• 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.

• New & Renewable Energy
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• v.4 no.2
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• pp.21-30
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• 2008

Anaerobic digestion (AD) is the most promising method of treating and recycling of different organic wastes, such as OFMSW, household wastes, animal manure, agro-industrial wastes, industrial organic wastes and sewage sludge. During AD, i.e. degradation in the absence of oxygen, organic material is decomposed by anaerobes forming degestates such as an excellent fertilizer and biogas, a mixture of carbon dioxide and methane. AD has been one of the leading technologies that can make a large contribution to producing renewable energy and to reducing $CO_2$ and other GHG emission, it is becoming a key method for both waste treatment and recovery of a renewable fuel and other valuable co-products. A classification of the basic AD technologies for the production of biogas can be made according to the dry matter of biowaste and digestion temperature, which divide the AD process in wet and dry, mesophilic and thermophilic. The biogas produced from AD plant can be utilized as an alternative energy source, for lighting and cooking in case of small-scale, for CHP and vehicle fuel or fuel in industrials in case of large-scale. This paper provides an overview of the status of biogas production and utilization technologies.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.202-205
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• 2008

Anaerobic digestion(AD) is the most promising method of treating and recycling of different organic wastes, such as OFMSW, household wastes, animal manure, agro-industrial wastes, industrial organic wastes and sewage sludge. During AD, i.e. degradation in the absence of oxygen, organic material is decomposed by anaerobes forming degestates such as an excellent fertilizer and biogas, a mixture of carbon dioxide and methane. AD has been one of the leading technologies that can make a large contribution to producing renewable energy and to reducing $CO_2$ and other GHG emission, it is becoming a key method for both waste treatment and recovery of a renewable fuel and other valuable co-products. A classification of the basic AD technologies for the production of biogas can be made according to the dry matter of biowaste and digestion temperature, which divide the AD process in wet and dry, mesophilic and thermophilic. The biogas produced from AD plant can be utilized as an alternative energy source, for lighting and cooking in case of small-scale, for CHP and vehicle fuel or fuel in industrials in case of large-scale. This paper provides an overview of the status of biogas production and utilization technologies.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.4
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• pp.69-76
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• 2010

After feeding mixed samples, VS ranged from 60 to 80% of total costs in 15 days. EC ranged from1.21 to 2.45, 1.25 to 2.1 and 1.2 to 1.88mS/cm when worms were fed with a mixture of by-products of tidal current and sewage sludge, a mixture of by-products of algae producy, and food wastes and a mixture of by-products of algae producy, sewage sludge and food wastes. That means the kinds of mixture don't have any negative impacts on worms survival. With the feed with a mixture of by-products of algae producy and food wastes and a mixture of by-products of algae producy, sewage sludge and food wastes, pH shows stable 5.4 to 6.7, and 6.2 to 7.4 where is suitable for worms. But a mixture of by-products of algae producy and sewage sludge is out of proper scope for raising worms, in other words, extra care will be necessary. In case of Eh, a mixture of by-products of algae producy and sewage sludge make eh negative (-) in early stage so also when feeding worms, also extra care will be needed. NaCl ranged from 0.32 to 0.82% or form 0.23 to 0.61% when a mixture of by-products of algae producy and food wastes and a mixture of by-products of algae producy, sewage sludge and food wastes were fed. So taking care of salts will be essential whenever feeding.

• Journal of the Korea Organic Resources Recycling Association
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• v.10 no.3
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• pp.59-67
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• 2002

This study was carried out to improve the utilization of food wastes known as major source of environmental pollution and to determine proper additional levels of methionine hydroxy analogue(MHA) on food wastes. 1%, 3% and 5% of MHA were added to 3 groups of food wastes gathered from small cafeteria. Each group has 3 reiteration. NaCl contents were tended to get higher as addition levels increased(p<0.05). And pH values were tended to get lower as additional levels increased(p<0.05). $NH_3-N$ contents were significantly decreased as additional levels increased(p<0.05). Total VFA(Volatile Fatty Acid) content was increased after 30 days of storage on control. On MHA treatments(1, 3, 5%), total VFA contents were decreased until 15 days of storage, and kept low values until the end of experiment. In terms of superficial change, mildew covered all over control, and covered by thin mildew on the surface of 1% MHA treatment. No superficial change found on 3% and 5% MHA treatments. In conclusion, over 1% addition of MHA was effective to prevent the decay and degeneration of food wastes.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.1
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• pp.85-93
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• 2013

The amount of salted food waste and non-salted food waste from household consisted of 4 family members was surveyed. And the feeding rate and growth rate of Eisenia fetida population upon the different food wastes such as vegetables, grains, fruits and salted food waste were investigated. Total amount of food waste from a household was 3,200g/week. i.e. 0.114kg/day/capita and non-salted food waste was 53.9% of food waste. Salt contents of vegetables, grains, fruits were 0.60, 0.36 and 0.33%, respectively, if they were assumed to have 70% water content. Salt content of salted food waste was 0.78%. Upon the non-salted vegetables and fruits, feeding rate of earthworm was high but growth rate was low. Upon the non-salted grains, feeding rate of earthworm was low but growth rate was high. Upon the food with 70% water content, earthworm could not feed and grow when salt content of food was over 0.6%, and earthworm could feed normally but showed low growth rate when salt content of food was 0.3%. These results indicated that earthworm could stabilize the non-salted food wastes with ease but could hardly stabilize the salted food wastes.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.3
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• pp.112-118
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• 2004

Laying hens' excrement from eating food wastes was mixed with paper mill sludge, aged for 21 days and then provided to the juvenile earthworms(Eisenia fetida) for 10 weeks. Biomass of earthworm population decreased by 5.7% of initially introduced population. Very few juvenile earthworms developed into the clitellates and clitellated earthworms could not produce cocoons at all, which was supposed to be caused by inhibition effects of salts in laying hens' excrement upon the sexual development of Eisenia fetida. But there was no significant effect on the survivorship of earthworm population.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.4
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• pp.213-218
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• 2010

In this study, a star screen model was constructed to predict the dynamic characteristics of interactive waste particles and to simulate separation capability of the particle using geared type screen(star screen). In order to approach this model, it is necessary to determine the design parameters of the screen such as driving torque, percentage of open space, and capability. Thus, a dynamic star screen model was developed with a total of 32 columns of geared assembly including screen part, wastes guide, and extra joints to rotate the screen using ADAMS. Each parameter was simulated to predict the screening capability for particle size, rotating speed, and particle condition. From the results, separation ability was predicted according to the affecting variables by using the dynamic star screen model.

• Resources Recycling
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• v.24 no.3
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• pp.11-15
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• 2015

In order to develop a technology for the recovery of pure tin from the Sn containing industrial wastes (SIWs), a process consisted of high temperature reduction and electrorefining was investigated. The tin which exists as oxide in SIWs was successfully reduced by two consecutive high temperature treatments and 92.7% of the tin was recovered. The purity of the tin thus obtained was increased to 99.87% by electrorefining. By applying the results obtained in this work, a commercial process can be developed to produce pure tin metals from domestic spent resources, which can reduce the amount of tin imported from abroad.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.2
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• pp.58-65
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• 2001

To produce the substitute for farmland were mixed concrete waste and organic wastes. To estirnate the application of the mixture for farmland components in the solid and the leachate from the mixture were analyzed according to the ordinance of the Waste Society in Germany. Plants were cultivated in the mixture and its harvests were measured. The results showed that the mixture from waste may be used for the reclamation of landfill and landscaping according to circumstances, and the best mixture was from 85% of concrete waste, 10% of sewage sludge and 5% of paper mill sludge.