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Ji Whan Ahn - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic Simulations for Determining the Recycling Path of a Spent Lead-Acid Battery Electrolyte Sample with Ca(OH)2
Applied Sciences, 2019Co-Authors: Toyohisa Fujita, Ji Whan AhnAbstract:By utilizing thermodynamic calculations, the possible removal path of spent lead-acid battery electrolytes was modeled. The Process was divided into precipitation and Carbonation Processes. In the Carbonation Process, two scenarios were discussed, namely Carbonation with and without pre-filtration of the precipitates resulted from the precipitation Process. The results showed that in the precipitation Process, the theoretical limit for the chemical removal of SO42− was 99.15%, while in the following Carbonation Process without filtration, only 69.61% of SO42− was removed due to the fact that CO2 reacts with Ca2+ ion in the solution, and thus leads to the production of CaCO3 and SO42− ions in the solution. In the Carbonation Process without filtration, with the increase of CO2 in the solution the removal ratio of SO42− further decreases. Thermodynamic simulation was effective in predicting the theoretical removal limits and helps in understanding and optimizing the removal Process.
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Synthesis of aragonite-precipitated calcium carbonate from oyster shell waste via a Carbonation Process and its applications
Korean Journal of Chemical Engineering, 2017Co-Authors: Chilakala Ramakrishna, Choon Han, Thriveni Thenepalli, Ji Whan AhnAbstract:Oyster shells are abundantly available in nature without eminent use and are dumped into landfills in vast quantities. Their improper disposal causes environmental problems, resulting in a waste of natural resources. Recycling shell waste could potentially eliminate the environmental problems and, moreover, convert the waste into high-valueadded products, such as synthetic precipitated calcium carbonate (PCC), which can be obtained from oyster waste and which is used to enhance the mechanical properties of various materials. It can also be used as a filler material in the plastic and paper industries. This study presents a simple method for the extraction of aragonite needles from oyster shell waste via a Carbonation Process. The obtained aragonite-precipitated calcium carbonate (PCC) is characterized by XRD and SEM, which is used to assess the morphology and particle size. Using the proposed Process, oyster shell waste powder was calcined at 1,000 °C for 2 h, after which the calcined shell powder was dissolved in water for hydration. The hydrated solution was mixed with an aqueous solution of magnesium chloride at 80 °C and CO2 was then bubbled into the suspension for 3 h to produce needle-shaped aragonite PCC. Finally, aragonite-type precipitated calcium carbonate was synthesized from the oyster shell powder via a simple Carbonation Process, yielding a product with an average particle size of 30-40 μm.
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Synthesis of nano precipitated calcium carbonate by using a Carbonation Process through a closed loop reactor
Journal of the Korean Physical Society, 2016Co-Authors: Thenepalli Thriveni, Chilakala Ramakrishna, Ji Whan Ahn, Young Jun Ahn, Choon HanAbstract:Nano calcium carbonate particles have a wide range of industrial applications due to their beneficial properties such as high porosity and high surface area to volume ratio and due to their strengthening the mechanical properties of plastics and paper. Consequently, significant research has been done to deliver a new approach for the synthesis of precipitated nano calcium carbonate by using a Carbonation Process through a closed loop reactor. Both the experimental and the instrumental parameters, i.e. the CO2 flow rate, the concentration of the starting materials (Ca(OH)2 and CaO), the pH, the orifice diameter, etc., were investigated. The Carbonation efficiency was increased due to the diffusion Process involved in the loop reactor. The particle size was affected by the CO2 flow rate, reaction time, and orifice diameter. Finally, precipitated nano calcite calcium carbonate (50 to 100 nm) was synthesized by optimizing all the experimental and the instrumental parameters. The synthesized precipitated nano calcium carbonate was characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. This study has proved that the Carbonation efficiency can be enhanced for a short time by using a loop reactor and that the Carbonation Process was more energy efficient and cost effective than other conventional methods.
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factors affecting the crystal growth of scalenohedral calcite by a Carbonation Process
Journal of The Korean Ceramic Society, 2014Co-Authors: Thenepalli Thriveni, Choon Han, Young Jun Ahn, Seongyoung Nam, Ji Whan AhnAbstract:In the present work, we report a novel microstructure of scalenohedral calcite synthesized without any additives by a simple and ecofriendly Carbonation Process carried out in a liquid-gas system as well as the effects of experimental conditions on the crystal growth of the scalenohedral calcite phase. Various Process parameters, pH, temperature, Ca(OH)₂ concentration, CO₂ flow rates, and the total volume concentration, were investigated to enhance the sensitivity of the Process. The highest average length of the scalenohedral calcite was obtained at pH 6.0, temperature of 45 0 C, Ca(OH)₂ concentration of 0.2M, CO₂ flow rate of 80mL/ min, and total volume of 1L. The synthesized calcite was characterized by XRD, SEM, and FTIR to identify the phases and surface morphology.
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Scalenohedral calcite crystal growth by Carbonation Process for CO2 sequestration
Journal of Metallurgy and Materials Science, 2013Co-Authors: Thenepalli Thriveni, Choon Han, Young Jun Ahn, Il Um Nam, Ji Whan AhnAbstract:The objective of the present research work is to intensify the CO2 sequestration Process via Carbonation Process to improve yield and kinetics in the formation of the scalenohedral calcite polymorph of calcium carbonate, which has some valuable applications in paper industry. In the present work, we have synthesized a novel microstructure of scalenohedral calcite by a simple and eco - friendly Carbonation Process and it has been carried out in liquid-gas system. Various parameters such as temperature, CO2 flow rates and the total volume concentration were investigated to enhance the sensitivity of the Process. The highest average length of the scalenohedral calcite was obtained at pH 6.0, temperature 45°C, Ca(OH)2 concentration 0.2M, CO2 flow rate 80mL/min and the total volume 1L. The synthesized calcite was characterized by XRD and SEM to identify the phases and surface morphology. The scalenohedral calcite was applied successfully as filler to improve the optical properties of waste paper recycling of the hand sheets (old newspaper, ONP).
Mehmet Yildirim - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of steelmaking slag for CO2 fixation by leaching-Carbonation Process
Particulate Science and Technology, 2017Co-Authors: Muhammet Bilen, Mahmut Altiner, Mehmet YildirimAbstract:ABSTRACTSteelmaking slag is a good alternative material for the fixation of CO2 gas as precipitated calcium carbonate (PCC) that are of used in many industrial applications such as paint, plastic, medical and so on. Therefore, the experimental conditions for production of PCC from steelmaking slag produced in Iskenderun Steelmaking Industry were determined via indirect Carbonation Process. At first, the influences of acid concentration, liquid-to-solid (L/S) ratio, particle size, reaction time and temperature on the dissolution of Ca from steelmaking slag were investigated, respectively. We determined that all parameters had strong effects on the dissolution of Ca from steelmaking slag except for the reaction time. Also, the effects of Na/CH3COO ratio, CO2 flow rate, reaction temperature and time on the precipitation of Ca ions as PCC particles were investigated. The properties of PCC were determined using chemical, SEM, XRD and particle size analyses. Furthermore, non-reacted CO2 left from the carbonatio...
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production and characterization of synthetic aragonite prepared from dolomite by eco friendly leaching Carbonation Process
Advanced Powder Technology, 2017Co-Authors: Mahmut Altiner, Mehmet YildirimAbstract:Abstract Dolomite is an alternative material for producing precipitated calcium carbonate (PCC) particles, which have widespread industrial applications depending on their morphology and particle sizes. These properties are readily controlled by the production conditions such as reaction time, temperature, stirring speed, and CO2 flow rate. In this paper, we investigate the influences of these experimental conditions on the production of synthetic aragonite crystals from dolomite using a leaching Carbonation Process. The proposed Process is believed so be more eco-friendly than other methods suggested in the literature because the CO2 released from the dolomite during the leaching stage is stored for use in the Carbonation stage. The experimental results indicate that the morphology of the produced PCC is influenced not only by the reaction time and temperature, but also the stirring speed and CO2 flow rate. The required reaction time decreases with an increase in the CO2 flow rates. However, calcite forms along with the aragonite crystals at higher CO2 flow rates. We successfully synthesized pure aragonite crystals in the reaction temperature range of 40–70 °C at a fixed CO2 flow rate of 3.00 l/min, and at a stirring speed of 750 rpm. The d90 values of the aragonite crystals at various temperatures ranged from 18.47 to 25.99 μm. We fit the experimental results by a single-term exponential model. Additionally, we obtained a Mg-rich solution and CO2 gas as by-products, which are in high demand.
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Production and characterization of synthetic aragonite prepared from dolomite by eco-friendly leaching–Carbonation Process
Advanced Powder Technology, 2017Co-Authors: Mahmut Altiner, Mehmet YildirimAbstract:Abstract Dolomite is an alternative material for producing precipitated calcium carbonate (PCC) particles, which have widespread industrial applications depending on their morphology and particle sizes. These properties are readily controlled by the production conditions such as reaction time, temperature, stirring speed, and CO2 flow rate. In this paper, we investigate the influences of these experimental conditions on the production of synthetic aragonite crystals from dolomite using a leaching Carbonation Process. The proposed Process is believed so be more eco-friendly than other methods suggested in the literature because the CO2 released from the dolomite during the leaching stage is stored for use in the Carbonation stage. The experimental results indicate that the morphology of the produced PCC is influenced not only by the reaction time and temperature, but also the stirring speed and CO2 flow rate. The required reaction time decreases with an increase in the CO2 flow rates. However, calcite forms along with the aragonite crystals at higher CO2 flow rates. We successfully synthesized pure aragonite crystals in the reaction temperature range of 40–70 °C at a fixed CO2 flow rate of 3.00 l/min, and at a stirring speed of 750 rpm. The d90 values of the aragonite crystals at various temperatures ranged from 18.47 to 25.99 μm. We fit the experimental results by a single-term exponential model. Additionally, we obtained a Mg-rich solution and CO2 gas as by-products, which are in high demand.
Concepcion Domingo - One of the best experts on this subject based on the ideXlab platform.
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Monitoring the Effect of Mineral Precursor, Fluid Phase CO2–H2O Composition, and Stirring on CaCO3 Crystallization in a Supercritical—Ultrasound Carbonation Process
Crystal Growth & Design, 2011Co-Authors: Ana M. López-periago, Roberta Pacciani, Lourdes F Vega, Concepcion DomingoAbstract:This study focuses on the evaluation of the different factors that affect the particle size distribution of precipitated calcium carbonate formed in a wet supercritical CO2 Carbonation Process and on the conversion rate from two different Ca2+ precursors (Ca(OH)2 or CaO). The operating factors investigated include the composition of the fluid phase (CO2/H2O) in contact with the solid precursor, the calcium cation source, and the stirring mode (no agitation, vertical mechanical, and ultrasound). The calcium carbonate particles were fabricated in batch mode in a stainless steel reactor filled with the solid precursor, water, and scCO2 at 130 bar and 40 °C. The particle size was estimated using scanning electron microscopy, while the precipitated solid phase composition was determined by a quantitative characterization method based on X-ray diffraction. The conversion of CaO or Ca(OH)2 to CaCO3 varied from 50 to >90 wt % depending on the reactor fill level and the existence of a rich-water phase in equilibri...
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monitoring the effect of mineral precursor fluid phase co2 h2o composition and stirring on caco3 crystallization in a supercritical ultrasound Carbonation Process
Crystal Growth & Design, 2011Co-Authors: Ana M Lopezperiago, Roberta Pacciani, Lourdes F Vega, Concepcion DomingoAbstract:This study focuses on the evaluation of the different factors that affect the particle size distribution of precipitated calcium carbonate formed in a wet supercritical CO2 Carbonation Process and ...
Mahmut Altiner - One of the best experts on this subject based on the ideXlab platform.
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Influences of CO2 Bubbling Types on Preparation of Calcite Nanoparticles by Carbonation Process
Periodica Polytechnica Chemical Engineering, 2017Co-Authors: Mahmut AltinerAbstract:This study investigates the comparison of influences of CO2 bubbling into the calcium hydroxide (Ca(OH)2) slurry through a microbubble generator (MBG) and an ordinary CO2 generator (OCG) on the preparation of calcite nanoparticles by a Carbonation method. Each obtained precipitate was characterized using XRD, SEM and particle size analyses. During the Carbonation Process at each CO2 flow rates, it was determined that the MBG generates tiny bubbles whereas an increase in CO2 flow rates led to an increase bubble size when the OCG was used. The flow rate of CO2 was not an important parameter with using the MBG as calcite nanoparticles were prepared (<125 nm) at each CO2 flow rates. The necessary time for the complete reaction decreases with an increase in the CO2 flow rates through the MBG in comparison to the OCG. To produce calcite nanoparticles with a high production recovery in shorter times, the MBG should be adopted to the Carbonation reactor.
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Evaluation of steelmaking slag for CO2 fixation by leaching-Carbonation Process
Particulate Science and Technology, 2017Co-Authors: Muhammet Bilen, Mahmut Altiner, Mehmet YildirimAbstract:ABSTRACTSteelmaking slag is a good alternative material for the fixation of CO2 gas as precipitated calcium carbonate (PCC) that are of used in many industrial applications such as paint, plastic, medical and so on. Therefore, the experimental conditions for production of PCC from steelmaking slag produced in Iskenderun Steelmaking Industry were determined via indirect Carbonation Process. At first, the influences of acid concentration, liquid-to-solid (L/S) ratio, particle size, reaction time and temperature on the dissolution of Ca from steelmaking slag were investigated, respectively. We determined that all parameters had strong effects on the dissolution of Ca from steelmaking slag except for the reaction time. Also, the effects of Na/CH3COO ratio, CO2 flow rate, reaction temperature and time on the precipitation of Ca ions as PCC particles were investigated. The properties of PCC were determined using chemical, SEM, XRD and particle size analyses. Furthermore, non-reacted CO2 left from the carbonatio...
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production and characterization of synthetic aragonite prepared from dolomite by eco friendly leaching Carbonation Process
Advanced Powder Technology, 2017Co-Authors: Mahmut Altiner, Mehmet YildirimAbstract:Abstract Dolomite is an alternative material for producing precipitated calcium carbonate (PCC) particles, which have widespread industrial applications depending on their morphology and particle sizes. These properties are readily controlled by the production conditions such as reaction time, temperature, stirring speed, and CO2 flow rate. In this paper, we investigate the influences of these experimental conditions on the production of synthetic aragonite crystals from dolomite using a leaching Carbonation Process. The proposed Process is believed so be more eco-friendly than other methods suggested in the literature because the CO2 released from the dolomite during the leaching stage is stored for use in the Carbonation stage. The experimental results indicate that the morphology of the produced PCC is influenced not only by the reaction time and temperature, but also the stirring speed and CO2 flow rate. The required reaction time decreases with an increase in the CO2 flow rates. However, calcite forms along with the aragonite crystals at higher CO2 flow rates. We successfully synthesized pure aragonite crystals in the reaction temperature range of 40–70 °C at a fixed CO2 flow rate of 3.00 l/min, and at a stirring speed of 750 rpm. The d90 values of the aragonite crystals at various temperatures ranged from 18.47 to 25.99 μm. We fit the experimental results by a single-term exponential model. Additionally, we obtained a Mg-rich solution and CO2 gas as by-products, which are in high demand.
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Production and characterization of synthetic aragonite prepared from dolomite by eco-friendly leaching–Carbonation Process
Advanced Powder Technology, 2017Co-Authors: Mahmut Altiner, Mehmet YildirimAbstract:Abstract Dolomite is an alternative material for producing precipitated calcium carbonate (PCC) particles, which have widespread industrial applications depending on their morphology and particle sizes. These properties are readily controlled by the production conditions such as reaction time, temperature, stirring speed, and CO2 flow rate. In this paper, we investigate the influences of these experimental conditions on the production of synthetic aragonite crystals from dolomite using a leaching Carbonation Process. The proposed Process is believed so be more eco-friendly than other methods suggested in the literature because the CO2 released from the dolomite during the leaching stage is stored for use in the Carbonation stage. The experimental results indicate that the morphology of the produced PCC is influenced not only by the reaction time and temperature, but also the stirring speed and CO2 flow rate. The required reaction time decreases with an increase in the CO2 flow rates. However, calcite forms along with the aragonite crystals at higher CO2 flow rates. We successfully synthesized pure aragonite crystals in the reaction temperature range of 40–70 °C at a fixed CO2 flow rate of 3.00 l/min, and at a stirring speed of 750 rpm. The d90 values of the aragonite crystals at various temperatures ranged from 18.47 to 25.99 μm. We fit the experimental results by a single-term exponential model. Additionally, we obtained a Mg-rich solution and CO2 gas as by-products, which are in high demand.
Chi Sun Poon - One of the best experts on this subject based on the ideXlab platform.
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a novel upcycling technique of recycled cement paste powder by a two step Carbonation Process
Journal of Cleaner Production, 2020Co-Authors: Xiaoliang Fang, Baojian Zhan, Dongxing Xuan, L I Weifeng, Chi Sun PoonAbstract:Abstract The construction industry, being a major consumer of natural resources and energy, is eager to develop novel upcycling techniques for converting secondary resources derived from concrete waste into new and value-added products. However, upcycling of demolished concrete waste is limited by the shortage of practical and economical techniques. This paper presents the development of an innovative upcycling technique to convert recycled fine cement waste to a Ca-rich residue and a Si-rich gel by using a two-step Carbonation Process. This two-step Process involves i) fine recycled cement powder reacting with a Na2CO3 solution to precipitate a calcium-rich residue and ii) after filtration, the filtrate containing Na2SiO3 and NaOH was subjected to a flow-through CO2 gas Carbonation to obtain the suspension with a silica-rich gel and the Na2CO3 solution. The physical and chemical properties of the precipitated products from both steps were analyzed by a range of techniques, including particle size distribution, Fourier-transformed infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM). The results indicated that the proposed technique was able to successfully convert recycled cement paste powder to two new value-added reaction products, containing calcite and silica gel.
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experimental study on co2 curing for enhancement of recycled aggregate properties
Construction and Building Materials, 2014Co-Authors: Baojian Zhan, Chi Sun PoonAbstract:Abstract In this paper, the results of an experimental program on studying the use of a Carbonation Process to enhance the properties of recycled aggregates are presented. Hardened concretes prepared by using different water-to-cement ratios in the laboratory, were crushed to produce recycled aggregates with different particle sizes. Before and after the laboratory Carbonation Process, the physical properties of the recycled aggregate, including water absorption and density were determined. The extent of CO 2 curing of the recycled aggregate was quantified by assessing the Carbonation percentage of the aggregates. Carbonation resulted in reduction in water absorption values and increase in density and these showed that the properties of recycled aggregate were improved. The factors influencing the CO 2 curing Process, including curing time, particle size and moisture contents of the recycled aggregate, were investigated.