• Corrosion Science and Technology
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• v.14 no.4
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• pp.166-171
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• 2015

Knowledge of how metal releases from the stainless steels used in food processing applications and cooking utensils is essential within the framework of human health risk assessment. A new European standard test protocol for testing metal release in food contact materials made from metals and alloys has recently been published by the Council of Europe. The major difference from earlier test protocols is the use of citric acid as the worst-case food simulant. The objectives of this study were to assess the effect of citric acid at acidic, neutral, and alkaline solution pH on the extent of metal release for stainless steel grades AISI 304 and 316, commonly used as food contact materials. Both grades released lower amounts of metals than the specific release limits when they were tested according to test guidelines. The released amounts of metals were assessed by means of graphite furnace atomic absorption spectroscopy, and changes in the outermost surface composition were determined using X-ray photoelectron spectroscopy. The results demonstrate that both the pH and the complexation capacity of the solutions affected the extent of metal release from stainless steel and are discussed from a mechanistic perspective. The outermost surface oxide was significantly enriched in chromium upon exposure to citric acid, indicating rapid passivation by the acid. This study elucidates the effect of several possible mechanisms, including complex ion- and ligand-induced metal release, that govern the process of metal release from stainless steel under passive conditions in solutions that contain citric acid.

• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.81-87
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• 1995

A novel biomaterial capable of incorporating biotinylated biomolecule has been synthesized. Our strategy is to biotinylate one-dimensional electroactive polymers and use a bridging streptavidin protein on Langmuir-Blodgett (LB) organized films. These copolymers are derivatized with long alkyl chains and biotin moieties to bind, respectively, to the hydrophobic surface and the biotinylated species, through the biotin and streptavidin complexation. We utilize the polymer assembly approach to attach a signal transducing biomolecule biotinylated phycoerythrin (B-PE) into this novel biomaterial by binding the unoccupied biotin binding sites on the bound streptavidin (4 sites total). The pressure-area isotherm of the protein injected monolayer showed area expansion. A characteristic fluorescent emission peak at 576nm was detected from the monolayer transferred onto a solid substrate. These observations demonstrated the promise of the organized thin polymer assemblies for their application to the sensor system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.307-311
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• 2003

The test did for the determine the optimized ratio of cation to anion in mixed ion exchange demineralizers. Binary, ternary, quaternary, and quinary cation and anion adsorption was performed to develop a comprehensive experimental data set from small-volume batch tests to obtain the selectivity coefficients of many cations and anions. The quantitative run time might be estimated by such ion exchange models as semi-empirical mass action and surface complexation models. The demineralizer can be used longer by increasing the ratios of cation to anion exchange resins in the bed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.198-201
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• 1994

Stability improvement of fragile LB films was attempted by polyion complexation of monolayers at the air-water interface and crosslinking of the resulting LB films. The spreading polymers were synthesized by radical copolymerization of monoalkyl itaconate with oligoethyleneglycol methyl vinylether, and poly(allylamine) was employed as the subphase polymer. Formation and characteristic of the monolayers were comfirmed by surface pressure-area($\pi$-A) isotherms. The two different polymers formed polyion-complexed monolayer through the formation of carboxylate/ammonium salt at the air-water interface. Y-type deposition occurred on solid substrates, and the transfer ratio was over 0.7. Pores (diameter, 0.1$\mu\textrm{m}$) of a membrane filter could be covered by polyion-complexed 6 layers. Interactions of the polymers with metal ions were investigated of the air-water interface and in the LB films. The structure change and macroscope morphology of the LB films were confirmed by FT-lR and SEM, respective1y.

• Journal of Sensor Science and Technology
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• v.19 no.6
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• pp.421-427
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• 2010

Alizarin Red S modified screen printed carbon electrodes were developed for the electrochemical detection of aluminum ion. The electrodes developed use screen-printed carbon electrodes(SPCEs) coupled with chemical modification with an organic chelator, Alizarin Red S(ARS), for aluminum ion detection in aqueous solution. For sensor fabrication ARS was directly immobilized on the surface of SPCEs using PVA-SbQ(The poly(vinyl alcohol) bearing stryrylpyridinium groups). Aluminum concentrations were indirectly estimated by amperometric determination of the non-complexed ARS immobilized on the electrodes, after its complexation with aluminum. The sensitivity of the sensor developed was $3.8\;nA{\mu}M^{-1}cm^{-2}$ and the detection limit for aluminum was $25\;{\mu}M$.

• Bulletin of the Korean Chemical Society
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• v.16 no.12
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• pp.1167-1172
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• 1995

A coverage of about 1 μm-sized pores of a membrane filter by four monolayers of maleic acids copolymers and poly(allylamine) (PAA) was attained by Langmuir-Blodgett (LB) technique through a covalent cross-linking followed a polyion complexation at the air-water interface. The copolymers were prepared to have side chains of hydrocarbon tail, carboxyl, and/or oligoether in the repeat unit. The surface pressure-area isotherms showed that the monolayers on an aqueous PAA have more expanded area than on pure water. The monolayers were transferable on a calcium fluoride substrate and a fluorocarbon membrane filter as Y deposition type, and the resulting LB films were characterized by FT-IR spectroscopy and scanning electron microscopy. A polymer network produced through interchain amide formation was confirmed in as-deposited films. The films were heat-treated in order to complete the cross-linking. SEM observation of the heat-treated film on a porous membrane filter showed that the four layer film was sufficiently stable to cover the filter pore of about 1 μm. Immersion of the film in water or in chloroform did not cause any change in its appearance on SEM and in FT-IR spectra.

• Journal of the Mineralogical Society of Korea
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• v.24 no.2
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• pp.73-82
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• 2011

X-ray absorption spectroscopy (XAS) study was conducted using arsenite-sorbed two-line ferrihydrite to investigate the mechanism of surface interactions between two-line ferrihydrite and As(III) (arsenite) which are ubiquitous in nature. The two-line ferrihydrite used was synthesized in the laboratory and the study was undertaken at pHs 4 and 10 to compare the difference in mechanisms of surface interaction between acidic and alkaline environments. The effect of arsenite-adsorbed concentrations on surface complexation was investigated at each pH condition as well. From the results of XAS analyses, the structural parameters of arsenite in the EXAFS revealed that the coordination number and distanceof As-O were 3.1~3.3 and 1.74~1.79 ${\AA}$, respectively, which indicate that the unit structure of arsenite complex formed on the surface of two-line ferrihydrite is $AsO_3$. The dominant structures of As(III)-Fe complex were examined to be bidentate binuclear comer-sharing ($^2C$) and the mixture of bidentate mononuclear edge sharing ($^2E$) and $^2C$ appeared as well. At pH 4, arsenite complex showed different structures on the surface of two-line ferrihydrite, depending on the adsorbed concentrations. At pH 10, on the contrary, the surface structures of arsenite complexes were interpreted to be almost identical, irrespective of the adsorbed concentrations of arsenite. Consequently, this microscopic XAS results support the results of macroscopic adsorption experiments in which the surface interaction between arsenite and two-line ferrihydrite is significantly influenced by pH conditions as well as arsenite concentrations.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.51-59
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• 2010

The sediments and soils around a mine are likely to be exposed to contamination of arsenic (As) through mining operations. In this study, the factors associated with As movement in soils around a closed zinc (Zn) mine were evaluated by the relationship of As distributions to physico-chemical properties of soils. A sequential extraction scheme, based on a soil P fractionation, was used to assess the As distributionsin solid phases. A significant difference in As distributions was found between paddy and upland soils. While As contents of paddy soils increased with soil depth, those of upland soils decreased with soil depth. In upland soils, As showed additional significant relationships to oxides of Si, Al and Fe. Although a major fraction of As in soils was found to be in the NaOH extractable fraction, As exhibited highly significant relationship to the Zn species that apparently originated from the mine. Therefore, As mobility around Zn mine seems to be governed by mass flow of the particulates containing As-associated Zn in paddy soils, whereas retention reactions such as adsorption, complexation, and precipitation seem to predominate in upland soils.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.421-429
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• 2018

Hydrazine based reductive dissolution applied on magnetite oxide was investigated. Dissolution of Fe(II) and Fe(III) from magnetite takes place either by protonation, surface complexation, or reduction. Solution containing hydrazine and sulfuric acid provides hydrogen to break bonds between Fe and oxygen by protonation and electrons for the reduction of insoluble Fe(III) to soluble Fe(II) in acidic solution of pH 3. In terms of dissolution rate, numerous transition metal ions were examined and Cu(II) ion was found to be the most effective to speed up the dissolution. During the cycle of Cu(I) ions to Cu(II) ions, the released electron promoted the reduction of Fe(III) and Cu(II) ions returned to Cu(I) ion due to the oxidation of hydrazine. In the experimental results, the addition of a very low amount of cupric ion (about 0.5 mM) to the solution increased the dissolution rate about 40% on average and up to 70% for certain specific conditions. It is confirmed that even though the coordination structure of copper ions with hydrazine is not clear, the $Cu(II)/H^+/N_2H_4$ system is acceptable regarding the dissolution performance as a decontamination reagent.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.352-359
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• 2024

Environmental pollution from heavy metal ions (HMIs) is a global concern. Recently, biosorption methods using cellulose sorbents have gained popularity. The objective of this study was to assess the removal efficiency of Cu(II), Pb(II), and Hg(II) ions at low concentration levels (100-700 ppb) from aqueous solutions using three different cellulose fiber-based filter media. Sample A was pure cellulose fiber, Sample B was 10% activated carbon-cellulose fiber, and Sample C was cellulose fiber-glass fiber-30% activated carbon-20% amorphous titanium silicate (ATS). The samples were characterized by several physicochemical techniques. The porosity measurements using N₂ sorption isotherms revealed that Samples A and B are nonporous or macroporous materials, whereas the addition of 50% filler materials into the cellulose resulted in a microporous material. The Brunauer-Emmett-Teller (BET) surface area and pore volume of Sample C were found to be 320.34 m²/g and 0.162 cm³/g, respectively. The single ion batch adsorption experiments reveal that at 700 ppb initial metal ion concentration, Sample A had removal efficiencies of 7.5, 11.5, and 13.7% for Cu(II), Pb(II), and Hg(II) ions, respectively. Sample B effectively eliminated 99.6% of Cu(II) ions compared to Pb(II) (14.2%) and Hg(II) (31.9%) ions. Cu(II) (99.37%) and Pb(II) (96.3%) ions are more efficiently removed by Sample C than Hg(II) (68.2%) ions. The X-ray photoelectron spectroscopy (XPS) wild survey spectrum revealed the presence of Cu(II), Pb(II), and Hg(II) ions in HMI-adsorbed filter media. The high-resolution C1s spectra of Samples A and B reveal the presence of -C-OH and -COOH groups on their surface, which are essential for HMIs adsorption via complexation reactions. Additionally, the ATS in Sample C facilitates the adsorption of Pb(II) and Hg(II) ions through ion exchange.