• Resources Recycling
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• v.31 no.4
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• pp.49-55
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• 2022

In this study, the heavy metal ions (of Pb, Cd, Cr, and Hg) in wastewater were removed using a spent Li₂O-Al₂O₃-SiO₂-based crystallized glass previously used as an induction top plate material. Changes in the removal efficiency of heavy metals according to different reaction parameters, such as the amount of zeolite used as a heavy-metal adsorbent, adsorption time, initial concentration of the heavy metals, and pH of the initial solution, were investigated. As the amount of zeolite added increased, the heavy-metal removal efficiency also increased. Adsorption time had a considerable influence on adsorption characteristics, and the removal efficiency of all heavy metals increased with increasing adsorption time. In the case of Cd, the removal efficiency was greatly improved depending on the adsorption time. The initial concentration of the heavy-metal solution did not affect the removal efficiency; however, the initial pH of the heavy-metal solution affected the removal efficiency. More specifically, the removal efficiency of Cd increased while that of Pb and Cr decreased with increasing pH. The adsorption characteristics of Hg were not significantly affected by pH.

• Composites Research
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• v.35 no.2
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• pp.98-105
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• 2022

In this study, polyvinyl alcohol (PVA)/graphene oxide (GO)/iron oxide (Fe₃O₄) magnetic microgels were prepared using a microfluidic approach and the dye adsorption capacity of the microgels was confirmed. The adsorption capacity (q_e) of the gels was evaluated by varying the dye concentration, pH, and contact time with the microgels. The dyes used in this work were methylene blue (MB), crystal violet (CV), and malachite green (MG), and microgels showed the highest adsorption capacity (191.1 mg/g) in methylene blue. The microgels exhibited the highest adsorption capacity in the dye aqueous solution at pH 10 due to the presence of atomic nitrogen ions (N⁺) on the dye molecules. The adsorption isotherm studies revealed that the Langmuir isotherm is the best fit isotherm model for the dye adsorption on the microgels, indicative of monolayer adsorption. The kinetic analysis exhibited that the pseudo-second order model fits better than the pseudo-first order model, confirming that the adsorption process is chemisorption. In addition, the magnetic microgels showed good reusability and recovery efficiency. It was confirmed that the adsorption capacity of the gels maintains more than 70% of the initial capacity after 5 times of cycle experiments.

• Clean Technology
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• v.28 no.3
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• pp.210-217
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• 2022

Boron(B) is a rare resource used for various purposes such as glass, semiconductor materials, gunpowder, rocket fuel, etc. However, Korea depends entirely on imports for boron. Considering the global boron reserves and its current production rate, boron will be depleted on earth in 50 years. Thus, a process including proper adsorbent materials recovering boron from seawater is demanded. This research proposed carbonized nanofibers prepared from electrospun PAN(polyacrylonitrile) mats as promising materials to adsorb boron in aqueous solution. First, the mechanism of boron adsorption on carbonized nanofibers was investigated by DFT(density functional method)-based molecular modeling and the calculated energetics demonstrated that the boron chemisorption on the nitrogen-doped graphene surface by a two-step dehydration is possible with viable activation energies. Then, the electrospun PAN mats were stabilized in air and then carbonized in an argon atmosphere before being immersed in the boric acid aqueous solution. Analytically, SEM(scanning electron microscopy) and Raman measurements were employed to confirm whether the electrospinning and carbonization of PAN mats proceeded successfully. Then, XPS(X-ray photoelectron spectroscopy) peak analysis showed whether the intended nitrogen-doped carbon nanofiber surface was formed and boron was properly adsorbed on nanofibers. Those results demonstrated that the carbonized nanofibers prepared from electrospun PAN mats could be feasible adsorbents for boron recovery in seawater.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.377-385
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• 2022

Surface morphology and adsorption characteristics of charcoals prepared from Korean traditional kiln were analyzed, and their moisture adsorption capacities were examined with respect to humidity and temperature change. Moisture adsorption capacities of red-clay powder, activated carbon fiber fabric (ACF fabric) and activated carbon fiber paper(ACF paper) were also examined to compare with those of charcoals. Moisture adsorption capacity of charcoal was low less than 45% humidity due to its hydrophobic property, but it slowly and linearly increased as increasing the humidity. Moisture adsorption capacity of red-clay powder was similar to charcoal at low level humidity, it increased exponentially as increasing the humidity showing Type V adsorption isotherm. Therefore, the weather forecast annal prepared by employee of weather centre in Joseon Dynasty is experimentally approved. ACF fabric and ACF paper show excellent moisture adsorption capacities, which can be used to humidity measuring sensor. Adsorption isotherm of charcoal slice was peculear showing the mixed Type I and Type IV due to low-pressure hysteresis that was occurred from embedment of nitrogen in crevice of charcoal. The specific surface area of charcoal increased by grinding charcoal slice to powder, resulted in increasing the desorption amount of adsorbent at low relative pressure.

• Journal of Applied Biological Chemistry
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• v.65 no.4
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• pp.457-462
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• 2022

Manganese (Mn) exists in various oxidation states and Mn(II) is the most mobile species of Mn, which is toxic to plants and limits their growth. Therefore, the purpose of this study was to reduce Mn toxicity by immobilizing Mn using various adsorbents including iron oxides and calcium compounds. Ferrihydrite, schwertmannite, goethite were synthesized, which was confirmed by X-ray diffraction. Hematite was purchased and used as Mn adsorbent. Calcium compounds such as CaNO₃, CaSO₄, and CaCO₃ were used to increase pH and oxidize Mn. For Mn adsorption, Mn(II) solution was reacted with four iron oxides, CaNO₃, CaSO₄, and CaCO₃ for 24 hours, filtered, and the remaining Mn concentrations in the solution were analyzed by inductively coupled plasma optical emission spectroscopy. The adsorption rate and adsorption isotherm were calculated. Among iron oxides, the adsorption rate was highest for hematite followed by ferrihyrite, but goethite and schwertmannite did not adsorb Mn. In the case of calcium compounds, the adsorption rate was high in the order of CaCO₃>CaNO₃>CaSO₄. In conclusion, treatment of CaCO₃ was the most effective in reducing Mn toxicity by increasing pH.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.9-15
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• 2023

The cement is a typical CO₂ emission industry. Manufacturing process improvements and increased use of alternative materials are needed to reduce energy consumption and CO₂ emissions. This study confirmed the basic characteristics of cement hydration by sintering CAF at low temperature as a CO₂ adsorbent material. For the hydration product of the synthetic CAF, crystal phase analysis, porosity, and structural images were confirmed, and the compressive strength was measured. The replacement rate of SCAF was 10, 20, and 100 %, and the compressive strength tended to decrease as the replacement rate increased. In addition, when the SCAF substitution rate is 100 %, the hydration products of the early age are calcium aluminum oxide hydrate (Ca₃Al₂O₆ x H₂O) and calcium iron hydroxide (Ca₃Fe(OH)₁₂), and at substitution rates of 10 and 20 %, CAF compounds other than general cement hydrates brownmillerite was observed. As for the porosity, the pore size increased and the porosity increased with the increase of the replacement ratio. As a result of this study, CAF manufactured by low-temperature sintering seems to be difficult to use alone and general curing for utilization as a CO₂ adsorbing material.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.2
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• pp.63-71
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• 2023

Increased nitrogen in the water system has become an important environmental problem around the world, as it causes eutrophication, algae bloom, and red tide, destroys the water system, and undermines water's self-purification. The most common form of nitrogen in the water system is ammonium ion (NH₄⁺), and the largest portion of ammonium ions comes from wastewater. NH₄⁺ is a major contributor to eutrophication, which calls for appropriate treatment and measures for ammonium removal. This study produced biochar by applying Sorghum × drummondii, a type of biomass with a great growth profile, analyzed the adsorption capacity of Sorghum × drummondii biochar produced from the changing carbonization temperature condition of 200 to 400℃ in the ammonium ion range of 10 to 100 ppm, and used the results to evaluate its potential as an adsorbent. Carbonization decomposed the chemical structure of Sorghum × drummondii and increased the content of carbon and fixed carbon in the biochar. The biochar's pH and electrical conductivity showed high adsorption potential for cations due to electrical conductivity as its pH and electrical conductivity increased along with higher carbonization temperature. Based on the results of an adsorption experiment, the biochar showed 54.5% and 17.4% in the maximum and minimum NH₄-N removal efficiency as the concentration of NH₄-N increased, and higher carbonization temperature facilitated the adsorption of pollutants due to the biochar's increased pores and specific surface area and subsequently improved NH₄-N removal efficiency. FT-IR analysis showed that the overall surface functional groups decreased due to high temperature from carbonization.

• Analytical Science and Technology
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• v.20 no.3
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• pp.237-245
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• 2007

The presence of benzene in 31 products of vitamin drinks purchased from 20 retail outlets was determined using headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). The sample (25 ml) was stirred at 1200 rpm for 4 min using a magnetic bar with a $100{\mu}m$ SPME fiber as an adsorbent for benzene which was then desorbed from the fiber for 1 min in the GC injector. Quantitation was achieved using the standard addition method. The limit of detection was determined as 0.56 ng/ml and over a concentration range 0-40 ng/ml the coefficient of correlation was greater than 0.999. The concentration of benzene in the drinks examined was in the range not detectable to 47.35 ng/ml. Benzene was detected in 15 of the drinks with concentration in 5 of them greater than 10 ng/ml which is the limit set for the presence of benzene in the Drinking Water Regulations. The concentrations of benzene in the 5 drinks which exceeded the limit of 10 ng/ml were 16.99, 35.14, 16.03, 47.35 and 14.28 ng/ml respectively.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.576-583
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• 2023

This study investigated the possibility of new adsorbent materials made from pig bone-based biomass. To this end, the properties of pig bone-based activated carbon (PAC) prepared from animal biomass were investigated, and its carbon dioxide adsorption performance was examined. KOH was used as the activation agent, and the specific surface area increased with increasing activation temperature, and the adsorption efficiency of carbon dioxide also increased. The sample activated at 800 ℃ exhibited the largest specific surface area of 1208.7 m²/g and the highest CO₂ adsorption efficiency of 3.33 mmol/g at 273 K, 1 bar. However, the specific surface area and the CO₂ adsorption efficiency decreased at activation temperatures above 900 ℃ due to crystallinity changes and overactivation. On the other hand, when the selectivity was calculated using the ideal adsorption solution theory, PAC-900 samples at 273 K and below 0.8 bar showed the best selectivity. These results suggest that the high selectivity of carbon dioxide/nitrogen adsorption at 273 K is due to the carbon dioxide adsorption capacity of hydroxyapatite formed by the decomposition of carbonate when pig bone is activated at 900 ℃ and its crystallinity.

• Korean Journal of Materials Research
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• v.34 no.1
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• pp.1-11
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• 2024

This research investigated the preparation of activated carbon derived from Krabok (Irvingia malayana) seed shells to improve the quality of crude glycerol obtained during biodiesel production. The activated carbon was prepared using a dry chemical activation method with NaOH, utilizing an innovative biomass incinerator. The results revealed that the resulting KC/AC-two-step exhibited favorable physicochemical adsorption properties, with a high surface area of 758.72 m²/g and an iodine number of 611.10 mg/g. These values meet the criteria of the industrial product standard for activated carbon No. TIS 900-2004, as specified by the Ministry of Industry in Thailand. Additionally, the adsorption efficiency for methylene blue reached an impressive 99.35 %. This developed activated carbon was then used to improve the quality of crude glycerol obtained from biodiesel production. The experimental results showed that the KC/AC-two-step increased the purity of crude glycerol to 73.61 %. In comparison, commercially available activated carbon (C/AC) resulted in a higher crude glycerol purity of 81.19 %, as analyzed by the GC technique. Additionally, the metal content (Zn, Cu, Fe, Pb, Cd, and Na) in purified glycerol using KC/AC-two-step was below the standards for heavy metals permitted in food and cosmeceuticals by the Food and Drug Administration of Thailand and the European Committee for Food Contact Materials and Articles. As a result, it can be inferred that Krabok seed shells have favorable properties for producing activated carbon suitable as an adsorbent to enhance crude glycerol purity. Furthermore, the improved crude glycerol from this research has potential for various industrial applications.