• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.106.1-106.1
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• 2010

본 연구는 팜 부산물로부터 바이오 에탄올을 생산하는 전처리-당화-발효 공정의 첫 번째 단계인 전처리 공정에서 팜 부산물을 NaOH를 이용하여 효율적으로 전처리하고자 하였다. 암모니아 침지법과 NaOH 침출법을 비교한 결과 팜 부산물에 대해서는 암모니아 침지에 의한 탈리그닌 효과가 적으며 NaOH 전처리가 적합한 방법임을 알 수 있었다. 40-100 mesh 크기의 팜 부산물을 이용하여 반응온도(110, 130, $150^{\circ}C$), 반응시간(20, 40, 60분) 및 NaOH 농도(5%, 11%)의 변화에 따른 팜 부산물의 탈리그닌율과 글루코스 및 자일로스 회수율 간의 상호관계를 확인하였다. $150^{\circ}C$까지의 온도 조건에서 온도에 의한 자일로스의 분해는 일어나지 않는 것으로 확인되었다. 팜 부산물의 탈리그닌율은 시간이 증가할수록 증가하였으며, 높은 NaOH 농도에서 더 높은 것으로 나타났다. 그러나 글루코스 및 자일로스의 회수율은 높은 농도에서 낮게 나타났으며, 시간이 지날수록 감소하여 손실이 많은 것으로 나타났다. 따라서 NaOH 농도가 낮을수록 당 회수율은 높게 나타나지만, 탈리그닌율이 낮아 당화 효율이 떨어지므로 효소 당화 후에 최종 당 회수율이 높은 NaOH 농도 조건을 결정하여야 하겠다.

• Resources Recycling
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• v.19 no.6
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• pp.70-76
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• 2010

It was to investigate the optimum leaching conditions for the NaOH hot digestion and hydrochloric acid leaching of Monazite. The optimum condition for NaOH hot digestion was that the concentration of NaOH/TREO mole ratio was 15, the temperature of decomposition $140^{\circ}C$, and reaction time 2 hrs. And the optimum condition for the hydrochloric acid leaching of NaOH hot digestion product was that the concentration of hydrochloric acid was 6N, leaching time 2 hrs and pulp density about 15%. The yield of rare earth oxide was above 90% on the above experimental condition.

• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Resources Recycling
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• v.26 no.6
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• pp.91-96
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• 2017

Tungsten (W) recovery from tungsten carbide (WC) was researched by alkali melt followed by water leaching. The experiments of alkali melt were carried out with the change of the sort of alkali material, heating temperature, and the heating duration. Water leaching of W was performed in the fixed conditions ($25^{\circ}C$, 2 hr., slurry density: 10 g/L). From the mixture of WC and sodium nitrate ($NaNO_3$) in the molar ratio of 1:2, treated at $400^{\circ}C$ for 6 hours, only 63.3% of W might be leached by water leaching. With the increase of sodium hydroxide (NaOH) as a melting additive, the leachability increased. Finally it reached to 97.8 % with the melted mixture of ($WC:NaNO_3:NaOH$) in the ratio of (1:2:2). This imply that NaOH may play a role as a reaction catalyst by lowering Gibb's free energy for alkali melt reaction for WC.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.73-79
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• 1997

Removal of the Arsenic components from the closed mine tailings has been attempted by the alkali-leaching method. Two tailings collected from the Daduck and Yuchon mine which were already closed many years ago were leached with caustic soda solutions. The Arsenic components in the leach liquor resulted from the alkali treatment of tailings could be removed fairly well in the form of insoluble calcium-Arsenic compound by the precipitation with calcium chloride. As a result, the extraction of about 60~90% Arsenic from the tailings could be obtained depending on the leaching conditions and the influence of temperature and the slurry density on the extraction of Arsenic was also found to be very small at the NaOH concentration more than 0.5N. In addition, it seemed that a caustic soda solution over 0.5N NaOH could be used repeatedly for the leaching of tailings since the consumption of NaOH was not so great in a leaching of them. As far as the precipitation of Arsenic components was concerned, more than 99% of Arsenic could be precipitated within 10 minutes by the addition of 2wt% CaC12 in to the leach liquor.

• Resources Recycling
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• v.8 no.1
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• pp.18-22
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• 1999

In order to utilize incineration fly ash of industrial wastes as resources, we present the recovery and separation of metals included in the fly ash by leaching with aqueous solution A great quantity of Cu, Pb, and Zn as well as a small amount oftoxic heavy metals are contained in the leach liquor of the fly ash, and the concentration of the ingredients of the fly ash depends on the industrial wastes which are fed into incinerators. In this paper, sequential Ieachiog operations are conducted using $H_2O$, $H_2SO_4$, $(NH_4)_2CO_3$ and NaOH as Icachants. Water soluble copper salt was leached by $H_2O$, Zn and Pb were separated by the NaOH leach liquor, and water insoluble copper was selectively leached as chelate ion with the $(NH_4)_2CO_3$ leach liquor of the third Ieaehant. Results show that the reduction percent of the fly ash in the leaching steps using $H_2O$, $H_2SO_4$, and $(NH_4)_2CO_3$ is 77%, and the other leaching procedures lose the weight of fly ash by above 60%.

• Resources Recycling
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• v.26 no.4
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• pp.42-49
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• 2017

As a fundamental study for the separation of vanadium and tungsten from the leaching solution obtained from the soda roasting and water leaching process of spent SCR (Selective Catalytic Reduction) catalyst was carried out. The precipitation behaviors of vanadium and tungsten using the artificial solution (V: $1g{\cdot}L^{-1}$, W: $10g{\cdot}L^{-1}$) was investigated depending on temperature, NaOH concentration and the amount of $CaCl_2$ (aq.) added. V (aq.) was selectively precipitated at lower temperature than 293 K while tungsten also was precipitated at higher temperature. Precipitation rate of V and W was decreased by the increasing concentration of NaOH. On the other hand, excess Ca addition induced the increase of precipitation rate for V and W due to the formation of $Ca(OH)_2$ following the pH decline. The response surface methodology was employed to optimize the selective precipitation. Vanadium of 99.5% and tungsten of 0.0% was precipitated at $0.5mol{\cdot}L^{-1}$ of aqueous NaOH and 1 equivalent ratio of $CaCl_2$ at 293 K.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.440-450
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• 1992

Three type extraction processes of rare earth metal component from rare earth metal bearing ore were sulfuric acid digestion, caustic soda leaching and decomposition with $(NH_4)_2SO_4$. From the overall results, both caustic soda leaching and sulfuric acrid digestion were better extraction processes for domestic monazite ore. The proper conditions of sulfuric acid digestion for domestic monazite ore were reaction temperature $210^{\circ}C$, reaction time 40 min, weight ratio of $H_2SO_4$ to monazite ore 1.5 and concentration of $H_2SO_4$ 95%. Under these conditions, 98% of rare earth metal component was extracted and also the reasonable conditions for caustic soda leaching were reaction temperature $140^{\circ}C$, weight ratio of NaOH to monazite 3.0, concentration of caustic soda solution 50% and leaching time 3hrs. Under these conditions, 97% of rare earth metal component was extracted.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.11
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• pp.603-610
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• 2016

This work studies the synthesis of birnessite (${\delta}-MnO_2$), a catalyst of oxidative-coupling reactions, from the powder of spent alkaline manganese batteries (SABP, <8 mesh) and evaluate its reactivity for 1-naphthol (1-NP) removals. Manganese oxides using commercial reagents ($MnSO_4$, $MnCl_2$) and the acid birnessite (A-Bir) by McKenzie method were also synthesized, and their crystallinity and reactivity for 1-NP were compared with one another. 96% Mn and 98% Zn were extracted from SABP by acid leaching at the condition of solid/liquid (S/L) ratio 1:10 in $1.0M\;H_2SO_4+10.5%\;H_2O_2$ at $60^{\circ}C$. From the acid leaching solution, 69% (at pH 8) and 94.3% (pH>13) of Mn were separated by hydroxide precipitation. Optimal OH/Mn mixing ratio (mol/mol) for the manganese oxide (MO) synthesis by alkaline (NaOH) hydrothermal techniques was 6.0. Under this condition, the best 1-NP removal efficiency was observed and XRD analysis confirmed that the MOs are corresponding to birnessite. Kinetic constants (k, at pH 6) for the 1-NP removals of the birnessites obtained from Mn recovered at pH 8 (${Mn^{2+}}_{(aq)}$) and pH>13 ($Mn(OH)_{2(s)}$) are 0.112 and $0.106min^{-1}$, respectively, which are similar to that from $MnSO_4$ reagent ($0.117min^{-1}$). The results indicated that the birnessite prepared from the SABP as a raw material could be used as an oxidative-coupling catalyst for removals of trace phenolic compounds in soil and water, and propose the recycle scheme of SAB for the birnessite synthesis.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.227-232
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• 2013

Al-based alloys have recently attracted considerable interest as structural materials and light weight materials due to their excellent physical and mechanical properties. For the investigation of the potential of Al-based alloys, a surface porous $Al_{88}Cu_6Si_6$ eutectic alloy has been fabricated through a chemical leaching process. The formation and microstructure of the surface porous $Al_{88}Cu_6Si_6$ eutectic alloy have been investigated using X-ray diffraction and scanning electron microscopy. The $Al_{88}Cu_6Si_6$ eutectic alloy is composed of an ${\alpha}$-Al dendrite phase and a single eutectic phase of $Al_2Cu$ and ${\alpha}$-Al. We intended to remove only the ${\alpha}$-Al phase and then the $Al_2Cu$ phase would form a porous structure on the surface with open pores. Both acidic and alkaline aqueous chemical solutions were used with various concentrations to modify the influence on the microstructure and the overall chemical reaction was carried out for 24 hr. A homogeneous open porous structure on the surface was revealed via selective chemical leaching with a $H_2SO_4$ solution. Only the ${\alpha}$-Al phase was successfully leached while the morphology of the $Al_2Cu$ phase was maintained. The pore size was in a range of $1{\sim}5{\mu}m$ and the dealloying depth was nearly $3{\mu}m$. However, under an alkaline NaOH, aqueous solution, an inhomogeneous porous structure on the surface was formed with a 5 wt% NaOH solution and the morphology of the $Al_2Cu$ phase was not preserved. In addition, the sample that was leached by using a 7 wt% NaOH solution crumbled. Al extracted from the Al2Cu phase as ${\alpha}$-Al phase was dealloyed, and increasing concentration of NaOH strongly influenced the morphology of the $Al_2Cu$ phase and sample statement.