Pilot-Scale Test On Removal Of Cesium From Water By A Hybrid Process Of Countercurrent Adsorption,Coagulation And Microfiltration

In this dissertation,the pilot-scale experiments were carried out using countercurrent adsorption-coagulation-microfiltration process and countercurrent adsorption-coagulation-sand filtration process to treat cesium-contaminated water.Firstly,the preparation scale of the adsorbent was enlarged,and the factors including the pH value of the solution,the reaction droplet addition rate and the concentration of the reaction solution were optimized.The particle size distribution of copper ferrocyanide prepared under the optimal condition was similar to that of the lab-scale test.Although the adsorption capacity coefficient was lower than the lab-scale test,adsorption strength coefficient was similar to the lab-scale test,it still had good adsorption performance.The countercurrent adsorption-coagulation-microfiltration pilot-test were conducted with the adsorbent dose of 40 mg/L using the immersion microfiltration membrane and the pressure microfiltration membrane for the solid-liquid separation,respectively.When using the immersion microfiltration membrane,the removal effect of cesium was poor due to a small amount of filament damaged,and the average decontamination factor was 225.After replacement with the pressure microfiltration membrane,the solid-liquid separation performance was good,and the average decontamination factor can reach 1035.However,because of the dense filling of the column membrane,which was appropriate at the low influent turbidity,the membrane fouling was serious.The result showed that it has little effect on reducing the membrane fouling by increasing the reflux ratio and coagulant dosage.The operating parameters of the countercurrent adsorption-coagulation-sand filtration pilot-test process was similar to the countercurrent adsorption-coagulation-microfiltration pilot-test,except to changing microfiltration.to sand filtration.The results showed that the countercurrent adsorption-coagulation-sand filtration pilot-test process was less effective compared with the lab-scale test.The effluent cesium ion concentration and turbidity of the sand filtration increased with the running time.It was also impossible to improve the settling effect at the adsorption reactor by changing the coagulant dosage and addingactivated carbon.In summary,the countercurrent adsorption-coagulation-microfiltration process can effectively remove cesium from cesium-contaminated water and operate stably,which can be used for emergency treatment in radioactive cesium polluted accidents.In the study,the average decontamination factor can reach about 1000.The pressure membrane fouling was more serious comparing with immersion microfiltration membrane.However,the filament of immersion membrane was more easier to be damaged,causing poor quality of treated water.