• Environmental Engineering Research
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• v.16 no.2
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• pp.55-60
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• 2011

The removal of hexavalent chromium from aqueous solutions onto modified holly sawdust was studied at varying initial hexavalent chromium concentrations, adsorbent doses, pHs and contact times. The removal of hexavalent chromium from aqueous solutions increased with increasing adsorbent dosage and contact time. The percentage of hexavalent chromium removed from the aqueous solutions decreased with increasing hexavalent chromium concentration and pH of the solution. The kinetics of the adsorption of hexavalent chromium onto modified holly sawdust was analyzed using pseudo first-order and pseudo second-order models. The pseudo second-order model described the kinetics of adsorption of hexavalent chromium. The Langmuir and Freundlich isotherm models were used for modeling of the adsorption equilibrium data. The Langmuir isotherm model well described the equilibrium data for the removal of hexavalent chromium by modified holly sawdust. The obtained maximum adsorption capacity was 18.86 mg/g at pH 7. The results showed that modified holly sawdust can be used as a low cost adsorbent for the treatment of aqueous solutions containing chromium.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.565-573
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• 2021

Isotherms, kinetics and thermodynamic properties for adsorption of Brilliant Green(BG), Quinoline Yellow(QY) dyes by activated carbon were carried out using variables such as dose of adsorbent, pH, initial concentration, contact time, temperature and competitive. BG showed the highest adsorption rate of 92.4% at pH 11, and QY was adsorbed at 90.9% at pH 3. BG was in good agreement with the Freundlich isothermal model, and QY was well matched with Langmuir model. The separation coefficients of isotherm model indicated that these dyes could be effectively treated by activated carbon. Estimated adsorption energy by Temkin isotherm model indicated that the adsorption of BG and QY by activated carbon is a physical adsorption. The kinetic experimental results showed that the pseudo second order model had a better fit than the pseudo first order model with a smaller in the equilibrium adsorption amount. It was confirmed that surface diffusion was a rate controlling step by the intraparticle diffusion model. The activation energy and enthalpy change of the adsorption process indicated that the adsorption process was a relatively easy endothermic reaction. The entropy change indicated that the disorder of the adsorption system increased as the adsorption of BG and QY dyes to activated carbon proceeded. Gibbs free energy was found that the adsorption reaction became more spontaneous with increasing temperature. As a result of competitive adsorption of the mixed solution, it was found that QY was disturbed by BG and the adsorption reduced.

• Journal of Environmental Health Sciences
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• v.24 no.1
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• pp.98-103
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• 1998

A study on the removal of mercury and lead by microorganisms, Saccharomyces cerevisiae and Aureobasidium pullulans, was performed, in which the comparison of adsorption model between these two heavy metals was done. The amounts of mercury removed were more than those of lead in both microorganisms. In case of mercury, the adsorption isotherm of S. cerevisiae was accorded with Langmuir model but A. pullulans was followed to Freundlich model. In the case of lead, however, the adsorption isotherm had opposite results. The adsorption rate of mercury to S. cerevisiae was faster than that of A. pullulans, but in the case of lead, it revealed contrary results. It seems, therefore, that the type of microorganisms used as biosorbents should be selected differently with the type of heavy metals removed for applying these to real adsorption process.

• Carbon letters
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• v.9 no.2
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• pp.97-104
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• 2008

In the present study Sisal fiber obtained from the leaves of Agave sisalana has been chosen to validate its viability as an adsorbent for the removal of Nickel from aqueous solutions. The material was also surface modified and its effect on adsorption of Nickel was also studied. Agave sisalana fiber was found to be a cheap and effective adsorbent doing away with the need to activate the material therby reducing processing cost. The equilibrium studies indicated that the adsorption capacity of raw fiber and the surface modified fiber was 8.66 and 9.77 mg/g respectively with the Langmuir isotherm describing the adsorption phenomena better than the Freundlich and Temkin isotherm. The adsorption was found to be exothermic from the thermodynamic studies and the kinetics showed that the adsorption phenomena were second order.

• Journal of Environmental Science International
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• v.11 no.4
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• pp.333-338
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• 2002

In this work, the characterization of adsorption of Cu, Zn and Cd on granular activated carbon in water has been studied. The factors that affect adsorption in boundary between activated carbon and wastewater are concentration, temperature, contact time, pH and so on. As the result of this study, the maximum adsorption amount of Cu occurred near pH 7, while that of Zn and Cd was near pH 9.6 and 10, respectively. As contact time and temperature are transformed, such factors as optimum contact time and temperature are taken into consideration in an adsorptive process of heavy metal because an adsorption and a reducing process occur. In isotherm of Freundlich, 1/n values of Cu, Cd capacity were between 0.16 and 0.5.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.160-167
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• 2006

S-Acetyl Isothiourea Acetate (S-AITA) was synthesized in the laboratory and this influence on the inhibition of corrosion of mild steel in 1.11 N hydrochloric and 1.12 N sulphuric acids was investigated by weight loss and potentiostatic polarization techniques at 303K, 353K and 403K. These results were confirmed by the impedance technique. The inhibition efficiency increased with increase in concentration of inhibitor and decreased with rise in temperature from 303K to 403K. The maximum inhibition efficiency of S-AITA was found to be 99.95% (0.5% of S-AITA) at 303K in sulphuric acid. The adsorption of this compound on the mild steel surface from the acids has been found to obey Temkin's adsorption isotherm. The potentiostatic polarization results revealed that S-AITA was a mixed type inhibitor. Some thermodynamic parameters i.e., activation energy (Ea), free energy of adsorption (${\Delta}G_{ads}$), enthalpy of adsorption (${\Delta}H$) and entropy of adsorption (${\Delta}S$) were also calculated from weight loss data.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.1
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• pp.8-18
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• 2005

Adsorption capacity for the charcoal were tasted in this study to verify the performance of them for the use of the sampling media in industrial hygiene field. Two set of experiments were conducted. The first experiment was to test performance of the tested charcoal tube that were assembled in the laboratory with the use of the GR grade charcoal. The other tests were investigate the adsorption capacity of the charcoal tested in this study and charcoals embedded in the commercial charcoal tubes. Known air concentration samples for benzene, toluene, and o-xylene were prepared by the dynamic chamber. 1. At low air concentration levels (0.1${\times}$TLV), there was no significant differences between the tested charcoal tubes and the SKC charcoal tubes. This implies that there is no defect with the adsorption capacity of the charcoal. 2. At high concentration with 60 minutes sampling, the breakthrough were found only in the tested charcoal while no breakthrough were shown in the SKC charcoal. 3. From the breakthrough tests for the charcoal, the micropore volume(Wo) were calculated by the curve fitting with the use of Dubinin/Radushkevich(D/R) adsorption isotherm equation. The calculated values were 0.687cc/g for SKC, 0.504cc/g for Sensidyne, and 0.419cc/g for the tested charcoal(Aldrich). 4. Adsorption capacities were obtained from the isotherm curves shown adsorption capacities at several levels of the challenge concentration. All range of the air concentration concerned in industrial hygiene, the SKC charcoal showed approximately two times of adsorption capacity compared to the tested charcoal.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2471-2476
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• 2014

The aim of the present study is to explore the possibility of utilizing loess for the adsorption of total phosphorous (T-P) and total nitrogen (T-N) in water. Batch adsorption studies were performed to evaluate the influences of various factors like initial concentration, contact time and temperature on the adsorption of T-P and T-N. The adsorption data showed that loess is not effective for the adsorption of T-N. However, loess exhibited much higher adsorption capacity for T-P. At concentration of $1.0mgL^{-1}$, approximately 97% of T-P adsorption was achieved by loess. The equilibrium data were fitted well to the Langmuir isotherm model. The pseudo-second-order kinetic model appeared to be the better-fitting model because it has higher $R^2$ compared with the pseudo-first-order and intra-particle kinetic model. The theoretical adsorption equilibrium $q_{e,cal}$ from pseudo-second-order kinetic model was relatively similar to the experimental adsorption equilibrium $q_{e,exp}$. The thermodynamic parameters such as free energy ${\Delta}G$, the enthalpy ${\Delta}H$ and the entropy ${\Delta}S$ were also calculated.

• Journal of Environmental Science International
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• v.32 no.8
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• pp.563-572
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• 2023

Scoria from Jeju-island (Jeju scoria) was converted into zeolitic material (Z-SA) via zeolitification using the fusion/hydrothermal method. Jeju scoria could be synthesized into Z-SA to from a surface covered with Na-A zeolite crystals, which was confirmed through an analysis of X-ray diffraction peak patterns and scanning electron microscopy images. Jeju scoria and Z-SA were employed as adsorbents to evaluate the adsorption rate and adsorption capacities for Cu²⁺ and Zn²⁺ ions. The adsorption rates and isothermal adsorption capacities could be well fitted by the pseudo-quadratic adsorption kinetics and Langmuir adsorption isotherm, respectively. The maximum adsorption capacities (q_m) of Z-SA for Cu²⁺ and Zn²⁺ ions were found to be 163.36 mg/g and 120.51 mg/g, respectively, using the Langmuir adsorption isotherm. When Z-SA is synthesized from Jeju scoria via zeolitification using the fusion/hydrothermal method, Z-SA exhibits an adsorption capacity that is more than approximately 100 times the value exhibited by Jeju scoria. As a result, the synthesized Z-SA was regarded as an effective, economic adsorbent.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.886-895
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• 1996

To fit the desorption isotherm and adsorption isotherm for Pangola grass, the modified Henderson model, Chung-Pfost model, modified Halsey model, and modified Oswin model were used to fit the experimental EMC /ERH data. A step-by -step ERH measuring technique was used in this study. The ERH data were collected at three temperature levels of 5 $^{\circ}C$, $25^{\circ}C$ and 5$0^{\circ}C$ for Pangola grass whole plant, stem , and foliage. The modified Halsey model has the best fit for both desorption isotherm and adsorption isotherm of Pangola grass whole plant as compared with other models.