Electrodialytic Handling of Radioactive Metal Ions for Preparation of Tracer Reagents

Phytotoxicity of radionuclides: A review of sources, impacts and remediation strategies

Various anthropogenic activities and natural sources contribute to the presence of radioactive materials in the environment, posing a serious threat to phytotoxicity. Contamination of soil and water by radioactive isotopes degrades the environmental quality and biodiversity. They persist in soils for a considerable amount of time and disturb the fauna and flora of any affected area. Hence, their removal from the contaminated medium is inevitable to prevent their entry into the food chain and the organisms at higher levels of the food chain. Physicochemical methods for radioactive element remediation are effective; however, they are not eco-friendly, can be expensive and impractical for large-scale remediation. Contrastingly, different bioremediation approaches, such as phytoremediation using appropriate plant species for removing the radionuclides from the polluted sites, and microbe-based remediation, represent promising alternatives for cleanup. In this review, sources of radionuclides in soil as well as their hazardous impacts on plants are discussed. Moreover, various conventional physicochemical approaches used for remediation discussed in detail. Similarly, the effectiveness and superiority of various bioremediation approaches, such as phytoremediation and microbe-based remediation, over traditional approaches have been explained in detail. In the end, future perspectives related to enhancing the efficiency of the phytoremediation process have been elaborated.

Electrodialysis for the volume reduction of the simulated radionuclides containing seawater

In this study, electrodialysis (ED) was performed to concentrate the radionuclides containing seawater for volume minimization. The concentration behaviors of the trace radioactive elements were also explored. Under the optimal voltage drop of 6 V and the volume ratio of 1:40, the concentration times of Cs⁺, Co²⁺, Sr²⁺ and I^- could reach 9.9, 9.5, 20.1 and 32.5, respectively. Furthermore, it enabled over 80% volume reduction and over 90% removal of all hazardous radionuclides. Hence, ED is a feasible and promising method to manage the radioactive wastewater due to its high concentration and decontamination performances. For identical ion contents, the concentration rate for the cations presented the order of Na⁺ > Cs⁺ > Sr²⁺ > Co²⁺; the hydration radius and hydration free energy played the dominant roles in ion concentration. In contrast, for the ED concentration of trace radioactive elements, of which the contents are several magnitudes lower than the predominant salt concentration, the concentration rate presented the order of Sr²⁺ > Cs⁺ > Co²⁺ > Na⁺; the specific charge began to play an important role when the predominant ion approached its saturated salt concentration. For the anions, I^- always migrated faster than Cl^- at diverse concentrations.

Electrodialytic Universal Synthesis of Highly Pure and Mixed Ionic Liquids

Ionic liquids (ILs) have attracted significant attention from researchers in various fields as a result of their unique properties. As new and important applications are identified for these materials, there is also a drive to develop methods for accessing a wider range of ILs. However, despite this demand, only a few techniques have so far been reported and, more importantly, general but efficient processes for IL synthesis have been lacking. Thus, it would be beneficial to devise a cost-effective, environmentally friendly means of producing a wide variety of pure ILs. The present work demonstrates a general purpose electrodialysis approach to the formation of highly pure ILs, based on the formation of nine different ILs from various combinations of cations and anions. In each case, the IL is obtained with a purity of greater than 99%. This method offers the advantages of avoiding the use of hazardous organic solvents and eliminating tedious and costly purification processes. Unlike conventional methods, this membrane-based technology also prevents the generation of side products. Mixed ILs have many potential applications, and the present technique readily generates various mixed ILs based on a simple adjustment of the applied current.

Highly Efficient Separation of Ultratrace Radioactive Copper Using a Flow Electrolysis Cell

Preparing compounds containing the radioisotope ⁶⁴Cu for use in positron emission tomography cancer diagnostics is an ongoing area of research. In this study, a highly efficient separation method to recover ⁶⁴Cu generated by irradiating the target ⁶⁴Ni with a proton beam was developed by employing a flow electrolysis cell (FE). This system consists of (1) applying a reduction potential for the selective adsorption of ⁶⁴Cu from the target solution when dissolved in HCl and (2) recovering the ⁶⁴Cu deposited onto the carbon working electrode by desorbing it from the FE during elution with 10 mmol/L HNO₃, which applies an oxidation potential. The ⁶⁴Cu was selectively eluted at approximately 30 min under a flow rate of 0.5 mL/min from the injection to recovery. The newly developed flow electrolysis system can separate the femtomolar level of ultratrace radioisotopes from the larger amount of target metals as an alternative to conventional column chromatography.

Electrodialytic Enrichment and Matrix Conversion for the Determination of Trace Metals in Ultra-Pure Water

The presence of trace contaminants in ultra-pure water (UPW) used in fabrication process can greatly affect the yield and quality of industrial products. In the present study, the electrodialytic enrichment of metal cations as a means of continuously monitoring the UPW quality was studied. A newly designed electrodialytic enrichment device (EED) was used to quantitatively transfer metal ions from samples to dilute nitric acid, which was then directly introduced into an inductively coupled plasma-mass spectrometry (ICP-MS) instrument. This process could be performed without contamination of the sample, and the enrichment factor was solely dependent on the flow rate ratio of the sample and acceptor solutions. The transference of analytes into the acidic solution improved the responsivity of the ICP-MS analysis, especially at low concentrations of less than 1 μg/L. Blank solutions to support the analysis of UPW could be produced using the EED effluent, from which metal ions were quantitatively removed. In addition, calibration curves with concentration ranges of several nanograms per liter were obtained by preparing standards using a dynamic gravimetric method while employing a single bottle and continuous mass monitoring to avoid any contamination from the volumetric flasks. The sensitivities associated with the ICP-MS analysis of a number of trace metal ions were improved by one or two orders of magnitude. The data show that the present EED is able to continuously produce enriched analyte solutions to allow the ongoing monitoring of UPW quality.