Activated Carbon Waste Pretreatment System for Boron Containing Radioactive Waste Upcycling

Ki Rak Lee,Hwan-Seo Park,Ga Yeong Kim,Sang Won Shin,Dong Chul Jang 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

In NPP (nuclear power plant), boric acid is used as a neutron absorbent. So radioactive boric acid waste are generated from various waste streams such as discharge or leakage of reactor coolant water, floor drains, drainage of equipment for operation or maintenance, reactor letdown flows and etc. Depending on KHNP, 20,015 drum (200 L drum) of concentrated boric acid waste were stored in KOREA NPP until 2019. In previous study, our group suggested the waste upcycling process synthesizing B4C neutron absorber using boric acid waste and activated carbon waste to innovatively reduce radioactive wastes. Radioactive activated carbon waste was utilized in off gas treatment system of NPP to capture nuclide such as I-131, C-14 and H-3. Activated carbon waste is treated as low-level radioactive waste and pre-treatment system for removing nuclide from the activated carbon waste is needed to use B4C up-cycling process. In this study, microwave treatment system is suggested to treat the activated carbon waste. Activated carbon waste was exposed to microwave for a few minutes and temperature of the waste was dramatically increased over 400°C. Nuclide in the activated carbon waste were selectively removed from the waste without massive production of secondary off gas waste.

열수가압탄화에 의해 제조한 폐목재 바이오차 (Bio-char) 활성탄의 특성화에 관한 연구

원민희,조우리,장진만,박지수,이재영 한국폐기물자원순환학회 2022 한국폐기물자원순환학회지 Vol.39 No.3

The market for activated carbon is growing due to environmental awareness and strengthening of environmental regulations. Biochar is a solid carbide that is produced through a hydrothermal carbonization (HTC) process. Wood is an ideal raw material for activated carbon and biomass waste wood because it has low energy consumption rates and does not require pre-treatment to remove moisture. The activated carbon samples in this study were prepared by a chemical activation process using KOH, which is mainly used for activation. The study analyzed the specific surface area, pore volume, pore size, and pore distribution by selecting four samples with high iodine adsorption capacity among the prepared activated carbon samples. The specific surface area for all four samples was between 1192.2 and 1387.1 m2/g, all of which were over 1,000 m2/g, and the pore volume was between 0.6510 and 0.8030 cm3/g. During this process, micropores with an average pore size of 21 to 25 Å were formed. SEM photography revealed that these pores were uniform and that the number of pores increased according to activation levels of the carbon samples. When the iodine adsorptivity and specific surface area of commercial activated carbon was compared with that of activated carbon prepared by waste wood biochar with KOH, the specific surface area was higher in the activated carbon samples prepared by waste wood biochar with KOH. These results indicate that the adsorption of activated carbon by waste wood biochar with KOH is successful when applied to activated carbon samples.

Activated Carbon Waste Pretreatment System for Radioactive Waste Up-cycling

Kirak Lee,Hwan-Seo Park,Geun-il Park,Sang Won Shin,Dong Chul Jang 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

In NPP (nuclear power plant), boric acid is used as a neutron absorbent. So radioactive boric acid waste are generated from various waste streams such as discharge or leakage of reactor coolant water, floor drains, drainage of equipment for operation or maintenance, reactor letdown flows and etc. Depending on KHNP, 20,015 drum (200 L drum) of concentrated boric acid waste were stored in KOREA NPP until 2019. In previous study, our group suggested the waste up-cycling process synthesizing B4C neutron absorber using boric acid waste and activated carbon waste to innovatively reduce radioactive wastes. Radioactive activated carbon waste was utilized in off gas treatment system of NPP to capture nuclide such as I-131, C-14 and H-3. Activated carbon waste is treated as low-level radioactive waste and pre-treatment system for removing nuclide from the activated carbon waste is needed to use B4C up-cycling process. In this study, microwave treatment system is suggested to treat the activated carbon waste. Activated carbon waste was exposed to microwave for a few minutes and temperature of the waste was dramatically increased over 400°C. Nuclide in the activated carbon waste were selectively removed from the waste without massive production of secondary off gas waste.

폐활성탄을 혼입한 콘크리트의 물리.역학적 성질

강현수,성찬용,Kang, Hyun-Soo,Sung, Chan-Yong 한국농공학회 2009 한국농공학회논문집 Vol.51 No.1

This study was performed to evaluate the physical and mechanical properties of concrete using waste activated carbon. Materials used were ordinary portlant cement, crushed coarse aggregate, natural fine aggregate, waste activated carbon, and superplasticizer. The substitution ratios of waste activated carbon were 0,1,2,3,4,5,6,7,8,9 and 10%. The unit weight was decreased and water absorption ratio was increased with increasing the waste activated carbon content, respectively. When the substitution ratio of waste activated carbon was 3%, compressive strength, flexural strength and dynamic modulus of elastisity were more higher than that of the ordinary portland cement (OPC), and it was decreased with increasing the waste activated carbon content, respectively. The most effective contents of waste activated carbon was 2% in performance and 4% in practical use Accordingly, waste activated carbon can be used for concrete material.

Comparisons of activated carbons produced from sycamore balls, ripe black locust seed pods, and Nerium oleander fruits and also their H2 storage studies

Osman ?ner,?nal Ge?gel,Tarık Avcu 한국탄소학회 2021 Carbon Letters Vol.31 No.1

Starting materials are very significant to produce activated carbons because every starting material has a different chemical structure; hence they affect the surface functional groups and surface morphologies of obtained activated carbons. In this study, sycamore balls, ripe black locust seed pods, and Nerium oleander fruits have been used as starting materials by ZnCl2 chemical activations for the first time. Firstly, activated carbons were obtained from these starting materials with ZnCl2 chemical activation by changing production conditions (carbonization time, carbonization temperature, and impregnation ratio) also affecting the structural and textural properties of the resultant activated carbons. Then, the starting materials and resultant activated carbons were characterized by utilizing diverse analysis techniques, such as TGA, elemental analysis, proximate analysis, BET surface areas, pore volumes, pore size distributions, N2 adsorption–desorption isotherms, SEM, FTIR spectra, and H2 adsorption isotherms. The highest surface areas were determined to be 1492.89, 1564.84, and 1375.47 m2/g for the activated carbons obtained from sycamore balls, ripe black locust seed pods, and N. oleander fruits, respectively. The yields of these activated carbons with the highest surface areas were calculated to be around 40%. As the carbonization temperature increased with sufficient ZnCl2 amount, N2 adsorption–desorption isotherms began to turn into Type IV isotherms given by mesoporous adsorbents with its hysteresis loops. Also, their hysteresis loops resembled Type H4 loop generally associated with narrow slit-like pores. Moreover, hydrogen uptakes under 750 mmHg at 77 K were determined to be 1.31, 1.48, and 1.24 wt% for the activated carbons with the maximum surface areas produced from sycamore balls, ripe black locust seed pods, and N. oleander fruits, respectively. As a result, the highest surface areas of the activated carbons with different structural properties produced in this study were obtained with different production conditions.

Analysis of environmental impact of activated carbon production from wood waste

Mi Hyung Kim,In Tae Jeong,Sang Bum Park,Jung Wk Kim 대한환경공학회 2019 Environmental Engineering Research Vol.24 No.1

Activated carbon is carbon produced from carbonaceous source materials, such as coconut shells, coals, and woods. In this study, an activated carbon production system was analyzed by carbonization and activation in terms of environmental impact and human health. The feedstock of wood wastes for the system reduced fossil fuel consumption and disposal costs. Life cycle assessment methodology was used to analyze the environmental impacts of the system, and the functional unit was one tonne of wood wastes. The boundary expansion method was applied to analyze the wood waste recycling process for activated carbon production. An environmental credit was quantified by avoided impact analysis. Specifically, greenhouse gases discharged from 1 kg of activated carbon production system by feeding wood wastes were evaluated. We found that this system reduced global warming potential of approximately 9.69E+00 kg CO₂-eq. compared to the process using coals. The environmental benefits for activated carbon production from wood wastes were analyzed in contrast to other disposal methods. The results showed that the activated carbon system using one tonne of wood wastes has an environmental benefit of 163 kg CO₂-eq. for reducing global warming potential in comparison with the same amount of wood wastes disposal by landfilling.

폐활성탄을 사용한 다공성 콘크리트의 물리.역학적 성질

윤준노,성찬용,김영익,Youn, Joon-No,Sung, Chan-Yong,Kim, Young-Ik 한국농공학회 2009 한국농공학회논문집 Vol.51 No.4

This study was performed to evaluate the physical and mechanical properties of porous concrete using waste activated carbon. Material used were ordinary portland cement, recycled coarse aggregate, waste activated carbon and superplasticizer. The replacement ratios of waste activated carbon were 0,1,2,3,4,5,6,7,8,9, and 10 %. The void ratio was decreased and ultrasonic pulse velocity was increased with increasing the waste activated carbon powder, respectively. The compressive strength and flexural strength of porous concrete using waste activated carbon powder were in the range of 8.21${\sim1}$6.58 MPa and 1.69${\sim1}$3.68 MPa, respectively. The pH degree of porous concrete in 1day and 77days were shown in 12.50${\sim1}$12.63 and 10.21${\sim1}$10.70, respectively. Accordingly, waste activated carbon can be used for porous concrete material.

Deep bed로 구성된 활성탄/모래 공정에서의 입자성 물질 저감연구

백영애 ( Baek Youngae ),조우현 ( Joe Woohyun ),이광제 ( Lee Kwangjae ),홍숭희 ( Hong Seounghee ),박현 ( Park Hyeon ) 한국수처리학회 2020 한국수처리학회지 Vol.28 No.6

A water purification plant does not have a filter-to-waste valve, and the lack of free space makes the installation of such a valve difficult. In this study, we tried to reduce particulate matter by laying sand under the activated carbon without installing additional facilities. As a result of laying the lower sand to reduce the leakage of granular activated carbon, it was possible to reduce the particulate matter by about 15-20 % compared to the granular activated carbon process alone. The operating head rose about 10-20 cm when sand was laid, but there was no sharp rise and it was considered to be acceptable on site. In addition, the bacterial activity in the granular activated carbon column immediately after backwashing was detected at a maximum of about 120 per 100 mL. Despite the low water temperature (below 15℃), bacteria that are uncommon in the sand-filtered water proliferate and act as biological activated carbon in the granular activated carbon process, but it was found that it decreased by about 20% when sand was laid under the activated carbon. Regarding backwashing, it was confirmed that the activated carbon and sand layers were well mixed during air washing and then well separated again during rinsing due to the difference in specific gravity between the activated carbon and sand. A result of this study is that, in order to reduce leakage particles from granular activated carbon, it is recommended to use sand with a commercially available sand size of 0.55-0.6 mm (uniformity coefficient of 1.4 or less) when laying sand under granular activated carbon with an effective size of 0.65 mm.

Simultaneous Recovery of Gold and Iodine from the Waste Rinse Water of the Semiconductor Industry Using Activated Carbon

Nguyen, Nghiem V.,Jeong, Jinki,Shin, Doyun,Kim, Byung-Su,Lee, Jae-chun,Pandey, B. D. The Japan Institute of Metals 2012 Materials Transactions Vol.53 No.4

<P>This research work focused on the simultaneous recovery of gold (40.5 mg/dm<SUP>3</SUP>) and iodine (748 mg/dm<SUP>3</SUP>) from the waste rinse water of the semiconductor industry using activated carbon. A batch study was conducted to optimize process parameters, such as contact time and carbon dose, for the recovery of gold and iodine from the waste water. The loading capacity of the activated carbon for adsorption of gold and iodine was found to be 33.5 mg Au/g carbon and 835 mg I<SUB>2</SUB>/g carbon, respectively. Gold was found to exist on the activated charcoal surface in two forms: ionic gold and elemental gold. Aqua regia was used to convert metallic gold to its ionic form, and the iodine and the small amount of ionic gold were removed from the activated carbon by elution with aqua regia. Gold was recovered from the eluate by reduction with hydrazine. Iodine from the diluted aqua regia was then precipitated by adding sodium hydrosulfite (Na<SUB>2</SUB>S<SUB>2</SUB>O<SUB>4</SUB>). A complete process flow sheet was developed to recover both gold and iodine from the waste water of the semiconductor industry, which conserves the resources while meeting environmental pollution requirements.</P>

Waste plastic for increasing softening point of pitch and specific surface area of activated carbon based on the petroleum residue

Kwak Cheol Hwan,서상완,김민일,허윤석,임지선 한국탄소학회 2021 Carbon Letters Vol.31 No.5

Pyrolysis fuel oil (PFO) is used for the manufacturing of high-purity pitch for carbon precursor due to its high carbon content, high aromaticity, and low heterogeneous element and impurity content. Pitch is commonly classifed with its softening point, which is most considerable physical property afecting to various characteristics of the carbon materials based on pitch, such as electrical and thermal conductivity, mechanical strength, and pore property. Hence, the softening point should be controlled to apply pitch to produce various carbon materials for diferent applications. Previous studies introduce reforming process under high pressure and two step heat treatment for the synthesis of pitch with high softening point from PFO. These methods lead to a high process cost; therefore, it is necessary to develop a process to synthesize the pitch with high softening point by using energy efective process at a low temperature. In this study, waste polyethylene terephthalate (PET) was added to control the softening point of PFO-based pitch. The pitch synthesized by the heat treatment with the addition of PET showed the softening point higher than that of the pitch synthesized with only PFO. The softening point of PFObased pitch synthesized at 420 °C was 138.3 °C, while that of the pitch synthesized by adding PET under the same process conditions was 342.8 °C. It is proposed that the efect of the PET addition on the increase in the softening point was due to the radicals generated from thermal degradation of PET. The radicals from PET react with the PFO molecules to promote the polymerization and fnally increase the molecular weight and softening point of the pitch. In addition, activated carbon was prepared by using the pitch synthesized by adding PET, and the results showed that the specifc surface area of the activated carbon increased by the addition of PET. It is expected that the pitch synthesis method with PET addition signifcantly contributes to the manufacture of pitch and activated carbon.