• Resources Recycling
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• v.33 no.4
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• pp.36-46
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• 2024

We investigated a hydrometallurgical process of nickel recovery from Inconel 713C scrap. The process proceeded with a series of i) comminution of pyrometallurgical treated scrap, ii) sulfuric acid leaching, iii) solvent extraction of unreacted acid, molybdenum, aluminum, and precipitation of chromium, iv) crystallization of nickel sulfate by vacuum evaporation, and v) nickel electrowinning. The nickel-aluminum intermetallic compound, Ni₂Al₃, was formed by the pyrometallurgical pretreatment readily grounded under 75 ㎛. Sulfuric acid leaching was done for 2 hours in 2 mol/L, 20 g/L solid/liquid ratio, and 80 ℃. It revealed that over 98 % of nickel and aluminum was dissolved, whereas 28 % of molybdenum was. A nickel sulfate solution with 2.34 g/L for the crystallization of nickel sulfate hydrate was prepared via solvent extraction and precipitation. Over 99 % of molybdenum and aluminum and 93 % of chromium was removed. Nickel metal with 99.9 % purity was obtained by electrowinning with the nickel sulfate monohydrate in the cell equipped with anion exchange membranes for catholyte pH control. The membrane did not work well, resulting in a low current efficiency of 73.3 %.

• Clean Technology
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• v.8 no.3
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• pp.151-165
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• 2002

In the treatment of the wastewater containing metals($Cu^{2+}$, $Zn^{2+}$, $Ni^{2+}$, $Cr^{3+}$) by using batch precipitation and flocculation followed by membrane filtration, permeate flux and removal efficiency were investigated according to by the effect of pH and coagulants, and the type of membranes used and pore size. It was found that it is most effective to use $0.45{\mu}m$-polysulfone membrane and coagulant(PAC) at the conditions of the pH of 10.0~10.5 for the case of copper containing wastewater, $0.1{\mu}m$-PVDF membrane and coagulant(PAC) at the conditions of the pH of 10.0~10.5 for the case of zinc containing wastewater, $0.1{\mu}m$-PVDF membrane and coagulant at the conditions of the pH of 11.0~11.5 for the case of nickel containing wastewater, $0.2{\mu}m$ membrane and coagulant at the conditions of the pH of 8.0~8.5 for the case of chromic containing wastewater, and $0.2{\mu}m{\sim}0.45{\mu}m$ membrane and coagulant at the conditions of the pH of 11.0~11.5 for the case mixture wastewater. The permeate flux could higher as to be used coagulants except for the case of copper containing wastewater.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.296-303
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• 2015

The concentration of solute in a $NaBH_4$ solution is limited due to the low solubility of $NaBO_2$. The performance of a hydrogen generation system was evaluated using various concentrations of $NaBH_4$ solution. First, a self-hydrolysis test and a hydrogen generation test for 30 min were performed. The composition of $NaBH_4$ solution was selected to be 1 wt% NaOH + 25 wt% $NaBH_4$+74wt% $H_2O$ by considering the amount of hydrogen loss, stability of hydrogen generation, $NaBO_2$ precipitation, conversion efficiency, and the purpose of its application. A hydrogen generation system for a 200 W fuel cell was evaluated for 3 h. Although hydrogen generation rate decreased with time due to $NaBO_2$ precipitation, hydrogen was produced for 3 h (conversion efficiency: 87.4%). The energy density of the 200 W fuel cell system was 263 Wh/kg. A small unmanned aerial vehicle with this fuel cell system can achieve 1.5 times longer flight time than one flying on batteries.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.679-684
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• 1997

The major constituents in spent FCC catalysts are Si, Al, Fe, Ti, alkali metals and some others. The spent catalyst is also composed small amounts of rare metals such as Ce, Nd, Ni and V. The selective adsorption and concentration of Ce and Nd from the leaching solution of spent FCC catalysts with sulfuric acid($0.25mol/dm^3$) were carried out by the column method with a chelate resin having a functional group of aminophosphoric acid type. Ce and Nd were separated from eluate liquor containing Al, Nd and V by the precipitation process with oxalic acid. Vanadium is purified from chloride ion coexistance by solvent extraction, employing tri-n-octyl phosphine oxide as extractant with Al in the raffinate solution. Rare metals with the purity of 99 percent were obtained from the spent FCC catalyst.

• Korean Journal of Food Science and Technology
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• v.34 no.4
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• pp.552-558
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• 2002

Polyphenol oxidase from Flammulina velutipes was purified and characterized. Purification of polyphenol oxidase was achieved by ammonium sulfate precipitation, Superdex G-200 gel filtration chromatography, Phenyl superose affinity chromatography, Mono-Q anion exchange chromatography and Superdex S-200 gel filtration chromatography on FPLC. After these purification steps specific activity of purified polyphenol oxidase increased to 199.1 units/mg. Polyphenol oxidase from F. velutipes was composed of a single polypeptide with molecular weight of about 40 kDa. Optimum pH and temperature for the enzyme reaction were found to be 6.0 and $25^{\circ}C$, respectively. The activity of the enzyme gradually decreased at acidic pH between 3 and 5, and the enzyme lost its activity at alkaline pH between 8 and 10. This enzyme exhibited high substrate specificity to o-diphenols. Km-values for L-DOPA and caffeic acid were found to be 3.97 mM and 1.78 mM, respectively. 2-mercaptoethanol, L-ascorbic acid, sodium bisulfite, EDTA and $Mg^{2+}$ inhibited the activity of pholyphenol oxidase and $Cu^{2+}$, $Fe^{2+}$, $Zn^{2+}$ and $Ni^{2+}$ increased enzyme activity. The activity of enzyme was well maintained at $-70^{\circ}C$ for over 4 months, and at $-20^{\circ}C$ for 1 months.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.28-39
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• 2016

Struvite (MgNH₄PO₄ ⋅ 6H₂O) and hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) precipitation in urine-separating toilets (NoMix toilets) causes severe maintenance problems and also reduce the phosphate and calcium content. Application of urine separating technique and extraction of by-products from human urine is a cost effective technique in waste water treatment. In this study, we extract urine calcite from human urine by batch scale method, using urease producing microbes to trigger the precipitation and calcite formation process. Extracted urine calcite (calcining at 800℃) is a potential adsorbent for removal of heavy metal(loid)s like (Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, Zn²⁺ and As³⁺) along with additional leaching analysis of total nitrogen (T-N), phosphate (T-P) and chemical oxygen demand (COD). The transformations of calcite during synthesis were confirm by characterization using XRD, SEM-EDAX and FT-IR techniques. In additional, the phosphate leaching potential and adsorbate (nitrate) efficiency in aqueous solution was investigated using the calcinedurine calcite. The results indicate that the calcite was effectively remove heavy metal(loid)s lead up to 96.8%. In addition, the adsorption capacity (q_e) of calcite was calculated and it was found to be 203.64 Pb, 110.96 Cd, 96.02 Zn, 104.2 As, 149.54 Cu and 162.68 Ni mg/g, respectively. Hence, we suggest that the calcite obtain from the human urine will be a suitable absorbent for heavy metal(loid)s removal from aqueous solution.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.2
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• pp.85-90
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• 2018

For the recovering rare earths in the spent nickel-metal hydride batteries, 10 M NaOH is added to the solution leached with sulfuric acid. The rare earth powders were precipitated at rate of 98 % at the condition of pH 2.0 or less. The recovered rare earth complex precipitate increased the leaching rate to nitric acid by heat treatment at $800^{\circ}C$ for 4 hours. Subsequently secondary precipitation was performed by adding oxalic acid to the solution in which the rare earth complex precipitate was dissolved. The re-precipitated rare earth powders were converted into oxide form through heat treatment at $800^{\circ}C$ for 4 hours with purity of 99.5 %.

• Journal of Microbiology and Biotechnology
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• v.18 no.4
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• pp.670-675
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• 2008

A laccase was isolated from the culture filtrate of the basidiomycete Fomitella fraxinea. The enzyme was purified to electrophoretical homogeneity using ammonium sulfate precipitation, anion-exchange chromatography, and gel-filtration chromatography. The enzyme was identified as a monomeric protein with a molecular mass of 47 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel-filtration chromatography, and had an isoelectric point of 3.8. The N-terminal amino acid sequence for the enzyme was ATXSNXKTLAAD, which had a very low similarity to the sequences previously reported for laccases from other basidiomycetes. The optimum pH and temperature for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) were 3.0 and $70^{\circ}C$, respectively. The enzyme also showed a much higher level of specific activity for ABTS and 2,6-dimethoxyphenol (DMP), where the $K_m$ values of the enzyme for ABTS and 2,6-DMP were 270 and $426{\mu}M$, respectively, and the $V_{max}$ values were 876 and $433.3{\mu}M/min$, respectively. The laccase activity was completely inhibited by L-cysteine, dithiothreitol (DTT), and sodium azide, significantly inhibited by $Ni^+,\;Mn^{2+}$, and $Ba^{2+}$, and slightly stimulated by $K^+$ and $Ca^{2+}$.

• Korean Journal of Microbiology
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• v.40 no.3
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• pp.199-204
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• 2004

The parathion hydrolase (OPH) produced by Pseudomonas rhodesiae H5 was purified by ammonium sulfate precipitation, DEAE-Toyopearl 650M ion exchange chromatography and Sephadex gel filtration chromatography. Parathion hydrolase from crude extracts of P. rhodesiae H5 has two components designated as OPH $I_1$ and OPH $I_2$, Optimum pH and temperature of OPH $I_1$and OPH $I_2$ were pH 7.2 and $30^{\circ}C$, and pH 7.6 and $37^{\circ}C$, respectively. The activation energy of OPH $I_1$ for the hydrolysis of parathion was 3.01 ㎉/I, II, III in the temperature range of $4^{\circ}C$ to $30^{\circ}C$, and Michaelis constant ($K_m$) for parathion was 69.2 ${\mu}M$. The activation energy of OPH $I_2$ for the hydrolysis of parathion was 4.07㎉/㏖ in the temperature range of $4^{\circ}C$ to $37^{\circ}C$, and Michaelis constant for parathion was 150.9${\mu}M$. Furthermore OPH $I_1$ was completely inhibited by 1 mM $Ca^2+$, $Cu^2+$, $Mg^2+$, $Ni^2+$, but OPH $I_2$ was less inhibited than OPH $I_1$ by the metals used in this study.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.4
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• pp.279-286
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• 2020

The objective of this study was to assess the impact of El Niño on highland kimchi cabbage production for the period from 1991-2016 in South Korea. Years with less than 1.0 Oceanic Niño index (ONI) were classified into non El Niño years, while years with equal to or greater than 1.0 ONI were defined as El Niño years. The national average production (3,444 kg 10a-1) of high kimchi cabbage in El Niño years tended to be less than that in non El Niño years (3,722 kg 10a-1) with significant differences (p = 0.0042) in the production between these groups of years. The averaged production of highland kimchi cabbage of El Niño end years (3,289 kg 10a-1) was less than those of El Niño start years and non El Niño years by 310 and 433 kg 10a-1, respectively. Such difference was significant statistically (p=0.035). According to our analysis, the differences in kimchi cabbage productions resulted from low temperature, short sunshine duration, and precipitation increase during the cultivation period of highland kimchi cabbage. This study may help for further analysis on the impact of extreme weather conditions during El Niño years on crop production.