• Journal of Environmental Health Sciences
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• v.45 no.6
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• pp.561-568
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• 2019

Objectives: The most commonly detected heavy metals in rocks and soils, including Pb, Cd, Cu, Fe, Mn and As, are representative pollutants discharged from abandoned mines and have been listed as potential sources of contamination in drinking water. This study focused on increasing the removal efficiency of heavy metals from drinking water resources by surface modification of natural adsorbents to reduce potential health risks. Methods: Iron oxide coating and graft polymerization with zeolites and talc was conducted for bipolar surface modification to increase the combining capacity of heavy metals for their removal from water. The removal efficiency of heavy metals was measured before and after the surface modification. Results: The removal efficiency of Pb, Cu, and Cd by surface modified zeolite showed 100, 92, and 61.5%, respectively, increases compared to 64, 64, and 38% for non-modified zeolite. This implies that bipolar surface modified natural adsorbents have a good potential use in heavy metal removal. The more interesting finding is the removal increase for As, which has both cation and anion characteristics showing 27% removal efficiency where as non-modified zeolite showed only 2% removal. Conclusions: Zeolite is one of the most widely used adsorptive materials in water treatment processes and bipolar surface modification of zeolite increases its applicability in the removal of heavy metals, especially As.

• Advances in environmental research
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• v.4 no.1
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• pp.49-68
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• 2015

Chemically activated and carbonized adsorbents were prepared from Moringa oleifera pod husks (MOP), characterized and evaluated for their ability to remove a common antibiotic - ofloxacin (OFX) from aqueous solution. The pulverized precursor was steeped in a saturated ammonium chloride solution for a day to give the chemically activated adsorbent (AMOP). A portion of AMOP was pyrolyzed in a muffle furnace at 623 K for 30 min to furnish its carbonized analogue (CMOP). The adsorbents showed favorable physicochemical attributes. The effects of operational parameters such as initial OFX solution pH and concentration, adsorbent dosage, temperature and contact time on OFX removal were investigated. At equilibrium, optimal removal efficiencies of 90.98% and 99.84% were achieved at solution pH 5 for AMOP and CMOP, respectively. The equilibrium adsorption data fitted into both the Langmuir and Freundlich isotherms. Gibbs free energy change (${\Delta}G^o$), enthalpy change (${\Delta}H^o$) and entropy change (${\Delta}S^o$) indicated that the adsorption of OFX was feasible, spontaneous, exothermic and occurred via the physisorption mode. Adsorption kinetics obeyed the Blanchard pseudo-second-order model. The results may find applications in the adsorptive removal of micro-contaminants of pharmaceutical origin from wastewater.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.1991-2003
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• 2022

The problem of water contamination by long-living cesium and strontium radionuclides is an urgent environmental issue. The development of facile and efficient technologies based on nanostructured adsorbents is a perspective for selective radionuclides removal. In this regard, current work aimed to obtain the nanostructured magnetic zeolite composites with high adsorption performance to cesium and strontium ions. The optimal conditions of hydrothermal synthesis were established based on XRD, SEM-EDX, N₂ adsorption-desorption, VSM, and batch adsorption experiment data. The role of chemical composition, textural characteristics, and surface morphology was demonstrated. The monolayer ionexchange mechanism was proposed based on adsorption isotherm modeling. The highest Langmuir adsorption capacity of 229.6 and 105.1 mg/g towards cesium and strontium ions was reached for composite obtained at 90 ℃ hydrothermal treatment. It was shown that magnetic characteristics of zeolite composites allowing to separate spent adsorbents by a magnet from aqueous solutions.

• Composites Research
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• v.35 no.6
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• pp.402-411
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• 2022

In this study, the channels-contained hybrid membranes have been fabricated through the incorporation of glass fibers and GO sheets (GO/glass fibers, GG), or a mixture of chitosan/GO (CS/GO/glass fibers, CGG), as hybrid membranes using in organic dye removal. The material properties are well investigated the terms in the morphological, chemical, crystal, and thermal characterizations for verifying interactions in their formed structure. These hybrid membranes have been fitted well in pseudo-second order and Langmuir models that are associated with chemical adsorption and a monolayer approach, respectively. The highest adsorption ability of methylene blue and methyl orange reached 59.40 mg/g and 229.07 mg/g (GG); and 287.47 mg/g and 252.91 mg/g (CGG), which is more enhanced than that of previous GO-based other adsorbents. Moreover, the dye separation on these membranes could be favorable to superb sealing and trapping dye molecules from water instead of only the dye connection occurring on their surface, regarding the physically sieving effect. The membranes can also be reused within two and three adsorbing-desorbing cycles on the GG and CGG ones, respectively. These membranes can become future adsorbents to be applied for wastewater treatment due to their structural features.

• Applied Chemistry for Engineering
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• v.33 no.4
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• pp.352-366
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• 2022

Nuclear power plant operations for electricity generation, rare-earth mining, nuclear medical research, and nuclear weapons reprocessing considerably increase radioactive waste, necessitating massive efforts to eradicate radioactive waste from aquatic environments. Cobalt (⁵⁸Co) and strontium (⁹⁰Sr) radioactive elements have been extensively employed in energy generation, nuclear weapon testing, and the manufacture of healthcare products. The erroneous discharge of these elements as pollutants into the aquatic system, radiation emissions, and long-term disposal is extremely detrimental to humans and aquatic biota. Numerous methods for treating radioactive waste-contaminated water have emerged, among which the adsorption process has been promoted for its efficacy in eliminating radioactive waste from aquatic habitats. The current review discusses the adsorptive removal of radioactive waste from aqueous solutions using low-cost adsorbents, such as graphene oxide, metal-organic frameworks, and inorganic metal oxides, as well as their composites. The chemical modification of adsorbents to increase their removal efficiency is also discussed. Finally, the current state of ⁵⁸Co and ⁹⁰Sr removal performances is summarized and the efficiencies of various adsorbents are compared.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.543-547
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• 1999

The utilization of fly-ash containing high levels of the unburned carbon was investigated. In this study adsorbents were manufactured from fly-ash ad a raw material and the manufactured adsorbents were applied to the waste-water treatment including heavy metals. Varying the anthracite(Jangsung coal) content, three types of pellet were made. The carbon content of pellet increased appreciably upon the addition of anthracite. After carbonization and activation using the pellets, adsorbents showed following characteristics; the range of hardness was between 85% and 96%, iodine number was from 100 mg/g to 300 mg/g. In proportion to the anthracite addition, hardness and iodine number increased. Through the adsorption experiments of heavy metals, removal efficiencies of Pb and Cr by manufactured adsorbents were over 90%. In case of fly-ash, removal efficiencies of Pb and Cr were 31.5% and 5.6% respectively. The reason why removal capacities of manufactured adsorbents were higher than fly-ash was postulated that adsorption capability was improved by unburned carbon and $SiO_2$ which included in fly-ash during steam activation.

• Clean Technology
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• v.19 no.4
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• pp.370-378
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• 2013

This review has shown the capability of MOFs and ZIFs materials to adsorb $CO_2$ under typical PSA temperatures and pressures. The usual operating conditions are adsorption temperatures of $15{\sim}40^{\circ}C$ and adsorption pressures of 4~6 bar based on numerous PSA processes which are widely employed in gases industry for adsorptive separation of $CO_2$. The extent of $CO_2$ adsorption on the microporous materials depends on the metal species and organic linkers existing in the frameworks. The pore size and the surface area, and the process variables are the key parameters to be associated with the efficiency of the adsorbents, particularly adsorption pressures if other variables are comparable each other. The MOFs and ZIFs materials require high pressures greater than 15 bar to yield significant $CO_2$ uptakes. They possess a $CO_2$ adsorption capacity which is very similar to or less than that of conventional benchmark adsorbents such as zeolites and activated carbons. Consequently, those materials have been much less cost-effective for adsorptive $CO_2$ separation to date because of very high production price and the absence of commercially-proven PSA processes using such new adsorbents.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.159-162
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• 2005

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.429-434
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• 2016

Here, we introduce a means of utilizing waste oyster shells which were obtained from temporary storage near coastal workplaces as $CO_2$ adsorbents. The calcined CaO can be easily dissociated to $Ca^{2+}$ cation and $CO_3{^{2-}}$ anion by hydrolysis and gas-liquid carbonation reaction and converted to precipitated calcium carbonate (PCC) in algae-containing water. The calcium hydroxide and carbonation combination in algae-containing water significantly contributed to improving water quality which is very dependent on the addition amount of calcined powders.

• YAKHAK HOEJI
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• v.36 no.6
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• pp.563-569
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• 1992

The sorption and desorption properties of four different solid adsorbents were evaluated for the trace enrichment of ibuprofen from biological samples. Chromosorb 107 gave the highest dynamic adsorption coefficient. Among the organic solvents examined, acetone gave the highest desorption coefficient. Using the Chromosorb 107 column, the optimum elution volume of the eluting solvent was evaluated from the breakthrough curve of ibuprofen. The usefulness of Chromosorb 107 as the solid adsorbent and acetone as the eluting solvent was examined for the solid-phase extraction of ibuprofen from serum in the concentration range of $20{\sim}40\;{\mu}g/ml$.