• Korean Journal of Materials Research
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• v.30 no.9
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• pp.447-452
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• 2020

In this work, α-Fe₂O₃ nanocrystals are synthesized by co-precipitation method and used as adsorbent to remove Cr⁶⁺, Cd²⁺, and Pb²⁺ from wastewater at room temperature. The prepared sample is evaluated by XRD, BET surface area, and FESEM for structural and morphological characteristics. XRD patterns confirm the formation of a pure hematite structure of average particle size of ~ 40 nm, which is further supported by the FESEM images of the nanocrystals. The nanocrystals are found to have BET specific surface area of ~ 39.18 m² g^-1. Adsorption experiments are carried out for the different values of pH of the solutions, contact time, and initial concentration of metal ions. High efficiency Cr⁶⁺, Cd²⁺, and Pb²⁺ removal occur at pH 3, 7, and 5.5, respectively. Equilibrium study reveals that the heavy metal ion adsorption of the α-Fe₂O₃ nanocrystals followed Langmuir and Freundlich isotherm models. The Cr⁶⁺, Cd²⁺, and Pb²⁺ adsorption equilibrium data are best fitted to the Langmuir model. The maximum adsorption capacities of α-Fe₂O₃ nanocrystals related to Cr⁶⁺, Cd²⁺, and Pb²⁺ are found to be 15.15, 11.63, and 20 mg g^-1, respectively. These results clearly suggest that the synthesized α-Fe₂O₃ nanocrystals can be considered as potential nano-adsorbents for future environmental and health related applications.

• KSBB Journal
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• v.15 no.4
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• pp.375-379
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• 2000

Alginate derivatives possessing various lengths of alkyl amine (C8, C12, C16) chain were prepared by oxidation followed by reductive amination of alginate and the products were characterized by spectral analysis. The surface tension critical micelle concentration (c. m. c) and solubility of a hydrophobic compound azobenzene were examined. Series of synthesized alginate-derived polymeric surfactants(APSs) reduced the surface tension. The dissolving capacity of APSs toward azobenzene was about half that of SDS. In order to investigate the capacity of metal adsorption Co and Pb were selected as a representative metal. The overall removal efficiency of APSs were high compared with that of alginate at pH 3.5 and 7 respectively. Major mechanism of the heavy metal removal is the complex of metal with carboxyl group.

• Journal of the Korean GEO-environmental Society
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• v.15 no.12
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• pp.25-34
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• 2014

The objective of this study was to investigate the removal characteristics and the elimination mechanism of heavy metals in Acid Mine Drainage (AMD) using spherical-type porous Zeolite-StarFish ceramics (porous ZSF ceramics) packed in a continuous column reactor system. The average removal efficiencies of heavy metals in AMD were Al 98.7, As 98.7, Cd 96.0, Cu 89.1, Fe 99.5, Mn 94.4, Pb 96.3 and Zn 80.8 % during 110 days of operation time. The average removal capacity of porous ZSF ceramics for heavy metals were measured to be Al 21.76, As 1.52, Cd 1.27, Cu 3.41, Fe 44.83, Mn 3.48, Pb 2.36 and Zn $3.76mg/kg{\cdot}day$. The analysis results of mechanism using SEM, EDS and XRD exhibited that the porous ZSF ceramics could act as a multi-functional ceramics for the removal of heavy metals in AMD through the reactions of precipitation, adsorption and ion-exchange. The experimental results of column reactor system displayed that the porous ZSF ceramics would be a consistently efficient agent for the removal of heavy metals in AMD for a long term.

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.229-234
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• 2004

All the applications of natural zeolites make use of one or more of their physical and chemical properties: adsorption, ion-exchange and related molecular sieve properties, dehydration and rehydration, and siliceous composition. Accordingly, the applications of zeolite have been carried out in the various aspects because of its large cation exchange capacity and adsorption properties. In this paper, the adsorption effect of heavy metal ions in wastewater on zeolite mineral by batch adsorption process is studied. The amounts of adsorbed ions were variable by original pH and ionic concentration, especially original pH of solution had an important effect on the adsorption. In case of low pH solution, e.g. below 3.0, clinoptilolite adsorbed $Pb^{2+}$ ,$ Cd ^{2+ }$ , $Cu^{2+}$ and $Zn^{ 2+}$ , but mordenite almost did not adsorb except $Pb^{2+}$ . Under the same conditions, these ions were more adsorbed on clinoptilolite than on mordenite mineral. The velocity of adsorption was relatively fast and it was confirmed by shaking test that the equilibrium of adsorption could be attained in about one hour. The species of exchangeable cation of zeolite had an effect on its removing ability and zeolite of the sodium-exchanged type was the best.

• Journal of Environmental Science International
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• v.7 no.6
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• pp.803-809
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• 1998

Heavy metal ions in water were removed using algal biomass as adsorbents. Absorbents were dried for 3 days, ground them by 40~60 mesh and then were swelled in a buffer solution for 1hr. After being packed in the column, commercially available standard solution of Cd(II) and Pb(II) ions were diluted to get the suitable concentration and then it was eluted with the rate of 1mι/min. Heavy metals on the adsorbents were recovered with nitric acid. More amounts of Cd(II) or Pb(II) ions in green algae, Ulva pertusa, than in brown algae, Sargassum horneri, were adsorbed. Pb(II) ion was adsorbed more than Cd(II) ion in both algae. The pH effect of adsorbed amounts of Cd(II), Pb(II) ions on the biomass was shown the following order ; pH 10.5 ＞ 8.5 ＞ 7.0 ＞ 5.5 ＞ 3.5. Recovery ratio of metal ions front algae is shown higher in acidic or neutral conditions than it in alkalic ones. Pb(II) ion is recovered relatively more than Cd(II) ion in our system.

• Environmental Engineering Research
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• v.17 no.3
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• pp.125-132
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• 2012

The removal of Cd(II) and Cu(II) from aqueous solution by an agricultural solid waste biomass prepared from Moringa oleifera bark (MOB) was investigated. The biosorbent was characterized by Fourier transform infrared spectroscopy and elemental analysis. Furthermore, the effect of initial pH, contact time, biosorbent dosage, initial metal ion concentration and temperature on the biosorption of Cd(II) and Cu(II) were studied using the batch sorption technique. Kinetic studies indicated that the biosorption process of the metal ions followed the pseudo-second order model. The biosorption data was analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. Based on the Langmuir isotherm, the maximum biosorption capacities for Cd(II) and Cu(II) onto MOB were 39.41 and 36.59 mg/g at 323 K, respectively. The thermodynamic parameters, Gibbs free energy (${\Delta}G^o$), enthalpy (${\Delta}H^o$), and entropy (${\Delta}S^o$) changes, were also calculated, and the values indicated that the biosorption process was endothermic, spontaneous and feasible in the temperature range of 303-323 K. It was concluded that MOB powder can be used as an effective, low cost, and environmentally friendly biosorbent for the removal of Cd(II) and Cu(II) ions from aqueous solution.

• Geotechnical Engineering
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• v.13 no.6
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• pp.123-138
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• 1997

Electroosmotic tests were performed on saturated marine clay specimens contaminated with lead to investigate the efficiency of the electrokinetic technique for removal of heavy metals from the cohesive soils. For this purpose, testing program included variable conditions such as the concentration of lead (500, 5, 000, 50, 000mg/kg), the level of electrical current (10, 50, 100 mA), operating duration (5, 15, 30days), and the application of three dirtferent chemicals for enhancement in efficiency. The pH of inflow and outflow, electroosmotic flow and electrical conductivity during the test, and the pH and the concentration of lead across the specimen after the test are presented. Test results came to the conclusion that the electrokinetic technique was very effective to remove heavy metals such as lead from the contaminated cohesive soil. Adding ecetic acid at the cathod to dissolve the procipitates of lead hydroxide as found to be effective for the enhancement of the efficiency in remediation.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.536-545
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• 2019

An experiment was conducted to evaluate the adsorptive removal of Pb(II) from an aqueous solution using a mixture of spent coffee grounds and chitosan on beads (CC-beads). Various parameters affecting the adsorption process of Pb(II) using CC-beads were investigated. Based on the experimental data, the adsorption kinetics and adsorption isotherms were analyzed for their adsorption rate, maximum adsorption capacity, adsorption energy and adsorption strength. Moreover, the entropy, enthalpy and free energy were also calculated by thermodynamic analysis. According to the FT-IR analysis, a CC-bead has a very suitable structure for easy heavy metal adsorption. The process of adsorbing Pb(II) using CC-beads was suitable for pseudo-second order kinetic and Langmuir model, with a maximum adsorption capacity of 163.51 (mg/g). The adsorption of Pb(II) using CC-beads was closer to chemical adsorption than physical adsorption. In addition, the adsorption of Pb(II) on CC-beads was exothermic and spontaneous in nature. CC-beads are economical because they are inexpensive and also the waste can be recycled, which is very significant in terms of the continuous circulation of resources. Thus, CC-beads can compete with other adsorbents.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.2
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• pp.81-88
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• 2007

A study on the removal of heavy metals using sawdust was performed. Among heavy metals such as lead, copper and cadmium ions, uptake capacity of lead ions was the highest as about 0.22 mmol/g-dry mass at pH 4. The surface condition and existence of lead ions onto the sawdust was confirmed by the FT-IR, SEM (Scanning Electron Microscopy), and EDX (Energy Dispersive X-ray) instrumental analyses. When 0.5g of sawdust was added to initial lead solution (100ppm) removal efficiency was approximately 90%. Isothermal adsorption curve for lead ions was described by the Langmuir model equation and experimental data well fitted to model equation. Most adsorption for lead ions was also completed within 60min and pH of lead solution from 5.8 to 4.5 decreased with time.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2198-2206
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• 2018

We addressed the development of a novel, low-cost, and high-efficient material from hybrid materials, known as microcapsules. Microcapsules are a composite adsorbent made of a mixture of tannin, sericite and chitosan. The FT-IR analysis showed that the microcapsules contain hydroxyl, carboxyl, carbonyl, and amino groups, which play an important role in the adsorption of heavy metals. The microcapsules were able to remove 99% of Pb(II) in 30 min, and obtained a removal efficiency of more than (13-50)%, compared with the single adsorbents of tannin, chitosan, and sericite. In adsorption kinetic analysis, pseudo-second-order adsorption was more suitable than pseudo-first-order adsorption, and chemical adsorption did not limit the adsorption rate of Pb(II) ion. In isothermal adsorption, Langmuir adsorption was more suitable than Freundlich adsorption, and the maximum Langmuir adsorption capacity was 167.82 (mg/g). Furthermore, desorption and reusability studies, as well as the applicability of the material for wastewater treatment, demonstrated that microcapsules offer a promising hybrid material for the efficient removal of significant water pollutants, i.e., Pb(II) from aqueous solutions.