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PubMed2006

Preparation and preliminary assessment of polymer-supported zirconium phosphate for selective lead removal from contaminated water.

In the present study, polymer-supported zirconium phosphate (ZrP-CP) was prepared for selective removal of lead from the contaminated water. ZrP-CP was characterized using nitrogen adsorption technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lead sorption on ZrP-CP was found to be pH dependent due to the ion- exchange mechanism. Also, ZrP-CP was proved to be more selective than the polystyrene strong-acid cation exchanger D-001 to remove lead ion from water, where other competing cations such as Na(+), Ca(2+), and Mg(2+) ions coexist at high concentrations. Generally, lead sorption isotherms on ZrP-CP can be divided into two distinct regions at different load levels, and isotherms at both regions can be well elucidated by Langmuir model. The distribution coefficients (K(d)) and binding constants (B(L)) obtained experimentally indicated that stronger sorption affinity of ZrP-CP towards the lead ion occurs at a relatively lower load level. Also, lead sorption onto ZrP-CP was found to be an endothermic and entropy-driven process. High selectivity of ZrP-CP towards the lead ion was possibly attributed to the crystal state of zirconium phosphate and a specific interaction between orthophosphate and lead ion. Fixed-bed column runs showed that lead sorption on ZrP-CP could result in a conspicuous decrease of this toxic metal from 0.5 mg/L to below 0.01 mg/L, which is recommended as the standard of drinking water by WHO (the treatment technique standard set by US EPA is 0.015 mg/L). Also, the spent sorbent can be readily regenerated for reuse by dilute HNO(3) or HCl solution.

Absorption↗
PubMed2003

Electrochemical behavior of pyrroloquinoline quinone immobilized on silica gel modified with zirconium oxide.

Pyrroloquinoline quinone (PQQ) was immobilized on the silica gel surface modified with zirconium oxide, designated as Si:Zr, by the carboxylic groups of the PQQ molecule and the zirconium oxide on the silica surface. The electrochemistry of PQQ immobilized on the Si:Zr matrix, incorporated in a carbon paste electrode, was evaluated using the cyclic voltammetry technique. The Si:Zr:PQQ-modified electrode showed a redox couple at E(m)=(E(pa1)+E(pc))/2=-0.150 V vs SCE at pH 7, close to that observed in aqueous solution, and another oxidation peak, E(pa2)=-0.100 V vs SCE. Studies in different pH solutions in the range of 3-7 showed that the first oxidation peak, E(pa1), is highly dependent on the solution pH shifting from to -0.175 to 0.100 V vs SCE, while E(pa2) remains practically constant at 0.100 V as the pH decreases from 7 to 3. The immobilized PQQ electrode presented the property to electrocatalyze the NADH at 150 mV vs SCE. The effect of addition of Ca(2+) ions on the electrode electroactivity for the NADH oxidation was also verified. Different from that observed for the PQQ immobilized on other electrode materials, the Ca(2+) ions did not influence the electrocatalytical response; however, the electrode stability was considerably improved in the presence of Ca(2+) ions, indicating that the matrix surface has a great influence on the electrochemical behavior of PQQ.

Benzoquinones↗
PubMed2004

New approach to oligonucleotide microarrays using zirconium phosphonate-modified surfaces.

A new approach to oligonucleotide arrays is demonstrated that utilizes zirconium phosphonate-derivatized glass slides. The active slides are prepared by binding Zr(4+) to surfaces terminated with organophosphonate groups previously deposited using either Langmuir-Blodgett or self-assembled monolayer methods. Oligonucleotide probes modified with a terminal phosphate bind strongly to the active zirconium phosphonate monolayer, and arrays for detecting fluorescent targets have been prepared using commercial spotting and scanning instruments. Preferred binding to the surface of the terminal phosphate of the modified probes instead of the internal phosphate diester groups is demonstrated and shown to yield increased fluorescence intensity after hybridization with labeled targets. A significant decrease in background signal is achieved by treating the slides with bovine serum albumin after spotting and before hybridization. A further increase in fluorescence after hybridization is observed when using a poly-guanine spacer between the probe oligomer and the terminal phosphate. Combining these modifications, an intensity ratio of nearly 1000 is achieved when comparing 5'-phosphate-modified 33-mer probes with unmodified probes upon hybridization with fluorescent targets.

Glass↗
PubMed2006

A comparative study of the surface structure, acidity, and catalytic performance of tungstated zirconia prepared from crystalline zirconia or amorphous zirconium oxyhydroxide.

Tungstated zirconias prepared from W deposition on zirconium oxyhydroxide are reportedly active for alkane isomerization, whereas solids synthesized by impregnation of zirconia are inactive. The origin of the differences between the two preparations is not fully understood. The present paper examines the influence of W surface density and the nature of the support on the surface structure, development of the acidity, and catalytic performance of WO(x)()/ ZrO(2) catalysts. Two series of catalysts containing W surface densities up to 5.2 at. W/nm(2) were prepared by pore volume impregnation of two different supports: zirconium oxyhydroxide and predominantly tetragonal zirconia (65% tetragonal, 35% monoclinic). The texture and structure of the catalysts were investigated by BET measurements, X-ray diffraction, Raman and infrared spectroscopy. The catalytic activity was tested for 2-propanol dehydration and n-hexane isomerization. For catalysts obtained by impregnation of Zr oxyhydroxide, Raman results showed that W was present as a surface phase. Infrared spectra indicated an increase in the degree of polymerization of W species with increasing W surface density. The development of the acidity was monitored by lutidine adsorption and desorption at 523 K, followed by infrared spectroscopy. The results indicated the presence of a threshold of W surface density at 1.3 at. W/ nm(2) for the detection of these acid sites, followed by a progressive increase in their abundance with increasing W surface density. The development of Brønsted acidity correlated with the evolution of the infrared bands attributed to "extensively" polymerized W species. A direct relationship was observed between the abundance of Brønsted acid sites and the catalytic activity for 2-propanol dehydration. For n-hexane isomerization, compared to 2-propanol dehydration, a higher threshold of W surface densities (3.4 at. W/ nm(2)) for the development of activity was observed. The difference was attributed to stronger Brønsted acid sites required for n-hexane isomerization. The catalysts prepared by impregnation of zirconia exhibited comparable behavior. For a given W surface density, the crystalline composition of the support (tetragonal/monoclinic zirconia), the W surface structure, abundance of Brønsted acid sites, and catalytic performance were similar. Thus, in an apparent variance with some of the results reported in the literature with respect to the influence of preparation methods, no significant effect of the initial form of the support (Zr oxyhydroxide versus predominantly tetragonal zirconia) was evidenced.

Catalysis↗
PubMed2004

Hydrogenation and cleavage of dinitrogen to ammonia with a zirconium complex.

Molecular nitrogen is relatively inert owing to the strength of its triple bond, nonpolarity and high ionization potential. As a result, the fixation of atmospheric nitrogen to ammonia under mild conditions has remained a challenge to chemists for more than a century. Although the Haber-Bosch process produces over 100 million tons of ammonia annually for the chemical industry and agriculture, it requires high temperature and pressure, in addition to a catalyst, to induce the combination of hydrogen (H2) and nitrogen (N2). Coordination of molecular nitrogen to transition metal complexes can activate and even rupture the strong N-N bond under mild conditions, with protonation yielding ammonia in stoichiometric and even catalytic yields. But the assembly of N-H bonds directly from H2 and N2 remains challenging: adding H2 to a metal-N2 complex results in the formation of N2 and metal-hydrogen bonds or, in the case of one zirconium complex, in formation of one N-H bond and a bridging hydride. Here we extend our work on zirconium complexes containing cyclopentadienyl ligands and show that adjustment of the ligands allows direct observation of N-H bond formation from N2 and H2. Subsequent warming of the complex cleaves the N-N bond at 45 degrees C, and continued hydrogenation at 85 degrees C results in complete fixation to ammonia.

Ammonia↗
PubMed2004

Chiral metal architectures in aminopyridinato complexes of zirconium.

Optically pure 2-alkylaminopyridines (HL) are synthesised readily from bromopyridines and chiral amines [(S)-1,2,3,4-tetrahydro-1-naphthylamine and (S)-(-)-alpha-methylbenzylamine] using palladium-catalysed amination. Protonolysis reactions of these proligands with ZrX(4)(X = NMe(2), CH(2)Ph, CH(2)Bu(t)) yield zirconium aminopyridinates, usually of the type [ML(2)X(2)], some of which have been characterised by X-ray crystallography. Control of absolute configuration at the metal centre is pursued by investigation of the effects of chiral amine substituent, substitution at the pyridine rings and the identity of co-ligands. Surprisingly the conformationally flexible [small alpha]-methylbenzyl based aminopyridinato ligands promote much better control of chirality-at-zirconium than do the cyclic tetrahydronaphthyl analogues. One complex of the former class displays complete control of stereochemistry at 193 K; only one diastereomer out of eight possible structures is observed. It is found that there is an excellent correlation between observed selectivities and calculated diastereomer energy differences from DFT. All the complexes studied are in dynamic exchange between diastereomers. The rate of these processes (DeltaH ca. 40 kJ mol(-1)) as studied by Selective Polarisation Transfer-Selective Inversion Recovery experiments (SPT-SIR) and lineshape analyses are significantly faster than those for aminopyridines containing bulkier amido substituents (DeltaH ca. 70 kJ mol(-1)). This type of dependence on steric effects, and the impact of the trans effect, is consistent with an N-dissociative mechanism, i.e. conversion from six- to five-coordinate structure followed by rapid intramolecular scrambling.

Amines↗
PubMed2002

Zirconium hydroxide effectively immobilizes and concentrates human enteric viruses.

BACKGROUND: Detection of human enteric viruses in foods and environmental samples requires concentration of viruses from complex matrices before application of molecular or cultural methods. Previous studies have described the use of zirconium hydroxide to concentrate bacteria from clinical, environmental, and food samples. AIMS: Our study describes the application of zirconium hydroxide to concentrate human enteric viruses. METHODS: Poliovirus type 1, hepatitis A virus (HAV) strain HM-175, and Norwalk virus (NV) were used as models. Virus recovery was evaluated both as loss to discarded supernatants and as recovery in the precipitated pellets. RESULTS: Poliovirus type 1, based on the plaque assay recoveries, ranged from 16 to 59% with minimal loss to the supernatant (1-5%). For both HAV and NV, RT-PCR amplicons of appropriate sizes were detected and confirmed in the pellet fraction with no visible amplicons from the supernatant. SIGNIFICANCE AND IMPACT OF THE STUDY: This rapid and inexpensive method shows promise as an alternative means to concentrate enteric viruses.

Hepatitis A virus↗
PubMed1996

A study of lung function and chest radiographs in men exposed to zirconium compounds.

Men working with zirconium compounds at one site in the North of England have been monitored since 1975 to evaluate effects on the lung of exposure (mainly < 10 mg/m3) over many years. Chest radiographs (in 1975, 1978, and 1982) and lung function measurements (from 1975-1988) were carried out on all men (178) known to have worked with the compounds and an estimate of cumulative exposure was computed from job title and likely exposures in each era. No evidence was found that zirconium exposure resulted in abnormal chest radiographs or impaired pulmonary function.

Adolescent↗
PubMed1991

Radioactivity in zirconium oxide powders used in industrial applications.

Recent work involving the decommissioning of a former ceramic manufacturing facility licensed by the Nuclear Regulatory Commission for activities involving depleted uranium oxide has uncovered the presence of unexpected high levels of natural radioactivity in non-licensed zirconium oxide powders also used in the same facility. A comparison between the levels of source material found in samples of this material and the current regulatory guidance for licensed activities and decommissioning has been conducted. It has been determined that the radioactivity in the zirconium oxide is of a high enough magnitude to raise health physics concerns in the areas of licensing and regulatory compliance, decontamination criteria, and worker health and safety. An examination of these areas has been conducted and the implications associated with our findings are presented.

Powders↗
PubMed1967

Single fallout particles and zirconium-95 from the Chinese nuclear explosion of 9 May 1966.

Daily fluctuations of the number of single fallout particles and activity of zirconium-95 in the groundlevel air were measured at Fayetteville (94 degrees W, 36 degrees N), Arkansas, for a period of about 3 months after the Chinese nuclear explosion of 9 May 1966. We found a cyclic pattern of variations for both zirconium-95 and fallout particles; this indicated that they were airborne for a long period and traveled far. Apparently, some of the particles circled the world more than once.

China↗
PubMed1996

Absence of skin sensitivity to oxides of aluminium, silicon, titanium or zirconium in patients with Crohn's disease.

BACKGROUND: Some metallic compounds, especially of zirconium, can cause cell mediated granulomatous inflammation of the skin. Pigment granules containing compounds of aluminium, silicon, and titanium have been observed within macrophages in the wall of the small intestine in health and in Crohn's disease. Zirconium compounds can be ingested in toothpaste. AIM: To determine in a pilot study if granulomatous sensitivity can be detected to compounds of these metals or silicon after injection into the skin of patients with Crohn's disease. SUBJECTS: Eight patients with Crohn's disease known to have had granulomata in the intestine and not currently treated with corticosteroids, and two healthy controls. METHOD: Two intradermal injections each of 0.1 ml of a 0.02% suspension of one of the compounds made in the abdominal wall of each subject. The site was marked and full thickness skin biopsy performed six weeks later. RESULT: A foreign body granuloma was observed on histological examination of two biopsy specimens but no evidence of a cell mediated response in any subject. CONCLUSION: No support was found for the hypothesis that Crohn's disease is due to a specific sensitivity to ingested metallic or silicon compounds.

Aluminum Oxide↗
PubMed1978

Effects of zirconium and aluminum salts on the alveolar macrophages.

Alveolar macrophages from the rabbit were exposed in the culture medium to zirconium and aluminum salts. The specific activities of the lysosomal hydrolases, that is acid phosphatase, beta-N-acetylglucosaminidase and beta-glucuronidase, were measured in the medium, whole cell homogenate, mitochondrial fraction, and in the supernatant fraction. A highly significant increase of these hydrolases was observed in the mitochondrial fraction from cells exposed to zirconium and aluminum salts as compared with those from control cell cultures. However, release of these enzymes into the medium was not much. The phenomenon of macrophage phagocytosis was observed morphologically in the cell cultures exposed in vitro to these metal compounds.

Acetylglucosaminidase↗
PubMedDate not supplied

Bonding of resin composite luting cements to zirconium oxide by two air-particle abrasion methods.

OBJECTIVE: This study evaluated the shear bond strength of two resin composite luting cements to zirconium oxide ceramic substrate using two air-particle abrasion methods. METHODS: Two resin composite cements, RelyX Unicem (3M ESPE) and Panavia F (Kuraray), each with an acidic composition, were used in combination with a zirconium oxide (DCS Dental AG) substrate containing Al2O3 and SiO2 (Rocatec system, 3M ESPE) and two air-particle abrasion methods. The shear bond strength of the resin composite cement to the substrate was tested after the samples were either water-stored for one week or thermocycled following 24 hours of water storage. RESULTS: The RelyX Unicem resin composite cement specimens with the Rocatec treatment (20.9 +/- 4.6 Mpa and 20.1 +/- 4.2 MPa, respectively, n = 12) demonstrated the highest shear bond strength. Alternatively, the lowest values were obtained for the Panavia F resin cement samples, with Al2O3 air-particle abrasion in both storage conditions, water storage for one week (17.7 +/- 8.9MPa) or thermocycling after 24 hours of water storage (16.3 +/- 4.9 MPa). Neither storage condition or particle abrasion system significantly affected shear bond strengths (ANOVA, p > 0.05). CONCLUSION: It was concluded that two different surface conditioning methods and storage conditions did not significantly affect the bonding properties of Panavia F and RelyX Unicem resin composite luting cements to Zirconia.

Air Abrasion, Dental↗
PubMed1997

Chronodynamic evaluation of the stages of osseointegration in zirconium laminar implants.

Osteogenesis occurs throughout all stages in life, due to both bone turnover and reparative processes. Thus, osseointegration (OI) can be described as the final step in a cascade of processes involved in bone healing in relation to implants. Ten groups of 5 Wistar rats each (mean = 90 g b.w.) were used. Under ether anesthesia a zirconium laminar implant was placed in the tibia following the method previously described by our laboratory (Cabrini et al Imp Dent 2:264-7, 1993). The animals were killed at Ohs, and 1, 2, 3, 6, 7, 10, 12, 14, and 60 days post-implantation. Tibiae were resected, radiographed and processed for their embedding in methyl methacrylate. Three sections, perpendicular to the major axis of the tibia, were obtained per implant and histologic and histomorphometric studies were carried out. Volume occupied by blood clot, woven bone, percentage of OI and OI bone tissue thickness, were determined. Histologic and histomorphometric studies as function of time revealed: a) at 6 days the presence of non-osseointegrated woven bone around the device is evident increasing in volume from 7 to 10 days post-implantation, and disappearing from day 12 to 14., b) at 14 days after implantation lamellar bone formation on the surface of the zirconium implants (OI) is noticeable. Additional bone growth is observed after 60 days. This study enables quantification of peri-implant reparative process response in an unloaded, necrotic trabeculae free model showing, in the different phases of the osseointegration process, the role of the blood clot and of the appearance and disappearance of woven bone and the final stages of osseointegration. Further investigation will allow comparison of results obtained under the effect of local and/or systemic factors that might affect osseointegration.

Animals↗
PubMedDate not supplied

[Use of zirconium alloys in endoprostheses and osteosynthesis appliances].

The application of titanium alloys to osteosynthesis appliances and endoprostheses in becoming difficult due to shortage of titanium. The composition of the BT5-I titanium alloy and comochromium and zirconium alloys was compared. In terms of mechanical properties, the zirconium alloys are acceptable for the above application.

Alloys↗
PubMedDate not supplied

Fit of a new pressure-sintered zirconium dioxide coping.

PURPOSE: The aim of this study was to determine in vitro the internal and marginal fit of zirconium dioxide ceramic copings manufactured using a recently introduced CAD/CAM-based technique (Denzir). MATERIALS AND METHODS: Two master models were produced in metal, representing the maxillary right central incisor and first premolar. Two A-silicone impressions were used for each of the master models, and from each of the impressions five stone dies with the corresponding ceramic copings were produced, for a total of 20 copings. The A-silicone replica of the misfit of the ceramic coping to the corresponding stone die and master model was sectioned buccolingually and mesiodistally. The obtained sections were measured at occlusal, axial, and marginal locations under light microscopy. Twenty-four measurements for each replica were made. The Student's t test was used to detect significant differences between coping-stone die and coping-master model misfits. RESULTS: For any combination, the marginal fit was superior to the axial and occlusal fit. In general, the misfit between the coping and the stone die did not differ significantly from the misfit detected between the coping and the master model. However, a better fit was recorded for the first premolar at the occlusal portion in the coping-stone die combination compared to the coping-master model combination. The mean marginal discrepancy between the copings and master models was clearly below 50 microm, with a range of 0 to 115 microm. CONCLUSION: The accuracy achieved by the Denzir manufacturing process for the production of zirconium dioxide copings is well within the range of clinical acceptability.

Bicuspid↗
PubMedDate not supplied

[The use of zirconium for implants in traumatology and orthopedics].

The use of new promising materials for implanting elements in traumatology and orthopedics is under discussion in the paper. Steel pins coated with zirconium do not cause any inflammatory complications when applied. The initial results of using the zirconium-coated implants offer the challenge for using such devices in future.

Bone Nails↗
PubMed2005

[Determination of trace zirconium and hafniumin sample by atomic emission spectrometry].

This paper describes the determination of trace Zr and Hf in the sample using carbon powder and titanium oxide as the buffer by Atomic Emission Spectrometry (AES). Titanium was selected for the internal standard line. Sample separation and chemical treatment were not required. The sample was directly loaded into an ordinary electrode. The method is simple, rapid and accurate. The conditions for the determination, and the factors of influence have been studied. A new method has been developed for the determination of zirconium and hafnium. The analytical lines of Zr and Hf were 327.3 and 286.6 nm respectively. The internal standard line of Ti was 308.8 nm. The linear range of the determination of Zr and Hf was 0-0.50% and 0-0.25% respectively. The detection limit of Zr and Hf was 0.0010% and 0.010% respectively. The range of the recovery of zirconium and hafnium was 96.67%-105.0%. The results for these elements in standard sample are in agreement with certified values with a precision of 3.61% RSD for Zr (n = 9), and 4.82% RSD for Hf (n = 9). The method has been applied to the determination of Zr and Hf with satisfactory results.

Hafnium↗