Research On Treatment Of Simulated Radioactivity-Contaminated Water Containing Iodide By Adsorption/Precipitation/Microfiltration Process

With the development of nuclear industry and the wide application of radionuclide iodine in medical and other scientific fields,the risk of radioactive iodine contamination in water increased gradually.It is urgent to reaserch on an appropriate process for the removal of radioactive iodine.In this paper,adsorption/microfiltration and precipitation/microfiltration process used for the treatment of simulated radioactivity-contaminated water containing iodide were studied,respectively.The results of lab-scale tests were as follows:Nano Cu₂O/Cu modified activated carbon were used as iodide removal adsorbent in the countercurrent two-stage adsorption-microfiltration combined process,the appropriate dosage was 1 g/L and the adsorption time of each stage was 45 min.When the dilution factor?F?was 0.2,the average I^-removal efficiency was 84.0%and the concentration factor?CF?was 438.The average I^-removal efficiency increased to89.4%and the CF decreased to 293 when the F was 0.4.That is to say,increasing the F value could improve I^-removal efficiency,but at the same time the volume of sludge produced also increased.The effluent qualities were stable during the continuous operation,the turbidity of effluent maintained below 0.3 NTU and the pH of effluent was basically the same as that of raw water.In addition,Cu²⁺was introduced during the process of removing I^-.The concentration of Cu²⁺in effluent increased with the increase of F value and was 0.31 mg/L and 1.42 mg/L,respectively,when F was 0.2 and 0.4.With the increase of the volume of water treated by unit membrane area,the specific flux?SF?of microfiltration membrane decreased slowly.The SF value could be restored to over 88.6%of the initial value by physical cleaning.CuCl was used as the iodide removal precipitator in predeoxygenation-precipitation-column membrane seperation combined process.Na₂SO₃ as deoxidizer and Cu²⁺as catalyst were used to remove the dissolved oxygen in advance from the raw water.The concentrations of Na₂SO₃ and Cu²⁺were 150 mg/L and 1 mg/L,respectively.After stable operation,when the CuCl dosage was 250 mg/L,the average I^-removal efficiency was as high as 97.1%and the CF was 1800.However,the concentration of copper ion in effluent was higher,the average value was 30.5 mg/L and the membrane fouling rate was faster.When the CuCl dosage was reduced to 100mg/L,the concentration of copper ion in effluent decreased to 14.0 mg/L and the membrane fouling rate also slowed down by about one-half.Intermittent effluent drawing could further reduce the membrane fouling.Howeve,the average I^-removal efficiency decreased to 93.9%under this dosage.The ratio of N₂ consumed to the amount of water treated was only about 0.1:1.The SF value of the colume membrane could be restored to over 90.8%of the initial value by physical cleaning.Compared with the countercurrent two-stage adsorption-microfiltration combined process,the predeoxygenation-precipitation-column membrane seperaion combined process had advantages in achieving higher I^-removal efficiency and CF in lab-scale tests.But the concentration of Cu²⁺in effluent was higher,which required further reaserch.