• Clean Technology
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• v.25 no.1
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• pp.91-97
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• 2019

Oxidative desulfurization (ODS) has received much attention in recent years because refractory sulfur compounds such as dibenzothiophenes can be oxidized selectively to their corresponding sulfoxides and sulfones, and these products can be removed by extraction and adsorption. In this work, The oxidative desulfurization of marine diesel fuel was performed in a batch reactor with hydrogen peroxide ($H_2O_2$) in the presence of various supported heteropoly acid catalysts. The catalysts were characterized by XRD, XRF, XPS and nitrogen adsorption isotherm techniques. Based on the sulfur removal efficiency of promising silica supported heteropoly acid catalysts, the ranking of catalytic activity was: $30\;H_3PW_{12}/SiO_2$ > $30\;H_3PMo_{12}/SiO_2$ > $30\;H_4SiW_{12}/SiO_2$, which appears to be related with their intrinsic acid strength. The $30\;H_3PW_{12}/SiO_2$ catalyst showed the highest initial sulfur removal efficiency of about 66% under reaction conditions of $30^{\circ}C$, $0.025g\;mL^{-1}$ (cat./oil), 1 h reaction time. However, through the recycle test of the $H_3PW_{12}/SiO_2$ catalyst, significant deactivation was observed, which was attributed to the elution of the active component $H_3PW_{12}$. By introducing cesium cation ($Cs^+$) into the $H_3PW_{12}/SiO_2$ catalyst, the stability of the catalyst was improved with changing the solubility, and the $Cs^+$ ion exchanged catalyst could be recycled for at least five times without severe elution.

• Clean Technology
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• v.25 no.2
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• pp.129-139
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• 2019

Bamboo is an evergreen perennial plant, and it is known as one of the most productive and fastest-growing plants in the world. It grows quickly in moderate climates with only moderate water and fertilizer. Traditionally in Asia, bamboo is used for building materials, as a food source, and as versatile raw materials. Bamboo as a biomass feedstock can be transformed to prepare activated carbon using the thermal treatment of pyrolysis. The effect of process variables such as carbonization temperature, activation temperature, activation time, the amount of steam, and the mixing ratio of phosphoric acid and bamboo were systematically investigated to optimize the preparation conditions. Steam activation was proceeded after carbonization with a vapor flow rate of $0.8{\sim}1.8mL-H_2O\;g-char^{-1}\;h^{-1}$ and activation time of 1 ~ 3 h at $700{\sim}900^{\circ}C$. Carbon yield and surface area reached 2.04 ~ 20.59 wt% and $499.17{\sim}1074.04m^2\;g^{-1}$, respectively, with a steam flow rate of $1.4mL-H_2O\;g-char^{-1}\;h^{-1}$ for 2 h. Also, the carbon yield and surface area were 24.67 wt% and $1389.59m^2\;g^{-1}$, respectively, when the bamboo and phosphoric acid were mixed in a 1:1 weight ratio ($700^{\circ}C$, 2 h, $1.4mL-H_2O\;g-char^{-1}\;h^{-1}$). The adsorption of methylene blue into the bamboo activated carbon was studied based on pseudo first order and second order kinetics models. The adsorption kinetics were found to follow the pseudo second order model, which is governed by chemisorption.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.574-583
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• 2021

Waste air containing ethanol (100 ppmv) and hydrogen sulfide (10 ppmv) was continuously treated by waste air-treating system composed of two annular photocatalytic reactors (effective volume: 1.5 L) packed with porous SiO₂ media carrying TiO₂-anatase photocatalyst, one of which was alternately operated for 32 d/run while the other was regenerated by 100 ℃ hot air with 15 W UV(-A)-light on. As its elimination-behavior of ethanol, the removal efficiencies of ethanol at 1^st, 2^nd and 3^rd operation of the photocatalytic reactor system(A), turned out to be ca. 60, 55 and 54%, respectively, at their steady state condition. Unlike the elimination-behavior of ethanol, its hydrogen sulfide-elimination behavior showed repeated decrease of hydrogen sulfide removal efficiency by its resultant arrival at a lower level of steady state condition. Nevertheless, the removal efficiencies of hydrogen sulfide at 1^st, 2^nd and 3^rd operation of the photocatalytic reactor system, turned out to be ca. 80, 75 and 73%, respectively, at their final steady state condition, higher by ca. 20, 20 and 19% than those of ethanol, respectively. Therefore, assuming that adsorption on porous SiO₂-photocatalyst carrier was regarded to belong to a reversible deactivation and that decreased % of removal efficiency due to the reversible deactivation of photocatalyst including the adsorption was independent of the number of its use upon regeneration, the increments of the decreased % of removal efficiency of ethanol and hydrogen sulfide, due to an irreversible deactivation of photocatalyst, for the 3^rd use of regenerated photocatalyst, compared with the 2^nd use of regenerated photocatalyst, were ca. 1 and 2%, respectively, which was insignificant or the less than those of ca. 5 and 5%, respectively, for the 2^nd use of regenerated photocatalyst compared with the 1^st use of virgin photocatalyst. This trend of the photocatalytic reactor system was observed to be similar to that of the other alternately-operating photocatalytic reactor system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.spc
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• pp.30-36
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• 2022

A sensor is needed to continuously and automatically measure the change in HNS concentration in industrial facilities that directly discharge to the sea after water treatment. The basic function of the sensor is to be able to detect ppb levels even at room temperature. Therefore, a method for increasing the sensitivity of the existing sensor is proposed. First, a method for increasing the conductivity of a film using a conductive carbon-based additive in a nanoparticle thin film and a method for increasing ion adsorption on the surface using a catalyst metal were studied.. To improve conductivity, carbon black was selected as an additive in the film using ITO nanoparticles, and the performance change of the sensor according to the content of the additive was observed. As a result, the change in resistance and response time due to the increase in conductivity at a CB content of 5 wt% could be observed, and notably, the lower limit of detection was lowered to about 250 ppb in an experiment with organic solvents. In addition, to increase the degree of ion adsorption in the liquid, an experiment was conducted using a sample in which a surface catalyst layer was formed by sputtering Au. Notably, the response of the sensor increased by more than 20% and the average lower limit of detection was lowered to 61 ppm. This result confirmed that the chemical resistance sensor using metal oxide nanoparticles could detect HNS of several tens of ppb even at room temperature.

• Journal of the Korea Organic Resources Recycling Association
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• v.32 no.3
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• pp.5-18
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• 2024

Chemical oxygen demand (COD), an organic material measurement index, has a limit to the management of the total amount of all organic materials including non-degradable organic materials due to low oxidation rate. So total organic carbon (TOC) that can measure organic materials more accurately is introduced and used as a measurement index. Several environmental companies including company A in Gyeonggi-do dilute raw wastewater first and then treats it with chemicals. And an activated carbon is used at the rear stage to treat total organic carbon even though various treatment processes can be applied to reduce TOC in wastewater. There are some problems such as use of a lot of diluting water and generation of an excessive amount of sludge, so it is urgent to come up with an alternative plan. Therefore, in this study, an application experiment was conducted on two different methods for improving the TOC reduction efficiency of waste water from Company A. The first method is the evaluation of the substitution potential of powered activated carbon(PAC), an adsorbent currently used, by manufacturing cellulose-based graphene like carbon (CGLC). This first study showed that CGLC had about 10% higher TOC adsorption efficiency than commercial PAC, showing the possibility of being applied as an alternative adsorbent for PAC in water treatment sites. The second method relates to the removal of TOC by sulfate radials produced by persulfate (PS) activation. Two activation methods were applied: using CGLC and PAC as carbon-based catalyst and using the high temperature of wastewater for PS activation. As a result of using PAC and CGLC as PS activation materials, the TOC removal rate was lower than the adsorption amount of TOC by CGLC and PAC due to excessive chlorine ions present in the real wastewater. However, as a result of using the high water temperature (55~60℃) of the field wastewater for PS activation, it showed a much greater TOC removal efficiency than PAC alone, CGLC alone, and using a carbon-based catalyst for PS activation. When PS was injected more than 0.5%, it showed a TOC removal efficiency of 95% or more within 24 hr. In addition, when PS was injected more than 0.3%, the TOC concentration could be lowered to less than 75 ppm, which is the wastewater discharge standard applied to company A. When these results were summarized, raw wastewater of high temperature can be treated with a simple process of only adding of PS and discharged by treating TOC below the wastewater discharge standard applied to company A.

• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.300-308
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• 2002

This study was conducted to investigate the downward mobility of pesticides using soil colunms and to compare the experimental results with predicted values from Convective mobility test model. Five pesticides including ethoprophos, procymidone, iprobenfos, isoprothiolane, and butachlor were subjected to soil column leaching test for three types of cultivation soils. The concentrations of ethoprophos, iprobenfos, procymidone, isoprothiolane and butachlor leached from soil column of 30 cm depth ranged $0.74{\sim}3.61mg/mL,\;0.36{\sim}1.67mg/L,\;0.16{\sim}0.84mg/L,\;0.16{\sim}0.67mg/L$ and lower than 0.15 mg/L, respectively. Elution volume to reach the peak of ethoprophos, iprobenfos, procymidone, isoprothiolane and butachlor in the leachate ranged $2{\sim}4PV,\;3{\sim}10PV,\;5{\sim}13PV,\;4{\sim}14PV\;and\;19{\sim}61PV$, respectively. Convection times predicted by Convective mobility test model at standard conditions were $9{\sim}18$ days for ethoprophos, $17{\sim}35$ days for iprobenfos, $24{\sim}54$ days for isoprothiolane, $21{\sim}65$ days for procymidone and $105{\sim}279$ days for butachlor. Based on these convection times, ethoprophos was classified as mobile or most mobile, isoprothiolane and procymidone as moderately mobile or mobile and butachlor as slightly mobile. On the same conditions, convection times from the model were coincided with those from soil column test in most of the soil-pesticide combinations applied. Therefore, Convective mobility test model could be applied to predict convection times of pesticides.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.9
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• pp.1344-1350
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• 2016

The purpose of this study was to evaluate the effect of edible coating on hygroscopicity and quality characteristics of a freeze-dried Actinidia arguta snack. Freeze-dried A. arguta snacks were coated with various edible coating materials such as albumin, dextrin, and whole soy flour. There were no significant effects of coating on major quality properties such as moisture content, water activity, yield, water soluble index, water absorption index, and rehydration properties of all samples. Compared with non-coated samples, edible coated samples effectively inhibited hygroscopicity as a function of hygroscopic time. The samples coated with dextrin showed lower hygroscopicity than the other coated samples. In addition, the effects of edible coating treatment on hardness, total phenolic content, and antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity were investigated. Edible coated samples had higher hardness, total phenolic content, and antioxidant activity than the non-coated samples as a function of hygroscopic time. Among edible coating materials, dextrin was the most effective coating material. Dextrin as an edible coating material for freeze-dried A. arguta snack may help to prevent hygroscopicity and extend market quality and shelf-life during storage.

• Korean Journal of Crystallography
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• v.15 no.2
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• pp.59-68
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• 2004

Three crystal structures of dehydrated partially $Co^{2+}-exchanged$ zeolite A treated with 0.6 Torr of K at $300^{\circ}C$ (for 12 hrs, 6 hrs, and 2 hrs) vapor have been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at 21(1)$^{\circ}C(a=12.181(1)\;{\AA},\;a=12.184(1)\;{\AA},\;and\;a=12.215(1)\;{\AA})\;respectively)$. Their structures were refined to the final error indices, R(weight) of 0.090 with 10 reflections, 0.091 with 82 reflections, and 0.090 with 80 reflections, respectively, for which $1>\sigma(I)$. In each structure, all four $Co^{2+}$ and four $Na^+$ ions to be reduced by K atoms. The cobalt and sodium atoms produced are no longer found in the zeolite. K species are found at five different crystallographic sites: three $K^+$ ions lie at the planes of 8-rings, filling that position, ca. 11.5 K^+$ ions lie on threefold axes, ca. 4.0 in the large cavity and ca. 4.0 in the sodalite cavity, and ca. 0.5 $K^+$ ion is found near a 4-ring. ca. three $K^0$ atoms are found deep into the large cavity on threefold axes. In these structures, crystallographic results show that cationic tetrahedral $K_4$ (and/or triangular $K_3$) clusters have formed in the sodalites of zeolite A. The $K_4$ and/or $K_3$ clusters coordinate trigonally to three oxygens of a six-oxygen ring. The partially reduced ions of these clusters interact primarily with oxygen atoms of the zeolite structure rather than with each other. ca. 14.5K species are found per unit cell, more than the twelve $K^+$ ions needed to balance the anionic charge of zeolite framework, indicating that sorption of $K^0$ has occurred. The three $K^0$ atoms in the large cavity are closely associated with three out of four $K^+$ ions in the large cavity to form $K_7^{4+}$ clusters. The $K_7^{4+}$ cluster not interacts primarily with framework oxygens.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.193-200
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• 2010

This study evaluated treatability of soluble Mn(II) using multifunctional sand media simultaneously coated with iron and manganese. In the preparation of IMCS(Iron and Manganese Coated Sand), 0.05 M Mn(II) solution and Fe(III) solution was mixed with sand at pH 7. The mineral type of IMCS was identified as the mixture of ${\gamma}-MnO_2$, goethite and magnetite($F_{e3}O_4$). The contents of Mn and Fe coated onto sand were 826 and 1676 mg/kg, respectively. The $pH_{pzc}$ of IMCS was measured as 6.40. The removal of soluble Mn(II) using IMCS and oxidants such as NaOCl and $KMnO_4$ was investigated with variation of the solution pH, reaction time and Mn(II) concentration in a batch test. The removal of Mn(II) on IMCS was 34% at pH 7.4 and the removals of Mn(II) on IMCS in the presence of NaOCl(13.6 mg/L) at pH 7 and $KMnO_4$(4.8 mg/L) at pH 7.6 were 96% and 89%, respectively. The removal of Mn(II) using IMCS and oxidants followed a typical cationic type, showing a gradual increase of removal as the solution pH increased. The removal of Mn(II) was rapid in the first 6 hrs and then a constant removal was observed. The maximum removed amount of Mn(II) on IMCS-alone and IMCS in the presence of oxidants such as NaOCl(13.6 mg/L) and $KMnO_4$(4.8mg/L) were 833.3, 1428.6 and 1666.7 mg/kg, respectively. Mn(II) removal onto the IMCS in the presence of oxidants was well described by second-order reaction and Langmuir isotherm expression.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.1
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• pp.35-43
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• 2010

We have developed a sodium fluoride containing gelatin and methyl cellulose gel. Cariostatic abilities of those gel were investigated and compared with APF gel and fluoride varnish($Cavityshield^{TM}$). We prepared the bovine tooth samples and divided into two surface, control side and experimental side in same specimen for exclusion of difference between specimens. The experiment was consisted of 4 groups : (I) APF gel : (II) $Cavityshield^{TM}$ : (III) Gelatin F gel : (IV) Methyl cellulose F gel Decalcification were produced by placing each specimen into artificial acidic solution(pH 4.0) for 72 hours. Surface microhardness were measured and depth of demineralization lesion were measured by polarizing light microscope. The results were as follows: 1. The difference of VHN between control and experimental side is smallest in group I (p<0.05). 2. The largest difference was shown in group II (p<0.05). 3. There were no significant difference between group III and IV in microhardness test (p>0.05). 4. The difference of lesion depth is smallest in group I (p<0.05). 5. There were no significant difference between group II, III and IV in lesion depth (p>0.05). The result of the present study indicate that the fluoride containing gelatin and methyl cellulose gel is more effective than APF gel and is similar to fluoride varnish application for prevention of demineralization.