• Title/Summary/Keyword: wet chemical

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Effect of chemical input during wet air oxidation pretreatment of rice straw in reducing biomass recalcitrance and enhancing cellulose accessibility

  • Morone, Amruta;Chakrabarti, Tapan;Pandey, R.A.
    • Korean Journal of Chemical Engineering
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    • v.35 no.12
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    • pp.2403-2412
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    • 2018
  • The present study was aimed at evaluating the effect of variable sodium carbonate ($Na_2CO_3$) loading during wet air oxidation (WAO) pretreatment of rice straw in reducing biomass recalcitrance. The research study was intended to increase the cellulose recovery, hemicellulose solubilization, lignin removal in the solid fraction and limiting the generation of inhibitors in the liquid fraction while reducing the chemical input. The operating condition of $169^{\circ}C$, 4 bar, 18 min and 6.5 g/L $Na_2CO_3$ loading resulted in maximum cellulose recovery of 82.07% and hemicellulose solubilization and lignin removal of 85.43% and 65.42%, respectively, with a total phenolic content of 0.36 g/L in the liquid fraction. The crystallinity index increased from 47.69 to 51.25 along with enzymatic digestibility with an increase in $Na_2CO_3$ loading from 0 to 6.5 g/L as a result of removal of barriers for saccharification via effective cleavage of ether and ester bonds cross-linking the carbohydrates and lignin as indicated by FT-IR spectroscopy. A further increase in the $Na_2CO_3$ loading to 9.5 g/L did not significantly increase the sugar release. Thus, it was concluded that 6.5 g/L $Na_2CO_3$ during WAO is sufficient to increase the delignification and deacetylation, leading to significant changes in apparent cellulose crystallinity inter alia improvement in cellulose accessibility and digestibility of rice straw.

Photovoltaic Performance of Crystalline Silicon Recovered from Solar Cell Using Various Chemical Concentrations in a Multi-Stage Process (습식 화학 공정에 의한 태양전지로부터 고순도 실리콘 회수 및 이를 이용한 태양전지 재제조)

  • Noh, Min-Ho;Lee, Jun-Kyu;Ahn, Young-Soo;Yeo, Jeong-Gu;Lee, Jin-Seok;Kang, Gi-Hwan;Cho, Churl-Hee
    • Korean Journal of Materials Research
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    • v.29 no.11
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    • pp.697-702
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    • 2019
  • In this study, using a wet chemical process, we evaluate the effectiveness of different solution concentrations in removing layers from a solar cell, which is necessary for recovery of high-purity silicon. A 4-step wet etching process is applied to a 6-inch back surface field(BSF) solar cell. The metal electrode is removed in the first and second steps of the process, and the anti-reflection coating(ARC) is removed in the third step. In the fourth step, high purity silicon is recovered by simultaneously removing the emitter and the BSF layer from the solar cell. It is confirmed by inductively coupled plasma mass spectroscopy(ICP-MS) and secondary ion mass spectroscopy(SIMS) analyses that the effectiveness of layer removal increases with increasing chemical concentrations. The purity of silicon recovered through the process, using the optimal concentration for each process, is analyzed using inductively coupled plasma atomic emission spectroscopy(ICP-AES). In addition, the silicon wafer is recovered through optimum etching conditions for silicon recovery, and the solar cell is remanufactured using this recovered silicon wafer. The efficiency of the remanufactured solar cell is very similar to that of a commercial wafer-based solar cell, and sufficient for use in the PV industry.

Comparative Rumen Degradability of Some Legume Forages between Wet and Dry Season in West Sumatra, Indonesia

  • Evitayani, Evitayani;Warly, L.;Fariani, A.;Ichinohe, T.;Abdulrazak, S.A.;Fujihara, T.
    • Asian-Australasian Journal of Animal Sciences
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    • v.17 no.8
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    • pp.1107-1111
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    • 2004
  • An experiment was conducted to evaluate the potential nutritive value of five legume forages (leaves and twigs) in West Sumatra during wet and dry seasons. The chemical composition, in vitro dry matter (IVDMD), organic matter (IVOMD) and crude protein digestibility (IVCPD), in vitro gas characteristics and estimated metabolizable energy (ME) showed variation among legume forages and between different seasons. Crude protein (CP) ranged from 14.2 to 27.8% DM in the wet season, with a significant (p<0.05) reduction in dry season. C. pubescens, G. maculata, L. leucocephala and P. phaseloides showed the least reduction in CP content. The NDF, ADF and lignin were about 39.0, 26.5 and 6.1% DM, respectively in the wet season, and significantly (p<0.05) increased in the dry season, except for NDF of C. mucunoides and C. pubescens. For IVDMD, IVOMD and IVCPD significantly increased in the wet season, but values remained as high as over 50.0% of DM. The in vitro gas characteristics and metabolizable energy were significantly (p<0.05) higher in wet season than the dry season. During both seasons, the rate of constant (c) for G. maculata and ME content for C. pubescens and P. phaseloides were not significantly (p<0.05). Results demonstrated that P. phaseloides and L. leucocephala have a good nutritive value during both wet and dry seasons. Further studies on feeding trials are needed to quantify the animal responses when offered these legume forages.

Processing of Porous Ceramics by Direct Foaming: A Review

  • Pokhrel, Ashish;Seo, Dong Nam;Lee, Seung Taek;Kim, Ik Jin
    • Journal of the Korean Ceramic Society
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    • v.50 no.2
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    • pp.93-102
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    • 2013
  • Macro porous ceramics possessing controlled microstructures and chemical compositions have increasingly proven useful in the industrial sphere. Their sintered structures have found application in both established and emerging, areas such as thermal insulation in buildings, filtration of liquids and molten materials, refractory insulation, bone scaffolds and tissue engineering. Stable ceramic foams can be formed by wet chemical methods using inorganic particles(e.g., $Al_2O_3$ or $SiO_2$). The wet foams are dried and sintered with improved porosity and mechanical properties. This review examines the different techniques used to prepare porous ceramics from ceramic foams, focusing on the explanation of this versatile method of direct foaming from the past to the present. Comparisons of the processes and the processing parameters are explained with the produced microstructures.

Photo-assisted GaN wet-chemical Etching using KOH based solution (KOH계열 수용액을 이용한 GaN 박막의 photo-assisted 식각 특성)

  • Lee, Hyoung-Jin;Song, Hong-Ju;Choi, Hong-Goo;Ha, Min-Woo;Roh, Cheong-Hyun;Lee, Jun-Ho;Park, Jung-Ho;Hahn, Cheol-Koo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.339-339
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    • 2010
  • Photo-assisted wet chemical etching of GaN thin film was studied using KOH based solutions. A $2{\mu}m-2{\mu}m$ titanium line-and-space pattern was used as a etching mask. It is found that the etching characteristics of the GaN thin film is strongly dependent on the pattern direction by unisotropic property of KOH based solution. When the pattern was aligned to the [$11\bar{2}0$] directions, ($10\bar{1}n$)-facet is revealed constructing V-shaped sidewalls.

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A Study on the Characteristics of the Functional Groups of the Alkanethiol Molecules in UV Laser Photochemical Patterning and Wet Etching Process (UV Laser를 이용한 광화학적 패터닝과 습식에칭에 따른 알칸티올 분자 작용기의 특성 연구)

  • Huh, Kab-Soo;Chang, Won-Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.5
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    • pp.104-109
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    • 2007
  • Photochemical patterning of self-assembled mono layers (SAMs) has been performed by diode pumped solid state (DPSS) 3rd harmonic Nd:$YVO_4$ laser with wavelength of 355 nm. SAMs patternings of parallel lines have subsequently been used either to generate compositional chemical patterns or fabricate microstructures by a wet etching. This paper describes a selective etching process with patterned SAMs of alkanetiolate molecules on the surface of gold. SAMs formed by the adsorption of alkanethiols onto gold substrate employs as very thin photoresists. In this paper, the influence of the interaction between the functional group of SAMs and the etching solution is studied with optimal laser irradiation conditions. The results show that hydrophobic functional groups of SAMs are more effective for selective chemical etching than the hydrophilic ones.

Wet Air Oxidation Pretreatment of Mixed Lignocellulosic Biomass to Enhance Enzymatic Convertibility

  • Sharma, A.;Ghosh, A.;Pandey, R.A.;Mudliar, S.N.
    • Korean Chemical Engineering Research
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    • v.53 no.2
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    • pp.216-223
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    • 2015
  • The present work explores the potential of wet air oxidation (WAO) for pretreatment of mixed lignocellulosic biomass to enhance enzymatic convertibility. Rice husk and wheat straw mixture (1:1 mass ratio) was used as a model mixed lignocellulosic biomass. Post-WAO treatment, cellulose recovery in the solid fraction was in the range of 86% to 99%, accompanied by a significant increase in enzymatic hydrolysis of cellulose present in the solid fraction. The highest enzymatic conversion efficiency, 63% (by weight), was achieved for the mixed biomass pretreated at $195^{\circ}C$, 5 bar, 10 minutes compared to only 19% in the untreated biomass. The pretreatment under the aforesaid condition also facilitated 52% lignin removal and 67% hemicellulose solubilization. A statistical design of experiments on WAO process conditions was conducted to understand the effect of process parameters on pretreatment, and the predicted responses were found to be in close agreement with the experimental data. Enzymatic hydrolysis experiments with WAO liquid fraction as diluent showed favorable results with sugar enhancement up to $10.4gL^{-1}$.

Optimization of Wet Reduction Processing for Nanosized Cobalt Powder (나노코발트 분말합성을 위한 액상환원공정의 최적화)

  • Hong, Hyun-Seon;Jung, Hang-Chul;Kim, Geon-Hong;Kang, Lee-Seung;Suk, Han-Gil
    • Journal of Powder Materials
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    • v.20 no.3
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    • pp.191-196
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    • 2013
  • Nano-sized cobalt powder was fabricated by wet chemical reduction method at room temperature. The effects of various experimental variables on the overall properties of fabricated nano-sized cobalt powders have been investigated in detail, and amount of NaOH and reducing agent and dropping speed of reducing agent have been properly selected as experimental variables in the present research. Minitab program which could find optimized conditions was adopted as a statistic analysis. 3D Scatter-Plot and DOE (Design of Experiments) conditions for synthesis of nano-sized cobalt powder were well developed using Box-Behnken DOE method. Based on the results of the DOE process, reproducibility test were performed for nano-sized cobalt powder. Spherical nano-sized cobalt powders with an average size of 70-100 nm were successfully developed and crystalline peaks for the HCP and FCC structure were observed without second phase such as $Co(OH)_2$.

Wet preparation of calcium phosphates from aqueous solutions

  • Lee, Byeong Woo;Hong, Il Gok
    • Journal of Ceramic Processing Research
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    • v.20 no.6
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    • pp.655-659
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    • 2019
  • Calcium phosphates such as HA (hydroxyapatite), β-TCP (tricalcium phosphate) and biphasic HA/β-TCP, were synthesized by wet chemical precipitation in aqueous solution combined with ball milling process. Nanosize powders of the calcium phosphates were synthesized using Ca(OH)2 and H3PO4. The effects of initial precursor Ca/P ratio (1.30, 1.50 and 1.67), ball milling process and post heat-treatment on the phase evolution behavior of the powders were investigated. The phase of resulting powder was controllable by adjusting the initial Ca/P ratio. HA was the only phase for as-prepared powders in both cases of Ca/P ratios of 1.50 and 1.67. The single HA phase without any noticeable second phase was obtained for the initial Ca/P ratio of 1.67 in the overall heat-treatment range. Pure β-TCP and biphasic calcium phosphate (HA/β-TCP) were synthesized from precursor solutions having Ca/P molar ratios of 1.30 and 1.50, respectively, after having been heat-treated above 700 ℃. The β-TCP phase has appeared on the pre-existing DCPD (dicalcium phosphate dihydrate) and/or HA phase. Dense ceramics having translucency were obtained at a considerably lower sintering temperature. The modified process offered a fast, convenient and economical route for the synthesis of calcium phosphates.

Total sizing system (총 사이징 시스템)

  • Proverb, Robert J.;Pawlowska, Lucyna;Komarowska, Kasia;Garro, Gina;Dilts, Kimberly
    • Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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    • 2004.07a
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    • pp.19-42
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    • 2004
  • Sizing properties in paper are generally developed through the application of both internal and surface sizes. Rosin, wax, and synthetic sizes including ASA, AKD, and stearic anhydride are and have been used to provide wet-end sizing to paper. In many cases, the use of some of these sizes leads to runnability problems that are inherent in the wet-end operation. Variability in furnish, fines, broke, filler, water chemistry, conductivity, and pH control impacts the wet-end operation. Size press chemicals including starch and polymers such as styrene-acrylic, styrene-maleic, and styrene acrylate emulsions are used in conjunction with internal sizes to improve the paper surface for printing and strength properties, porosity, and opacity improvement. This paper will discuss results from a new, proprietary formulation and process that allows application of sizing chemistry more totally at the size press with reduced emphasis on wet end sizing. Runnability issues are thus minimized at the wet-end, chemical usage is more efficient, and significant cost savings can be realized. Case histories will be presented illustrating the advantages of this new application in commercial trials.

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