• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.385-388
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• 2008

Recycled fine aggregate has low quality because it contains large amount of old mortar. So, its usage is limited to a lower value-add, such as the roadbed material etc. Also, alkaline water occurred from treatment process of the waste concrete is becoming the cause of environmental problem. Accordingly, this study is to develop on the high quality recycled fine aggregate produced by low speed wet abraser using sulphuric. We investigated the properties of compressive strength of the mortar which was manufactured using recycled fine aggregate containing calcined gypsum produced by earlier mentioned process. Test results indicate that concrete using recycled fine aggregate containing calcined gypsum is higher compressive strength than concrete using other sands.

• Clean Technology
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• v.19 no.3
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• pp.313-319
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• 2013

To produce biodiesel efficiently from fish oil containing 4% free fatty acid, esterification and trans-esterification were carried out with Vietnam catfish oil, which was kindly provided from GS-bio company. Heterogeneous solid acid catalysts such as Amberlyst-15 and Amberlyst BD-20 and sulfuric acid as homogeneous acid catalyst were used for the esterification of free fatty acids in the fish oil. Sulfuric acid showed the highest removal efficiency of free fatty acid and the shortest reaction time among three acid catalysts. The base catalysts for trans-esterification such as KOH, $NaOCH_3$ and NaOH were compared with each other and KOH was determined to be the best transesterification catalyst. Some solid material, which assumed to be saponified product from glycerol and biodiesel, were observed to form in the fish oil biodiesel when using $NaOCH_3$ and NaOH as the transesterification catalyst. The initial acid value of fish oil was proven to have a negative effect on biodiesel conversion. Of the three catalysts, KOH catalyst transesterification was shown to have high content of FAME and the optimal ratio of methanol/oil ratio was identified to be 9:1.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.602-609
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• 1997

The seed formation and growth of $\alpha$-ferric oxyhydroxide with aerial oxidative precipitation from aqueous solution of ferrous sulfate with KOH, NaOH, $Na_2CO_3$ and $K_2CO_3$ as precipitants have been studied by free pH drift experiment. It has been shown that all precipitants give same particle formation and growth path, and average particle length from KOH and NaOH as precipitants was about 1.5 times shorter than that of $K_2CO_3$ and $Na_2CO_3$. When initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$ of KOH was decreased the particle was grown oxyhydroxide seed growth from aqueous solution of ferrous sulfate with KOH has been studied. The influence of the air flow rate, reaction temperature and initial mole ratio, $R_o=[Fe^{2+}]_o/[OH^-]_o$, on the kinetics of seed growth are investigated by static pH experiment. The oxidation rate of seed growth increased with increase in the air low rate, reaction temperature and initial mole patio. The activation energy of seed growth is 16.16 KJ/mol and the rate equation of seed growth can be written as follows: $-\frac{d[Fe^{2+}]}{dt}=1.46{\times}10^4[P_{o2}]^{0.66}[OH^-]^{2.19}exp(-\frac{16.16}{dt})$.

• Resources Recycling
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• v.30 no.1
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• pp.44-52
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• 2021

This study investigated the effect of the type of alkaline precipitant used on the synthesis of lithium hydroxide by examining the behavior of lithium hydroxide produced using lithium sulfate recovered from a waste lithium secondary battery as a raw material. The double-replacement reaction (DRR) process was used to remove the impurities contained in the lithium salt precursor of lithium sulfate and to improve the efficiency of the synthesis of lithium hydroxide. The experiment was conducted by control the molar ratio of the precursor ([Li]/[OH]), the reaction temperature, and the composition of the alkaline precipitant (KOH, Ca(OH)2, Ba(OH)2) used for the production of highly-crystalline lithium hydroxide. A secondary solid-liquid separation was performed following the reaction to remove the impurities generated, and the purified aqueous solution of lithium hydroxide was evaporated to remove the moisture and obtain the product as a powder. The crystallinity and synthesis behavior of the product were examined.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.704-707
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• 1997

The preparation of alumina sol for fine chemical field from kaolin-derived aluminum sulfate solution is performed. Noncrystalline AlO(OH) was prepared by dropping ammonia water into aluminum sufate solution with stirring. Acetetic acid was added to form the electrical double layers on the particle surface of the slurry, which resulted in a stable sol. The influence of the reaction temperature, reaction time, acetetic acid concentration on the preparation of alumina sol were investigated. Dispersed colloid particles of AlO(OH) were prepared at the reaction temperature of $50{\sim}90^{\circ}C$ and 1.6 A/C = 1.6 (molar ratio), regardless of the reaction time. Stable alumina sol having a particle size of about 5~10 nm was prepared in the range 1~5 vol% alumina content.

• Resources Recycling
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• v.30 no.5
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• pp.49-56
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• 2021

In this study, using strontium sulfate (SrSO₄) recovered from magnetite ore in Hongcheon, the Black Ash process was used to produce strontium carbonate (SrCO₃). In the carbothermic reaction step, SrSO₄ was reacted with carbon (C) at 1273 K under Ar gas atmosphere using a gas-tight quartz reactor to produce strontium sulfide (SrS). Afterward, water leaching of the residues produced from the carbothermic reaction at 353 K and carbonation of the leaching solution using sodium carbonate (Na₂CO₃) at 298 K were conducted to produce SrCO₃. The results of this study demonstrate the feasibility of the production of SrCO₃ via the Black Ash process using domestic magnetite ore containing strontium (Sr).

• Proceedings of the Korean Fiber Society Conference
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• 1998.04a
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• pp.315-319
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• 1998

셀룰로오스 용매계는 크게 직접용매계와 간접용매계로 나뉠 수 있으며, 잘 알려진 "비스코스 레이온(viscose rayon)"공정은 공정 중간단계에 이황화탄소(CS$_2$)를 사용하여 셀룰로오스 크산테이트 유도체를 만들고 이를 다시 수산화나트륨에 용해시키는 간접용매계에 속한다. 수산화나트륨 수용액에 용해된 비스코스 용액은 응고 욕내에서 황산과 반응하여 셀룰로오스로 재생이 되는데 비스코스 용액의 재생과정에서 발생하는 이황화탄소는 그 자체가 독성이 심한 가연성 액체일 뿐만 아니라 부반응을 통하여 삼황화소다(sodium trithiocarbonate) 및 황화수소(H$_2$S)를 발생한다.(중략)

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.756-762
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• 1997

The experiment was carried out to fabricate alumina membrane which has a cylindrical pore structure by anodizing aluminium plate in sulfuric acid solution with the electrochemical technique. The aluminium plate for anodizing was prepared by the pretreatment process such as chemical, electro-polishing and thermal treatment. The pore size distribution and the film thickness of alumina membrane were investigated by the implementation of scanning electron microscope(SEM) and BET method. The results show that the oxide film has a geometrical structures like a Keller model and that the membrane has a uniform pore distribution. The pore size and the oxide film thickness are dependent on the anodizing process variables such as the electrolyte concentration, the reation temperature and the anodizing current density.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.843-848
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• 1996

Porous resin beads of Poly(styrene-co-divinylbenzene) have been prepared by suspension polymerization. The bead could be made porous in the region above 30wt% of the crosslinking agent(divinylbenzene ) and the porogenic agent(toluene), respectively. The specific surface area of porous beads increased with increasing the concentrations of divinylbenzene and toluene. The specific surface area of the porous resin bead decreased, when sulfonated with concentrated sulfuric acid. The catalytic activity of sulfonated resin catalyses increased with increasing the degree of crosslinking in the liquid-phase reesterification of ethyl acetate with 1-propanol. The adsorbed quantity of sodium dodecylbenzene sulfonate in an aqueous solution also increased with increasing surface area of porous resins.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1047-1052
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• 1998

The porous alumina membrane was prepared from aluminum metal(99.8%) by anodic oxidation using DC power supply of constant current mode in aqueous solution of sulfuric, oxalic, phosphoric and chromic acid. Pore size and distribution, membrane thickness, morphology and crystal structure were examined with several anodizing conditions : reaction temperature, electrolyte concentration, current density and electrolyte type. It was found that ultrafiltration membrane was fabricated in electrolyte of sulfuric, and oxalic acid. On the other hand, microfiltration membrane was fabricated in electrolyte of phosphoric, and chromic acid. Also, it was shown that crystal structure of porous alumina membrane prepared in sulfuric, oxalic, and phosphoric acid was amorphous, whereas porous alumina membrane prepared in chromic acid had ${\gamma}$ type of crystal structure.