• Resources Recycling
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• v.16 no.1 s.75
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• pp.59-67
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• 2007

Recovery of acids from the waste etching solution of containing acetic, nitric and hydrofluoric acid discharged from silicon wafer manufacturing process has been attempted by using solvent extraction method. EHA(2-Ethylhexlalcohol) for acetic acid and TBP(Tri-butly Phosphate) for nitric and hydrofluoric acid as a extraction agent was used to the experiment to obtain the process design data in separation procedure. From the experimental data and McCabe-Thiele diagram analysis, we obtained the optimum conditions of phase ratio(O/A) and stages to separate each acid sequently from the mixed acids. The recovery yield was obtained above 90% for acetic acid from the acid mixtures, 90% for nitric acid from acetic acid extraction raffinate and then above 67% for hydrofluoric acid from final extraction raffinate.

• Resources Recycling
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• v.2 no.4
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• pp.1-9
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• 1993

A study on the recovery of nitric and hydrofluoric acids is carried out with pulsed column extractor in order to the industrial application of this process. Firstly, from the continuous experiments about the recovery of acids using domestic stainelss steel pickling solution, it is found out that the free nitric and hydrofluoric acids are only extracted by 70% TBP and the heaby metals such as Fe, Cr and Ni are not extracted. The effectiveness of extraction and stripping generally improves as the pulse velocity(product of amplitude and frequency) is increased, optimum performance typically occuring slightly below an amplitude-frequency product which results in flooding the column because of excessive emulsification. When the pickling solution is treated by 70% TBP at a phase ratio of A/O=1/2 in the extraction and by distilled water at a phase ratio of O/A=1 in the stripping, the concentration of refined acides are 102g/$\ulcorner$ $HNO_3$and 8.8g/$\ulcorner$ HF, respectively and the recovery of $HNO_3$and HF are 90.7% and 75.2%, respectively.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2006.05a
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• pp.47-55
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• 2006

Recovery of acids from the waste etching solution of containing nitric, hydrofluoric and acetic acid discharged from silicon wafer manufacturing process has been attempted by using solvent extraction method. With EHA (2-Ethylhexlalcohol) for acetic acid and TBP(Tri-butly Phosphate) for nitic and hydrofluoric acid as extraction agent was carried on experiment to obtain the process design data in separation procedure. From the McCabe-Thiele diagram analysis, we obtained the optimum conditions of phase ratio(O/A) and stages to separate the each acid sequently from the mixture acids. The recovery yield was obtained 90% above for acetic acid from the acid mixtures, 90% above for nitric acid from acetic acid extraction raffinate and then 67% above for hydrofluoric acid from final extraction raffinate.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.259-263
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• 2001

There are several steps such as slicing, lapping, chemical etching and mechanical polishing in the silicon wafer production process. The chemical etching step is necessary to remove damaged layer caused In the slicing and lapping steps. The typical etching liquor is the acid mixture comprising nitric acid, acetic acid and hydrofluoric acid. At present, the waste acid is treated by a neutralization method with a high alkali cost and balky solid residue. A solvent extraction method is applicable to separate and recover each acid. Acetic acid is first separated from the waste liquor using 2-ethlyhexyl alcohols as an extractant. Then, nitric acid is recovered using TBP(Tri-butyl phosphate) as an extractant. Finally hydrofluoric acid is separated with the TBP solvent extraction. The expected recovered acids in this process are 2㏖/l acetic acid, 6㏖/1 nitric acid and 6㏖/l hydrofluoric acid. The yields of this process are almost 100% for acetic acid and nitric acid. On the other hand, it is important to recover and reuse the metal values contained in various industrial wastes in a viewpoint of environmental preservation. Most of industrial products are made through the processes to separate impurities in raw materials, solid and liquid wastes being necessarily discharged as industrial wastes. Chemical methods such as solvent extraction, ion exchange and membrane, and physical methods such as heavy media separation, magnetic separation and electrostatic separation are considered as the methods for separation and recovery of the metal values from the wastes. Some examples of the application of solvent extraction to the treatment of wastes such as Ni-Co alloy scrap, Sm-Co alloy scrap, fly ash and flue dust, and liquid wastes such as plating solution, the rinse solution, etching solution and pickling solution are introduced.

• Journal of Soil and Groundwater Environment
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• v.19 no.6
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• pp.6-12
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• 2014

We reviewed literature focusing on the amounts of domestic production, distribution, and consumption of strong acids and their spill cases. In particular, we investigated the chemistry and toxicity of four strong acids classified as "accident preparedness substances," including hydrochloric, nitric, sulfuric, and hydrofluoric acid. We recommend sulfuric and hydrofluoric acid as the chemicals of priority control based on the amounts used and toxicity. An advanced prevention/response system needs to be established along with an improved human and social infrastructure to prevent and efficiently respond to chemical accidents. Understanding the behavior and transport of spilled strong acids in the soil and groundwater environments requires a multi-disciplinary approach since they go through a variety of chemical and biogeochemical reactions with complex geomedia. However, no such research has been done in this area in Korea to the best of our knowledge. We expect the results of this study to contribute as basic data to future research.

• Resources Recycling
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• v.20 no.1
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• pp.61-68
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• 2011

Impurity removal from metallurgical grade silicon by acid washing at $50^{\circ}C$ was investigated by employing sulfuric, nitric acid and the mixture of hydrochloric and hydrofluoric acid. Acid washing treatment had no effect on the removal of boron and the concentration of this clement after treatment was rather increased. In our experimental range, the removal percentage of phosphorus was 60%. In the acid washing with sulfuric and nitric acid, the removal percentage of major impurities was below 50%, which indicates that refining effect was not great with these acids. Acid washing with the mixture of hydrochloric and hydrofluoric acid led to removal percentage of higher than 90%. Data on the purity of silicon after acid washing at various conditions are reported.

• Resources Recycling
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• v.1 no.1
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• pp.23-28
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• 1992

The process for recovery of acids and valuable metals such as nickel and chromium from the stainless-steel pickling acids has been developed vased on the use of solvent extraction technique. Until now, several processes for the treatment of waste acids were already developed in such countries as Japan, Swden and Canada. Those methods are, however, forcussed on the recovery of acids from them discarding the metals included in them as the hydroxides sludge. In the present work, the recovery of nickel and chromium in addition to nitric acid and hydrofluoric acid has been aimed so as to recycle them to the stainless-steel pickling lines and also to minimize the amount of sludge generated during the treatment of waste acids. The establishment of the process to recover the acids has been carried out based on the solvent extraction with TBP. The iron was eliminated from the waste solutions by precipitating in the form of hydroxide through the adjustment of pH with calcined limestone and the selective extration of chromium and nickel from the resultant solutions has been conducted by using D2EHPA as extractant.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.24-33
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• 2013

Renewable energy industries, including sola cell plants, has been ever increasing ones for reducing fossil fuel consumption and strengthening national energy policy. In this paper we tried to identify occupational health hazards in solar cell-related industries operated in Korea. Poly silicon, silicon ingot and wafer, solar cell and module are major processes for producing solar cells. Poly silicon operations may cause hazards to workers from metal silicon, silanes, silicon, hydro fluoric acid and nitric acid. Solar cells could not be constructed without using metals such as aluminum and silver, acids such as hydrofluoric acid and nitric acid, bases such as sodium hydroxide and potassium hydroxide, and solvent and phosphorus chloride oxide. Workers in module assembly process may exposed to isopropanol, flux, solders that contain lead, tin and/or copper. To prevent occupational exposure to these hazards, it is essential to identify the hazards in each process and educate workers in industries with proper engineering and administrative control measures.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.3
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• pp.310-321
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• 2019

Objectives: The purpose of this study was to investigate types and characteristics of chemical substances used in LCD(Liquid crystal display) panel manufacturing process. Methods: The LCD panel manufacturing process is divided into the fabrication(fab) process and module process. The use of chemical substances by process was investigated at four fab processes and two module processes at two domestic TFT-LCD(Thin film transistor-Liquid crystal display) panel manufacturing sites. Results: LCD panels are manufactured through various unit processes such as sputtering, chemical vapor deposition(CVD), etching, and photolithography, and a range of chemicals are used in each process. Metal target materials including copper, aluminum, and indium tin oxide are used in the sputtering process, and gaseous materials such as phosphine, silane, and chlorine are used in CVD and dry etching processes. Inorganic acids such as hydrofluoric acid, nitric acid and sulfuric acid are used in wet etching process, and photoresist and developer are used in photolithography process. Chemical substances for the alignment of liquid crystal, such as polyimides, liquid crystals, and sealants are used in a liquid crystal process. Adhesives and hardeners for adhesion of driver IC and printed circuit board(PCB) to the LCD panel are used in the module process. Conclusions: LCD panels are produced through dozens of unit processes using various types of chemical substances in clean room facilities. Hazardous substances such as organic solvents, reactive gases, irritants, and toxic substances are used in the manufacturing processes, but periodic workplace monitoring applies only to certain chemical substances by law. Therefore, efforts should be made to minimize worker exposure to chemical substances used in LCD panel manufacturing process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.109-115
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• 2022

The demand for metal 3D printing technology is increasing in various industries. The materials commonly used for metal 3D printing include aluminum alloys, titanium alloys, and stainless steel. In particular, for applications in the aviation and defense industry, aluminum alloy 3D printing parts are being produced. To improve the corrosion resistance in the 3D printed aluminum alloy outputs, a post-treatment process, such as chromate coating, should be applied. However, powdered materials, such as AlSi7Mg and AlSi10Mg, used for 3D printing, have a high silicon content; therefore, a suitable pretreatment is required for chromate coating. In the desmut step of the pretreatment process, the chromate coating can be formed only when a smut composed of silicon compounds or oxides is effectively removed. In this study, suitable desmut solutions for 3D printed AlSi7Mg and AlSi10Mg materials with high silicon contents were presented, and the chromate coating properties were studied accordingly. The smut removal effect was confirmed using an aqueous desmut solution composed of sulfuric, nitric, and hydrofluoric acids. Thus, a chromate coating was successfully formed. The surfaces of the aluminum alloys after desmut and chromate coating were analyzed using SEM and EDS.