Study On Removal Of Cesium Containing Simulated Liquid Waste By Adsorption/Coagulation Separation Combined Process

Countercurrent two-stage adsorption-microfiltration process was developed for cesium removal from simulated radioactive wastewater in previous research.Although the decontamination efficiency was excellent,the membrane fouling caused by copper ferrocyanide suspension in membrane separator could not be ingored,which would severally limit the application of this process.Therefore,based on the previous results,a new hybrid process of adsorption/coagualtion-separation was developed to remove cesium contained in simulated radioactive wastewater.This reaearch aimed to three sections.First,the determination of coagulant type,optimum coagulant dosage,sedimentation time and the effect of coagulation on adsorption were carried out by jar tests.Second,a adsorption/coagulation-microfiltration process was developed to remove cesium from the simulated radioactive wastewater with different temperature;the last,the decontamination characteristic of hybrid process of adsorption/coagulation-sand filtration was investigated in terms of different filtering velocity.The results of jar test showed that aluminum sulfate was more applicable,which could improve sedimentation performance of copper ferrocyanide than poly aluminium chloride.Contrast with the test without coagulant dosing,the turbidity of the supernatant decreased by 73.5% when the dosage of Al3+ and sedimentation time were 4.05 mg/L and 15 min,respectively.For optimal coagulation results of aluminum sulfate,the range of pH value was 7~8 which came within the range of pH value of raw water.The result of isotherm test showed Freundlich isotherm still could be used when aluminum sulfate was used as coagulant.There was no significant changes of adsorption behavior on cesium by copper ferrocyanide after aluminum sulfate was added.The results of adsorption/coagulation-microfiltration process indicated that the rise of temperature was advantageous to cesium removal from the raw water by the adsorption/coagulation-microfiltration process.When water temperature varied from 8 to 17℃,the decontamination factors were all about 103.Variations of temperature had great influence on the effect of coagulation.The membrane pores were quickly blocked,the membrane resistance was increased,the membrane flux was decreased quickly when temperature was low.As a result,the treatment capacity of the laboratory scale device at water temperature of 13 or 17℃ was twice as much as that at water temperature of 8℃.The lab-scale tests results of hybrid process adsorption/coagulation–sand filtration demonstrated that the hybrid process had good decontamination efficiency.The effluent turbidity was below 0.20 NTU.The average decontamination factor of the three tests was 868.The treatment capacity of the lab-scale test would increase with the appropriate increase of filtering velocity.Sand filtration has several advantages such as simple backwashing,more practical applicability as well as longer operation time when used for radioactive wastewater treatment.Therefore,the process of sand filtration shows a good prospect.