Elution Of Metal Ions Research Articles

Effect of Crown Ether Additives on the Enhanced Performance of Metallic Bipolar Plates for Proton Exchange Membrane Fuel Cells.

One of the key components of the fuel cell stack is a metallic bipolar plate (MBP) that plays multiple roles, such as current collector, fuel and oxidant distributor, and mechanical support. However, corrosion and consequent metal elution are major drawbacks of the MBP because they diminish the efficiency and power performance of membrane-electrode assemblies (MEAs). Herein, we show that the crown ether (CE) additive can simultaneously inhibit surface corrosion of the MBP and act as a scavenger for eluted metal ions to alleviate contamination of other components. From the electrochemical measurement, high-resolution imaging, and elemental analysis, we have found that the CE undergoes electrolytic decomposition and makes an efficient protective layer in an in situ manner. This layer prevents direct contact between the MBP and electrolyte as well as the dissolution of metal ions into the electrolyte. In addition, we demonstrate that the CE can improve the recovery protocol of the MEA owing to the formation of host-guest complexes between the CE and metal cations. These results provide key insights into the design of high-performance MBPs for proton-exchange membrane fuel cells.

Fretting tribocorrosion properties of anodized TiNbSn implant alloy

Titanium and its alloys have poor wear resistance, and the biological response to generated wear debris leads to aseptic loosing and pathological bone resorption. In the fretting wear of artificial hip joints, a significant part of the wear surface is contacted by elastic deformation, and electrochemical anodization is a promising method to control the mechanical properties of the surface and improve wear resistance. To suppress wear debris generation and metal ions elution from implant materials into body fluids, the tribocorrosion properties of a newly developed anodized TiNbSn implant alloy were evaluated in the presence of simulated body fluid and compared to those of pure Ti. During anodization under high voltage, spark discharge occurred due to dielectric breakdown occurred for the TiNbSn electrode, but not for the Ti electrode. The primary phase of the anodic oxide layer on TiNbSn alloy was rutile TiO2, whereas that on Ti was anatase TiO2. The anodic oxide layer on TiNbSn had a higher thickness, roughness, and surface area than that on anodized Ti. In addition, the hardness and exfoliation strength were higher than those of Ti. The coefficient of friction of anodized TiNbSn in fretting tests was similar or slightly lower than that of anodized Ti, and the open circuit potential remained unchanged for anodized TiNbSn but shifted to a more negative voltage for anodized Ti. The results suggest that the hard and strongly-adhered rutile TiO2 on TiNbSn formed by spark discharge during the high-voltage anodization process improves fretting wear resistance and reduces the generation of wear debris and elution of metal ions.

Viscosity increase/gelation of therapeutic IgG monoclonal antibodies induced by Zn2+: One possible root cause of clogging of staked-in-needle prefilled syringes

We investigated the elution of zinc ions (Zn2+) from the elastomer of rigid needle shields (RNS) attached to staked-in-needle prefilled syringes (SIN-PFS) and the physicochemical impacts of Zn2+ on therapeutic IgG monoclonal antibody (mAb) solutions. The elution of metal ions from typical RNS elastomer under realistic buffer and storage conditions was investigated by inductively coupled plasma-mass spectrometry. Among the metal ions examined, only Zn2+ was detected. The elution of Zn2+ from RNS elastomer was found to be buffer-dependent. We investigated the influence of Zn2+ on the viscosity of seven mAb solutions at 180 mg/mL. The effect of Zn2+ clearly depended on antibody type. Drastic increases in viscosity or gelation were observed in four out of the seven mAbs. Dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) showed the effect of Zn2+ on mAb viscosity was explained by the colloidal destabilization of mAb solutions. Thus, Zn2+ leaching from RNS elastomer may possibly increase viscosity or cause gelation, and consequently cause possible needle clogging during long-term storage. DLS and SAXS can predict reactivity of mAbs to Zn2+, and require only small amounts of samples. This makes it possible to predict compatibility with RNS elastomer and evaluate needle clogging risk in SIN-PFSs in the early stages of mAb development.

Fluorinated Agents Effects on Orthodontic Alloys: A Descriptive In Vitro Study.

Fluoride-based mouthwashes and gels are preventive measures in countering demineralization and caries but, modifying environmental acidity, can reduce the wet corrosion resistance of orthodontic alloys. To evaluate chemical stability, in vitro experiments were conducted on stainless steel and nickel–titanium wires, weighed before and after immersion in household fluorinated mouthwashes and gels, measuring weight variations and elution of metal ions from acid corrosion phenomena. Elution samples were analyzed by inductively coupled plasma mass spectrometry, detecting residual ion concentration, while surface changes were analyzed under scanning electron microscopy. Results showed stainless steel wires do not undergo significant erosion when exposed to most fluorinated mouthwashes but, at prolonged exposure, alloys elute gradually greater amounts of metals and Ni–Ti wires become more sensitive to some mouthwashes. Ions’ elution varies considerably, especially for Ni–Ti wires, if exposed to household fluorinated gels, for which significant negative values were obtained. Changes, affecting wires’ outer layer, negatively act on shiny appearance and luster, reducing corrosion resistance. Although examined orthodontic wires showed good chemical stability and low toxicity, surface corrosion from exposure to fluorinated agents was observed. Home use must be accompanied by clinician prescription and, for household dental gels, must follow manufacturers’ recommendations, ensuring prophylactic action without damaging alloys surfaces.

Recovery of rare earth elements from NdFeB magnet by mono- and bifunctional mesoporous silica: Waste recycling strategies and perspectives

Rare earth elements (REEs) such as Nd3+ and Dy3+ were recovered from simulated and real leaching solution of the NdFeB magnet via solid phase extraction (SPE). Extraction of REEs from simulated solutions was investigated using silica functionalized with NH2-, EDTA and/or phosphonic groups. The effects of several experimental factors (pH, efficiency of adsorbents, selectivity, and elution of metal ions) on extraction of REEs were investigated. Exploiting specific affinities of adsorbents toward REEs in the presence of competing ions, selective separation of REEs was achieved successfully. The affinity of phosphorous/nitrogen containing adsorbents had the descending order of adsorption: Fe3+ > Dy3+ > Nd3+ > Ni2+ > Al3+ for multi-component systems. In the first approach, a procedure based on precipitation of Fe3+ ions combined with SPE was evaluated for the recovery of REEs in two steps. Most of the Fe3+ ions (85%) were efficiently separated by adding an ammonia solution (pH ~ 2.5). Chemical analysis of precipitate showed, though, a high content of REEs. Extraction of REEs from supernatant liquid via bi-functional mesoporous silica with EDTA and/or phosphonic groups recovered ~97.0% of Nd3+ with Ni2+ and Al3+ ions as impurities. Non-ordered silica functionalized with phosphonic groups, showed economical superiority over other mesoporous adsorbents studied for REEs extraction. Complete recovery (97.8%) of REEs was achieved after several stages of SPE with adsorbents functionalized by P/N-containing groups. The in-advance removal of Fe3+ ions was a prerequisite for successful implementation of this approach. Finally, separation of Nd3+ and Dy3+ was performed from nitric acid media using the gradient elution to obtain 98.4% purity Nd3+. The proposed step-by-step SPE procedure by P/N-containing functionalized silica was successfully applied for extraction of REEs (95.5%) in an industrial magnet. This study opens up possibilities for application of the developed approach for the End-of-Life materials recycling.

Titanium Nitride Plating Reduces Nickel Ion Release from Orthodontic Wire

The leaching of metal ions from orthodontic appliances is a problem for their use in patients with metal allergies. Despite the development of a number of non-metal orthodontic appliances, including brackets, non-metal wires are not yet available. Therefore, it is necessary to modify the surfaces of orthodontic wires to prevent the leaching of metal ions into the oral environment for use in such patients. This study was performed to examine whether plating of orthodontic wire with titanium nitride (TiN), which does not impair its mechanical properties, could prevent the leaching of metal ions from the wire on immersion in acid. To investigate the acid corrosion resistance of the wire, the amount of metal ions eluted from the wire immersed in acid was measured by using inductively coupled plasma mass spectrometry (ICP-MS) and the dimethylglyoxime (DMG) test, the properties of the wire surface were examined by stereomicroscopy and scanning electron microscopy, and the surface roughness was measured using a surface roughness tester. The results indicated that TiN plating of orthodontic wire significantly suppressed the elution of metal ions on immersion in acid.

Copper Recovery and Reduction of Environmental Loading from Mine Tailings by High-Pressure Leaching and SX-EW Process

The flotation tailings obtained from Bor Copper Mine contain pyrite (FeS2) and chalcopyrite (CuFeS2), these sulfide minerals are known to promote acid mine drainage (AMD) which poses a serious threat to the environment and human health. This study focuses on the treatment of mine tailings to convert the AMD supporting minerals to more stable forms, while simultaneously valorizing the mine tailings. A combination of hydrometallurgical processes of high-pressure oxidative leaching (HPOL), solvent extraction (SX), and electrowinning (EW) were utilized to recover copper from mine tailings which contain about 0.3% Cu content. The HPOL process yielded a high copper leaching rate of 94.4% when water was used as a leaching medium. The copper leaching kinetics were promoted by the generation of sulfuric acid due to pyrite oxidation. It was also confirmed that a low iron concentration (1.4 g/L) and a high copper concentration (44.8 g/L) obtained in the stripped solution resulted in an improved copper electrodeposition current efficiency during copper electrowinning. Moreover, pyrite, which is primarily in the mine tailings, was converted into hematite after HPOL. A stability evaluation of the solid residue confirmed almost no elution of metal ions, confirming the reduced environmental loading of mine tailings through re-processing.

Anticorrosion of DLC coating in acid solutions

Diamond-like carbon (DLC) coatings are known to have good properties for industrial use such as low friction, wear resistance, and chemical stability. In recent years, the corrosion of metallic materials has been a problem, causing significant financial losses. Therefore, we studied the improvement in the corrosion resistance of metallic materials using a DLC coating. In this study, a DLC coating was deposited on the entire surface of SUS304 stainless steel (SUS) using ionized evaporation method. The corrosion resistance against hydrochloric acid, nitric acid, and sulfuric acid solutions was evaluated using an immersion test method of JIS T 0304. The metal ions eluted from the solutions after the immersion test were measured, and the DLC coating reduced the amount of metal ion elution by more than 90% for each acid solution. It was also found that the corrosion resistance was improved through the multi-coating of the DLC films. The film stability of the DLC coating of the specimens was examined using Raman spectroscopy and FE-SEM after immersion in each acid solution. These results confirmed the film stability of a DLC coating in an acidic solution. These results also suggest that a DLC coating effectively improves the corrosion resistance of metallic materials to acid solutions and that the multiple DLC coatings improves the corrosion resistance.

Self-Assembled Monolayer Formation on a Dental Orthodontic Stainless Steel Wire Surface to Suppress Metal Ion Elution

Metal ion elution, including Cr and Ni from dental orthodontic stainless steel, accounts for some allergies. In this study, a self-assembled monolayer (SAM) on a wire surface is proposed for suppressing such elution. This method involves modifying the stainless steel surface using phosphonic acid containing a long alkyl chain. The uncoated and coated wires are immersed in different acidic solutions, and the supernatant is analyzed by inductively coupled plasma mass spectrometry after 1–4 weeks. The results reveal that Cr and Ni ion elution is significantly suppressed by SAM modification. These findings will help in minimizing potential allergens from dental orthodontics.

Effects of eluted metal ions on the properties of ceramic slurry and slip-casted green bodies

ABSTRACT The characteristics of ceramics produced by wet forming are determined by the particle dispersion in the utilized slurry, obtained by mixing ceramic powder and a solvent. Evaluation and control of the particle dispersion is thus important. In the case of ceramic powder containing a sintering aid, metal ions may be eluted from the particles during preparation of the aqueous slurry. It remains unclear, however, how the metal ions affect the particle dispersion and the green body characteristics. Hence, in the present study, Mg2+ or Al3+ ions were added to common water-based alumina slurries, and their effects on the slurry and green body characteristics were investigated. It was found that the presence of about 10 mM of metal ions caused agglomeration of the slurry particles and decreased the green body packing fraction. The effects were particularly significant for small amounts of the added dispersant. When the dispersant dosage exceeded a certain level, the added metal ions produced no observable change in the slurry or green body characteristics. In addition, higher-valence metal ions were found to decrease the maximum green body packing fraction and increase the dispersant dosage required to reach the maximum packing fraction.

Dynamically modified C18 silica monolithic column for the rapid determinations of lead, cadmium and mercury ions by reversed-phase high-performance liquid chromatography

In this article, a new reversed-phase high-performance liquid chromatography (RP-HPLC) method for the rapid, selective and sequential separation of toxic heavy metal ions namely, Pb2+, Hg2+, and Cd2+ is reported. For this RP-HPLC method, a C18 silica monolith column (Chromolith RP-18e, 100 × 4.6 mm) has been surface modified using a laboratory-synthesized amphiphilic organic ligand namely, 1,5-dioctanoyl-1,5-diphenylcarbazide (DODPC), which acts an ion-selective receptor, for the separation of the target analytes. The eluted metal ions were subjected to post-column derivatization reaction with 4-(2-pyridylazo) resorcinol (PAR) prior to their detection using a UV–vis detector (at 520 nm). The post-column reagent (PAR; 4.7 × 10−4 M; pH 9.0; 1.5 mL/min) was mixed with the column eluate through an ingeniously designed T-connector. An ultra-fast separation of Pb2+, Cd2+, and Hg2+ ions with a retention time of 1.67, 1.88 and 3.62 min, respectively was achieved, using 0.0526 mmol of DODPC coated C18 monolithic column along with tartaric acid solution (1.0 × 10−2 M; pH 4.0; 1.0 mL/min), as the isocratic eluent (mobile phase). The chromatographic parameters such as linearity, accuracy, recovery, limits of detection and quantification were validated to achieve superior analytical results. The influence of various analytical parameters such as nature of mobile phase and its concentration, solution pH, flow rate, post-column reagent and its concentration were studied and optimized. The studies revealed a lower detection limits of 0.075, 0.090 and 0.120 μg/L, and a quantification limits of 0.225, 0.270 and 0.450 μg/L, for Pb2+, Cd2+ and Hg2+ ions, respectively. A linear signal response in the concentration range of 0.05–50.0 μg/mL, was observed for the target metal ions, with an average r2 value of 0.9994. The method was selective for the target metal ions, with excellent data reliability and reproducibility that accounts for an average recovery value of 99.76%, with a relative standard deviation of ≤1.83%.

Chemical modification to suppress metal ions elution of dental orthodontic wire surface

ABSTRACTIn this study, we investigated on suppression of metal ions elution on dental orthodontic wire. To suppress metal ion elution from stainless wire, two types of surface chemical modifications were carried out. The obtained wire were immersed into several aqueous solution then the eluted ions (Cr and Ni, which are well known to cause a metal allergy) were determined using coupled plasma mass spectrometry (ICP-MS). By both electropolymerization and self-assembly monolayer formation, the ion elution was effectively reduced. These results suggested that these surface modifications succeeded to suppress the metal ions.

Cytocompatibility of magnesium and AZ31 alloy with three types of cell lines using a direct in vitro method.

Magnesium alloys have been investigated by many researchers as a new absorbable biomaterial owing to their excellent degradability with non-maleficence or low-maleficence in living tissues. In the present work, the in vitro cytocompatibility of an Magnesium alloy was investigated by culturing cells directly on it. Investigations were carried out in terms of the cell viability along with the use of scanning electron microscopy to observe its morphology. The cell lines used were derived from fibroblast, endothelial, and smooth muscle cells. Pure magnesium and AZ31 alloy composed of magnesium (96 %), aluminum (3 %), and zinc (1 %) were adopted as models. The viability of cells on the metal samples and on the margin area of a multi-well plate was investigated. For direct culturing on metal, a depression in the viability and morphologically stressed cells were observed. In addition, the cell viability was also depressed for the margin area. To clarify the factors causing the negative effects, the amount of eluted metal ions and pH changes in the medium because of the erosion of the Magnesium samples were investigated, together with the cytotoxicity of sole metal ions corresponding to the composition of the metals. It was found that Mg(2+), Zn(2+), and Al(3+) ions were less toxic at the investigated concentrations, and that these factors will not produce negative effects on cells. Consequently, these factors cannot fully explain the results.

Characterization of eluted metal ions by sequential extraction from Krepoljin coal basin, Serbia: Mechanisms of metal interaction

ABSTRACTEight samples of powdered brown coal (Krepoljin coal basin, Miocene age) were successively extracted by two extractants at room temperature: bidistilled water, Me1, and 2 M MgCl2 solution, Me2. Large amounts of Ni and Zn are leached from the coal deposit by water. On the contrary, no significant amounts of Pb and Cu are washed under normal conditions. Also, the mobility of Zn and Ni especially depends, to a high extent, on ionic strength. It can be assumed that the humic acids co-extracted during water leaching, Me1, and being a highly competitive ligand for metal ions, will act as a disturbing agent in metal speciation procedure in coals. This assumption is supported by the obtained significant correlation between the Me1:Me2 ratio and the humic acid complex stability constants.

Electrochemical Behavior of Type 304 Stainless Steel in Ionic Liquid Containing Small Amount of Water

The influences of the water content on the electrochemical properties of Type 304 stainless steel were studied through cyclic voltammetry and chronoamperometry in the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI). The electrochemical behavior of stainless steel was explained by the reactivity of water in the ionic liquid with the main constituent elements of the stainless steel, such as Fe, Cr, and Ni. A protective passive film formed on the surface of stainless steel in EMI-TFSI with the water content controlled in the range of 5.5 ppm to 5000 ppm. For a water content less than 5.5 ppm, however, the stainless steel was not passivated and, therefore, was corroded by the dissolution. The amount of eluted metal ions from Type 304 stainless steel were much less than Fe and Ni. Furthermore, the dissolution process did not change in a wide temperature range from room temperature to 120°C.

Bioremoval of heavy metals by bacterial biomass

Heavy metals are among the most common pollutants found in the environment. Health problems due to the heavy metal pollution become a major concern throughout the world, and therefore, various treatment technologies such as reverse osmosis, ion exchange, solvent extraction, chemical precipitation, and adsorption are adopted to reduce or eliminate their concentration in the environment. Biosorption is a cost-effective and environmental friendly technique, and it can be used for detoxification of heavy metals in industrial effluents as an alternative treatment technology. Biosorption characteristics of various bacterial species are reviewed here with respect to the results reported so far. The role of physical, chemical, and biological modification of bacterial cells for heavy metal removal is presented. The paper evaluates the different kinetic, equilibrium, and thermodynamic models used in bacterial sorption of heavy metals. Biomass characterization and sorption mechanisms as well as elution of metal ions and regeneration of biomass are also discussed.

Study on the blood compatibility and biodegradation properties of magnesium alloys.

Lately, several magnesium alloys have been investigated as a new class of biomaterials owing to their excellent biodegradability in living tissues. In this study, we considered AZ series of Mg alloy containing aluminum (3% to 9%) and zinc (1%) as a model magnesium alloy, and investigated their biodegradation in whole blood and blood compatibility in vitro. The results of the elution property of metal ions determined using chromogenic assay and the associated pH change show that the degradation resistance of the AZ series alloys in blood is improved by alloying aluminum. Furthermore, the blood compatibility of the alloys was investigated in terms of their hemolysis, factor Xa-like activity, using spectrophotometry and chromogenic assay, respectively, and coagulation time measurements (prothrombin time and activated partial thromboplastin time). The results indicated that the blood compatibility of the AZ series alloys is excellent, irrespective of the alloy composition. The excellent blood compatibility with the coagulation system could be attributed to the eluted Mg(2+) ion, which suppresses the activation of certain coagulation factors in the intrinsic and/or extrinsic coagulation pathways. In terms of the degradation resistance of the AZ series alloys in blood, the results of pH change in blood and the amount of the eluted metal ions indicate that the performance is markedly improved with an increase in aluminum content.

Highly durable Pt/graphene oxide and Pt/C hybrid catalyst for polymer electrolyte membrane fuel cell

We report a highly durable hybrid catalyst composed of Pt/graphene oxide (GO) and Pt/C catalyst for polymer electrolyte membrane fuel cell (PEMFC). The accelerated durability tests in half-cell and full cell systems shows that the addition of small amount of Pt/GO catalyst significantly enhances the durability of commercial Pt/C catalyst without sacrificing initial electrochemical active surface area (ECSA). The XRD and TEM analysis reveal that the GO not only exhibits the high resistance to Pt agglomeration but also prevents the Pt agglomeration in Pt/C catalyst by providing the anchoring sites of eluted metal ions. We believe that this simple and effective approach can open a new way to fabricate highly durable electrocatalyst for the commercialization of fuel cell vehicles.

A solid phase extraction procedure based on electrospun cellulose-g-oxolane-2,5-dione nanofibers for trace determination of Cd, Cu, Fe, Pb and Zn in gasoline samples by ICP-OES

Cellulose-g-oxolane-2,5-dione nanofibers were prepared as an adsorbent for simultaneous separation and preconcentration of trace amounts of Cd, Cu, Fe, Pb and Zn ions in gasoline samples prior to ICP-OES detection. The nanofibers were chemically and morphologically characterized by FTIR, solid-state 13C NMR, BET and SEM techniques. The influences of experimental parameters such as pH, HNO3 concentration on metal ion elution from the nanofibers, flow rate and sample volume were investigated. The metal ions were retained on 0.5 g of the adsorbent at pH 6 and recovered with 5.0 mL of 2.0 mol L−1 HNO3. The adsorption capacities for the adsorbent were 273.1, 183.6, 195.5, 236.2 and 182.4 mg g−1 for Cd, Cu, Fe, Pb and Zn, respectively. The relative standard deviation was <3% (n = 15), limits of detection and quantification were 0.13–0.68 μg L−1 and 0.42–2.2 μg L−1, respectively, and the maximum preconcentration factor was 60. It was observed that cellulose-g-oxolane-2,5-dione nanofibers can be used for more than 30 adsorption–elution cycles without decreasing the extraction efficiency. The accuracy of the method was confirmed by analyzing a certified reference material and by performing the spike recovery test. The accuracy and recovery for different metal ions were in the range of 97–102% and 96–99%, respectively. The optimized method was applied for the separation and preconcentration of metal ions in gasoline samples.

Elution behaviour and environmental impact of heavy metals and rare-earth elements from volcanic ashes of Mt. Oyama, Miyake Island

To obtain information on the environmental impact of materials eluted from volcanic ashes of Mt. Oyama, Miyake Island, which erupted in July 2000, the dissolution behaviours of heavy metals and rare-earth elements from the volcanic ashes were examined. The most important characteristic of the Mt. Oyama eruption is that sulphur dioxide (SO2) gas has been continuously released, and all persons living on Miyake Island have been required to evacuate. To estimate in terms of the volcanic eruption using SO2 gas, the ash nature in Mt. Usu, Hokkaido, was also examined and compared with that in Mt. Oyama. When rain water mixed the ashes, the water from the ashes of Mt. Oyama became acidic because of the sulphuric acid. Therefore, SO2 gas in Mt. Oyama can accelerate the dissolution of protons and heavy metals in the ashes, whereas the rain water in Mt. Usu was not acidic and the dissolution of the heavy metals was not so evident compared with that in the case of Mt. Oyama. With this sulphuric acid, heavy metals such as As, Cd, Pb and Hg in the ashes in Mt. Oyama easily dissolved owing to the low pH. The ashes in Mt. Oyama had been released for eight years and the amount of fallen ashes was estimated to be 33 billion tons. The weights of the harmful heavy metals in the volcanic ashes, such as As, Cd, Pb and Hg, were estimated to be 3.8 × 102, 1.3 × 103, 1.1 × 103 and 29 kg, respectively, and these heavy metals were dissolved and diluted in seawater. Therefore, the concentration and species (chemical form) of these metals should be carefully monitored in the future. Moreover, SO2 gas, which has a direct effect on human health and has been monitored continuously, causes other effects, such as facilitation of metal ion elution and rock aeration.