• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.417-420
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• 2012

This study is about reduction reaction making 2, 4-dinitrotoluene (2, 4-DNT) to 2, 4-toluene diisocyanate (2,4-TDI) with Pd/$SiO_2$. Catalytic systems based on Pd/$SiO_2$ at about $200^{\circ}C$ and under 100 bars of carbon monoxide. We studied the effect of pyridine on the yield of the TDI. TDI was not created without pyridine, but created with pyridine, at the reaction result. According to research, homogeneous synthesis of TDI with direct carbonylation, palladium and pyridine complexion is known to catalyze. When adding pyridine the reason of TDI synthesis is palladium leaching, ICP-AES was performed to confirm it. As a result, the proportion of Pd loaded in $SiO_2$ was decreased 52% than before, after the reaction by adding 20 vol% pyridine. Generating TDI by adding pyridine might be the effect of the complex ion, which is composed of leached palladium and pyridine.

• Food Science and Preservation
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• v.24 no.8
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• pp.1088-1093
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• 2017

This study was conducted to investigate the effects of drying methods for Citrus junos peels on quality characteristics of the hot-water leachate from teabags containing those peels. Fresh peels were hot-air ($50^{\circ}C$), cold-air ($30^{\circ}C$), or freeze-dried ($-45^{\circ}C$), powdered to a size of 40 mesh, packaged with a paper sachet, and then the packaged teabags were leached for 10 min with hot-water ($70^{\circ}C$). $L^*$ value (lightness) and $-a^*$ value (greenness) of the peel powder were the highest in the freeze-dried samples. Soluble solids and titratable acidity of the teabag leachate were in the following order; cold-air, freeze, and hot-air dried samples. Among free sugar contents in all samples, fructose content was the highest, followed by glucose and sucrose. Fructose and glucose contents were not affected by drying methods. There was no significant difference in the flavonoid content among the peels dried using three drying methods. DPPH radical-scavenging activity of the leachate was the highest in the cold-air dried sample. These results suggest that cold-air drying would be an effective method to enhance the quality of hot-water leachate of teabags prepared from C. junos peels.

• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.403-411
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• 1984

Amberlite XAD-7 and XAD-4 resins impregnated with DXHQ (5,7-dihalo-8-hydroxyquinoline) were prepared for the adsorption, separation and recovery of heavy metal ions from aqueous solutions. The characteristics of the impregnated resins, DXHQ (X : Cl, Br, I)-XAD were studied to find out the proper pairs of resin and DXHQ for the adsorption of metal ions. The increasing order of the impregnated amount of DXHQ onto XAD-7 resin was as follows: DCHQ < DBHQ < DIHQ. It was observed from the plot of log $K_d$ vs. pH that the optimum pH range for the adsorption of DIHQ onto XAD-4 resin was from 3.0 to 7.0. The stabilities of the DXHQ-XAD resins were investigated by measuring the amount of DXHQ remained on the XAD resin after shaking the DXHQ-XAD resins in various solutions of pH ranging from 2 to 12 and hydrochloric acid solutions. The impregnated resins were considerably stable in both acidic and neutral solutions. The amount of DIHQ leached from DIHQ-XAD-4 resin by eluting with various HCl solutions (1 ∼ 5M) was negligible, but in the case of XAD-7 resin it increases as the concentration of HCl solution increases. The optimum pH ranges, absorption mole ratio (M : DXHQ) and adsorption capacities (mmol metal per gram of resin) for the adsorption of metal ions onto the DXHQ-XAD resins were determined respectively. The stability of metal ion absorbed by the DXHQ-XAD resins was observed as the following order: M-DCHQ-XAD-7 < M-DBHQ-XAD-7 < M-DIHQ-XAD-7. The adsorbed metal ions were quantitatively recovered by eluting with HCl (0.5 ∼ 5M) and DXHQ-XAD resins could be reused over 5 times without re-impregnation of DXHQ.

• Journal of the Korean Chemical Society
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• v.17 no.4
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• pp.306-313
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• 1973

With the intention of obtaining technical data for the industrial production of ${\gamma}-MnO_2$ for dry cell depolarizer by electrolytic oxidation of acidic manganese sulfate solution made from domestic rhodochrosite, optimum conditions of ore leaching, purification of leached solution and electrolytic oxidation of divalent manganes to tetravalent were investigated using simulated micro pilot plant having a production capacity of 4 kg of $MnSO_4$ per day. The nature and quality of the products were investigated by means of chemical analysis, DTA, X-ray diffraction and electron microscopy. The cell activity of $MnO_2$were examined by cell discharging character measurements. The optimum electrolysis conditions were as follow: Temperature of the electrolyte, above $90^{\circ}C$; current density, 0.7${\sim}A/dm^2$; anode materials, graphite or lead ; concentration of electrolyte, $MnSO_4 50{\sim}150g/l $ g/l and $H_2SO_4/MnSO_4 = 0.15{\sim}0.25$. Under the best condition the current efficiency was 99% and the products were almost pure ${\gamma}-MnO_2$. The cell discharging character were good and almost the same as that of regular grade commercial electrolytic manganese dioxide.

• Resources Recycling
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• v.29 no.2
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• pp.62-68
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• 2020

In new millennium, wide-reaching demands for selective catalytic reduction (SCR) catalyst have been increased gradually in new millennium. SCR catalyst can prevent the NO_x emission to protect the environment. In SCR catalyst the main composition of the catalyst is typically TiO₂ (70~80%), WO₃ (7~10%), V₂O₅ (~1%) and others. When the SCR catalysts are used up and disposed to landfills, it is problematic that those should exist in the landfill site permanently due to their extremely low degradability. A new advanced technology needs to be developed primarily to protect environment and then recover the valuable metals. Hydrometallurgical techniques such as leaching and liquid-liquid extraction was designed and developed for the spent SCR catalyst processing. In a first stage, V and W selectively leached from spent SCR catalyst, then both the metals were processed by liquid-liquid extraction process. Various commercial extractants such as D2EHPA, PC 88A, TBP, Cyanex 272, Aliquat 336 were tested for selective extraction of title metals. Scrubbing and stripping studies were tested and optimized for vanadium and tungsten extraction and possible separation. 3^rd phase studies were optimized by using iso-decanol reagent.

• Resources Recycling
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• v.29 no.2
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• pp.69-77
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• 2020

With rapid increasing production and installation, recycling of photovoltaic modules has become the main issue. According to the research, the accumulation of waste modules will reach to 8600 tons in 2030. Moreover, Crystalline-silicon (c-Si) Photovoltaic modules account for more than 90% of the waste. C-Si PV modules contain 1.3% of weight of photovoltaic ribbon inside which contains the most of lead, tin and copper in the PV modules, which would cause environmental and humility problem. This study provided a valuable metal separation process for PV ribbons. Ribbons content 82.1% of Cu, 8.9% of Sn, 5.2% of Pb, and 3.1% of Ag. All of them were leached by 3M of hydrochloric acid in the optimal condition. Ag was halogenated to AgCl and precipitated. Cu ion was extracted and separated from Pb and Sn by Lix984N then stripped by 3M H2SO4. The effect of the optimal parameters of extraction was also studied in this essay. The maximum extraction efficiency of Cu ion was 99.64%. The separation condition of Pb and Sn were obtained by adjusting the pH value to 4 thought ammonia to precipitate and separate Pb and Sn. The recovery of Pb and Sn can reach 99%.

• Resources Recycling
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• v.29 no.3
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• pp.61-74
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• 2020

This study was conducted to improve the recycling process of waste fluorescent lamp, and investigate the possibility of using the waste fluorescent lamp glass as a raw material for glass beads, the leaching method of rare earth from the waste phosphor powder, and the possibility of solvent extraction of rare earth from the rare earth leaching solution. The waste phosphor contained 28.9% yttrium oxide, 3.46% cerium oxide, 1.95% europium oxide, 1.76% terbium oxide, and 1.43% lanthanum oxide. As a result of the trial production of glass beads using waste fluorescent lamp glass, it was judged that the production yield and quality were excellent, so that waste fluorescent lamp glass could be used as a raw material for glass beads. The soda roasted waste phosphor was leached in water and thereby the aqueous solution was blown with CO₂ to drop the pH to about 7, Then, Al, Si and residual N₂CO₃ were dissolved, and NaAlCO₃(OH)₂ and SiO₂ were precipitated in the aqueous solution. In the solvent extraction of cyanex272-hydrochloric acid, cyanex272-sulfuric acid, D2EHPA-hydrochloric acid, D2EHPA-sulfuric acid, Ionquest290-hydrochloric acid, Ionquest290-sulfuric acid, p507-hydrochloric acid using xylene as a diluent, the extraction yield of Y, Eu, Ce, La, and Tb are close to 100%. However, in this conditions, the difference in extraction yield for each element, that is, selectivity is 16% or less.

• Resources Recycling
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• v.14 no.6 s.68
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• pp.3-9
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• 2005

In this study, the separation and recovery of cerium hydroxide was investigated from the wasted cerium polishing powders. Waste cerium polishing powder contains $64.5\;wt\%$ of rare earth oxide and the content of cerium oxide is $36.5\;wt\%$. Since cerium oxide, $56.3\%$ of rare earths, is the most stable state in rare earth, the dissolution of cerium oxide in acid solution is not easy. Therefore the process of rare earth oxide by sulfation and water leaching was examined in order to increase the recovery of rare earth. Rare earth elements were recovered in the form of $\Re{\cdot}Na(SO_{4})_{2}$ by the addition of sodium sulfate to leached solution. The slurry of rare earth hydroxide was prepared by the addition of $\Re{\cdot}Na(SO_{4})_{2}$ to sodium hydroxide solution. After the oxidation of cerous hydroxide($CE(OH)_{3}$) to ceric hydroxide($CE(OH)_{3}$) by aeration, ceric hydroxide was separated from other rare earth hydroxides by controlling the acidity of solution.

• Resources Recycling
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• v.14 no.1
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• pp.17-25
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• 2005

In order to recover valuable metals from the waste electronic scrap, bioleaching of Cu, Zn, Al, Co, Ni, Sn and Pb was carried out using Thiobacillus ferrooxidans as a leaching microorganism in a shaking flask. In a preliminary study, to obtain the data on the leaching of Cu, Zn, Al, Co and Ni, the metal leaching was accomplished using metal powers instead of electronic scrap. The leaching percentaga of Cu, Zn, Co, Al and Ni powers was reduced with the increase of metal power concentration in solution. Below the metal concentration of 0.5 g/L, more than 85% of Cu, Co and Zn powers was leached out. At the electronic scrap concentration of 100 g/L, Thiobacillus ferrooxidans were able to leach more than 90% of the available Cu and Co while Al, Zn and Ni were able to leach less than 40%. Pb and Sn were not detected in the leachate. Pb was precipitated as PbSO$_4$, whereas Sn precipitated probably as SnO.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.45-53
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• 2005

Electro-generated chlorine leaching of waste printed circuit boards was investigated in hydrochloric acid solutions. Non-magnetic component of $0.6{\sim}1.2mm$ was prepared by grinding, magnetic separation, and sieving. The non-magnetic component of pulverized printed circuit board contained about 45% of metal component, in which copper was about 83.6%. The leaching rate of copper was greatly affected by current density and agitation speed. The leaching of copper up to 98% was achieved at $20mA/cm^2$, $50^{\circ}C$, 180 minutes, and 600 rpm in 1M HCl solutions. Increasing agitation and lowering current density enhanced utilization efficiency of electro-generated chlorine. Leaching of copper was suppressed at the initial stage, while the minor metal elements, such as aluminum, lead, and tin, were dominantly leached out.