• 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.

• Journal of Surface Science and Engineering
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• v.47 no.3
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• pp.128-136
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• 2014

In the present study, we successfully developed an eco-friendly chemical etching solution and proper condition for plating on ABS material. The mechanism of forming Ni plating layer on ABS substrate is known as following. In general, the etching solution used for the etching process is a solution of chromic acid and sulfuric acid. The etching solution is given to the surface resulting in elution of butadiene group, so-called anchor effect. Such a rough surface can easily adsorb catalyst resulting in the increase of adhesion between ABS substrate and Ni plating layer. However a use of chromic acid is harmful to environment. It is, therefore, essential to develop a new alternative solution. In the present study, we proposed an eco-friendly etching solution composed of potassium permanganate, sulfuric acid and phosphoric acid. This solution was testified to observe the surface microstructure and the pore size of electrical Ni plating layer, and the adhesive correlation between deposited layers fabricated by electro Ni plating was confirmed. The result of the present study, the newly developed, eco-friendly etching solution, which is a mixture of potassium permanganate 25 g/L, sulfuric acid 650ml/L and phosphoric acid 250ml/L, has a similar etching effect and adhesion property, compared with the commercially used chromium acid solution in the condition at $70^{\circ}C$ for 5 min.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.81-90
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• 1989

High purity alumina and amorphous silica were prepared from Ha-dong kaolin by means of appliance of sulfuric acid. The effect of sulfuric acid concentration, reaction temperature and reaction time on the formation of aluminum sulfate was investigated. The precipitation conditions ofaluminum sulfate from the sulfuric acid solution with ethanol and ammonium hydroxide were deteremined. In the optimum condition, the conversion of aluminum oxide in kaolin to aluminum oxide powder was 85.0 percent. Alumina powder was prepared by calcination of the precipitates, and its purity was 99.0 percent.

• Journal of Surface Science and Engineering
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• v.57 no.1
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• pp.8-13
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• 2024

Anodizing of Al6061 alloy was conducted in two different electrolytes of 20% sulfuric acid and 8% sulfuric acid + 3 % oxalic acid solutions at a constant current or decreasing current density conditions, and its dielectric breakdown voltage was measured. The surface morphology of anodic oxide films was observed by TEM and thermal treatment was carried out at 400 ℃ for 2 h to evaluate the resistance of the anodic oxide films to crack initiation. The anodic oxide film formed in 8% sulfuric acid + 3 % oxalic acid solution showed higher dielectric breakdown voltage and better resistance to crack initiation at 400 ℃ than that formed in 20% sulfuric acid solution. The dielectric breakdown voltage increased 6 ~12% by applying decreasing current density comparing with a constant current density.

• Journal of Surface Science and Engineering
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• v.45 no.5
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• pp.198-205
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• 2012

The corrosion properties of anodized films on aluminium 6070 alloy in a sulfuric acid have been studied. Comparison to evaluate the anodized A6070 and pure 6070 specimen, corrosion tests in $HNO_3$ vapor environment of the 20 wt.% were performed up to 72 hours. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM, and EDS. The oxide film anodized in the sulfuric acid solution contained 5 to 10 wt.% of sulfur. In the initial stages of corrosion, anodized specimens exhibited corrosion resistance than the pure specimen. However, the corrosion conditions in 24 hours, corrosion was far more anodized specimen than pure specimen. Therefore, anodized films contained sulfur, nitric acid vapor in the environment is thought to stimulate corrosion.

• Structural Engineering and Mechanics
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• v.64 no.2
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• pp.243-257
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• 2017

Investigating the properties and durability of high-strength concrete exposed to sulfuric acid attack for the purpose of its application in structures exposed to this acid is of outmost importance. In this research, the resistance and durability of high-strength concrete containing macro-polymeric or steel fibers together with the pozzolans of silica fume or nano-silica against sulfuric acid attack are explored. To accomplish this goal, in total, 108 high-strength concrete specimens were made with 9 different mix designs containing macro-polymeric and steel fibers at the volume fractions of 0.5, 0.75, and 1.0%, as well as the pozzolans of silica fume and nano-silica with the replacement levels of 10 and 2%, respectively. After placing the specimens inside a 5% sulfuric acid solution in the periods of 7, 21, and 63 days of immersion, the effect of adding the fibers and pozzolans on the compressive properties, ultrasonic pulse velocity (UPV), and weight loss of high-strength concrete was investigated and the respective results were compared with those of the reference specimens. The obtained results suggest the dependency of the resistance and durability loss of high-strength concrete against sulfuric acid attack to the properties of fibers as well as their fraction in concrete volume. Moreover, compared with using nano-silica, using silica fume in the fibrous concrete mix leads to more durable specimens against sulfuric acid attack. Finally, an optimum solution for the design parameters where the crushing load of high-strength fibrous concrete is maximized was found using response surface method (RSM).

• Resources Recycling
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• v.30 no.3
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• pp.41-46
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• 2021

Methanesulfonic acid (MSA) can be considered effective in the leaching of metals because of its advantageous physical and chemical properties. The chemical reactivities of MSA and sulfuric acid were compared based on their structures and the dissolution data of Co and Ni metal. The inductive and resonance effects play a vital role in the chemical reactivities of these two acids. The dissolution percentages of Co and Ni in the sulfuric acid solution were higher than those in the MSA solution under the same experimental conditions. Considering the strong acidity of MSA and the high solubility of its metal salts, MSA can be employed as a leaching agent for the recovery of metals.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.432-436
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• 2001

In this study, calcium sulfate(gypsum) powder was obtained using waste sulfuric acid and stainless refinery sludge by- produced from chemical reagent and the iron industry, by the neutralization of waste sulfuric acid. As variables for the experiment the mole ratio of the H$_2$SO$_4$ : Ca(OH)$_2$, the pH, the reaction temperature and time, the amount of catalyst were used. The crystal shape and microstructure of obtained powder were observed by XRD and SEM, and the thermal property was investigated by DTA. As the NaCl is added 0~20wt% as a catalyst to the H$_2$SO$_4$ : Ca(OH)$_2$, system it can be found that the crystal shape goes through the processes as follows : gypsum dihydratlongrightarrowgypsum hemihydrate＋gypsum dihydratelongrightarrowgypsum hemihydrate. And gypsum hemihydrate is $\beta$-type as the result of DTA. As waste sulfuric acid and stainless refinery sludge were used, the pH of reacted solution (which was 0.8) was rapidly raised up to 8~9 by the addition of stainless sludge and gypsum dihydrate was produced as a by-product. Therefore, it was found that stainless refinery sludge is sufficiently applicable for the neutralization of waste sulfuric acid.

• New & Renewable Energy
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• v.19 no.4
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• pp.11-19
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• 2023

Levulinic acid (LA) derived from cellulosic biomass, serves a crucial intermediate that can be used in various chemical conversions. This study focused on optimizing the production of LA using two types of pretreated rice husk (de-ashed and delignificated cellulosic biomass) in a batch reaction system through catalytic conversion with sulfuric acid. To determine the optimal conditions, the conversions of glucose and α-cellulose were examined to compare the effects of pretreatment on the rice husk. The experimental parameters covered a broad spectrum, including temperatures ranging from 140℃ to 200℃, a reaction time was up to 600 minutes, and a substrate to catalyst (acid solution) ratio of 100 g/L. The highest LA yield was 44.8%, achieved from de-ashed rice husk with 3.0 wt.% of sulfuric acid at 180℃ and with a reaction time of 180 minutes. In the case of the delignificated rice husk, a LA yield of 43.6% was obtained with 3.0 wt.% of sulfuric acid at 200℃ and with reaction time of 30 minutes.

• Journal of the Korean Chemical Society
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• v.54 no.2
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• pp.240-247
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• 2010

The purposes of this study were to analyze the contents of sulfuric acid in Science textbooks and Chemistry II textbooks, and to survey 10 pre-service teachers' perceptions who majored chemistry education related to sulfuric acid. As results, most of the Science textbooks represented that sulfuric acid was divided into two $H^+$ and one $SO_4{^{2-}}$. But this mistake might be corrected because sulfuric acid was divided into one $H^+$and one $HSO_4{^-}$. Most of Chemistry II textbooks represented ionization steps of sulfuric acid, but same mistake was represented in some of Chemistry II textbooks. $HSO_4{^-}$ is a weak acid, but some Chemistry II textbooks represented $HSO_4{^-}$ as a strong acid. As results of the survey related to pre-service teachers' perceptions, some pre-service teachers didn't know the situation of particles in sulfuric acid solution, and they were affected on by the learning of high school classrooms.