• Environmental Engineering Research
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• v.21 no.2
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• pp.109-120
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• 2016

Conventional treatment techniques cannot meet the stringent modern water quality regulations emanating from the need to provide high quality drinking water. Therefore, a number of studies have suggested low pressure membrane filtration as a worthwhile alternative. However, a major constraint to the extensive use of this technology in low and middle income countries is the high operating and maintenance costs caused by the inherent predisposition to membrane fouling. Notwithstanding, pretreatment of feed water using techniques such as coagulation, adsorption, oxidation and bio-filtration is believed to control fouling. In this review paper, the existing scientific knowledge on membrane fouling and pretreatment techniques for controlling fouling in low pressure membranes is analyzed with the aim of providing new and valuable insights into such techniques, as well as unveiling crucial issues noteworthy for further studies. Among the techniques reviewed, coagulation was observed to be the most cost-effective and will remain the most dominant in the coming years. Although oxidants and magnetic ion exchange resins can also control fouling, the propensity of oxidants to form health treating precursors and the high economic implications of magnetic ion exchange resins will hinder their adoption in developing countries.

• Environmental Engineering Research
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• v.16 no.4
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• pp.205-212
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• 2011

Reverse osmosis (RO) technology has developed over the past 40 years to control a 44% market share in the world desalting production capacity and an 80% share in the total number of desalination plants installed worldwide. The application of conventional and low-pressure membrane pretreatment processes to seawater RO (SWRO) desalination has undergone accelerated development over the past decade. Reliable pretreatment techniques are required for the successful operation of SWRO processes, since a major issue is membrane fouling associated with particulate matter/colloids, organic/inorganic compounds, and biological growth. While conventional pretreatment processes such as coagulation and granular media filtration have been widely used for SWRO, there has been an increased tendency toward the use of ultrafiltration/microfiltration (UF/MF) instead of conventional treatment techniques. The literature shows that both the conventional and the UF/MF membrane pretreatment processes have different advantages and disadvantages. This review suggests that, depending on the feed water quality conditions, the suitable integration of multiple pretreatment processes may be considered valid since this would utilize the benefits of each separate pretreatment.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.1
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• pp.117-126
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• 2000

Solubilization pretreatments were conducted to enhance the anaerobic digestion of the waste activated sludge. Four pretreatment techniques including heating, sonication freezing and thawing, and enzyme addition were employed to solubilize the waste activated sludge under various conditions. Thermal pretreatment by heating showed the highest efficiency compared with other methods, and freezing and thawing was confirmed as a feasible alternative of solubilization as well as the pretreatment of dewatering. There is a clear correlation between the solubilization efficiency of the waste activated sludge and the gas production. Batch digestion results showed the cumulative gas production as much as four times after thermal pretreatment as compared with that by the control sludge without pretreatment. As a result, hydrolysis or solubilization pretreatment might play a significant role in the high rate digestion of the waste activated sludge.

• Journal of Ecology and Environment
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• v.41 no.7
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• pp.191-201
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• 2017

Background: Limited availability of corn stover due to the competing uses (organic manure, animal feed, bio-materials, and bioenergy) presents a major concern for its future in the bio-economy. Furthermore, biomass research has exhibited different results due to the differences in the supply of enzymes and dissimilar analytical methods. The effect of the two leading pretreatment techniques (dilute acid and alkaline) on glucose yield from three corn stover fractions (cob, stalk, and leaf) sourced from a single harvest in Uganda were studied at temperatures 100, 120, 140, and $160^{\circ}C$ over reaction times of 5, 10, 30, and 60 min. Results: From this study, the highest glucose concentrations obtained from the dilute acid (DA) pretreated cobs, stalks, and leaves were 18.4 g/L (66.8% glucose yield), 16.2 g/L (64.1% glucose yield), and 11.0 g/L (49.5% glucose yield), respectively. The optimal pretreatment settings needed to obtain these yields from the DA pretreated samples were at a temperature of $160^{\circ}C$ over an incubation time of 30 min. The highest glucose concentrations obtained from the alkaline (AL) pretreated cobs, stalks, and leaves were 24.7 g/L (81.73% glucose yield), 21.3 g/L (81.23% glucose yield), and 15.0 g/L (51.92% glucose yield), respectively. To be able to achieve these yields, the optimal pretreatment settings for the cobs and stalks were $140^{\circ}C$ and for a retention time of 30 min, while the leaves require optimal conditions of $140^{\circ}C$ and for a retention time of 60 min. Conclusions: The study recommends that the leaves could be left on the field during harvesting since the recovery of glucose from the pretreated cobs and stalks is higher.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.17-22
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• 2015

International interests in chemical warfare agents (CWAs) have been increased recently because of the use of sarin (GB) in Syrian civil war which caused around 1,300 casualties in 2013. After exposing to natural environments, CWAs undergo hydrolysis or photodegrade to non-toxic degradation byproducts. Generally, CWAs and their degradation byproducts are present at very low concentration (e.g. several ppb), thus pretreatment processes including separation, extraction and concentration are required prior to any analyses. Liquid-liquid extraction and solid-phase extraction (SPE) are common techniques to pretreat environmental samples. Recently, a novel pretreatment method, liquid phase miecoextraction (LPME), has been applied to CWAs analysis, which could reduce amounts of solvent used but promote analytical efficiencies. Fundamental backgrounds of LPME and its application to CWAs analysis were reviewed.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.2
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• pp.191-198
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• 2000

For a characterization of the pretreated waste automotive catalyst the following analysis techniques were applied : EA(Elemental Analysis) BET(Brunaure-Emmett-Teller) and ICP-AES(Inductively Coupled Plasma-Atomic Emission Spectrometry). The combustion activity of waste automotive catalyst was investigated for methanol acetaldehyde and toluene as model VOCs in a fixed bed reactor. carbon deposit amount was decreased with increasing catalyst showed a good catalytic activity for VOCs combustion at 40$0^{\circ}C$. Catalytic activity for methanol acetaldehyde and toluence combustion was very excellent and decreased with mileage. The catalytic activity of a waste automotive catalyst for methanol combustion increased after acid treatment. The acid effect of catalytic activity was summarized as follows: HNO3>HCI>H2SO4>CH3COOH. The waste automotive catalyst regenerated by the pretreatment method might have a excellent catalytic activity for VOCs combustion.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.435-438
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• 2004

MOCVD is one of the major deposition techniques for Cu thin films and Ta-Si-N is one of promising barrier metal candidates for Cu with high thermal stability. Effects of hydrogen plasma pretreatment of the underlying Ta-Si-N film surface on the Cu nucleation in Cu MOCVD were investigated using scanning electron microscopy, X-ray photoelectron spectroscopy and Auger electron emission spectrometry analyses. Cu nucleation in MOCVD is enhanced as the rf-power and the plasma exposure time are increased in the hydrogen plasma pretreatment. The optimal plasma treatment process condition is the rf-power of 40 Wand the plasma exposure time of 2 min. The hydrogen gas flow rate in the hydrogen plasma pretreatment process does not affect Cu nucleation much. The mechanism through which Cu nucleation is enhanced by the hydrogen plasma pretreatment of the Ta-Si-N film surface is that the nitrogen and oxygen atoms at the Ta-Si-N film surface are effectively removed by the plasma treatment. Consequently the chemical composition was changed from Ta-Si-N(O) into Ta-Si at the Ta-Si-N film surface, which is favorable for Cu nucleation.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1116-1123
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• 2020

Velvet antler (VA) is a historically traditional medicinal supplement and is well known in Asian countries for its pharmaceutical and health benefits. The objectives for this study were to optimize the hot water extraction (HWE) of VA for the Korean VA industry, and to determine the most effective pretreatment method among microwave (MW), ultrasonication (US), and enzymatic (EZ) techniques. Using response surface methodology, optimum extraction temperatures and times were determined by central composite design configuration based on extraction yield and sialic acid content. Various quality parameters of VA extract including yield, soluble solid, protein, and sialic acid contents were also compared with the conjunction of HWE and pretreatment. The yield and sialic acid content of VA extract were determined to be 40% and 0.73 mg/g, respectively, under an optimum temperature of 100℃ at 24 h of extraction time. The yields from VA extracts pretreated with MW, US, and EZ were 17.42%, 19.73%, and 29.15%, respectively. Among the tested commercial enzymes, pepsin was the most effective proteolytic enzyme and led to the highest yield (47.65%), soluble solids (4.03 °brix), protein (1.12 mg/ml), and sialic acid (3.04 mg/ml) contents from VA extract.

• Journal of Microbiology and Biotechnology
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• v.34 no.3
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• pp.622-633
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• 2024

For quality standardization, the application of functional lactic acid bacteria (LAB) as starter cultures for food fermentation is a well-known method in the fermented food industry. This study assessed the effect of adding a non-thermally microbial inactivated starter culture to kimchi, a traditional Korean food, in standardizing its quality. In this study, pretreatment based on sterilization processes, namely, slightly acidic electrolyzed water (SAEW) disinfection and ultraviolet C light-emitting diode (UVC-LED) of raw and subsidiary kimchi materials were used to reduce the initial microorganisms in them, thereby increasing the efficiency and value of the kimchi LAB starter during fermentation. Pretreatment sterilization effectively suppressed microorganisms that threatened the sanitary value and quality of kimchi. In addition, pretreatment based on sterilization effectively reduced the number of initial microbial colonies in kimchi, creating an environment in which kimchi LAB starters could settle or dominate, compared to non-sterilized kimchi. These differences in the initial microbial composition following the sterilization process and the addition of kimchi LAB starters led to differences in the metabolites that positively affect the taste and flavor of kimchi. The combined processing technology used in our study, that is, pre-sterilization and LAB addition, may be a powerful approach for kimchi quality standardization.

• Corrosion Science and Technology
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• v.13 no.6
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• pp.224-232
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• 2014

Effect of pretreatments on the graphene coated bipolar plate of proton exchange membrane fuel cell(PEMFC) was investigated in simulated environments for PEMFC by using electrochemical measurement techniques. Interfacial contact resistance(ICR) between the graphene coated bipolar plate and the gas diffusion layer(GDL) was measured. The value of ICR decreased with an increase in compaction stress($20N/cm^2{\sim}220N/cm^2$). ICR of graphene coated bipolar plate was higher than that of bare 316L stainless steel. However, Potentiodynamic measurement results showed that the corrosion resistance of graphene coated bipolar plate was higher than that of bare 316L stainless steel. $H_2SO_4$ acid pretreatment was the most effective among various pretreatments. The lowest ICR and the corrosion current density were obtained when using $H_2SO_4$ solution pretreatment.