• 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.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.430-434
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• 1998

Preparative HPLC (High-Performance Liquid Chromatography) is mainly used for separating useful component from biological samples. By reversed-phase HPLC packed with preparative packings ($15{\mu}m$), the adsorption characteristics with sample size were investigated. Sample was 5'-GMP, a flavor enhancer, and the composition of mobile phase was 20mM $KH_2PO_4$ solution:methanol (97:3 vol.%). From the experimental results, the effect of sample size on retention factor was negligible, but the peak was asymmetrical above $1{\mu}g$ of sample. In addition, the increase in sample size deteriorated the number of theoretical plates, and at small concentration, the number of theoretical plates was less because of large peak width. In the experimental condition, the adsorption isotherm of 5'-GMP was relatively well represented by Freundlich equation.

• Analytical Science and Technology
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• v.12 no.2
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• pp.105-110
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• 1999

The studies on the adsorption properties and the antibacterial effects of the Cd and Cu-treated activated carbon were carried out. From the adsorption studies on the series of these metal-treated activated carbons, typical Type-I isotherm was observed. The surface areas of the treated carbon obtained from BET equation were in the range of $1101-1418m^2/g$ for Cd-AC and of $1084-1361m^2/g$ for Cu-AC. Using ${\alpha}_s$-plot, the micropore volumes and pore size distribution were obtained. From the SEM study, it is also observed that many of micropores in activated carbon are blocked by window blocking effect of metals after the impregnation. Finally, antibacterial effects of M-activated carbon against Escherichia coli was discussed. From the study, the area of antibacterial activity becomes larger with the increase of the amount of metal treated.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.384-388
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• 2006

The adsorption ability of polar and toxic substance was greatly enhanced by treating activated carbon with acid solution and impregnating iron, copper, or silver by using in 0.1 M $FeSO_4{\cdot}7H_2O,\;CuSO_4{\cdot}5H_2O,\;AgNO_3$ 300 mL per activated carbon 50 g. Physical and chemical properties of the metal impregnated activated carbons were measured using specific surface area, pore volume and size distribution, scanning eletron microscope(SEM), adsorption isotherm. When activated carbon was treated with acid, the quantity of impregnated metal increased about 1.3 times since the micropores were converted to mesopores or macropores. Both the physical absorption by micropores and chemical absorption by metal ions could be achieved simultaneously with the metal impregnated activated carbon because the capacity of micro pores did not change even after metal ions were impregnated.

• Environmental Engineering Research
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• v.14 no.3
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• pp.164-169
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• 2009

A powder form of aluminum (hydr)oxides is not suitable in wastewater treatment/filtration systems because of low hydraulic conductivity and large sludge production. In this study, aluminum (hydr)oxide-coated sand (AOCS) was used to remove phosphate from aqueous solution. The properties of AOCS were analyzed using a scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectrometer (EDS) and an X-ray diffractometer (XRD). Kinetic batch, equilibrium batch, and closed-loop column experiments were performed to examine the adsorption of phosphate to AOCS. The XRD pattern indicated that the powder form of aluminum (hydr)oxides coated on AOCS was similar to a low crystalline boehmite. Kinetic batch experiments demonstrated that P adsorption to AOCS reached equilibrium after 24 h of reaction time. The kinetic sorption data were described well by the pseudo second-order kinetic sorption model, which determined the amount of P adsorbed at equilibrium ($q_e$ = 0.118 mg/g) and the pseudo second-order velocity constant (k = 0.0036 g/mg/h) at initial P concentration of 25 mg/L. The equilibrium batch data were fitted well to the Freundlich isotherm model, which quantified the distribution coefficient ($K_F$ = 0.083 L/g), and the Freundlich constant (1/n = 0.339). The closed-loop column experiments showed that the phosphate removal percent decreased from 89.1 to 41.9% with increasing initial pH from 4.82 to 9.53. The adsorption capacity determined from the closed-loop experiment was 0.239 mg/g at initial pH 7.0, which is about two times greater than that ($q_e$ = 0.118 mg/g) from the kinetic batch experiment at the same condition.

• Environmental Engineering Research
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• v.21 no.2
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• pp.152-163
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• 2016

Present study investigates the potential of cassava peel and rubber tree bark for the removal of Cr (VI) from aqueous solution. Removal efficiency of more than 99% was obtained during the kinetic adsorption experiments with dosage of 3.5 g/L for cassava peel and 8 g/L for rubber tree bark. By comparing popular isotherm models and kinetic models for evaluating the kinetics of mass transfer, it was observed that Redlich-Peterson model and Langmuir model fitted well ($R^2$ > 0.99) resulting in maximum adsorption capacity as 79.37 mg/g and 43.86 mg/g for cassava peel and rubber tree bark respectively. Validation of pseudo-second order model and Elovich model indicated the possibility of chemisorption being the rate limiting step. The multi-linearity in the diffusion model was further addressed using multi-sites models (two-site series interface (TSSI) and two-site parallel interface (TSPI) models). Considering the influence of interface properties on the kinetic nature of sorption, TSSI model resulted in low mass transfer rate (5% for cassava peel and 10% for rubber tree bark) compared to TSPI model. The study highlights the employability of two-site sorption model for simultaneous representation of different stages of kinetic sorption for finding the rate-limiting process, compared to the separate equilibrium and kinetic modeling attempts.

• Journal of environmental and Sanitary engineering
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• v.14 no.2
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• pp.46-55
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• 1999

This study compared the adsorption characteristics of heavy metal ions by crab shell, treated crab shell with 2N-HCl, treated crab shell with 4%-NaOH, chitin and chitosan.Using crushed crab shell, the heavy metal ions removal rates of $Cd^{2+}$ and $Zn^{2+}$ were about 70-80% in 45minutes, but the removal rates of $Cu^{2+}$, $Cr^{6+}$ and $Pb^{2+}$ was less than 10%, 10% and 30%, respectively. For the by-products crab shell by 2N-HCl treatment, it was shown that the removal rates of $Cu^{2+}$ and $Pb^{2+}$ were about 70-80% in 45minutes reaction. But, some problems were observed, that the contained protein in crab shell was changed into gel in the mixing solution after a few hours. For the by-products of crab shell by 4%-NaOH treatment, the removal rates of Pb and Zn were about 90% in 45 minutes, and those of capacity of chitin and chitosan powder was better than those of the other by-products. The more adding to the adsorbent dosages increased the removal rates, and the adsorption reaction was rapidly occurred in a few minute. Using 1.0 wt% chitin powder, the heavy metal removal rates were ordered $Cu^{2+}$(94%) > $Zn^{2+}$(89%) > $Cd^{2+}$(88%) > $Pb^{2+}$(77%) > $Cr^{6+}$(58%) in 45 minutes. Using 1.0 wt% chitosan powder, the heavy metal removal rates were ordered $Cu^{2+}$(99%) > $Pb^{2+}$(96%) > $Cd^{2+}$(79%) > $Zn^{2+}$(71%) > $Cr${6+}$(46%) in 45minutes. The degree of degree of deacetylation by prepared chitosan was 91%.The Freundlich adsorption isotherm of $Cu^{2+}$, $Cd^{2+}$ and $Zn^{2+}$, when it was applied to 1.0 wt% chitosan powder in minutes, can be acceptable very strictly. The equation constant (1/n) for $Cu^{2+}$, $Cd^{2+}$ and $Zn^{2+}$ were 0.54 0.41 and 0.23 respectively.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.1-10
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• 1996

Gibbs' adsorption isotherms are studied to assay the structural effects of ethylene oxide (EO) and propylene oxide (PO) moieties on the molecular area and the interfacial tension behavior of molecules at the interface. Several industrial alcohols and isomerically pure alcohols, which have a general stucture of C4H9O(EO)m(PO)nH, are examined for their cosurfactant properties. They are high molecular weight alcohols and more surface active than the cosurfactants usually used. Results show that the number and the sequence of EO and PO units significantly affect the molecular areas and the interfacial tension (IFT) behavior of these molecules at the water/oil interface. The following conclusions are drawn from the result: 1) PO is more efficient in lowering the IFT and less effective in adsorption than EO. 2) For molecules having the same molecular weight but different structures, smaller molecules are more efficient in lowering the IFT. 3) When more EO, PO, or both units are added to the same hydrophobe, the molecule become bigger and more efficient in lowering the IFT.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1097-1103
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• 2007

We report a novel method to synthesize nanocomposites composed of titania nanoparticles and phosphotungstate ions with various composition ratios ranging from W/Ti = 12/10 to 12/500 by inducing the electrostatic interaction between the positively charged protonated titania sol-particles and the negatively charged phosphotungstate anions to flocculate and precipitate. The precipitates showed varied features depending on the composition. The precipitate from the tungsten-richest W/Ti = 12/10 reaction is amorphous in its powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy data. This material shows the Type II adsorption characteristics in its N2-adsorption isotherm, but with quite low surface area of 34 m2/g. To the contrary, the precipitates from the titanium-richer reactions (W/Ti = 12/50- 12/500) are composed of anatase nanoparticles of 2-6 nm by XRD, TEM and Raman and show the Type I adsorption characteristics. The surface area linearly increases with the titanium content from 131 m2/g for W/ Ti = 12/50 to 228 m2/g for 12/500. The precipitate from the reaction with the intermediate composition W/Ti = 12/20 is composed of anatase nanoparticles and does not have any pore accessible to N2. With the wide variety of the physical properties of the precipitates, the present method can be a novel, viable means to tailor synthesis of nanocomposite materials. A formation mechanism of the precipitates is based on the electrostatic interactions between the titania nanoparticles and phosphotungstate ions.

• Clean Technology
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• v.20 no.3
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• pp.277-282
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• 2014

In this study, PU-LMO was made by immobilization of LMO on urethane foam (PU) with using an EVA as a binder. PU-LMO was characterized by using X-Ray Diffractometer (XRD) and Scanning Electron Microscopy (SEM). The optimal ratio of EVA/LMO for preparation of PU-LMO was 0.26 gEVA/gLMO. The adsorption of lithium ions by PU-LMO was found to follow the pseudo-second-order kinetic model. The equilibrium data fitted well with Langmuir isotherm model and the maximum removal capacity of lithium ions was 17.09 mg/g. The PU-LMO was found to have a remarkably high selectivity of lithium ions and high adsorption capacity because the distribution coefficient ($K_d$) of lithium ion was higher than those of other metal ions.