• Applied Chemistry for Engineering
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• v.32 no.2
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• pp.139-142
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• 2021

Coal-fired power plants use coal as the main raw material, and when a coal is moved, a dust generation and spontaneous ignition of coal occur. To prevent this, water is sprayed. As a result, wastewater called "coal-dust water" flows out of coal dust and water mixed together, causing environmental pollution. In this study, in order to solve this problem, we developed a natural flocculant that can purify water by aggregating fine dust using chitosan and tried to prove its applicability. It was found that the optimum flocculation concentration was 4 ppm by adding various concentrations of flocculant to the coal-dust water, and it was confirmed that the developed material had very good coal-dust flocculation capacity through permeability and coal-dust removal efficiency. In addition, the cytotoxicity of the flocculant was evaluated through the MTT assay and it was found that there is no toxicity at all. We believe that the flocculant developed in this study can effectively adsorb coal-dust without affecting human and natural ecosystems.

• Environmental Engineering Research
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• v.24 no.1
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• pp.38-44
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• 2019

The Biochemical Methane Potential (BMP) of fresh leachate and domestic wastewaters codigestion was determined by laboratory Bach Tests at $35^{\circ}C$ over a period of 90 d using a wide range of leachates volumetric ratios from 0% to 100%. To simulate wastewaters plant treatment step, all the ratios were first air stripped for 48 h before anaerobic incubation. The kinetic of biogas production was assessed using modified Gompertz model and exponential equation. The results obtained showed that cumulative biogas production was insignificant in the case of wastewaters monodigestion while the codigestion significantly improves the BMP. Air stripping pretreatment had positive effect on both ammonium concentration and volatiles fatty acids with reduction up to 75% and 42%, respectively. According to the Modified Gompertz model, the optimal anaerobic co-digestion conditions both in terms of maximal biogas potential, start-up period and maximum daily biogas production rate, could be achieved within large leachate volumetric ratios from 25% to 75% with a maximum BMP value of 438.42 mL/g volatile solid at 50% leachate ratio. The positive effect of codigestion was attributed to a dilution effect of chemical oxygen demand and volatile fatty acid concentrations to optimal range that was between 11.7 to $32.3gO_2/L$ and 2.1 to 7.4 g/L, respectively. These results suggested that the treatment of fresh leachate by their dilution and co digestion at wastewaters treatment plants could be a promising alternative for both energetic and treatment purposes.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.4
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• pp.243-250
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• 2019

This objective of this study was to investigate the degradation characteristics of phenol, a refractory substance, by using a submerged dielectric barrier discharge (DBD) plasma reactor. To indirectly determine the concentration of active species produced in the DBD plasma, the dissolved ozone was measured. To investigate the phenol degradation characteristics, the phenol and chemical oxygen demand (COD) concentrations were evaluated based on pH and the discharge power. The dissolved ozone was measured based on the air flow rate and power discharged. The highest dissolved ozone concentration was recorded when the injected air flow rate was 5 L/min. At a discharge power of 40W as compared to 70W, the dissolved ozone was approximately 2.7 - 6.5 times higher. In regards to phenol degradation, the final degradation rate was highest at about 74.06%, when the initial pH was 10. At a discharged power of 40W, the rate of phenol decomposition was observed to be approximately 1.25 times higher compared to when the discharged power was 70W. It was established that the phenol degradation reaction was a primary reaction, and when the discharge power was 40W as opposed to 70W, the reaction rate constant(k) was approximately 1.72 times higher.

• Korean Journal of Agricultural Science
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• v.46 no.1
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• pp.183-194
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• 2019

Adulteration of argan oil with some other cheaper oils with similar chemical compositions has resulted in increasing demands for authenticity assurance and quality control. Fast and simple analytical techniques are thus needed for authenticity analysis of high-priced argan oil. Raman spectroscopy is a potent technique and has been extensively used for quality control and safety determination for food products In this study, Raman spectroscopy in combination with a net analyte signal (NAS)-based methodology, i.e., hybrid linear analysis method developed by Goicoechea and Olivieri in 1999 (HLA/GO), was used to predict the different concentrations of olive oil (0 - 20%) added to argan oil. Raman spectra of 90 samples were collected in a spectral range of $400-400cm^{-1}$, and calibration and validation sets were designed to evaluate the performance of the multivariate method. The results revealed a high coefficient of determination ($R^2$) value of 0.98 and a low root-mean-square error (RMSE) value of 0.41% for the calibration set, and an $R^2$ of 0.97 and RMSE of 0.36% for the validation set. Additionally, the figures of merit such as sensitivity, selectivity, limit of detection, and limit of quantification were used for further validation. The high $R^2$ and low RMSE values validate the detection ability and accuracy of the developed method and demonstrate its potential for quantitative determination of oil adulteration.

• Research in Plant Disease
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• v.24 no.4
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• pp.292-301
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• 2018

Alternaria leaf spot disease has been a concern during a tomato production in greenhouse. In vitro antifungal activities of vapours of four plant essential oils, cinnamon oil, fennel oil, origanum oil and thyme oil, were investigated during in vitro conidial germination and mycelial growth of Alternaria alternata causing the tomato leaf spots to find eco-friendly alternatives for chemical fungicides. The four plant essential oils showed different antifungal activities against in vitro conidial germination of A. alternata in dose-dependent manners, and cinnamon oil vapour was most effective to suppress the conidial germination. The four plant essential oils showed similar antifungal activities against the in vitro mycelial growth of A. alternata in dose-dependent manners, but low doses of thyme oil vapour slightly increased in vitro mycelial growth of A. alternata. Necrotic lesions on the A. alternata-inoculated tomato leaves were reduced differently depending on kinds and concentrations of plant essential oils. Delayed conidial germination and germ-tube elongation of A. alternata were found on the tomato leaves treated with cinnamon oil and origanum oil vapours at 6 hpi. These results suggest that volatiles from cinnamon oil and origanum oil can be provided as alternatives to manage Alternaria leaf spot during the tomato production eco-friendly.

• Journal of Environmental Science International
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• v.27 no.11
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• pp.1095-1104
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• 2018

The adsorption characteristics of bisphenol A (BPA) were investigated using activated carbon based on waste citrus peel (which is abandoned in large quantities in Jeju Island), denoted as WCP-AC, and surface-modified with various $P_2O_5$ concentrations (WCP-SM-AC). Moreover, coconut-based activated carbon (which is marketed in large amounts) was surface-modified in an identical manner for comparison. The adsorption equilibrium of BPA using the activated carbons before and after surface modification was obtained at nearly 48 h. The adsorption process of BPA by activated carbons and surface-modified activated carbons was well-described by the pseudo second-order kinetic model. The experimental data in the adsorption isotherm followed the Langmuir isotherm model. With increasing $P_2O_5$ concentration (250-2,000 mg/L), the amounts of BPA adsorbed by WCP-SM-AC increased till 1,000 mg/L of $P_2O_5$; however, above 1,000 mg/L of $P_2O_5$, the same amounts adsorbed at 1,000 mg/L of $P_2O_5$ were obtained. With increasing reaction temperature, the reaction rate increased, but the adsorbed amounts decreased, especially for the activated carbon before surface modification. The amounts of BPA adsorbed by WCP-AC and WCP-SM-AC were similar in the pH range of 5-9, but significantly decreased at pH 11, and increased with increasing ionic strength due to screening and salting-out effects.

• Membrane and Water Treatment
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• v.10 no.5
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• pp.339-352
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• 2019

Long term water quality change was analyzed to evaluate the effect of the Total Maximum Daily Load (TMDL) policy. A trend analysis was performed for biochemical oxygen demand (BOD) and total phosphorus (TP) concentrations data monitored at the outlets of the total 41 TMDL unit watersheds of the Nakdong River in the Republic of Korea. Because water quality data do not usually follow a normal distribution, a nonparametric statistical trend analysis method was used. The monthly mean values of BOD and TP for the period between 2004 and 2015 were analyzed by the seasonal Mann-Kendall test and the locally weighted scatterplot smoother (LOWESS). The TMDL policy effect on the water quality change of each unit watershed was analyzed together with the results of the trend analysis. From the seasonal Mann-Kendall test results, it was found that for BOD, 7.8 % of the 41 points showed downward trends, 26.8 % and the rest 65.9% showed upward and no trends. For TP, 51.2% showed no trends and the rest 48.8% showed downward trends. From the LOWESS analysis results, TP began to decrease in most of the unit watersheds from mid-2010s when intensive chemical treatment processes were introduced to existing wastewater treatment plants. Overall, for BOD, relatively more points were improved in the main stream compared to the points of the tributaries although overall trends were mostly no trend or upward. For TP, about half of the points were improved and the rest showed no trends.

• Journal of Environmental Health Sciences
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• v.45 no.1
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• pp.54-61
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• 2019

Objectives: In this study, we investigated an assessment for exposure levels of hazardous substances to kids cafes that unregulated by law. Methods: Heavy metals, volatile organic compounds, formaldehyde, pesticides and phthalate were measured at 20 kids cafes in Gyeonggi-do and Incheon. Samplings were conducted from April to July in 2018. Results: Heavy metals were detected over the standard mainly around the floor and walls in the 19 kids cafes. Pesticides were detected in 7 locations with chlorpyrifos, diazinon and cypermethrin, and showed the highest detection level of chlorpyrifos. The concentrations of DEHP in all kids cafes were exceeded with standard. The risk assessment results showed that HCHO as carcinogen had a safety level and DEHP as non-carcinogens had a safety level as assessed to be under than 0.1. Conclusions: Considering the exposure investigation results and the importance of child health protection, kids cafe should be included in the legal management list of children's activities zones.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.6
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• pp.667-672
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• 2018

We investigated the quality of 12 commercial salted and fermented anchovy Engraulis japonicas sauces by measuring their chemical compositions, bacteria concentrations, and biogenic amine contents. The sauces had a moisture content of 67.13-69.83% (mean: 68.17%), salinity of 20.00-25.84% (mean: 22.29%), pH of 5.14-6.28 (mean: 5.63), volatile basic nitrogen content of 119.12-273.37 mg/100 g (mean: 199.19 mg/100 g), total nitrogen content of 0.82-1.50% (mean: 1.30%) and amino nitrogen content of 550.17-1,086.62 mg/100 g (mean: 774.99 mg/100 g). The viable cell counts ranged from not detected to $1.6{\times}10^3CFU/mL$, and the number of biogenic amine-forming bacteria was very low or undetectable. The tested samples contained 372.32-2,111,61 mg/kg (mean 813.48 mg/kg) histamine, 29.62-144.29 mg/kg (mean 98.14 mg/kg) cadaverine, 87.89-530.84 mg/kg (mean 329.91 mg/kg) tryptamine, 20.89-127.17 mg/kg (mean 60.49 mg/kg) putrescine, and 13.08-109.91 mg/kg (mean 57.74 mg/kg) tyramine. Whereas no spermidine or spermine was detected in any sample. These results strongly suggest the necessary of monitoring the biogenic amine contents of commercial salted and fermented anchovy sauces carefully to ensure consumer health.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3051-3057
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• 2021

The concrete is considered as an important radiation shielding material employed widely in nuclear reactors, particle accelerators, laboratory hot cells and other different radiation sources. The present research is dedicated to the shielding properties study of the ordinary concrete reinforced with different weight fractions of lead oxide micro/nano particles. Lead oxide particles were fabricated by chemical synthesis method and their properties including the average size, morphological structure, functional groups and thermal properties were characterized by XRD, FESEM-EDS, FTIR and TGA analysis. The gamma ray mass attenuation coefficient of concrete composites has been calculated and measured by means of the Monte Carlo simulation and experimental methods. The simulation process was based on the use of MCNP Monte Carlo code where the mass attenuation coefficient (μ/ρ) has been calculated as a function of different particle sizes and filler weight fractions. The simulation results showed that the employment of the lead oxide filler particles enhances the mass attenuation coefficient of the ordinary concrete, drastically. On the other hand, there are approximately no differences between micro and nano sized particles. The mass attenuation coefficient was increased by increasing the weight fraction of nanoparticles. However, a semi-saturation effect was observed at concentrations more than 10 wt%. The experimental process was based on the fabrication of concrete slabs filled by different weight fractions of nano lead oxide particles. The mass attenuation coefficients of these slabs were determined at different gamma ray energies using ²²Na, ¹³⁷Cs and ⁶⁰Co sources and NaI (Tl) scintillation detector. The experimental results showed that the HVL parameter of the ordinary concrete reinforced with 5 wt% of nano PbO particles was reduced by 64% at 511 keV and 48% at 1332 keV. Reasonable agreement was obtained between simulation and experimental results and showed that the employment of nano PbO particles is more efficient at low gamma energies up to 1Mev. The proposed concrete is less toxic and could be prepared in block form instead of toxic lead blocks.