 10.7 L·(m2·h)-1,99.93% and 5.66 g·(m2·h)-1 for the single-nuclide system.The water flux,the Co(II),Sr(II),Cs(I)retentions and the reverse NaCl flux were 14.2 L·(m2·h)-1,99.89%,96.90%,95.51%,3.08 g·(m2·h)-1 for the multi-nuclides system.Surface charge of active layer of FO membrane was the main factor affecting the radionuclide retention.The structure of support layer mainly influenced the water flux and reverse NaCl flux.For the radioactive wastewater with boron,CTA-ES membrane featured higher nuclide retention than the CTA-NW and TFC-ES membranes.AL-FS mode performanced better than AL-DS mode.The boric acid concentration affected the water flux and the reverse NaCl flux,which both reached the maximum values at the boric acid concentration of 800 mg·L-1.The maximum water flux and reverse NaCl flux were 15.3 L·(m2·h)-1 and 3.73 g·(m2·h)-1,respectively.Boric acid had almost no effect on radionuclide retention.The Co(II),Sr(II),Cs(I)retentions were 99.63~99.89%,96.90~97.85%,95.20~95.51%,respectively.After operated for 30 d for the simulated radioactive wastewater treatment,the water flux reduced by 9.9 L·(m2·h)-1.The Co(II),Sr(II),Cs(I)retentions decreased by 1.77%,6.09%,26.38%.Membrane surface became rougher and more hydrophobic.The amounts of Co(II),Sr(II),Cs(I),Na(I)in the foulants on the membrane surface were 5.32 mg·m-2,52.2 mg·m-2,45.5 mg·m-2,2.71×104 mg·m-2,respectively.After the fouled membrane was washed by deionized water,the water flux was recovered by 39%.