• Applied Chemistry for Engineering
• /
• v.9 no.2
• /
• pp.278-285
• /
• 1998

In a fixed bed reactor, adsorption capacity of $SO_2$ in simulated flue gases was investigated with NMO(natural manganese ore), composed of various metal oxides, iron ore and $CuO/{\gamma}-Al_2O_3$ as adsorbents. The experiment carried out in a fluidized bed reactor with variables such as gas velocity, temperature and particle size. Iron ore was excluded in the fluidized bed reactor experiment for the lower adsorption capacity. The adsorption of $SO_2$ in metal oxide is a typical chemisorption because the adsorption capacity of all adsorbents increased with temperature. The effect of particle size on the adsorption capacity was varied with the ratio, $U_o/U_{mf}$ and the difference of $U_o-U_{mf}$. $U_o$ is the gas velocity, $U_{mf}$ is the minimum fluidization gas velocity. $U_o/U_{mf}$ and $U_o-U_{mf}$ explain the behavior of the gas and solids in the fluidized bed reactor. From the performance equation of the fluidized bed reactor, kinetic reaction rate constants were obtained by the non-linear least square method. The adsorption capacity of NMO proved the potential use of $SO_2$ adsorbents.

• Korean Chemical Engineering Research
• /
• v.45 no.2
• /
• pp.143-148
• /
• 2007

In hydrogen production for fuel cell by reforming city-gas, sulfur compounds, odorant in city-gas, are detrimental to reforming catalyst and fuel cell electrodes. We prepared metal salt impregnated ${\beta}-zeolite(BEA)$ to remove sulfur compound in city-gas by adsorption. The sulfur breakthrough adsorption capacity was changed depending on the concentration and species of metal salt. $AgNO_3$ impregnated BEA showed the highest sulfur breakthrough capacity among adsorbents used in this experiment(41.1 mg/g). But metal salt impregnated BEA such as $Ni(NO_3)_2/BEA$, $Fe(NO_3_)_3/BEA$, $Co(NO_3)_2/BEA$ showed a certain amount of sulfur adsorption capacity comparable to $AgNO_3/BEA$. Adsorption temperature effect, desorption study, and x-ray photoelectron spectroscopy analysis revealed that the dominant interaction between metal impregnated adsorbent and sulfur compounds was not chemisorption but physisorption.

• Applied Chemistry for Engineering
• /
• v.35 no.1
• /
• pp.8-15
• /
• 2024

In this study, nitrogen plasma treatment was performed in 5, 10, and 15 minutes to improve the tetracycline adsorption performance of activated carbon. All nitrogen plasma-treated activated carbons showed improved tetracycline adsorption compared to untreated activated carbons. The nitrogen functional groups in activated carbon lead to chemisorption with tetracycline via π-π interactions and hydrogen bonding. In particular, in the nitrogen plasma treatment at 80 W and 50 kHz, the activated carbon treated for 10 minutes had the best adsorption performance. At this time, the nitrogen content on the surface of the activated carbon was 2.03% and the specific surface area increased to 1,483 m²/g. As a result, nitrogen plasma treatment of activated carbon improved its physical and chemical adsorption capabilities. In addition, since the adsorption experimental results were in good agreement with the Langmuir isotherm and pseudo-second order model, it was determined that the adsorption of tetracycline on the nitrogen plasma-treated activated carbon was dominated by chemical adsorption through a monolayer. As a result, nitrogen plasma-treated activated carbon can be used as an adsorbent to efficiently remove tetracycline from water due to the synergistic effect of physical adsorption and proactive chemical adsorption.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.2
• /
• pp.231-243
• /
• 2019

The methanolic extracts of the leaves and stem of the plant Lepidagathis keralensis were evaluated for anticorrosion behavior against mild steel in 1M HCl. Corrosion inhibition studies were done by gravimetric method, electrochemical impedance spectroscopy and potentiodynamic polarization methods. Surface morphology of mild steel in the presence and absence of inhibitors were studied using SEM analysis. UV-Vis studies were also done to evaluate the mechanism of inhibition. Both the extracts showed good inhibition efficiency which increased with increase in concentration of the inhibitor and decreased with increase in temperature. The mechanism of inhibition was explained by adsorption which obeyed Langmuir adsorption isotherm. Thermodynamic calculations revealed a combination of both physisorption and chemisorption of the inhibitor on the surface of mild steel. The extracts behaved as mixed type inhibitors as determined by polarization studies. Quantum chemical studies on Phenoxyethene, one of the major components in the leaf extract of the plant was also carried out to support the experimental results.

• Journal of Industrial and Engineering Chemistry
• /
• v.67
• /
• pp.99-108
• /
• 2018

In this paper, novel thiadiazole-thione surfactants including 5-heptyl-1,3,4-thiadiazole-2-thione (HpSDT), 5-phenyl-1,3,4-thiadiazole-2-thione (PSDT) and 5-(2-hydroxyphenyl)-1,3,4-thiadiazole-2-thione (HPhSDT) were synthesized and originally introduced as collectors in froth flotation. Microflotation tests showed that HpSDT exhibited better flotation response to malachite than PSDT and HPhSDT, as well as excellent flotation selectivity against quartz. The contact angle results inferred that the hydrophobization intensity of these collectors toward malachite was in the order as HpSDT> PSDT> HPhSDT. ${\zeta}$-potential recommended a chemisorption of HpSDT on malachite surfaces. FTIR deduced that cupric or cuprous atoms might bond with the S and N atoms of HpSDT to form a conjugated ring. XPS further gave an additional evidence that HpSDT-Cu(I) complexes were produced on malachite surfaces via combining surface Cu atoms with HpSDT's N and S atoms, with reducing surface Cu(II) to Cu (I). The tighter orientation arrangement on malachite and stronger hydrophobicity rendered HpSDT to possess better flotation affinity toward malachite than PSDT and HPhSDT.

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

• Applied Science and Convergence Technology
• /
• v.26 no.5
• /
• pp.95-109
• /
• 2017

There are several contributions to the gas load of a system of which often the most important is outgassing. Adsorption occurs via two main processes, physisorption and chemisorption, and can be described using five (or six) classifying isotherms. Outgassing is the result of desorption of previously adsorbed molecules, bulk diffusion, permeation and vapourisation. Looking at the desorption rate, pumping speed and readsorption on surfaces, the net outgassing of the system can be calculated. There is significant variation in measured outgassing rates between different materials but also between published rates for the same materials, in part due to the number of different methods used to measure outgassing. This article aims to review the outgassing process, outgassing rates, measurement methods and techniques that can be used to reduce the outgassing of a system.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.3
• /
• pp.934-938
• /
• 2011

The curvature dependence of the physisorptions of $H_2$ on graphene surface and their barrier to the chemisorptions has been studied. The graphene with steeper curvature can adsorb $H_2$ stronger due to the more $sp^3$ character of the carbon. However, for the negative curvature, the binding strength of the physisorption and the barrier to the chemisorptions are determined by steric repulsion as well as the $sp^3$ character.

• Bulletin of the Korean Chemical Society
• /
• v.13 no.1
• /
• pp.30-32
• /
• 1992

The apparent depth of space charge region on the ZnO $(10{\bar{1}}0)$ surface in chemisorption of oxygen has been estimated from the capacitance of two contacting faces. When the sample (donor concentration: $2.4{\times}10^{22}\;m^{-3}$) was evacuated at 773 K for 1 hr the depth reached to 40-100 ${\AA}$ depending on sample assembly. Admission of oxygen to the sample resulted in an increase of the depth to 3600 ${\AA}$ where the increment was greater at higher oxygen pressure between 6.6-1600 $N/m^2$. Admission of CO to the sample previously exposed to oxygen yields a decrease in the depth. The results of the measurement support that oxygen is adsorbed as an acceptor on ZnO $(10{\bar{1}}0)$.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.11
• /
• pp.1028-1032
• /
• 1995

The structure and electronic properties of the Si(100) surface is studied using the atom superposition and electron delocalization method. The energy released when the symmetric dimer surface is reconstructed to form the buckled dimer surface with p(2X2) symmetry is calculated to be 0.99 eV per dimer in the case of ideal clean surfaces. This indicates that the surface dimer buckling is intrinsic from the viewpoint of thermodynamics. The relaxation energy, when water is adsorbed on the clean symmetric dimer surface to form the buckled dimer surface, is 2.25 eV per dimer for appropriate coverages. These results show that H2O molecule could induce a reconstruction of the surface structure through adsorption. The buckling of the surface dimer is, therefore, more favorable under the existence of water vapour. This conclusion supports the recently obtained experimental observations by Chander et al.