• Clean Technology
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• 제26권1호
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• pp.30-38
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• 2020

The kinetic and thermodynamic parameters of Acid Red 66, adsorbed by granular activated carbon, were investigated on areas of initial concentration, contact time, and temperature. The adsorption equilibrium data were applied to Langmuir, Freundlich, Temkin, Redlich-Peterson, and Temkin isotherms. The agreement was found to be the highest in the Freundlich model. From the determined Freundlich separation factor (1/n = 0.125 ~ 0.232), the adsorption of Acid Red 66 by granular activated carbon could be employed as an effective treatment method. Temkin's constant related to adsorption heat (B_T = 2.147 ~ 2.562 J mol^-1) showed that this process was physical adsorption. From kinetic experiments, the adsorption process followed the pseudo-second order model with good agreement. The results of the intraparticle diffusion equation showed that the inclination of the second straight line representing the intraparticle diffusion was smaller than that of the first straight line representing the boundary layer diffusion. Therefore, it was confirmed that intraparticle diffusion was the rate-controlling step. From thermodynamic experiments, the activation energy was determined as 35.23 kJ mol^-1, indicating that the adsorption of Acid Red 66 was physical adsorption. The negative Gibbs free energy change (ΔG = -0.548 ~ -7.802 kJ mol^-1) and the positive enthalpy change (ΔH = +109.112 kJ mol^-1) indicated the spontaneous and endothermic nature of the adsorption process, respectively. The isosteric heat of adsorption increased with the increase of surface loading, indicating lateral interactions between the adsorbed dye molecules.

• Journal of Radiation Protection and Research
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• 제27권1호
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• pp.27-35
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• 2002

Characteristics of Amberlite IRN 77, a cation exchange resin, and the mechanisms of its adsorption equilibria with Co(II), Ni(II), Cr(III) and Fe(III) ions were investigated for the application of the demineralizing process in the primary coolant system of a pressurized water reactor (PWR). The optimum dosage of the resin for removal of the dissolved metal ions at $200mgL^{-1}$ was 0.6 g for 100 mL solution. Most of each metal ion was adsorbed onto the resin in an hour from the start of the reaction. Each metal adsorption onto the resin could be well represented by Langmuir isotherms. However, in the case of Fe(III) adsorption, continuous formation of Fe-oxide or -hydroxide and its subsequent precipitation inhibited the completion of the equilibrium between the metal and the adsorbent Cobalt(II) and Ni(II), which have an equivalent electrovalence, were adsorbed to the resin with a similar adsorption amount when they coexisted in the solution. However, Cr(III) added to the solution competitively replaced Co(II) and Ni(II) which were already adsorbed onto the resin, resulting in desorption of these metals into the solution. The result was likely due to a higher adsorption affinity of Cr(III) than Co(II) and Ni(II). This implies that the interactively competitive adsorption of multi-cations onto the resin should be fully considered for an efficient operation of the demineralizing ion exchange process in the primary coolant system.

• Korean Journal of Microbiology
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• 제30권4호
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• pp.310-315
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• 1992

Absorption of $\textrm{Pb}^{2-}$ from aqueous solution was studied using Staphylococcus epidermidis. Cells of exponential phase were employed as absorbents. Uptake ratio defined as the ratio of amount of $\textrm{Pb}^{2+}$ absorbed to that of initial $\textrm{Pb}^{2+}$. Absorption of $\textrm{Pb}^{2+}$ increased with increase in cell concentration. while amount of $\textrm{Pb}^{2+}$ per unit cell mass decreased. Uptake ratio of $\textrm{Pb}^{2+}$ augmented and then diminished after exhibiting a maximum as the pH of the solution increased. Equilibrium absorption of $\textrm{Pb}^{2+}$ deviated from Freundlich isotherm especially at higher concentration of $\textrm{Pb}^{2+}$ due to the precipitation phenomena. HCI and EDTA were founded to desorb $\textrm{Pb}^{2+}$ more effectively than $\textrm{Na}_{2}\textrm{CO}_{3}$ or $\textrm{NaHCO}_{3}$. After 10 cycles of absorption and desorption. $\textrm{Pb}^{2+}$ absorption capability remained almost unchanged and the biomass had leaked out 30-40 wt/%. Uptake ratio of Pb2+ decreased in the presence of other heavy metal ions due to the competitive absorption The inhibition of $\textrm{Pb}^{2+}$ absorption appeared to have a strong correlation with ionic radius of the competing ions. Especially $\textrm{Cr}^{3-}$, $\textrm{Co}^{2+}$ or $\textrm{Fe}^{2+}$ having smaller ionic radius depressed more significantly the uptake of $\textrm{Pb}^{2+}$ than any other metal ions tested.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.694-702
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• 2002

Activated carbons have been used as adsorbents in various industrial application, such as solvent recovery, gas separation, deodorization, and catalysts. In this study, the effects of residual water on the activated carbon adsorbent surface on the adsorption capacity of $CCl_4$ were investigated. Adsorption behavior in a fixed bed was studied in terms of feed concentration, flow rate, breakthrough curve and adsorption capacity for $CCl_4$. Desorption characteristics of residual water on activated carbon were also studied. The water contents of the activated carbon were varied in the range of 0-20%(w/w) and all experiments were performed at 298.15 K. The adsorption equilibrium data $CCl_4$ on the activated carbon were well expressed by Langmuir isotherm. The adsorption capacity of $CCl_4$ decreased with increasing residual water content. Desorption of residual water in activated carbon decreased expotentially with $CCl_4$ adsorption. The obtained breakthrough curves using LDF(linear driving force) model represented our experimental data.

• Journal of the Korea institute for structural maintenance and inspection
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• 제24권4호
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• pp.1-9
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• 2020

This study conducted to understand effects of CA (CaAl₂O₄) and CA₂ (CaAl₄O₇) ratio on chloride binding ability and compressive strength and pore structure of cement mortar incorporating mixture of CA and CA₂. The Portland cement based specimens were mixed with the clinkers CA and CA₂, and these calcium aluminate clinker mixture were replaced 0, 5, 10% by weight of cement. After all the test specimens were cured for 28 days under water curing, they were immersed in the distilled water and NaCl solution. As a result, 28 days compressive strength of all specimens was similar, and As the replacement ratio of calcium aluminate clinker in the specimen increased, Friedel's salt production tended to increase. However, it was dependent on the amount of Al₂O₃ in the level of 5% replacement and CA ratio in the level of 10% replacement. Through equilibrium isotherm result, it was also indicated that as replacement ratio of calcium aluminate clinker in cement matrix increased, chloride binding capacity was improved, and chloride penetration was suppressed. In this study, the specimen replaced with 10% of the calcium aluminate clinker mixture (CA 39%, CA₂ 60%) was remarkable to control chloride attack. We figured out necessity to understand optimal CA/CA₂ ratio to effectively apply CA₂ as a sustainable building material by improving the chloride binding ability in Portland cement based system.

• Journal of the Korean Chemical Society
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• 제55권2호
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• pp.208-217
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• 2011

The effects of pH and temperature on the removal of two dyes (neutral red; NR and malachite green oxalates; MG) from aqueous effluents using Maghnia montmorillonite clay in a batch adsorption process were investigated. The results showed the stability of the optical properties of MG in aqueous solution and adsorbed onto clay under wide range of pH 3-9. However, the interaction of NR dye with clay is accompanied by a red shift of the main absorption bands of monomer cations under pH range of 3-5, whereas, those of neutral form remains nearly constant over the pH range of 8-12. The optimal pH for favorable adsorption of the dyes, i.e. ${\geq}$90% has been achieved in aqueous solutions at 6 and 7 for NR and VM respectively. The most suitable adsorption temperatures were 298 and 318 K with maximum adsorption capacities of 465.13mg/g for NR and 459.89 mg/g for MG. The adsorption equilibrium results for both dyes follow Langmuir, Freundlich isotherms. The numerical values of the mean free energy $E_a$ of 4.472-5.559 kj/mol and 2.000-2.886 kj/mol for NR and MG respectively indicated physical adsorption. Various thermodynamic parameters, such as ${\Delta}H^{\circ}$, ${\Delta}S^{\circ}$, ${\Delta}G^{\circ}$ and Ea have been calculated. The data showed that the adsorption process is spontaneous and endothermic. The sticking probability model was further used to assess the potential feasibility of the clay mineral as an alternative adsorbent for organic ion pollutants in aqueous solution.

• Food Science and Preservation
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• 제15권3호
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• pp.332-339
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• 2008

This study was performed to investigate the sorption characteristics and shelf-life of coated ascorbic acid Stability of ascorbic acid, which oxidizes easily during storage and processing, was achieved by applying a fluidized bed coating using Zein-DP and HPMC-FCC as covering materials. The monolayer moisture content calculated using the GAB equation showed a higher level of significance than when calculated using the BET equation. The fit to the isotherm curve was in the order of Halsey, Caurie, Oswin and Khun. The equilibrium relative humidity prediction model was established in terms of time and water activity, it had higher significance. The stability of the coated ascoribic acid during storage was investigated in terms of radical-scavenging activity, which decreased with increasing time of storage and was more affected at higher storage temperatures. The quality reduction rate constant (k) was calculated by a first-order reaction rate. The reaction rate constant increased with increasing storage temperature. The shelf-life of Zein-DP-coated ascorbic acid was estimated to be 45.83 days at 20C and 63.19 days at 10C, and the shelf-life for HPMC-FCC-coated ascorbic acid was estimated to be 28.84 days at 20C and 36.14 days at 10, the ascorbic acid was 24.52 days at $20^{\circ}C$ and 27.22 days at $10^{\circ}C$, respectively. Therefore, the fluidized bed coating effectively increased the stability of ascorbic acid.

• Korean Chemical Engineering Research
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• 제56권1호
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• pp.96-102
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• 2018

In this study, adsorption characteristics of coconut shell-based granular activated carbon (CS-GAC) on Basic Blue 3 (BB3) were evaluated. As the dosage of CS-GAC increased, the removal efficiency of BB3 tended to increase and the initial dye concentration of 50 mg/L was completely removed at 0.2 g dosage. Adsorption equilibrium achieved within 270 and 420 min at the initial concentrations of 25 and 50 mg/L, respectively, and the experimental data were represented by the pseudo-second-order model. The maximum uptakes ($q_{max}$) predicted by the Langmuir model were 34.45, 46.63 and 53.10 mg/g at 298, 308 and 318 K, respectively. The $q_{max}$ value increased as the temperature increased. Also, the Gibbs free energy (${\Delta}G$) was changed to -7.37, -8.19 and -10.40 kJ/mol with increasing temperature. The enthalpy change (${\Delta}H$) and the entropy change (${\Delta}S$) were 34.47 kJ/mol and 0.15 J/mol K, respectively. Therefore adsorption of BB3 by CS-GAC was spontaneous and endothermic.

• Korean Journal of Environmental Agriculture
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• 제22권4호
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• pp.284-289
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• 2003

Titanium mesoporous materials have received increasing attention as a new photocatalyst in the field for photocatalytic degradation of organic compounds. The photocatalytic degradation of chlorothalonil by mesoporous titanium oxo-phoswhate (Ti-MCM) was investigated in aqueous suspension for comparison with $TiO_2$, (Degussa, P25) using as an effective photocatalyst of organic pollutants. Mesoporous form of titanium Phosphate has been prepared by reaction of sulfuric acid and titanium isopropoxide in the presence or n-hexadecyltrimethylammonium bromide. The XRD patterns of Ti-MCM are hexagonal phases with d-spacings of 4.1 nm. Its adsorption isotherm for chlorothalonil reached at reaction equilibrium within 60 min under dark condition with 28% degradation efficiency. The degradation ratio of chlorothalonil after 9 hours under the UV radiation condition (254 nm) exhibited 100% by Ti-MCM and 88% by $TiO_2$. However, these degradation kinetics in static state showed a slow tendency compared to that of stirred state because of a low contact between titanium matrices and chlorothalonil. Also, degradation efficiency of chlorothalonil was increased with decreasing initial concentration and with increasing pH of solution. As results of this study, it was clear that mesoporous titanium oxo-phosphate with high surface area and crystallinity could be used to photo- catalytic degradation of various organic pollutants.

• Korean Journal of Environmental Agriculture
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• 제7권2호
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• pp.96-101
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• 1988

It is important to assess the effects of ionic strength and type of anions when studying the adsorption of heavy metals on zeolite because the background salt may complex with heavy metals and compete for adsorption sites. This experiment was carried out to determine the effect of ionic strength and anion species($Cl^-$, $SO^{2-}\;_4$, and $ClO^-\;_4$) on heavy metal adsorption. Heavy metal adsorption by zeolite from solutions in the range of 10 to 50ppm was studied in the presence of NaCl, $Na_2SO_4$ and $NaClO_4$, with different concentrations. The ionic strength ranged from 0.01 to 1.00. Adsorption of heavy metal cations could be described by the Freundlich isotherm equation. Increasing the ionic strength of equilibrium solutions, the amounts of heavy metal adsorbed on the zeolite surfaces decreased in all three of the anion systems. This fact could be attributed to the competition of background salt cation and the decrease in initial activity of heavy metal cations. In the presence of Cl anion, less adsorption resulted than in the presence of $SO_4$ or $ClO_4$ anions of the same ionic strength, indicating the presence of uncharged and negatively charged complexes of heavy metal with Cl ligands.