• Clean Technology
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• v.15 no.1
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• pp.38-41
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• 2009

Red mud is generated as a waste byproduct during the production of aluminum hydroxide/alumina from bauxite ore in the Bayer process. In this study coagulants for wastewater treatment were prepared by leaching iron and aluminum from red mud with hydrochloric acid. The removal efficiency of heavy metal ions by the red mud coagulant increased with increasing the adjusted pH value of the synthetic wastewater. When the red mud coagulant was prepared, the leaching efficiency of Fe decreased with increasing the weight of red mud, while the pH value of the red mud coagulant increased. The solution of the red mud coagulant mixed with water was reacted again with red mud to produce the leached solution, which had higher concentrations of Fe and Al and a higher pH value than the red mud coagulant. Also, its pH value was comparable to that of other coagulants: $FeCl_3$ and $Fe_2(SO_4)_3$.

• Food Science and Preservation
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• v.15 no.2
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• pp.311-316
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• 2008

We studied changes in a high-proof maesil liqueur during a 5 month leaching and ripening period at $10^{\circ}C,\;20^{\circ}C$, and $30^{\circ}C$. Titratable acidity increased after 2 months at all temperatures, but pH only changed after 2 months at $30^{\circ}C$. The absorbance at 420 nm increased significantly during a high temperature leaching and ripening period. The alcohol concentration was similar for maesil liqueurs held at $10^{\circ}C$ and $20^{\circ}C$ for 2 months. The levels of reducing sugars and polyphenols were also higher for liqueurs stored at higher temperatures. The major free sugars present after one month (in order of decreasing concentration) were fructose, glucose, sucrose, and maltose. The major organic acids were citric, lactic, malic, succinic and acetic acid The total organic acid content of maesil liqueur decreased after 1 month at $10^{\circ}C$ but increased until 2 months at $20^{\circ}C$ and $30^{\circ}C$.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1207-1212
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• 2006

In this study, Chemical Oxygen Demand(COD) which is the measure of organic substances, Total nitrogen(T-N), Total phosphorous(T-P), Fe and Mn were analyzed in the sediments of dam reservoir. The purpose of this study were to understand the relevances among the analytical methods adopted and the applicabilities of those methods. For the determination of COD, Standard Method for the Examination of Marine Environment(SMEME) and Standard Method for the Examination of Sanitary(SMES) was used. Both method had wide dynamic range and the deviations of the values obtained by two methods were small because $KMnO_4$ method closely reflected BOD and organic substances. For the determination of T-N and T-P, Standard Method for the Examination of Food(SMEF) and Standard Method for the Examination of Sanitary(SMES) were used. Two methods for T-N were both the acid-base titration but SMES gave less T-N values than SMEF because of the differences in digestion and distillation steps. Two methods for T-P gave the comparable values after acid digestion of $HNO_3$ and $HClO_4$. The determination of heavy metals as a Fe, Mn was mainly divided to the leaching method and acid digestion method. The values obtained by leaching method were less than those by digestion method. It is thought that the condition of acid digestion was more severe than that of leaching method.

• Textile Coloration and Finishing
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• v.13 no.4
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• pp.264-271
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• 2001

Catalytic wet oxidation of ethylene glycol as refractory compound was studied in a batch slurry reactor using lwt% $Pt/A1_2O_3$, lwt% $Pt/TiO_2,\;Mn/CeO_2$(1:1) and 5wt% $Mn/Al_2O_3$. Experiments were conducted to investigate theeffects of temperature, initial ethylene glycol concentration, catalyst dosage and PH on the ethylene glycol decomposition. When compared with the uncatalyzed reaction, the use of catalysts could increase the rate of ethylene glycol decomposition. The lwt% $Pt/A1_2O_3$ catalyst was preferable to the other catalysts for the destructive oxidation of ethylene glycol. The reaction rate was first order with respect to initial concentration of ethylene glycol. In acidic condition the removal efficiency of ethylene glycol was good, but there was a significant leaching of platinum. Small amount of acetic acid, oxalic acid, masonic acid and formic acid as intermediates were detected during catalytic wet air oxidation of ethylene glycol.

• Resources Recycling
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• v.30 no.5
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• pp.57-66
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• 2021

In this study, we attempted to separate and recover Cu from low-grade copper ore by a hydrometallurgical process. The leaching sample obtained after crushing and sieving by 0.355 mm of low-grade copper ore contained 1.5% Cu, 4.7% Fe, 1.0% Mn, and 0.3% Zn. The Cu in the oxide ore was very well leached into sulfuric acid and 97% Cu leaching efficiency was achieved at 80℃ and 3 M sulfuric acid (H₂SO₄). From the leaching solution, Cu was separated by solvent extraction from Fe, Mn, and Zn using LIX984N. The separation tendency between Cu and other metals was confirmed through the distribution ratio and separation factor. By plotting the McCabe-Thiele Diagram, the optimum condition for recovering Cu is 5 vol.% LIX984N, 2-stage counter-current solvent extraction, and an O/A ratio of 0.5. Using this method, 99% of the Cu was extracted and a CuSO₄ solution was finally obtained that contained 1.6 g/L Cu after the stripping process using 2 M H₂SO₄.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.409-419
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• 2023

Acid mine drainage(AMD) treatment is classified as both passive and active treatment. During the treatment, about 5,000 tons of neutralization sludge is generated as a by-product per year in Korea. This study was conducted to evaluate the characteristics of sludge generated from physico·chemical treatment processes as an active treatment from 5 different sources (D, H, S, T, Y) and the possibility of the sludges being recycled. The sludges have a pH range of 5.86 ~ pH 7.89, and a water content range of 51% ~ 82%. Most of particle sizes were less than 25 ㎛. In analysis of inorganic elements, the concentration of Al, Fe, and Mn were between 1,189 mg/kg ~ 129,344 mg/kg, 106,132 mg/kg ~ 338,011 mg/kg, and 3,472 mg/kg ~ 11,743 mg/kg, respectively. The concentration of As and Zn in sludge-T, Cd in sludge-D, Ni in sludge-H, Zn in sludge-S, and Cd in sludge-Y exceeded the soil contamination standards of Korea. The results from 2 separate kinds of leaching test, the Korea Standard Leaching Test(KSLT) and Toxicity Characteristic Leaching Procedure(TCLP), showed that all the sludges met the Korea groundwater standards. From the XRD and SEM-EDS analysis, the peaks of calcite and quartz were found in the sludges. The sludge also had a high proportion of Fe and O, and the majority of the composition was amorphous iron hydroxide.

• Economic and Environmental Geology
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• v.40 no.2 s.183
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• pp.141-151
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• 2007

This study was focused on iron removal from illite by L-ascorbic and oxalic acids. Iron has been shown as a secondary mineral such as iron oxides and hydroxides in illite ores. It is also known as a primary agent to degrade brightness index of the ores. Methods such as physical separation and chemical leaching with strong inorganic acids have been widely used to remove the iron from the ores. However, these methods are expensive and give rise to environmental problems. In this study, we examined an alternative method using solutions with different set of combination of sulfuric, hydrochloric, L-ascorbic, and oxalic acids. Compared to chemical treatments with only inorganic acids, our results demonstrate that an addition of L-ascorbic acid in inorganic acids results in decreasing both total concentrations of the inorganic acids and time for the treatments. The treatment with 0.15 M L-ascorbic acid and 0.25 M sulfuric acid in solution for 60 min significantly improved the brightness index from 42.4% to 74.4%. This improvement is similar to that of treatment with only 2.5 M sulfuric acid alone for 150 min. Mineralogical and chemical analyses were performed to compare the effect of acid leaching on illite powders. No obvious differences are observed in the mineralogical characteristics and particle size distributions of the samples. These results suggest that the treatment with the addition of L-ascorbic acid in sulfuric acid could effectively remove iron without modifying the physicochemical properties of illite under conditions used in this study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.906-913
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• 2015

The red mud generated from the Bayer alumina production process seriously threatens the environment and human safety. Therefore, the reduction and recycling of red mud is an urgent topic in the aluminum industry. In this study, the effects of four parameters, ultrasound power, reaction temperature, time, and acid concentration, on the leaching of Fe, Al from red mud was investigated. The major parameters influencing the metal recovery efficiency from red mud were ultrasound power and reaction temperature. The use of ultrasonic irradiation resulted in 1.72 and 1.28 times higher recovery efficiency for Fe and Al, respectively. The proper conditions for the recovery of the metal components present in the red mud is the ultrasound intensity (150 W), sulfuric acid concentration (4-6N), reaction temperature ($70^{\circ}C$), and reaction time (2 hours), etc.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.619-619
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• 2009

Recently, silica nanostructures are widely used in various applicationary areas such as chemical sensors, biosensors, nano-fillers, markers, catalysts, and as a substrate for quantum dots etc, because of their excellent physical, chemical and optical properties. Additionally, these days, semiconductor silica and silicon with high purity is a key challenge because of their metallurgical grade silicon (MG-Si) exhibit purity of about 99% produced by an arc discharge method with high cast. Tremendous efforts are being paid towards this direction to reduce the cast of high purity silicon for generation of photovoltaic power as a solar cell. In this direction, which contains a small amount of impurities, which can be further purified by acid leaching process. In this regard, initially the low cast rice-husk was cultivated from local rice field and washed well with high purity distilled water and were treated with acid leaching process (1:10 HCl and $H_2O$) to remove the atmospheric dirt and impurity. The acid treated rice-husk was again washed with distilled water and dried in an oven at $60^{\circ}C$. The dried rice-husk was further annealed at different temperatures (620 and $900^{\circ}C$) for the formation of silica nanospheres. The confirmation of silica was observed by the X-ray diffraction pattern and X-ray photoelectron spectroscopy. The morphology of obtained nanostructures were analyzed via Field-emission scanning electron microscope(FE-SEM) and Transmission electron microscopy(TEM) and it reveals that the size of each nanosphares is about 50-60nm. Using the Inductively coupled plasma mass spectrometry(ICP-MS), Silica was analyzed for the amount of impurities.

• Resources Recycling
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• v.15 no.6 s.74
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• pp.41-47
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• 2006

A study for recovering of copper and lead from electronic scraps has been carried out using a combination of bioleaching and solvent extraction. It was found that the citric acid generated by Aspergillus niger could be an imporant leaching agent acting in the solubilization of copper, iron, lead and tin from the electronic scrap. Copper could be selectively extracted by 10% LIX84 from the leaching solution and it recoved 99.9% of metallic copper by electrowinning process. Tin and iron were extracted from the remaining solution by 10% Alamine336 and stripped by NaCl solution. Finally, tin could be recovered as a metallic precipitates from the mixed solution of tin and iron by cementation with iron powder.