Jesik Park

Application of Ionic Liquids in Hydrometallurgy

Ionic liquids, low temperature molten salts, have various advantages manifesting themselves as durable and environmentally friendly solvents. Their application is expanding into various fields including hydrometallurgy due to their unique properties such as non-volatility, inflammability, low toxicity, good ionic conductivity, and wide electrochemical potential window. This paper reviews previous literatures and our recent results adopting ionic liquids in extraction, synthesis and processing of metals with an emphasis on the electrolysis of active/light, rare earth, and platinum group metals. Because the research and development of ionic liquids in this area are still emerging, various, more fundamental approaches are expected to popularize ionic liquids in the metal manufacturing industry.

Synthesis of Lithium Thin Film by Electrodeposition from Ionic Liquid

Synthesis of metallic lithium thin film was investigated from two ionic liquid of [EMIM]Tf2N and PP13Tf2N with LiTFSI as a lithium source. Cyclic voltammograms on Au electrode showed the possibility of the electrodeposition of metallic lithium, the reduction current in [EMIM]Tf2N was higher than the value in PP13Tf2N. The metallic lithium thin film could be synthesized on the Au electrode by the potentiostatic condition, which was confirmed by various analytical techniques including x-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. The lithium surface electrodeposited was uniformly without dendrite, any impurity was not detected except trace oxygen contaminated during handling for analyses.

A Study on Corrosion Resistance and Electrical Surface Conductivity of an Electrodeposited Ni-W Thin Film

A Ni-W thin-film was synthesized by electrodeposition, and its corrosion resistance and electrical surface conductivity were investigated. Amount of tungsten in the Ni-W thin-film increased linearly with current density during the electrodeposition, and crack-free and low-crystalline Ni-21 at.%W coating layer was obtained. Corrosion resistances of the Ni-W thin-films were examined with an anodic polarization method and a storage test in a strong sulfuric acid solution. As a result, the Ni-21 at.%W thin-film exhibited the greatest corrosion resistance, and maintained the electrical surface conductivity even after the severe corrosion test, which could be applicable as a surface treatment for advanced metallic bipolar plates in fuel cell or redox flow battery systems.

Room temperature magnesium electrorefining by using non-aqueous electrolyte

The increasing usage of magnesium inevitably leads to a fast increase in magnesium scrap, and magnesium recycling appears extremely beneficial for cost reduction, preservation of natural resources and protection of the environment. Magnesium refining for the recovery of high purity magnesium from metal scrap alloy (AZ31B composed of magnesium, aluminum, zinc, manganese and copper) at room temperature is investigated with a non-aqueous electrolyte (tetrahydrofuran with ethyl magnesium bromide). A high purity (99.999%) of electrorefined magneisum with a smooth and dense surface is obtained after potentiostatic electrolysis with an applied voltage of 2 V. The selective dissolution of magnesium from magnesium alloy is possible by applying an adequate potential considering the tolerable impurity level in electrorefined magnesium and processing time. The purity estimation method suggested in this study can be useful in evaluating the maximum content of impurity elements.

Mineralogical Analysis and Mechano-Chemical Purification of Natural Silica Ore for High Purity Silica Powder

To produce 4N grade high-purity silica powder from natural ore, the mineralogical characteristics of natural silica ore were investigated and their effects on the purification process were revealed. The Chinese silica mineral ore used was composed of iron and aluminum as main impurities and calcium, magnesium, potassium, sodium, and titanium as trace impurities; these trace impurities generally exist as either single oxides or complex oxides. It was confirmed that liberation and acidic washing of the impurities were highly dependent on the particle size of the ground silica ore and on its mineralogical characteristics such as the distribution and phases of existing impurities. It is suggested that appropriate size reduction of silica ore should be realized for optimized purification according to the origin of the natural silica ore. A single step purification process, the mechano-chemical washing (MCW) process, was proposed and verified in comparison with the conventional multi step washing process.

Magnesium Electrorefining in Non-Aqueous Electrolyte at Room Temperature

Magnesium, of which application is often limited by its poor corrosion resistance, is more vulnerable to corrosion with existence of metal impurities such as Fe. Therefore, for the refining and recycling of magnesium, high temperature electrolysis using molten salts has been frequently adopted. In this report, the purification of magnesium scrap by electrolysis at room temperature is investigated with non-aqueous electrolytes. An aprotic solvent of tetrahydrofuran (THF) was used as a solvent of the electrolyte. Magnesium scrap was used as anode materials and ethyl magnesium bromide (EtMgBr) was dissolved in THF for magnesium source. The purified magnesium can be uniformly electrodeposited on copper electrode under potentiostatic conditions. The deposits were confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis.

Corrosion Behavior of Stainless Steel 304, Titanium, Nickel and Aluminium in Non-Aqueous Electrolytes

The corrosion behavior of stainless steel 304 (SS 304), titanium, nickel and alumin- ium is studied by immersion and anodic polarization tests in non-aqueous electrolytes. Tetra- ethyl ammonium tetrafluoroborate is used as a supporting electrolyte in the three kinds of solvents. The immersion test shows that chemical corrosion rate in propylene carbonate-based electrolyte is lower than those in acetonitrile- or γ-butyrolactone-based electrolytes. Surface analyses do not reveal any corrosion product formed after the immersion test. In the anodic polarization tests, a higher concentration of supporting electrolyte gives a higher current density. In addition, a higher temperature increases the current density in the active region and reduces the potential range in the passive region. SS 304 shows the highest corrosion potential while Al shows the lowest corrosion potential and the highest current density in all studied conditions. Based on the conducted corrosion tests, the corrosion resistance of metal substrates in the organic solvents can be sorted in descending order as follows: SS 304 - Ti - Ni - Al.

Evaluation of Corrosion and Surface Resistance of Ni-Px/C Multi Layer

Research Center, Jiodeco Co. Ltd.(Received August 14, 2012 ; revised August 29, 2012 ; accepted August 30, 2012)Abstract Ni-P/C multi-layer was synthesized by electroless plating and paste coating for better corrosion and surfaceconductance as a metallic bipolar plate. The Ni-P layer could be synthesized with the range of 2.6~22.4at.% P contents and its surface morphology and corrosion resistance depend on content of P. Corrosion resis-tance of the Ni-P layer in sulfuric acid by electrochemical test is similar with pure Ni. Surface resistanceof pure Ni after corrosion was increased about 8% compared to pure Ni. On the other hand, that of theNi-P/C composite with 20% carbon content was increased only 1%.