Study On Removal Of Radioactive Iodine From The Water By Percipitation Of Cuprous Chloride

Radioactive iodine is toxic element;the water pollution resulting from radioactive iodine can cause serious threat to the health and environment.The radioactive iodine was detected in several nuclear accidents in the history,and surface water,seawater,groundwater especially the drinking water had been polluted,after the Fukushima nuclear accident happened in Japan.Nuclide iodine as one of the main radioactive contaminant in the water has drawn increasing attention and has been investigated by many researchers.In this paper,a new method of precipitation of cuprous chloride for the removal of radioactive iodine from the water was proposed.Under the condition of deoxygenization,CuCl was used as precipitant,and Cu+ reacted with I-in the solution to generate Cu I,then the precipitates were filtered by 0.45 ?m membrane and the iodide could be efficiently removed from water.Optimizing the feasibility of process was based on a jar tests,and the device of batch experiments was designed on our previous work.In the lab-scale experiment,the results of jar tests was reappeared and operation parameters were further optimized according to the actual condition.Moreover,the performance of the process and the removal of iodide were evaluated and analyzed comprehensively.In a jar test,the effects of the dosage of cuprous chloride,reaction time,initial concentrations of iodide and co-existing anions including chloride and bicarbonate on iodide removal were investigated,and the produced sediment in the solid-phase were analyzed aiming at the further investigation of the reactions in this process.The results showed that the changing concentrations of initial iodide?5-40 mg/L?and chloride?0-400 mg/L?had little effect on iodide removal.When the dosage of CuCl was 150 mg/L and the reaction time was 15 min,the removal rate of iodide was 95.8% under the optimal operation condition.But it leaded to higher concentration of Cu₂+ and the slightly lower pH value in the effluent.Adding HCO₃^-can effectively improve the pH,and it was found that the concentration of Cu₂+ in the effluent was reduced while increasing the concentration of HCO₃^-.When the concentration of HCO₃^-was 87.14 mg/L,the concentration of Cu₂+ in the effluent could be achieved the standard of drinking water?<1 mg/L?,but the removal rate of iodide reduced to 81.2%.The result of XPS revealed that these compounds,such as Cu I,Cu,Cu₂ O,CuO,Cu?OH?2 existed in the solid-phase in the absence of HCO₃^-.When HCO₃^-was added into the solution,it showed that the precipates also included the CuxS?1<x?2?,and SO42-in the effluent was not detectable.In the lab-scale experiment,the powder of CuCl was dissolved into the hydrochloric acid of 0.02 mol/L to achieve an accurate suspension dosing.The total amount of treated water was 1540 L after the device had a stable operation for 7 days,due to the quality of the wastewater was different from that in a jar test,the optimal dosage of CuCl was 250 mg/L,and the result showed that the average removal rate of iodide was 97%,and the concentrations of Cl-and SO42-in the effluent were stable,which were respectively 85 mg/L and 31 mg/L after deducting the background values.The initial SF was 63.36 L/?m2·h·m?and decreased to 9 L/?m2·h·m?at the end of the experiment,and the average concentration of Cu₂+ in the effluent was 20 mg/L.Besides,the result of XPS in the solid phase was consistent with that in the jar test.In order to reduce the concentration of Cu₂+ in the effluent,different amounts of CO32-was added into after the supernatant in the stirred reactor was pumped into the membrane separator,the results of this test showed that the concentration of Cu₂+ was 0.72 mg/L when the concentration of CO32-was 80 mg/L,the pH value was 8.21 in the effluent and the removal rate of iodide decreased to 57%.In conclusion,this process should be further studied in the future work in order to reduce the concentration of Cu₂+ in the effluent to meet standard and to ensure the removal rate of iodide over 90%.