Zirconium Hydroxide Research Articles

Thermodynamic complexity of sulfated zirconia catalysts

A series of sulfated zirconia (SZ) catalysts were synthesized by immersion of amorphous zirconium hydroxide in sulfuric acid of various concentrations (1–5N). These samples were fully characterized by X-ray diffraction (XRD), thermogravimetric analysis and mass spectrometry (TGA-MS), and aqueous sulfuric acid immersion and high temperature oxide melt solution calorimetry. We investigated the enthalpies of the complex interactions between sulfur species and the zirconia surface (ΔHSZ) for the sulfated zirconia precursor (SZP), ranging from −109.46±7.33 (1N) to −42.50±0.89 (4N) kJ/mol S. ΔHSZ appears to be a roughly exponential function of sulfuric acid concentration. On the other hand, the enthalpy of SZ formation (ΔHf), becomes more exothermic linearly as sulfur surface coverage increases, from −147.90±4.16 (2.14nm−2) to −317.03±4.20 (2.29nm−2) kJ/mol S, indicating formation of energetically more stable polysulfate ​species.

Reactive removal of 2-chloroethyl ethyl sulfide vapors under visible light irradiation by cerium oxide modified highly porous zirconium (hydr) oxide

Highly porous cerium oxide modified Zr(OH)4 samples were synthesized using a simple one stage urea precipitation method. The amorphicity level of zirconium hydroxide did not change upon addition of cerium oxide particles. A unique aspect of the cerium oxide-modified materials is the presence of both the oxide (CeO2) and hydroxide (Zr(OH)4) phases resulting in a unique microporous structure of the final material. Extensive characterization using various chemical and physical methods revealed significant differences in the surface features. All synthesized materials were microporous and small additions of cerium oxide affected the surface chemistry. These samples were found as effective catalysts for a decontamination of mustard gas surrogate, 2-chloroethyl ethyl sulfide (CEES). Cerium oxide addition significantly decreased the band gap of zirconium hydroxide. Ethyl vinyl sulfide and 1,2-bis (Ethyl thio) ethane were identified as surface reaction products.

The miaskitic-to-agpaitic transition in peralkaline nepheline syenite (white foyaite) from the Pilanesberg Complex, South Africa

The Mesoproterozoic Pilanesberg Complex, South Africa, is built up by several distinct, ring-shaped intrusions of syenite and peralkaline nepheline syenite. A mildly peralkaline ((Na+K)/Al=1.04–1.09), medium-to coarse grained nepheline syenite makes up the outermost ring in the southwestern part of the complex (“Matooster type white foyaite”). In this rock, mafic silicate minerals (amphibole, biotite, aegirine) and Ti-bearing minerals (ilmenite, astrophyllite, aenigmatite, lorenzenite, bafertisite, jinshajiangite) are interstitial to feldspar and nepheline, and define a series of mineral assemblages reflecting a change from a miaskitic crystallization regime (with Na-Ca amphibole, titanite and ilmenite) to increasingly agpaitic conditions (with arfvedsonite, aegirine, astrophyllite, aenigmatite, lorenzenite). The main driving force behind the evolution was an increase in peralkalinity of the trapped liquid, mainly by adcumulus growth of alkali feldspar and nepheline, which in the later stages of evolution was combined with increases in oxygen fugacity and water activity. Unlike in most other agpaitic rock complexes, Zr remained compatible in aegirine (and to some extent in amphibole) almost to the end of the process, when a hydrous zirconium silicate mineral (hilairite) crystallized as the only mineral in the rock having essential zirconium. The presence of minerals such as hilairite, bafertisite, jinshajiangite and a Na-REE-Sr rich apatite group mineral (fluorcaphite ?) in the latest assemblages suggests that the last remaining interstitial melt or fluid approached a hyperagpaitic composition. The isolated melt pockets in the Pilanesberg white foyaite follow a pattern of evolution that can be seen as a miniature analogue of the fractional crystallization processes controlling magma evolution in large, alkaline igneous rock complexes.

Molecular-Cage Method: An Improvement of the Precipitation Method in Synthesizing Nanoparticles

The molecular-cage method is a convenient and universal way of synthesizing nanoparticles in aqueous phase. In this paper, hydroxyapatite (HA) and zirconium hydroxide nanoparticles are made by the molecular-cage method with a hydroxyl-rich solute. The structure, morphology, and particle size of the product were analyzed by differential scanning calorimetry and scanning electron microscopy. The chemical structures of the particles are not affected by the molecular-cage effect. The sizes of the nanoparticles and the concentration of the solute have a corresponding relationship in a limited range. The higher the concentration of the solute, the smaller the nanoparticles. Besides, HA nanoparticles are also made by the molecular-cage method in a water/ethanol mixture.

Formation of WO x –ZrO2 isomerization catalysts from anion-modified zirconium hydroxide

The formation of zirconia-based isomerization catalysts during thermal conversions of hydroxide modified with different amounts of tungstate groups has been studied by differential scanning calorimetry and X-ray diffraction analysis. The mechanism of formation of tungstated zirconia from a hydroxide precursor has been formulated.

Peculiarities of structural transformations in zirconia nanocrystals

The transitions of metastable tetragonal phase as well as high-temperature tetragonal phase into the low-temperature monoclinic phase upon heating and cooling were thoroughly studied in zirconia nanoparticles. High-temperature X-ray diffraction, thermal analysis and Raman spectroscopy were used to provide the systematic approach to the investigation of zirconia nanoparticles thermal behavior. A phase transformation sequence in the ZrO2–H2O system was determined, and the mechanisms of tetragonal-to-monoclinic transition upon heating and cooling were suggested. Here, the phenomenon was found and described, which was determined as “self-powdering” of nanoparticles occurring during structural transition. This phenomenon was observed by in situ investigation of the evolution of crystalline nanoparticles from amorphous zirconium hydroxide during thermal treatment in air. The tetragonal-to-monoclinic phase transition, induced by cooling from the temperature of equilibrium of tetragonal zirconia (i.e., above 1170 °C), is accompanied by a significant crystallite size decrease (with corresponding 3–4 times decrease of crystallite volume). The experimental results facilitate applications of zirconia nanoparticles to obtain high-performance nanopowders for nanoceramics.

THERMAL PROPERTIES AND CONDUCTIVITY OF NAFION-ZIRCONIA COMPOSITE MEMBRANE

The application of composite membranes for high temperature polymer electrolyte membrane fuel cell has attracted interests. Nafion-metal dioxide composite membranes are considered among the research niche. In this study, Nafion membranes and Nafion-zirconia composite membranes with 1, 3 and 5 wt. % of hydrous zirconia were prepared accordingly. All membranes were characterized by quantitative analysis techniques such as thermogravimetry analyse, diffraction scanning calorimetry and Fourier transform infrared. All composite membranes showed high glass transition temperatures and improved water retention properties, compared to the Nafion membrane. The composite membrane with 3 wt. % of zirconia showed the highest thermal resistance at 90°C.

Shaping of Sulfated Zirconia Catalysts by Extrusion: Understanding the Role of Binders

Sulfated zirconia hydroxide shaping by extrusion is studied based on elucidating the impact of zeta-potential and rheological characteristics on physical and chemical properties of technical catalysts. Zeta potential measurements of sulfated zirconium hydroxide prior and after poly(vinyl alcohol) (PVA) additions were made. Rheological curves of sulfated zirconium hydroxide suspensions with different amounts of PVA were recorded at different zeta-potential values. The addition of PVA nonlinearly decreased shear yield stress. Experimental data were quantified with the Krieger–Dougherty equation. The influence of a boehmite-type binder on the zeta-potential confirmed that the surface properties of the particles to a large extent are determined by the presence of binder. The pore structure of shaped catalysts was unaffected by rheological parameters when zeta-potential is close enough to zero. At the same time deviations of the zeta potential from the zero-value afforded more uniform pore size distribution.

Temperature-mediated phase transformation, pore geometry and pore hysteresis transformation of borohydride derived in-born porous zirconium hydroxide nanopowders.

Development of in-born porous nature of zirconium hydroxide nanopowders through a facile hydrogen (H2) gas-bubbles assisted borohydride synthesis route using sodium borohydride (NaBH4) and novel information on the temperature-mediated phase transformation, pore geometry as well as pore hysteresis transformation of in-born porous zirconium hydroxide nanopowders with the help of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) isotherm and Transmission Electron Microscopy (TEM) images are the main theme of this research work. Without any surfactants or pore forming agents, the borohydride derived amorphous nature of porous powders was stable up to 500 °C and then the seed crystals start to develop within the loose amorphous matrix and trapping the inter-particulate voids, which led to develop the porous nature of tetragonal zirconium oxide at 600 °C and further sustain this porous nature as well as tetragonal phase of zirconium oxide up to 800 °C. The novel hydrogen (H2) gas-bubbles assisted borohydride synthesis route led to develop thermally stable porous zirconium hydroxide/oxide nanopowders with an adequate pore size, pore volume, and surface area and thus these porous materials are further suggested for promising use in different areas of applications.

Novel dilacunary phosphotungstate supported onto zirconia: Synthesis, characterization and versatile catalytic activity

Efficient strategy to synthesize dilacunary phosphotungstate has been introduced and a successful attempt was made to stabilize it onto hydrous zirconia. Characterization of the catalyst was carried out by various physicochemical techniques, further confirming its high stability after supporting. Catalytic activity was evaluated for esterification of alcohols as well as oxidation of alkenes with high turn-over numbers. The catalyst was recyclable up to three cycles without any significant loss in the catalytic activity.

Microwave-induced synthesis of pyrophosphate Zr1-xTixP2O7 and TiP2O7 with enhanced sorption capacity for uranium (VI)

A series of nanostructured pyrophosphates Zr1-xTixP2O7 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0), have been prepared via a facile microwave induced route in which zirconium hydroxide, titanium hydroxide and phosphoric acid were used as Zr, Ti and P sources, respectively. It is demonstrated the isomorphous substitution of Zr4+ by Ti4+ results in a decrease of the size and an enhancement of the adsorption capacity of the obtained particles for U(VI) in aqueous solution. The maximum amount of TiP2O7 for U(VI) reached up to 309.8 mgg−1 under the experimental conditions (pH=5, t=60min and T=303K). The as-obtained specific metal pyrophosphates exhibit a considerably higher adsorption capability for U(VI) in aqueous solution compared with Zr1-xTixP2O7 prepared by calcined method, showing a high potential for U(VI) sequestration applications. The adsorption kinetics and thermodynamic analysis of Zr1-xTixP2O7 on adsorption of U (VI) were performed, and a possible adsoprtion mechanism was also proposed.

Synthesis of hydrous zirconium oxide-impregnated chitosan beads and their application for removal of fluoride and lead

A composite adsorbent capable of simultaneous removal of both cationic and anionic contaminants from aqueous solutions was developed by impregnating hydrous zirconium oxide (HZO) into chitosan beads (CB). The optimal mass ratio of chitosan to HZO was 2:2. The composite adsorbent (HZOCB) had the rugged surface (52.74m2g−1) with irregular cracks caused by HZO inclusion and amine functional groups. The rate of Pb2+ adsorption by HZOCB was relatively rapid. Most of Pb2+ (89%) was adsorbed within 2.5h. A binary sorbate system was noticeably favorable for F− adsorption as compared to single sorbate system. Adsorption of F− and Pb2+ followed pseudo-second order kinetics. The maximum sorption capacities obtained from Langmuir isotherm model were 22.1 and 222.2mgg−1, respectively. The study demonstrates that the developed composite could be a potential adsorbent for the simultaneous remediation of F− and Pb2+ contamination in water.

Aqueous sodium borohydride induced thermally stable porous zirconium oxide for quick removal of lead ions.

Aqueous sodium borohydride (NaBH4) is well known for its reducing property and well-established for the development of metal nanoparticles through reduction method. In contrary, this research paper discloses the importance of aqueous NaBH4 as a precipitating agent towards development of porous zirconium oxide. The boron species present in aqueous NaBH4 play an active role during gelation as well as phase separated out in the form of boron complex during precipitation, which helps to form boron free zirconium hydroxide [Zr(OH)4] in the as-synthesized condition. Evolved in-situ hydrogen (H2) gas-bubbles also play an important role to develop as-synthesized loose zirconium hydroxide and the presence of intra-particle voids in the loose zirconium hydroxide help to develop porous zirconium oxide during calcination process. Without any surface modification, this porous zirconium oxide quickly adsorbs almost hundred percentages of toxic lead ions from water solution within 15 minutes at normal pH condition. Adsorption kinetic models suggest that the adsorption process was surface reaction controlled chemisorption. Quick adsorption was governed by surface diffusion process and the adsorption kinetic was limited by pore diffusion. Five cycles of adsorption-desorption result suggests that the porous zirconium oxide can be reused efficiently for removal of Pb (II) ions from aqueous solution.

Codoping of scandium-containing zirconia-based solid electrolytes with iron, cerium, and copper oxides

Codoping with iron, cerium, and copper oxides has been proposed as a means of improving the performance of scandium-containing zirconia-based solid electrolytes. We have examined three procedures for the synthesis of the (ZrO2)0.825(CeO2)0.07(Sc2O3)0.07(Fe2O3)0.035 solid solution through precipitation from solution. It has been shown that the highest oxygen ion conductivity is ensured by the synthesis procedure that includes the mechanochemical activation of presynthesized scandium ferrate (Sc1.33Fe0.67O3) with cerium and zirconium hydroxides and a solution containing 0.5 mol % Cu.

A fiber optic, ultraviolet light-emitting diode-based, two wavelength fluorometer for monitoring reactive adsorption.

Construction and use of an ultraviolet light-emitting diode-based fluorometer for measuring photoluminescence (PL) from powder samples with a fiber optic probe is described. Fluorescence at two wavelengths is detected by miniature photomultiplier tubes, each equipped with a different band pass filter, whose outputs are analyzed by a microprocessor. Photoluminescent metal oxides and hydroxides, and other semiconducting nanoparticles, often undergo changes in their emission spectra upon exposure to reactive gases, and the ratio of the PL intensities at two wavelengths is diagnostic of adsorption. Use of this instrument for reactive gas sensing and gas filtration applications is illustrated by measuring changes in the PL ratio for zirconium hydroxide and zinc oxide particles upon exposure to air containing low concentrations of sulfur dioxide.

Quantitative validation and analysis of the regime map approach for the wet granulation of industrially relevant zirconium hydroxide powders

The objective of this work was to study the granulation behavior of three different types of zirconium hydroxide, each varying in particle size and density. Different concentrations of yttrium (III) nitrate hexahydrate (Y(NO3)3·6H2O) solutions were used as a doping agent and also acted as binder. Experiments were performed using a high shear wet granulation process by adjusting two parameters, 1. liquid to solid mass ratio and 2. impeller speed, to obtain four parameter settings (referred as bounds in the paper) for a two factorial design of experiment for each powder. To understand the granule growth behavior, a regime map analysis using the growth regime map first proposed by Iveson and Litster (1998) , was carried out on the bounds. The granule growth behavior observed experimentally was compared with the regime map results. Different growth behavior was observed for different powders. Furthermore, an attempt was made to obtain a steady growth for those parameter settings that initially resulted in an induction growth. A surfactant, SDS (Sodium dodecyl sulfate), was used to improve the wetting properties of the powder and its addition to the binder solution resulted in a steady growth that is more controllable for granulation manufacturing operations compared to induction growth.

Phosphate adsorption from wastewater using zirconium (IV) hydroxide: Kinetics, thermodynamics and membrane filtration adsorption hybrid system studies

Excessive phosphate in wastewater should be removed to control eutrophication of water bodies. The potential of employing amorphous zirconium (Zr) hydroxide to remove phosphate from synthetic wastewater was studied in batch adsorption experiments and in a submerged membrane filtration adsorption hybrid (MFAH) reactor. The adsorption data satisfactorily fitted to Langmuir, pseudo-first order and pseudo-second order models. Langmuir adsorption maxima at 22 °C and pHs of 4.0, 7.1, and 10.0 were 30.40, 18.50, and 19.60 mg P/g, respectively. At pH 7.1 and temperatures of 40 °C and 60 °C, they were 43.80 and 54.60 mg P/g, respectively. The thermodynamic parameters, ΔG° and ΔS° were negative and ΔH° was positive. FTIR, zeta potential and competitive phosphate, sulphate and nitrate adsorption data showed that the mechanism of phosphate adsorption was inner-sphere complexation. In the submerged MFAH reactor experiment, when Zr hydroxide was added at doses of 1–5 g/L once only at the start of the experiment, the removal of phosphate from 3 L of wastewater containing 10 mg P/L declined after 5 h of operation. However, when Zr hydroxide was repeatedly added at 5 g/L dose every 24 h, satisfactory removal of phosphate was maintained for 3 days.

Comparative study on polyester epoxy powder coat and amide cured epoxy liquid paint over nano-zirconia treated mild steel

Abstract The effect of commercial nano-sized zirconium hydrous oxide (NT) coating of mild steel (MS) on corrosion resistance and its adhesion to polyester epoxy powder coat (PEP) and amide cured epoxy white finish paint (EPF) was investigated. The corrosion rate of untreated and NT treated MS was evaluated from linear potential parameters such as corrosion current, corrosion potential and Tafel plots. NT base coat was characterized by EIS (electrochemical impedance spectroscopy), FESEM (field emission scanning electron microscopy), EDX (energy-dispersive X-ray spectroscopy), AFM (atomic force microscopy), XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) studies. The dry film properties of the top coats of PEP and EPF were compared by neutral salt spray test, humidity resistance, impact resistance and adhesion tape tests as per ASTM (American Society for Testing and Materials) methods. The mechanism of zirconia deposition on the hydroxyl sites of the mild steel surface was evident from the results of XPS. The corrosion resistance and adhesion of PEP/NT coating system were found to be superior to that of EPF/NT system from salt spray resistance test and cross hatch test by adhesive tape. The superior corrosion resistance of EPF/NT to EPF/MS shows the efficacy of the NT conversion coating on MS.

Separation of fluorine/cerium from fluorine-bearing rare earth sulfate solution by selective adsorption using hydrous zirconium oxide

Hydrous zirconium oxide can take the F− from [CeF2]2+, leading to the separation of fluorine and cerium.

Synthesis of reversible carbon dioxide absorber based on hydrated zirconium oxide, intended for concentration and removal of CO2 in habitable closed objects

Carbon dioxide absorber based on hydrated zirconium oxide was synthesized with ammonium carbonate and hydrogen peroxide. The effect of the molar ratio between ammonium carbonate and hydrogen peroxide on the sorption characteristics of the absorber was examined. The structural-sorption properties of the absorber were analyzed. It was shown tat the absorber has a high absorption capacity for CO2.