Removal of trace Cs(I), Sr(II), and Co(II) in aqueous solutions using continuous electrodeionization (CEDI)

Abstract

Nuclear power plants produce low-level radioactive wastewaters (LLRW) that contain radioactive nuclides. Prior to discharge, these radioactive nuclides need to be safely and efficiently removed. Continuous electrodeionization (CEDI) has shown potential for the treatment of LLRW. Here, we measured the performance of CEDI stacks on the removal of three different trace nuclides: Cs(I), Sr(II) and Co(II). Our results indicated that Cs(I) and Sr(II) actively migrated in the resin particles and were distributed in the resin profile according to the applied electric field. Nuclide removal was improved by increasing the working current. At a working current of 0.5 A, the removal efficiencies of Cs(I), Sr(II), and Co(II) amounted to 99.7%, 98.1%, and 77.1%, respectively. However, excessive working current resulted in the hydrolysis and formation of Co(OH) 2, which deposited on the surface of the cation exchange resin. The adsorption rate of Cs(I), Sr(II), and Co(II) for the resin was in the following order: Cs(I) > Sr(II) > Co(II). This order was also positively related to the removal efficiency of the CEDI stack. However, we found no significant relationship between resin adsorption capacity and CEDI removal efficiency.

Selective and Chemical-Free Removal of Toxic Heavy Metal Cations from Water Using Shock Ion Extraction

“…This observation is supported by the measured increase in the hydrodynamic resistance (and, in turn, pressure drop) in our device, and it implies that the metal hydroxides form films on the resin beads and physically plug the compartments of the wafer. This phenomenon also occurs in EDI systems when used to remove heavy metal cations from water, − and one proposed solution is to design a vertically layered bed of cation, anion, and mixed-ion exchange resins to better manage ion removal and prevent precipitation reactions. , This kind of system requires complex stack design and operation, whereas shock IX can potentially achieve the same device durability by using a homogeneous cation exchange resin wafer with cation exchange membranes. Future work will thus focus on designing homogeneous and layered IERWs to reduce water splitting and prevent precipitation of metal hydroxides in shock IX.…”

“… , In mixed-ion exchange resin beds and wafers, it is known that hydroxide is generated via water splitting in regions of ion depletion at the interfaces between oppositely charged surfaces (e.g., cation exchange membrane and anion exchange resin). , The results in Figure c show accumulation (μ < 1) of species in the device, which may be explained by the fact that heavy metal cations react with these hydroxide ions to produce insoluble metal hydroxides . This observation is supported by the measured increase in the hydrodynamic resistance (and, in turn, pressure drop) in our device, and it implies that the metal hydroxides form films on the resin beads and physically plug the compartments of the wafer. This phenomenon also occurs in EDI systems when used to remove heavy metal cations from water, − and one proposed solution is to design a vertically layered bed of cation, anion, and mixed-ion exchange resins to better manage ion removal and prevent precipitation reactions. , This kind of system requires complex stack design and operation, whereas shock IX can potentially achieve the same device durability by using a homogeneous cation exchange resin wafer with cation exchange membranes.…”

“…56,57 The results in Figure 4c show accumulation (μ < 1) of species in the device, which may be explained by the fact that heavy metal cations react with these hydroxide ions to produce insoluble metal hydroxides. 56 This observation is supported by the measured increase in the hydrodynamic resistance (and, in turn, pressure drop) in our device, and it implies that the metal hydroxides form films 58 on the resin beads and physically plug the compartments of the wafer. This phenomenon also occurs in EDI systems when used to remove heavy metal cations from water, 56−58 and one proposed solution is to design a vertically layered bed of cation, anion, and mixed-ion exchange resins to better manage ion removal and prevent precipitation reactions.…”

Electrodialysis Applications in Wastewater Treatment for Environmental Protection and Resources Recovery: A Systematic Review on Progress and Perspectives

“…Other experiments conducted with a four-compartment EDI device removed up to ~99.9% of Cs + from model waste solutions (e.g., 50 mg/L) [235]. Different radionuclides (Cs + , Sr 2+ and Co 2+ ) in traces were removed by 77.1-99.7% [236]. Th 4+ was removed at rates of up to ~99% (from 30-90 mg/L) in experiments optimized by response surface methodology [237].…”