In KAERI’s previous phosphate precipitation tests, the dispersed powder of lithium phosphate (Li3PO4) as a precipitation agent reacted with various metal chlorides in a simulated LiCl-KCl molten salt. The reaction of metal chlorides composed of actinides such as uranium and three rare earths (Nd, Ce and La) with lithium phosphate is a solid-liquid reaction. A phosphorylation reaction rate is very fast and the metal phosphates as a reaction product precipitated on the bottom of the molten salt crucible. One of the recovery methods of the metal phosphate precipitates is segregation the lower part (precipitates) of the salt ingot using the various cutting tools. Recently, a new phosphorylation experiment using lithium phosphate ingots carried out in order to collect the metal phosphate precipitates into a small recovering vessel, and the test result of this new method was feasible. However, the reaction rate of test using lithium phosphate ingot is extremely slower than that of test using lithium phosphate powder. In this study, the precipitation reactor design (a tapered crucible with polished inner surface) used for phosphorylation reaction showed that the salt ingot with metal phosphate precipitates could be detached from a tapered stainless steel crucible. We propose that the recovery of precipitates from a salt ingot is possible by introducing a dividing plate structure into a molten salt and by positioning it at the interface between salt and precipitated metal phosphate.

Decontamination of spent nuclear fuel from decommissioned nuclear reactors is crucial to reduce the volume of intermediate-level waste. Fuel cladding hulls are one of the important parts due to high radioactivity. Their decontamination could possibly enable reclassification as low-level waste. Fuel cladding hulls used in research reactors and being developed for conventional light water reactors are Al-Mg and Fe-Cr-Al alloys, respectively. Therefore, the recovery of these component metals after decontamination is necessary to reduce the volume of highly radioactive waste. Electrochemical approach is often chosen due to its simplicity and effectiveness. Non-aqueous solvents, such as molten salts (MSs) and ionic liquids (ILs), are preferred to aqueous solvents due to the absence of hydrogen evolution. However, MSs and ILs are limited by high temperature and high synthesis cost, along with toxicity issues. Deep eutectic solvents (DESs) are synthesized from a hydrogen bond acceptor (HBA) and donor (HBD) and exhibit outstanding metal salt solubility, wide electrochemical window, good biocompatibility, and economic production process. These characteristics make DES an attractive candidate solvent for economic, green, and efficient electrodeposition compared with aqueous solvents such acids or nonaqueous solvents such as MSs or ILs. In this research, the feasibility of electrodeposition of Al-Mg and Fe-Cr-Al alloys in ChCl:EG, the most common DES synthesized from choline chloride (ChCl) and ethylene glycol (EG), will be tested. A standard three-electrode electrochemical cell with an Au plated working electrode and Al wires for counter and reference electrodes is utilized. Two electrolyte solutions (Al-Mg and Fe-Cr-Al) are prepared by dissolving 100 mM of each anhydrous metal chloride salts (AlCl3, MgCl2, CrCl3, and FeCl2) in ChCl:EG. Cyclic voltammogram (CV) is measured at 5, 10, 15, and 20 mV·s−1 to observe the redox reactions occurring in the solutions. Electrodeposition of each alloy is performed via chronoamperometry at observed reduction potentials from CV measurements. The deposited surfaces and cross-sections are examined by scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) to analyze the surface morphology, cross-section composition, and thickness. Authors anticipate that the presence of different metals will greatly affect the possibility of electrodeposition. It is expected that although all metals are distributed throughout the surface, the morphology, in terms of particle size and shape, would differ depending on metals. Different metals will be deposited by layers of an approximate thickness of a few μm each. This research will illustrate a potential for recovery and electrodeposition of other precious radioactive metals from DES.

전기⋅전자산업이 급격하게 발전함에 따라 유가금속 및 희소금속의 수요가 급증하고 있다. 유가금속들은 주로 제련산업 공정에서 다량 방출되며, 회수기술 부족으로 중화, 치환, 흡착을 통해 폐기되어 큰 비용으로 경제적이지 못하다. 이에 분리막을 통한 유가금속회수 소재개발의 필요성이 강조되고 있다. 유가금속이 포함된 습식제련 공정 침출액(15% 황산 용액, 온도 60°C)은 다량의 다가이온과 1가이온을 포함하고 있기 때문에 이온별 분리가 가능해야 하며, 특히 구리와 같은 2가 유가금속 분리성능이 우수해야 한다. 또한, 지속적인 분리/농축을 위해 산에 대한 안정성이 중요하다. 따라서 본 연구를 통해 2가 금속 배제율 98%, 유량 33GFD 성능을 1개월 이상 유지하는 나노분리막 제조 연구 개발을 수행하고 있다.

본 연구에서는 제련 공정에서 발생되는 희소금속 및 유가금속 회수를 위하여 상용화 된 나노여과막인 NE40, 70, 90 (Toray Chemical Korea) 와 내산성 분리막인 NP030 (Nadir), Duracid (GE), NanoPro (AMS)를 선정 하였으며, 습식 제련 공정을 모사하기 위해 황산 15% 용액에 침지한 시간 (0 ~ 63일)에 따라 투과 특성을 평가하였다. 공급 용액으로는 대표적인 1가 이온으로 NaCl을, 2가 이온으로는 MgSO4를 2,000 ppm 사용하여, 황산 15% 용액에 63일 동안 노출하였을 때의 투과 성능 변화를 측정 하였다. 이러한 투과 특성 평가를 이용하여, 제련 공정에서 발생되는 희소금속 및 유가금속 회수를 위한 최적의 분리막을 선정 할 수 있었다.

본 연구에서는 제련 공정에서 발생되는 희소금속 및 유가금속 회수를 위한 나노여과막으로 도레이 케미칼에서 생산되는 NE40, 70, 90을 선정하였으며, 습식 제련 공정을 모사하기 위해 황산 15% 용액에 침지하여 시간에 따라 표면 특성을 분석하였다. 황산 노출 전/후의 표면 특성 분석을 위해, 주사전자현미경(SEM), 원자간력현미경 (AFM), 감쇠전반사-푸리에변환 적외선분광기 (ATR-FTIR), 광전자분광기 (XPS)를 이용하여 분석하였다. 이를 바탕으로 Piperazine 기반의 NE40, 70의 분리막이 m-Phenylenediamine (MPD) 기반의 NE90 분리막과 비교하여 산에 대한 영향이 많음을 알 수 있었으며, 내산성을 가지는 분리막을 위해 MPD 기반의 분리막이 유리함을 보여주었다.

EAF dust which is contained around 30% of zinc, 15% of iron and 3% of lead individually, is chemically treated by ammonium chloride, ammonia water, ammonia gas and carbon dioxide, and also tested and identified the ratios of the recovery of In by applied the variations of particle size, pH and heating temperature as well, in order to getting optimized recovery of the In metal after performing all of those processes. Experimental results showed that the rate of Zn recovery is 97% when the mixture of 1.3 of NH4Cl/EAF is heated to the temperature of 400℃ and leached by water, and 95% recovery of In when ammonia gas and carbon dioxide is added simultaneously and adjust the 9.5 of pH to the same mixture above. For the purpose of remove the impurities in the mixed sample, which is prepared by the two samples, indicated above showing as the ratio of 95% and 97% recovery, in case of applied the cementation process to it, and also by electrolytic process, produced the In plate of 95~97%, and acquired 99-99.5% of In metal ingot finally by applied the heating process at 470~500℃.

Heavy metal adsorption by microbial cells is an alternative to conventional methods of heavy metal removal and recovery from metal-bearing wastewater. The waste Saccharomyces cerevisiae is an inexpensive, relatively available source of biomass for heavy metal biosorption. Biosorption was investigated by free and immobilized-S. cerevisiae. The order of biosorption capacity was Pb>Cu>Cd with batch system. The biosorption parameters had been determined for Pb with free cells according to the Freundlich and Langmuir model. It was found that the data fitted reasonably well to the Freundlich model. The selective uptake of immobilized-S. cerevisiae was observed when all the metal ions were dissolved in a mixed metals solution(Pb, Cu, Cr and Cd). The biosorption of mixed metals solution by immobilized-cell was studied in packed bed reactor. The Pb uptake was investigated in particular, as it represents one of the most widely distributed heavy metals in water. We also tested the desorption of Pb from immobilized-cell by using HCl, H_2SO_4 and EDTA.