Chemical State Of Zn Research Articles

Enhanced flotation of smithsonite from calcite based on the synergistic action of carboxylated chitosan and sodium carbonate

As carbonate minerals, smithsonite and calcite have similar surface properties, and unavoidable ions will further narrow the difference in their floatability. Therefore, flotation separation of smithsonite from calcite has been a difficult problem in industrial production. In this study, carboxychitosan and sodium carbonate were combined to improve the efficiency of separating smithsonite from calcite with the use of sodium lauroylsarcosinate as a collector. The results of flotation tests showed that the recovery difference between smithsonite and calcite was higher than 83 % under optimum flotation conditions. In addition, the interaction mechanism between reagents and minerals was analyzed by Fourier Transform Infrared Spectroscopy (FTIR) analysis, zeta potential measurements and X-ray Photoelectron Spectroscopy (XPS) detection. The mechanistic analysis showed that for Zn(II) activation, sodium lauroylsarcosinate was able to adsorb onto the calcite surface by chemisorption, even in the presence of carboxylated chitosan. Upon addition of Na2CO3, the chemical state of Zn(II) adsorbed on the calcite surface changed and reacted with CO32– to form ZnCO3 precipitate. As a result, the inhibition of calcite flotation by carboxylated chitosan was reactivated and the separation of smithsonite from calcite was achieved.

Improvement of acid resistance of Zn-doped dentin by newly generated chemical bonds

Dental caries, the world’s most prevalent infectious disease, is caused by the diffusion of hydroxyl ions into tooth structures. To prevent dental caries, the application of fluoride (F) and zinc (Zn) ions to teeth surfaces are potential effective measures. In this study, The ionic influence, especially the chemical bond of F and Zn, on the acid resistance of dentin were investigated by particle induced X-ray / gamma-ray emission, X-ray diffraction, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The results showed Zn was distributed in the limited surface layer of dentin without altering its crystal structure. From the Zn K edge extended X-ray absorption fine structure, Zn incorporated into dentin was surrounded by oxygen and demonstrated four-fold coordination. The bond length and chemical state of Zn–O in Zn doped dentin suggested newly generated Zn–O covalent bond, which may improve acid resistance of dentin. This study showed that the atomic and molecular structures, such as the molecular distances and chemical state, influenced acid resistance of teeth, emphasizing the validity of chemical state analysis for understanding properties in biomaterials.

Effect of heat treatment process on microstructure and corrosion resistance of Al–10%Si–24%Zn coating

Al–10%Si coating has been widely used in the surface treatment of hot-press-forming steel such as 22MnB5 steel, and it exhibits excellent high-temperature oxidation resistance but poor corrosion resistance; thus, Zn was added to Al–10%Si coating to improve its corrosion resistance. The microstructural evolution and elemental distribution of AS24Z (Al–10%Si–24%Zn) coating before and after undergoing two-step heat treatment (pre-alloying and then austenitizing) were investigated. The results show that the coating was composed of Fe2Al5 and FeAl after holding at 900 °C for 5 min, while it was composed of FeAl and Fe3Al after holding at 1000 °C for 5 min. The location and the chemical state of Zn in the coating after heat treatment were determined. After holding at 900 °C for 5 min, the Zn in the Fe2Al5 phase was expected to accumulate at the Fe2Al5 grain boundaries due to the Zn content (approximately 10 at.%) in the AS24Z coating, which was lower than the solubility limit (approximately 30 at.%) of Zn in Fe2Al5. However, the Zn in the Fe2Al5 phase dissolved to form the Fe2Al5Znx phase in the form of substituted atoms with a Zn content in the range of 3–4 at.%. The content of Zn in the entire coating was very low after holding at 1000 °C for 5 min due to the volatilization of Zn. The effect of Zn on the susceptibility of liquid metal embrittlement was studied. It was difficult for the liquid Zn to penetrate the thick Fe2Al5 layer in the AS24Z coating with relatively high Al content; thus, the Fe2Al5 layer prevented the liquid metal embrittlement of 22MnB5 steel. The corrosion resistances of the Al–10%Si and AS24Z coatings were compared using a polarization curve. Compared with the Al–10%Si coating, the AS24Z coating exhibited a lower self-corrosion potential, which indicates that after austenitization at 900 °C or 1000 °C, the AS24Z coating can still provide excellent cathodic protection for the steel substrate.

Hydrothermal synthesis of C doped ZnO nanoparticles coupled with BiVO4 and their photocatalytic performance under the visible light irradiation

For the first time, C-ZnO/BiVO4 heterostructured nanocomposite has been synthesized from BiVO4 and carbon-doped ZnO nanoparticles. X-ray diffraction (XRD) study showed themonoclinic scheelite structure of BiVO4 and the hexagonal wurtzite structure of ZnO in the C-ZnO/BiVO4 composite. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) images revealed the spherical nanoparticles of size 20 to 30 nm for C-ZnO. The band gap of the ZnO has turned towards the visible region by doping with carbon as well as a composite formation with visible light active material BiVO4. The chemical states of Zn, O, C and Zn, O, C, Bi, V species in C-ZnO, and C-ZnO/BiVO4 composite respectively were confirmed by X-ray photoelectron microscopy (XPS) analysis. Also, the XPS spectra showed the significant peaks shift in the electronic states of Zn, O, and C for the heterojunction composite. The suppression of the electron-hole recombination rate was confirmed from the quenching of photoluminescence (PL) intensity for the composite. The adsorption study has performed, and the experimental results fit well with the Langmuir isotherm model for understanding the catalytic activity of the samples. The possible Z-scheme photocatalytic mechanism of the C-ZnO/BiVO4 nanocomposite photocatalyst has proposed. The nanocomposite exhibited the enhanced catalytic activity with the higher degradation rate constant of 0.050 min−1 for 50 min irradiation of visible light compared with their counterparts.

Cathodoluminescence degradation study of the green luminescence of ZnO nanorods

Bright green luminescence at 500 nm was obtained from chemical bath deposited ZnO nanorods after annealing in a reducing atmosphere (H2/Ar) at 700 °C for 30 min. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and secondary electron microscopy (SEM) were used to study the effect of electron beam irradiation on the cathodoluminescence (CL) and the surface state of the sample. The CL intensity was monitored concurrently with the Auger peak-to-peak heights (APPHs) using the same electron beam for both techniques. CL intensity degradation was studied in vacuum and in an oxygen ambient. According to the AES spectra, all the principal elements (zinc and oxygen) were detected as well as carbon, which was removed at the initial stage of electron beam irradiation. No chemical change was observed during electron beam irradiation. In vacuum, the CL intensity decreased to almost half of its initial intensity after 100 C/cm2 electron dose and then stabilized. In the oxygen atmosphere, the CL intensity also decreased initially up to a dose of ~10 C/cm2 and thereafter recovered to about 90% of its original intensity and stabilized after a dose of ~100 C/cm2. No difference in the chemical state of Zn was observed with XPS for the original sample and the degraded ones. Only a small change in the defect contribution part of the O peak was observed. SEM images for the original and degraded samples showed that the electron beam irradiation induced surface changes in the morphology of the ZnO nanorods. Generally, the CL intensity was very stable under electron beam irradiation, suggesting that the material may be suitable for application in optoelectronics devices.

Study on Zn relative concentration and chemical state in broilers duodenum by micro-X-ray fluorescence and micro-X-ray absorption fine structure

Micro-X-ray fluorescence (μ-XRF) and micro-X-ray absorption fine structure (μ-XAFS) are not widely used in animal science. The objective of this experiment was to employ μ-XRF and μ-XAFS technique to determine the change of Zn quantity, distribution and chemical state (Zn2+ chemical state, organic zinc chemical state) into intestinal wall using different zinc sources. 45 newly hatched healthy (1-d-old) commercial male broilers were used in this experiment. The chicks were fed a corn–soybean meal basal diet (90.50mg/kg) from day 1 to 21, but were fed a semipurified diet (12.51mg/kg) after day 21 to deplete the body Zn stores. At 28d of age, after an overnight fast, 45 birds were randomly allotted to 3 perfusion groups (ZnMet, ZnLys, ZnSO4) with 15 replicates/group for in situ ligated intestinal loops of broilers in experiment. Duodenum of each bird was used as 1 replication of intestinal segments. The solutions injected into the duodenal loops were buffered with 15.5mmol/L of morpholineoethanesulfonic acid. In the treatment groups of different Zn sources, 0.616mmol/L (40mg/L) was added to the media. The 3.5mL of Zn dose was injected and incubated 30min in the abdomen cavity. The μ-XRF and μ-XAFS were used to analyze the relative quantity, distribution and chemical state of Zn in the intestinal wall, and atomic absorption spectrometry (AAS) was used to verify Zn concentration in the whole intestinal sac. The results showed that ZnMet and ZnLys group samples have a greater amount of zinc in the intestinal wall specific region than ZnSO4 group. The Zn chemical state of organic Zn and ZnSO4 group were identical in intestinal wall specific region. In addition, the Zn concentration achieved using ZnMet was greater than that for ZnLys and ZnSO4 (P<0.05) as measured by AAS. As observed in this experiment, organic zinc was more easily absorbed than inorganic Zn.

Composite calcium phosphate coatings with sustained Zn release

Zinc-substituted tricalcium phosphate/fluoridated hydroxyapatite (ZnTCP/FHA) biphasic composite coatings and Zinc containing fluoridated hydroxyapatite (ZnFHA) coating were prepared on Ti6Al4V substrates through a modified sol–gel method. The release of zinc ions from these coatings was characterized through a designed cycled immersion test: the coatings were soaked in the TRIS solution with pH of 7.25 at 37 °C for 96 h (one cycle). This process was repeated twice with the solution refreshed at the end of the each cycle. The Zn concentrations were measured at a 24-hour interval during the first cycle and at the end of each cycle. The results indicated that ZnTCP/FHA coatings released Zn at a rather slow and sustained rate while ZnFHA coatings released Zn at a rapid and therefore unsustained rate. This Zn release behavior difference is attributed to the different chemical states of Zn in the coatings. The current results demonstrated that the designed biphasic composite approach could potentially be a good way to tailor the release of Zn through combinations of different Zn chemical states, with the durability of the coatings not impaired.

New Features in Electroless Deposition of Ternary Coatings on the Base of Ni-P and Co-P

Abstract The new features in the electroless (autocatalytic) deposition, structure and properties of Ni-Cu-P, Ni-Sn-P, Ni-Zn-P, Ni-W-P, Co-W-P, and Co-Re-P as well as the quaternary coatings Ni-Sn-Cu-P, Ni-W-Re-P, and Co-Re-Ni-P established in the Institute of Physical Chemistry of the Bulgarian Academy of Sciences (IPC BAS) are reviewed. The role of disproportionation reactions of Cu(I), Sn(II) and Re(VI) during electroless deposition of Ni-Cu-P, Ni-Sn-P and Co-Re-P is considered. The data about the localization and chemical state of Zn, W and Re are presented. The influence of Cu and Sn added to high P (&gt; 10 wt. %) Ni-P coatings on the thermal stability of their amorphous state is illustrated. A comparison of the corrosion resistance of Ni-Cu-P and Ni-Sn-P with that of Ni-P with the same quantity of phosphorus is given. The application of Ni-Cu-P in a hybrid multilayer with TiN is demonstrated.

A study of Zinc Contained in Yellow and Black Discolored Nails by X-ray Fluorescence and X-ray Absorption Fine Structure Analyses

Synopsis The elements in discolored nails were assessed by X-ray fluorescence analysis (XRF), and the chemical state of Zn in the nail samples was assessed by X-ray absorption fine structure (XAFS) analysis. Compared to the normal nail, a part of the yellow nail contained a considerably high amount of Ca, whereas the black nail contained higher amounts of Ca and Zn. The chemical state of Zn in the yellow nail was similar to that in the normal nail. The Zn in the black nail was in a slightly different chemical state, suggesting the existence of different chemical species of Zn in the black nail.

Comparison of sediment pollution in the rivers of the Hungarian Upper Tisza Region using non-destructive analytical techniques

The rivers in the Hungarian Upper Tisza Region are frequently polluted mainly due to mining activities in the catchment area. At the beginning of 2000, two major mining accidents occurred in the Romanian part of the catchment area due to the failure of a tailings dam releasing huge amounts of cyanide and heavy metals to the rivers. Surface sediment as well as water samples were collected at six sites in the years 2000–2003, from the northeast-Hungarian section of the Tisza, Szamos and Túr rivers. The sediment pollution of the rivers was compared based on measurements of bulk material and selected single particles, in order to relate the observed compositions and chemical states of metals to the possible sources and weathering of pollution. Non-destructive X-ray analytical methods were applied in order to obtain different kinds of information from the same samples or particles. In order to identify the pollution sources, their magnitude and fate, complementary analyses were carried out. Heterogeneous particulate samples were analyzed from a large geographical territory and a 4-year time period. Individual particles were analyzed only from the “hot” samples that showed elevated concentrations of heavy metals. Particles that were classified as anthropogenic were finally analyzed to identify trace concentrations and chemical states of heavy metals. Although the Tisza river was affected by water pollution due to the two major mining accidents at the beginning of 2000, the concentration of heavy metals in sediments decreased to the mineral background level 1 year after the pollution event. In the tributaries Szamos and Túr, however, no significant decrease of the heavy metal concentrations was observed in the recent years, indicating a continuous pollution. Among the water suspended particles collected from river Túr, fibers of unknown origin were observed by electron microscopy; these particles were aluminosilicates enriched in Zn and Mn. Cd was also concentrated in this particle type. Zn in the sulfide form was observed by microbeam X-ray absorption near-edge structure analysis only in the samples collected from river Tisza in 2000, while this metal was connected to carbonates and silicates in the other samples. The dissolved Zn content of the river water and the chemical state of Zn in the fibers collected from river Túr indicate that the heavy metal pollution arrived to the Hungarian section originally mostly in the dissolved phase. The accidental heavy metal pollution of River Tisza, however, was in the form of microscopic metal sulfide particles.

A Study of Zn-Co Alloy Electrodeposits by Auger Spectroscopy and XPS

SUMMARYAES and XPS techniques have been used to analyse thin Zn-Co films obtained by electrodeposition at different potentials and to characterise the interface between the substrate and the deposits. Measurement of depth profiles of the thin films has been carried out by Auger spectroscopy to determine the homogeneity of the deposit and to explore the influence of the substrate on the alloy composition. It was found that the composition of the thin film is affected by the deposition potential as well as by the substrate.XPS has been used to determine the chemical states of Zn and Co at the surface, in the bulk and at the interface with the substrate. The results showed that zinc occurs as zinc oxide and zinc metal at the surface, however in the bulk and at the interface only zinc and cobalt metals have been detected. The analyses do not provide evidence for the inclusion of zinc hydroxide in the deposit by precipitation during the deposition process. This may be significant in considering the mechanism of deposition.