Papers by Keyword: Electrorefining

Abstract: A novel method proposed by Korea Atomic Energy Research Institute has been applied to the treatment of chloride salt wastes coming from electrorefining of spent nuclear fuel, which allows to separate uranium from fission products. It is based on a matrix, SAP (SiO₂-Al₂O₃-P₂O₅), synthesized by a conventional sol-gel process, able to stabilize the volatile salt wastes due to the formation of metalaluminosilicates, metalaluminophosphates and metalphosphates. With this method a higher disposal efficiency and a lower waste volume can be obtained. Eutectic melt LiCl-KCl (59-41 mol%) has been used to simulate the waste salt. The composite SAP has been prepared by using tetraethyl ortosilicate (TEOS), aluminum chloride (AlCl₃^.6H₂O) and phosphoric acid (H₃PO₄) as sources of Si, Al, and P, respectively. All reagents were dissolved in EtOH/H₂O and the mixture, tightly sealed, was placed in an electric oven at 70 C. After a gelling/ageing for 3 days, the transparent hydrogels were dried at 110 C for 3 days and then thermally treated at 600 C for 2 hours. The final product (SAP) was reacted with metal chlorides at increasing temperatures for 20 hours inside an Argon-atmosphere glove-box, after mixing them at a SAP/metal chloride mixing ratio of 2. The obtained products have been characterized by means of density measurements, scanning electron microscopy, thermal analysis, as well as by XRD, FTIR and Raman spectra. Financial support from the Nuclear Fission Safety Program of the European Union (project SACSESS, contract FP7-CP-2012-323282) is gratefully acknowledged.

Abstract: The NaCl-KCl-K₂HfCl₆ electrolyte successfully prepared by the reaction of HfCl₄ with equimolar NaCl-KCl. Microstructure, surface morphology and components of the electrolyte were analyzed by XRD, SEM, and EDS. The results show that HfCl₄ preferentially reacts with KCl when KCl and NaCl coexist or conversion relationship exist between Na₂HfCl₆ and K₂HfCl₆. The removal rates of oxygen reached 96.98%in electrorefining of hafnium attributed to high stability and low volatility of the electrolyte.

Abstract: Copper electro-refining (Cu-ER) is the principal method for producing >70% of high or 99.97% pure copper cathodes from 97-99% pure blister/fire refined-scrap copper anodes. While the inert and most of less soluble impurities settle as anode slime/sludge, other soluble impurities, particularly the metalloids (group VA/15 elements or Q: As, Sb and Bi) and some transition metals (Mt) co-dissolved with Cu(II). Since the soluble impurities build up in the copper refining electrolyte (CRE) which need monitoring and control to prevent contamination of the cathodes and passivation of the anodes before bleeding for spent CRE reprocessing. There is a high demand for pure electrorefined copper and electrolyte additives are added to the CRE to prevent nodulation or control the chemical and physical properties of copper cathodes. Various hydrometallurgical methods such as precipitation, adsorption, electro-dialysis, electro-winning, ion exchange and solvent extraction have been developed with some success to control the CRE impurities. So some emerging technologies for improved monitoring and control of the metalloid impurities in CRE and slime as well as development of saleable byproduct recovery (As, Sb, Bi) are briefly reviewed with particular emphasis on the precipitation for the metalloid slime resource recycling and product development.

Abstract: A flexible and efficient process of tin electrorefining has been devised, using aqueous solutions of relatively low HCl and tin chloride concentrations. Any additives have been avoided, which enhances purity but also incurs the difficulty of obtaining compact cathode deposits. This feature is however assisted by the natural inhibition in complexing chloride solutions and the modulation of the current. Due to the rough dendritic crystal growth, special provisions are required to avoid short circuiting. Using short pulses in the 50-250 μs range of periodically reversed or interrupted currents, the lengths of the usually large dendrites can be moderated. The periodic current with extremely short cycle times and special electrode arrangement can be utilized for averting short circuits and for achieving better coverage of the cathode surface. This technique can be applied efficiently to obtain pure tin from soldering waste materials.

Abstract: Studied on electrorefining metallurgical grade silicon to prepare solar grade silicon(SOG-Si) with electrochemical method in molten KCl and NaF mixture salt. Molten KCl and NaF mixture salt as electrolyte, the metallurgical grade silicon as anode and little metal nickel crucible for collecting silicon powder as cathode, electrorefining experiments were performed at 800 and 2.0V for 14h under dry argon atmosphere. The results showed that the metallurgical grade silicon could be dissolved and deposited on the cathode through molten potassium chloride (KCl) and sodium fluoride (NaF) mixture salt electrolyte. The nickel crucible was full of deposit, which was pure silicon by XRD and EDS. Purity of refined silicon was close to 99.99%, most of impurities like B and P were reduced significantly. Impurity level of silicon was reduced to the desired range for SOG-Si by advancement of the materials for the cell components.