Research On Removal Of Iodide From Simulated Radioactive Wastewater Using Novel Countercurrent Two-stage Adsorption Process

The radioactive iodine was detected in the several major nuclear accidents in history,especially in Japan after the Fukushima nuclear accident.Radioactive iodine is one of the main elements in the early stage of nuclear pollution,which brings great threat to human life.The removal of radioactive iodine is one of the main issues in the field of water pollution control in recent years.Based on the preliminary research,modified-carbons were prepared by using coconut-shell activated carbon under two different conditions in this paper.The adsorption performance of modified-carbons on iodine ions was studied,and the kinetics and thermodynamic properties under complex water quality were determined.The jar test was conducted for treatment of simulated radioactive iodide waste with modified-carbons.The initial iodide concentration was 2.00 mg/L.The adsorption process fitted with Langmuir adsorption isotherm well.The equilibrium was reached within 90 minutes for both adsorbents.The obvious desorption of I^-from the loaded adsorbent was observed.In order to solve the problem of the low iodide removal efficiency in the tap water,a novel countercurrent two-stage adsorption process was developed to eliminate the interference of the desorption,and a lab-scale experiment was carried out to research the removal of I^-.Based on the adsorption performance of iodide,a novel countercurrent two-stage adsorption process was developed and the corresponding mathematical model was established.The concentration of iodide in the effluent could be predicted accurately by the model.In the first stage,when the dosage of adsorbent was 1.00 g/L,the iodide removal efficiency attained 75.0%-76.0%;when the dosage was 1.25 g/L,the iodide removal efficiency was 76.5%-78.0%.Modified-carbons used to treat iodine containing wastewater with the novel countercurrent two-stage adsorption process.The results showed that the effluent quality was stable when the dosage of adsorbent was 1.25 g/L,the average removal rate of iodide reached 92.5%-93.7%.The measured value was close to the calculated value with the model developed.Higher iodide removal efficiency can be achieved at the same adsorbent dosage compared to the conventional single stage adsorption process.The average Cu²⁺concentration was about 1.60 mg/L,in line with the Guidelines for Drinking Water Quality issued by World Health Organization,but slightly higher than that in Chinese Standards for Drinking Water Quality（GB5749-2006）.Futher study is necessary.