• Resources Recycling
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• v.12 no.4
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• pp.30-37
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• 2003

A kinetics study on the dissolution reaction of zinc-ferrite has been made with aqueous sulfuric acid in various temperature and concentration. Fraction reacted(R) and apparent rate constant(K) increased with increasing temperature and concentration of sulfuric acid solution. The rate of dissolution is shown by $1-(1-K)^{1/3}=Kt$ for the initial stage of the reaction in aqueous sulfuric acid, where K is apparent rate constant, R is fraction reacted and t is reaction time, respectively. Activation energy associated with reaction was determined to be 16.3 kcal/mole. The dissolution of zinc-ferrite in sulfuric acid solution is dissolved by sto-ichiometric composition, but Fe and Zn did not dissolved, respectively.

• Resources Recycling
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• v.13 no.1
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• pp.14-21
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• 2004

Spent catalysts containing platinum were generated in petroleum refinery and other chemical industries. The reclamation of platinum metals from such wastes has long been attempted in view of their rare, expensive and indispensable nature. In this study, the recovery of platinum from petroleum catalysts was attempted by a method consisting mainly of dissolving alumina carrier with sulfuric acid thereby concentrating insoluble platinum. Also, platinum dissolved partially in sulfuric acid was recovered by a cementation method using aluminum metal as a reductive agent. The effect of temperature, time, concentration of sulfuric acid, and pulp density on the dissolution of carrier was investigated. When the carrier of platinum catalyst was $\Upsilon-Al_2$O$_3$ about 95% alumina was dissolved in 6.0 M sulfuric acid at $100^{\circ}C$ for 2 hours. When the carrier was the mixture of $\Upsilon-Al_2$$O_3$ and $\alpha$-$Al_2$$O_3$ about 92% was dissolved after 4 hours. As a result, more than 99% of platinum could be recovered by this method and aluminum sulfate was also obtained as byproduct.

• Resources Recycling
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• v.18 no.2
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• pp.56-61
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• 2009

The dissolution of domestic aluminum hydroxide of 99.7% purity has been performed with mineral and organic acid prior to the synthesis of aluminum compounds from aluminum solution. Mean particle size of aluminum hydroxide used in the work was $14.4{\mu}m$, $22.9{\mu}m$ and $62.3{\mu}m$, respectively and the effect of reaction temperature, concentration of acid and reaction time on the dissolution of aluminum hydroxide has been examined. As a result, the dissolution of aluminum hydroxide was increased with the concentration of HCl and more than 70% dissolution was obtained with 5 mole/l HCl at $70^{\circ}C$ for reaction time of 4 hr. As far as the dissolution of aluminum hydroxide with sulfuric acid was concerned, it was found that the optimum concentration of sulfuric acid was about 6 mole/l for the effective dissolution of aluminum hydroxide. When oxalic acid was used for the dissolution of aluminum hydroxide, nearly complete dissolution could be obtained by the dissolution for 16 hr with 1.0 mole/l oxalic acid at $90^{\circ}C$.

• Resources Recycling
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• v.29 no.6
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• pp.27-34
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• 2020

In order to remove sulfate(SO42-) and purify the Li2CO3, dissolution and recrystallization of crude Li2CO3 using distilled water and HCl solution was performed. When Li2CO3 was dissolved using distilled water, the amount of dissolved Li2CO3(wt.%) increased as the solution temperature decrease and showed about 1.50 wt.% at 2.5℃. In addition, when Na2CO3 was added and the Li2CO3 solution was recrystallized, the recrystallization(%) increased with increasing temperature, resulting in a 49.00 % at 95 ℃. On the other hand, when Li2CO3 was dissolved using HCl solution, there was no effect of reaction temperature. As the concentration of HCl solution increased, the amount of dissolved Li2CO3(wt.%) increased, indicating 7.10 wt.% in 2.0 M HCl solution. When the LiCl solution was recrystallized by adding Na2CO3, it exhibited a recrystallization(%) of 86.10 % at a reaction temperature of 70 ℃, and showed a sulfate ion removal(%) of 96.50 % or more. Finally, more than 99.10 % of Na and more than 99.90 % of sulfate were removed from the recrystallized Li2CO3 powder through water washing, and purified Li2CO3 with a purity of 99.10 % could be recovered.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.32-32
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• 2003

Calcuim borate 화합물의 하나인 Colemanite 천연원광을 출발물질로 붕산을 제조하는 공정에 대한 연구로 황산 첨가량과 처리온도, 건조온도와 시간에 따라 생성되는 붕산의 결정상과 수득률, 순도 및 입자의 형상을 관찰하였다. 황산 첨가로 붕소 성분은 용해되어 액상에 남고, SO$_4$$^{2-}$ 와 결합하여 불용성 고체로 분리되고, 붕소의 온도에 따른 용해도 차를 이용하여 재결정화하는 방법으로 99% 이상의 순도를 갖는 붕산(H$_3$BO$_3$)을 얻었다. 공정의 각 단계에서 생성되는 화합물을 TG, NMR, IR, XRD, ICP 등의 방법으로 분석하여 최적 제조 조건을 찾았다.

• The Korean Journal of Zoology
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• v.33 no.4
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• pp.468-475
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• 1990

An In vitro protein sulfation in the soluble fraction of rat brain was charaderized further by an improved method of alkaline hydrolysis and thin layer ceflulose electrophoresis TLE) The protein sulfation was carried out in a reaction system containing [35 S] 3'-phosphoadenosine-5'-phosphosulfate (PAPS), Tris-maleate buffer (pH 8), MgCI$_2$, and soluble proteins from rat brain. The sulfated proteins were precipitated by acetone and alkaline hydrolysis was performed to obtain sulfated amino acids. The hydrolysate was separated further by TLE and the separated residues were identified by fluorography. The Iluorography of one-dimensional The showed at least nine sulfated residues including tryosine-O-sulfate. The other spots were not identified yet positively. General properties of protein sulfotransferases (PST) using this method were re-examined such as effects of concentrations of PAPS, pH, incubation temperature and $Mg^2$+. These results suggest a possible occurrence of several PST corresponding to each sulfated residue in rat brain and that the sulfation can occur not only in tyrosine but also in other residues as well.

• Resources Recycling
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• v.26 no.1
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• pp.30-36
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• 2017

Leaching experiments of anode slime were performed with several inorganic acids (HCl, $HNO_3$ and $H_2SO_4$) together with thiourea and thiosulfate solution to recover gold and silver. Gold was not dissolved at all into these inorganic acids in the absence of any oxidizing agents. At the same concentration of inorganic acid, the leaching of percentage of Ag was the highest in the sulfuric acid solution. The leaching percentage of silver increased with the increase of HCl concentration owing to the formation of $AgCl_2{^-}$. Copper, nickel and zinc except tin was almost dissolved in these inorganic acids but no tin was dissolved in nitric acid solution. Most of Au and Ag were dissolved into the mixture of sulfuric acid and thiourea solution. Thiosulfate could dissolve some silver from the anode slime but no gold was dissolved by this agent.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.155-162
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• 2012

We observed characteristic oxidation and dissolution phenomena induced by dissolved oxygen for mackinawite that is produced via sulfate-reducing bacteria (SRB) living in anaerobic environments such as soils and groundwater. We tried to recognize the role of the sulfide minerals that usually coexist with some stabilized radionuclides (e.g., reduced uranium), which can be reoxidized and redissolved by an oxygen-rich groundwater invaded into a contaminated area. The mackinawite produced by 'Desulfovibrio desulfuricans', a sulfate-reducing bacterium, was conducted to be dissolved for 2 weeks by some oxidants such as 'hydrogen peroxide' and 'sodium nitrite'. Although mineralogical oxidation and dissolution characteristics were different from each other according to the oxidants, the initially oxidized solution was early stabilized through the oxygen consumption by ${\mu}m$-sized sulfide particles and the resultant increase of sulfate in solution. From these results, we can anticipate that the large amount of sulfide minerals generated by SRB can not only repress the anoxic environment to be disturbed by the consumption of oxygen in groundwater, but also contribute to stabilize the reduced/precipitated radionuclides as a buffer material for a long time.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2001.06a
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• pp.171-174
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• 2001

식물의 대사과정을 통하여 흡수된 대기오염물질은 많은 단계의 해독과정 거치게 된다. SO$_2$ 의 경우는 세포질에서 그 대부분이 SO$_{3}$$^{2-}$ 로 용해되고 일부는 HSO$_{3}$ $^{-}$의 형태로 용해된다. 용해된 SO$_{3}$$^{2-}$ 는 아황산산화효소에 의해서 엽록체에서 생성된 $O_{2}$$^{-}$와 산화 반응하여 비교적 독성이 낮은 SO$_{4}$$^{2-}$ 로 변화한다.(중략)

• Korean Journal of Materials Research
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• v.8 no.2
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• pp.126-130
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• 1998

Aluminum sulfate, $AI_{2}(SO_4)_3\cdot18H_2O$ was prepared by adding of kaolin-dissolved sulphuric acid into ethanol and its thermal decomposition behavior was discussed. As-synthesized high purity precipitate particles were platelike shapes of $2\mu\textrm{m}$ size. With increasing drop rate of leach liquor into ethanol, the crystallite sizes of the precipitate decreased. The apparent activation energies for dehydration and sulfate decomposition of the precipitate were $11.9Kcal mol^{-1}$ and $48.2kcal mol^{-1}$ respectively.