• Environmental Engineering Research
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• v.25 no.1
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• pp.88-95
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• 2020

An investigation of rare metals recovery from LiNi_xCo_yMn_zO₂ cathode material of the end-of-life lithium-ion batteries is presented. To determine the influence of reductant on the leach process, the cathode material (containing Li 7.6%, Co 20.4%, Mn 19.4%, and Ni 19.3%) was leached in H₂SO₄ solutions either with or without H₂O₂. The optimal process parameters with respect to acid concentration, addition dosage of H₂O₂, temperature, and the leaching time were found to be 2.0 M H₂SO₄, 4 vol.% H₂O₂, 70℃, and 150 min, respectively. The yield of metal values in the leach liquor was > 99%. The leach liquor was subsequently treated by precipitation techniques to recover nickel as Ni(C₄H₇N₂O₂)₂ and lithium as Li₂CO₃ with stoichiometric ratios of 2:1 and 1.2:1 of dimethylglyoxime:Ni and Na₂CO₃:Li, respectively. Cobalt was recovered by solvent extraction following a 3-stage process using Na-Cyanex 272 at pH_eq ~5.0 with an organic-to-aqueous phase ratio (O/A) of 2/3. The loaded organic phase was stripped with 2.0 M H₂SO₄ at an O/A ratio of 8/1 to yield a solution of 114 g/L CoSO₄; finally recovered CoSO₄.xH₂O by crystallization. The process economics were analyzed and found to be viable with a margin of $476 per ton of the cathode material.

• Journal of the Korean Chemical Society
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• v.33 no.4
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• pp.366-370
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• 1989

A new macrocyclic ligand 1,15,18-triaza-3,4;12,13-dibenzo-5,8,11-cycloeicosane (NdienOdien$H_4$ = $N_3O_3$) has been synthesized and identified by element analysis, NMR and IR spectrophotometry. Stepwise protonation constants of ligand are determined by potentiometry in 95% methanol solution(I = 0.1 mol $dm^{-3}$, $Me_4$NCl). log $K_1$;log $K_2$;log $K_3$ = 9.1;8.1;3.6.The kinetics of the acid-promoted dissociation reactions of complex cations of nickel(II) and copper(III) with NdienOdien and NdienOen macrocyclic ligands having, respectively, 17 and 20 ring members, have been studied spectrophotometrically in HCl$O_4$ NaCl$O_4$ aqueous solutions. From the temperature effect on kinetic constant ($k_{obs}$), the parameters of activation(${\Delta}H^{\neq}$, ${\Delta}S^{\neq}$) of dissociation reaction for $ML^{2+}$ with $H^+$ ion have been determined. We have proposed the possible mechanism of the reaction from the data obtained.

• Journal of Oral Medicine and Pain
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• v.42 no.4
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• pp.102-108
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• 2017

Purpose: Many metal ions released from dental casting alloys have been reported to influence the intraoral symptoms of oral lichen planus (OLP) and burning mouth syndrome (BMS). The aim of this study was to investigate the relationship between salivary metal ion levels and the prosthetic duration as well as to evaluate the time-dependent morbid effects of metal ions in OLP and BMS patients. Methods: Three study groups consist of the following subjects respectively: 17 OLP patients, 12 BMS patients, and 12 patients without oral symptoms. The salivary concentrations of 13 metal ions (copper, cobalt, zinc, chromium, nickel, aluminum, silver, iron, titanium [Ti], platinum, tin, palladium, and gold) were measured by Laser Ablation Microprobe Inductively coupled Plasma Mass Spectrometry. Results: The Ti ions had statistically significant differences among the groups with a prosthetic duration of less than 5 years. There were no significant differences between all ion levels among the groups wearing dental cast alloys for over 5 years. In the BMS group, the level of Ti ions in patients with prosthetic restorations less than 5 years old were significantly high (p<0.05). Conclusions: In the BMS group, 3-60 months during which salivary Ti levels were higher were matched with the duration of burning symptoms ($15.6{\pm}17.1months$). Furthermore, Ti ions were statistically high in the oral cavity of BMS patients fitted with dental casting alloys for 5 years. These results suggest that Ti ions released from dental implants and oral prostheses could attribute to burning sensation of BMS.

• The korean journal of orthodontics
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• v.25 no.1 s.48
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• pp.43-54
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• 1995

This study was conducted to examine the metal release of TiN-plated stainless steel orthodontic appliances by constructing the simulated orthodontic appliances equivalent to maxillary half arch, by dividing into TiN-plated and TiN-nonplated Bloops and by dividing again these groups into welded and nonwelded groups. And then, the total quantity of metal release was obtained by measuring the amounts of both soluble and precipitated nickel and chromium after immersing in artificial saliva for 15 days. And then, the corrosion appearance of surface structure was observed by using SEM. The results of this study were summarized as follows. 1. The total amounts of released nickel and chromium showed that the TiN-plated group after welding(Group 1) was 25.46 ${\mu}g$, respectively, and 17.4 ${\mu}g$, while the TiN-nonplated group after welding(Group III) was 54.69 ${\mu}g$, respectively, and 85.27 ${\mu}g$. Then, the TiN-Plated group indicated less amounts of metal release(p<0.05). 2. The total amounts of the TiN-plated group without welding(Group II) was 0.05${\mu}g$ and 0.34${\mu}g$, respectively. Then, it was shown that the TiN-plated group without welding(Group II) indicated less metal release than that of the TiN-Plated group after welding(Group I)(p<0.01, p<0.05). 3. When observing their surface structure, there were a lot of precipitate and pitting corrosion in the groups with welding(Group I & III), when the TiN-plated group(Group I) showed lower level than the TiN-nonplated group(Group IIII). On the other hand, the groups without welding(Group II & IV) indicated a little of pitting corrosion. 4. In case of observation with the naked eyes, it was shown that there were significant disco1oration and corrosion in the groups with welding(Group I & III), while there was no any remarkable change in the groups without welding(Group II & IV).

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.105-112
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• 2020

Transition metal oxide, which undergoes a conversion reaction in the negative electrode material for a lithium-ion batteries, has a high specific capacity, but still has several critical problems. In this study, manganese pyrophosphate (Mn₂P₂O₇), nickel pyrophosphate (Ni₂P₂O₇), and carbon composite materials with pyrophosphates as novel negative electrode materials instead of transition metal oxide, are synthesized through simple solid-state reaction. The initial reversible capacity of Mn₂P₂O₇ and Ni₂P₂O₇ are 333 and 340 mAh g^-1, and when the composite materials are composed with carbon, the reversible capacity increases to 433 and 387 mAh g^-1, respectively. The initial Coulombic efficiency is also improved by about 10%. The Mn₂P₂O₇ and carbon composite material has the highest initial capacity and efficiency, and has the best cycle performance. Mn₂P₂O₇ containing polyanion, has a lower specific capacity due to the large mass of polyanion compared to MnO (manganese oxide). However, since Mn₂P₂O₇ shows a voltage curve with a slope, the charging (lithiation) voltage increases from 0.51 to 0.57 V (vs. Li/Li⁺), and the discharge (delithiation) voltage decreases from 1.15 to 1.01 V (vs. Li/Li⁺). Therefore, the voltage efficiency of the cell is improved because the voltage difference between charging and discharging is greatly reduced from 0.64 to 0.44 V, and the operating voltage of the full cell increases because the negative electrode potential is lowered during the discharging process.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.120-132
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• 2021

Although the development of high-Nickel is being actively carried out to solve the capacity limitation and the high price of raw cobalt due to the limitation of high voltage use of the existing LiCoO₂, the deterioration of the battery characteristics due to the decrease in structural stability and increase of the Ni content. It is an important cause of delaying commercialization. Therefore, in order to increase the high stability of the Ni-rich ternary cathod material LiNi_0.6Co_0.2Mn_0.2O₂, precursor Ni_0.6Co_0.2Mn_0.2-x(OH)₂/xTiO₂ was prepared using a nanosized TiO₂ suspension type source for uniform Ti substitution in the precursor. It was mixed with Li₂CO₃, and after heating, the cathode active material LiNi_0.6Co_0.2Mn_0.2-xTi_xO₂ was synthesized, and the physical properties according to the Ti content were compared. Through FE-SEM and EDS mapping analysis, it was confirmed that a positive electrode active material having a uniform particle size was prepared through Ti-substituted spherical precursor and Particle Size Analyzer and internal density and strength were increased, XRD structure analysis and ICP-MS quantitative analysis confirmed that the capacity was effectively maintained even when the Ti-substituted positive electrode active material was manufactured and charging and discharging were continued at high temperature and high voltage.

• Journal of the Korean Electrochemical Society
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• v.16 no.2
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• pp.85-90
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• 2013

Graphite is a commercial anode material to have the specific capacity of 372 mAh/g and the true density of 2.2 g/ml. Many effort had been pouring to find out the better material than graphite. Good candidates are silicon, tin, etc. Zinc is also a plausible candidate to have the specific capacity of 412 mAh/g and the true density of 7.14 g/ml. In this study, the Zn based anode material including indium and nickel as minor additives was synthesised. In order to get the homogeneouly mixed Zn-In-Ni composite material, the sol-gel method was used. The anode prepared by Zn-In-Ni composite material has the $1^{st}$ specific capacity of 910 mAh/g. Through prolonged charge-discharge cycling, the specific capacities were reduced to 365 (at $31^{st}$ cycle) and 378 mAh/g (at $62^{th}$ cycle). The $1^{st}$ Ah efficiency was 45% and Ah efficiencies were exhibited at the prolonged cycle.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.141-149
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• 1999

The correlation was investigated between the observed heat of ligation and calculated quantum chemical quantities for octahedral $[M(H_2O)_{6-x}(NH_3)_x]^{2+} (M=Fe(II),\;Ni(II))$ complexes by EHMO(Extended Huckel Molecular Orbital) and ZINDO/1(Zerner's Intermediate Neglected of Differential Overlap)method. The net charge of $Fe^{2+}$ and $Ni^{2+}$ ion of octahedral $[M(H_2O)_{6-x}(NH_3)_x]^{2+}(M=Fe(II),\;Ni(II))$ complexes(x=O, 1, …, 6) decreased with substituting $NH_3$ for $H_2O$ molecules. It has found that a good correlation exists between the observed heat of ligation and the calculated quantum chemical quantities such as net charge of central atom, enthalpy of formation, and total dissociation energy. From this finding, we have obtained the following semiempirical linear equation ${\Delta}H_{obs}=-0.2858_{qFe}+0.8813(r=0.97),\;{\Delta}H_{obs}=-0.8981_{qNi}+1.7929(r=0.95),\;{\Delta}H_{obs}=-0.0031H_{f(Fe)}+0.5725(r=0.97),\;{\Delta}H_{obs}=-0.0095H_{f(Ni)}+0.9193(r=0.97),\;{\Delta}H_{obs}=0.0476E_{diss(Fe)}+0.6434(r=0.94),\;{\Delta}H_{obs}=0.1401E_{diss(Ni)}+1.1393(r=0.93)$.

• Journal of Applied Biological Chemistry
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• v.54 no.2
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• pp.94-100
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• 2011

A gene encoding a putative phospholipase D was isolated from Bacillus licheniformis and cloned into pGEM-T easy vector. The gene was expressed in E. coli BL21 (DE3) using a pET-21(a) vector containing His6 tag. Affinity purification of the recombinant phospholipase D with nickel-nitrilotriacetic acid (Ni-NTA) resin resulted major one-band by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The purified enzyme showed a molecular weight of 44 kDa. The optimum activity of enzyme was around pH 7.0 and the enzyme was also the most stable around this condition. The optimum temperature was about $40-45^{\circ}C$ and the enzyme still showed considerable activities at wide range of temperature. Among various detergents, Triton X-100 significantly increased the enzyme activity, resulting in 181% activity of control at 0.6 mM of the detergent. Calcium ion did not significantly affect the enzyme activity, suggesting that the enzyme might be classified into $Ca^{2+}$-independent PLD.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.1-8
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• 2016

Capacity of layered lithium nickel-cobalt-manganese oxide ($LiNi_{1-x-y}Co_xMn_yO_2$) cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. $Li/Li^+$, but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of $198-173mAhg^{-1}$ over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.