• Journal of Korean Society of Environmental Engineers
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• v.35 no.3
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• pp.226-232
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• 2013

Several pretreatment processes such as softening, coagulation and precipitation, activated carbon adsorption, ion-exchange and neutralization processes were studied to remove organics and inorganics for selection of the RO based reusing system of metal industry wastewater. The effects of the hydrophobic/hydrophilic fractions of the organics on DOC removal were tested and used to optimize the combination process. Among various pretreatment processes, softening could reduce 93.4% of hardness and could remove all hydrophobic organics from the effluent of metal industry wastewater. Softening followed by coagulation process could reduce DOC (Dissolved Organic Carbon) from 5.1 mg/L to 1.6 mg/L. In addition, as a result of physiochemical pretreatment to raw wastewater of metal industry, neutralization with NaOH showed an efficient removal of iron and TDS (Total Dissolved Solids) without increase in the hardness.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.639-645
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• 2008

The objectives of this research are to (1) observe changes in particle size distribution due to formation of microflocs during coagulation process (2) identify the membrane fouling potential on cross flow system (3) investigate the mechanism of membrane fouling. The rate of flux decline for the hydrophobic membrane was significantly greater than for the hydrophilic membrane, regardless of pretreatment conditions. The pretreatment of the raw water significantly reduced the fouling of the UF membrane. Also, the rate of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying coagulation process before membrane filtration showed not only reducing membrane fouling, but also improving the removal of dissolved organic materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle size distribution occurred under rapid and slow mixing condition due to the simultaneous formation of microflocs and NOM precipitates. Therefore, combined pretreatment using coagulation not only improved dissolved organics removal efficiency but also flux recovery efficiency.

• Journal of Korea Foundry Society
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• v.41 no.2
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• pp.139-143
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• 2021

A type of titanium alloy, ferro-titanium, is the main material used to manufacture steel and stainless steel. Considering economic aspects, ferro-titanium ingots are intended to be manufactured using low-cost titanium scrap, and the best pretreatment process for removing impurities from recycled titanium scrap surfaces was studied here. Instead of ordinary acid or organic solvents, ecofriendly methods were researched and applied, and chip scrap materials were used. A high-quality ferro-titanium ingot was manufactured from titanium scrap after a pretreatment process was applied, and the impurities and properties were analyzed and compared with commercial material standards through a component analysis.

• Journal of Forest and Environmental Science
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• v.36 no.2
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• pp.69-77
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• 2020

Lignocellulosic biomass has recalcitrant characteristics against chemical and biological conversion due to its structural heterogeneity and complexity. The pretreatment process to overcome these recalcitrant properties is essential, especially for the biochemical conversion of lignocellulosic biomass. In recent years, pretreatment methods using ionic liquids (ILs) and deep eutectic solvents (DESs) as the green solvent has attracted great attention because of their advantages such as easy recovery, chemical stability, temperature stability, nonflammability, low vapor pressure, and wide liquids range. However, there are some limitations such as high viscosity, poor economical feasibility, etc. to be solved for practical use. This paper reviewed the research activities on the pretreatment effect of various ILs including DESs and their co-solvents with organic solvents on the enzymatic saccharification efficiency of lignocellulosic biomass and the nanocellulose preparation from the pretreated products.

• Journal of Soil and Groundwater Environment
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• v.27 no.4
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• pp.63-74
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• 2022

In analyzing heavy metals in soil samples, the standard protocol established by Korean Minstry of Environment (KSTM) requires two different pretreatments (A and B) based on soil particle size. Soil particles < 0.15 mm in diameter after sieving are directly processed into acid extraction (method A). However, if the quantity of soil particles < 0.15 mm are not enough, grinding of the particles within 0.15 mm ~ 2 mm is required (method B). Grinding is often needed for some field samples, especially for the soil samples retrieved from soil washing process that contain relatively large-sized soil grains. In this study, two soil samples with different particle size distribution were prepared and analyzed for heavy metals concentrations using two different pretreatment to investigate the effect of grinding. The results showed that heavy metal concentrations tend to increase with the increase of the fraction of small-sized particles. In comparison of the two pretreatments, pretreatment A yielded higher heavy metal concentration than pretreatment B, indicating significant influence of grinding on analytical results. This results suggest that the analytical values of heavy metals in soil samples obtained by KSTM should be taken with caution and carefully reviewed.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.430-435
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• 2014

Physical and chemical barriers, caused by the close association of the main components of cellulosic biomass, hinder the hydrolysis of cellulose to fermentable sugars. Since the main goal of pretreatment is to increase the enzyme accessibility improving digestibility of cellulose, development of an effective pretreatment process has been considered to be important. In this study, SAA (Soaking in Aqueous Ammonia) was chosen as pretreatment because this is the simple and low-cost method. Rice straw of which the production is outstandingly high in domestic agriculture residues in Korea was chosen as raw material. SSA pretreatment with various reaction time of 3 h to 72 h was tested. The enzymatic hydrolysis and SSF (Simultaneous Saccharification and Fermentation) were performed at three different temperature (30, 40 and $50^{\circ}C$) to investigate performance of SSF upon various pretreatment conditions. As a result, this SAA treated-rice straw was found to have great potential for effective enzymatic hydrolysis and SSF with lower enzyme dosage at lower temperature ($30^{\circ}C$) than its conventional SSF. In SAA addition, SAA reduced fermentation time to 24 h owing to increase the initial hydrolysis rate substantially.

• Environmental Engineering Research
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• v.24 no.4
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• pp.662-669
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• 2019

Anaerobic digestion is a popular sewage sludge (Ss) treatment method as it provides significant pollution control and energy recovery. However, the low C/N ratio and poor biodegradability of Ss necessitate pretreatment methods that improve solubilization under anaerobic conditions in addition to anaerobic co-digestion with other substrates to improve the process efficiency. In this study, three pretreatment methods, namely microwave irradiation, ultrasonication, and heat treatment, were investigated, and the corresponding improvement in methane production was assessed. Additionally, the simplex centroid design method was utilized to determine the optimum mixture ratio of food waste (Fw), livestock manure (Lm), and Ss for maximum methane yield. Microwave irradiation at 700 W for 6 min yielded the highest biodegradability (62.0%), solubilization efficiency (59.7%), and methane production (329 mL/g VS). The optimum mixture ratio following pretreatment was 61.3% pretreated Ss, 28.6% Fw, and 10.1% Lm. The optimum mixture ratio without pretreatment was 33.6% un-pretreated Ss, 46.0% Fw, and 20.4% Lm. These results indicate that the choice of pretreatment method plays an important role in efficient anaerobic digestion and can be applied in operational plants to enhance methane production. Co-digestion of Ss with Fw and Lm was also beneficial.

• Journal of Environmental Science International
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• v.31 no.7
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• pp.609-616
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• 2022

In this study, the effect of different reaction times for thermal-alkaline pretreatment on the solubilization and biogasification of polyhydroxybutyrate (PHB) were evaluated. Thermal-alkaline pretreatment tests were performed at 73 ℃ and pH 13 at 0-120 h reaction times. The mesophilic anaerobic batch tests were performed with untreated and pretreated PHB samples. The increase in the pretreatment reaction time results in a 52.8-98.8% increase of the abiotic solubilization efficiency of the PHB samples. The reaction time required to achieve solubilization efficiencies of 50%, 90%, and 95% were 10.5, 52.0, and 89.6 h, respectively. The biogasification of the untreated PHB samples achieved a specific methane production rate of 3.6 mL CH₄/g VSS/d and require 101.3 d for complete biogasification. The thermal-alkaline pretreatment significantly improved specific methane production rate (10.2-16.0 time increase), lag time (shortened by 76-81%), and time for complete biogasification (shortened by 21-83%) for the biogasification of the PHB samples when compared to those of the untreated PHB samples. The improvement was higher as the reaction time of the thermal-alkaline pretreatment increased. The findings of this study could be used as a valuable reference for the optimization of the biogasification process in the treatment of PHB wastes.

• Journal of Environmental Health Sciences
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• v.23 no.1
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• pp.34-42
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• 1997

A laboratory experiments were performed to investigate the treatment of photographic processing wastewater by chemical oxidation and biological treatment system. The effect of reaction conditions such as hydrogen peroxide dosage, ferrous sulfate dosage and pH on the COD removal in Fenton oxidation were investigated. The optimal dosage of hydrogen peroxide was 2.58 M and 3.87 M for the developing and fixing process wastewater, respectively. The Fenton oxidation was most efficient in the pH range of 3-5 and the optimal condition for initial reaction pH was 5 for a developing process wastewater. With iron powder catalyst, the COD for a developing process wastewater was removed in lower pH than with ferrous sulfate catalyst. The removal efficiency of COD for refractory compounds such as Diethyleneglycol, Benzylalcohol, Hydroxylamine Sulfate, Ammonium Thiosulfate, Ammonium Ferric EDTA and Disodium EDTA in the photogaphic wastewater was found than 90% except Potassium Carbonate. When the photographic processing wastewater after pretreatment by Fenton oxidation was treated with batch activated sludge process, the addition of $KH_2PO_4$ as a phosphorous compound improved the removal efficiency of COD. During the continuous biological treatment of developing and fixing process wastewater after pretreatment by Fenton oxidation, the effluent COD concentration less than 100 mg/l was obtained at 0.425 and 0.25 kgCOD/m$^3$.d, respectively.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.849-858
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• 2015

This study set the pyroprocess facility at an engineering scale as a cost object, and presented the cost consumed during the unit processes of the pyroprocess. For the cost calculation, the activity based costing (ABC) method was used instead of the engineering cost estimation method, which calculates the cost based on the conceptual design of the pyroprocess facility. The calculation results demonstrate that the pyroprocess facility's unit process cost is $194/kgHM for pretreatment, $298/kgHM for electrochemical reduction, $226/kgHM for electrorefining, and $299/kgHM for electrowinning. An analysis demonstrated that the share of each unit process cost among the total pyroprocess cost is as follows: 19% for pretreatment, 29% for electrochemical reduction, 22% for electrorefining, and 30% for electrowinning. The total unit cost of the pyroprocess was calculated at $1,017/kgHM. In the end, electrochemical reduction and the electrowinning process took up most of the cost, and the individual costs for these two processes was found to be similar. This is because significant raw material cost is required for the electrochemical reduction process, which uses platinum as an anode electrode. In addition, significant raw material costs are required, such as for $Li_3PO_4$, which is used a lot during the salt purification process.