Zirconium Oxyhydroxide Research Articles

COF-supported zirconium oxyhydroxide as a versatile heterogeneous catalyst for Knoevenagel condensation and nerve agent hydrolysis

A composite of catalytic Lewis acidic zirconium oxyhydroxides (8 wt%) and a covalent organic framework (COF) was synthesized. X-ray diffraction and infrared (IR) spectroscopy reveal that COF's structure is preserved after loading with zirconium oxyhydroxides. Electron microscopy confirms a homogeneous distribution of nano- to sub-micron-sized zirconium clusters in the COF. 3D X-ray tomography captures the micron-sized channels connecting the well-dispersed zirconium clusters on the COF. The crystalline ZrOx(OH)y@COF's nanostructure was model-optimized via simulated annealing methods. Using 0.8 mol% of the catalyst yielded a turnover number of 100-120 and a turnover frequency of 160-360 h-1 for Knoevenagel condensation in aqueous medium. Additionally, 2.2 mol% of catalyst catalyzes the hydrolysis of dimethyl nitrophenyl phosphate, a simulant of nerve agent Soman, with a conversion rate of 37% in 180min. The hydrolytic detoxification of the live agent Soman is also achieved. Our study unveils COF-stabilized ZrOx(OH)y as a new class of zirconium-based Lewis+ Bronsted-acid catalysts.

High mass loading paper-based electrode material with cellulose fibers under coordination of zirconium oxyhydroxide nanoparticles and sulfosalicylic acid

With the rapid expansion of the flexible electronics market, it is critical to develop high-performance flexible energy storage electrode materials. Cellulose fibers, which are sustainable, low cost, and flexible, fully meet the requirements of flexible electrode materials, but they are electrically insulating and cause a decrease in energy density. In this study, high-performance paper-based flexible electrode materials (PANI:SSA/Zr-CFs) were prepared with cellulose fibers and polyaniline. A high mass loading of polyaniline was wrapped on zirconia hydroxide-modified cellulose fibers under metal-organic acid coordination through a facile in situ chemical polymerization process. The increase in mass loading of PANI on cellulose fibers not only improves the electrical conductivity but also enhances the area-specific capacitance of the flexible electrodes. The results of electrochemical tests show that the area specific capacitance of the PANI:SSA/Zr-CFs electrode is 4181 mF/cm2 at 1 mA/cm2, which is more than two times higher than that of the electrode with PANI on pristine CFs. This work provides a new strategy for the design and manufacture of high-performance flexible electronic electrodes based on cellulose fibers.

Oscillatory Behaviour of Ni Supported on ZrO2 in the Catalytic Partial Oxidation of Methane as Determined by Activation Procedure.

Ni/ZrO2 catalysts, active and selective for the catalytic partial oxidation of methane to syngas (CH4-CPO), were prepared by the dry impregnation of zirconium oxyhydroxide (Zhy) or monoclinic ZrO2 (Zm), calcination at 1173 K and activation by different procedures: oxidation-reduction (ox-red) or direct reduction (red). The characterization included XRD, FESEM, in situ FTIR and Raman spectroscopies, TPR, and specific surface area measurements. Catalytic activity experiments were carried out in a flow apparatus with a mixture of CH4:O2 = 2:1 in a short contact time. Compared to Zm, Zhy favoured the formation of smaller NiO particles, implying a higher number of Ni sites strongly interacting with the support. In all the activated Ni/ZrO2 catalysts, the Ni–ZrO2 interaction was strong enough to limit Ni aggregation during the catalytic runs. The catalytic activity depended on the activation procedures; the ox-red treatment yielded very active and stable catalysts, whereas the red treatment yielded catalysts with oscillating activity, ascribed to the formation of Niδ+ carbide-like species. The results suggested that Ni dispersion was not the main factor affecting the activity, and that active sites for CH4-CPO could be Ni species at the boundary of the metal particles in a specific configuration and nuclearity.

Zirconia-Based Aerogels for Sorption and Degradation of Dimethyl Methylphosphonate

Inspired by recent breakthroughs with Zr(OH)4-type materials that decompose chemical warfare agents (CWAs), we explore aerogel forms of zirconium oxyhydroxide (ZrOxHy) as reactive sorbents for dime...

High mass loading polyaniline layer anchored cellulose fibers: Enhanced interface junction for high conductivity and flame retardancy

Novel cellulose fibers-based composite consisted of zirconium oxyhydroxide and phytic acid doped polyaniline was prepared via a two-step method of simple chemical precipitation and followed by in situ polymerization process. Cellulose fibers were firstly modified with zirconium oxyhydroxide to enhance the binding of phytic acid doped polyaniline to the surface. A compact coating of phytic doped polyaniline was developed on zirconium oxyhydroxide modified cellulose fibers through the chelating of zirconium ions to phytic acid. The resulting composite possessed a controllable mass loading of polyaniline, which could significantly improve the conductivity, flame retardancy and electrochemical stability. Therefore, the expected chelating between zirconium ions on cellulose fibers and phytic acid doped in polyaniline supported the excellent properties of the composite paper. Notably, the developed strategy is efficient, low-cost and environmental friendly, and the work opens up new doors to the development of other cellulose fibers-related interface enhancement applications.

ZrW catalyzed cellulose conversion in hydrothermal conditions: Influence of the calcination temperature and insights on the nature of the active phase

Tungstated zirconia, ZrW, is reported as an efficient solid acid catalyst in the conversion of cellulose into lactic acid in hydrothermal conditions. The active phase of ZrW is generally ascribed to more or less polymerized WOx domains dispersed on zirconia. In this study, commercial uncalcined and calcined tungstated zirconia were used as catalysts for the conversion of cellulose under hydrothermal conditions at 190 °C. Their activities were also compared with uncalcined zirconium oxyhydroxide, ZrO2-x(OH)2x and calcined zirconia, ZrO2. Contrary to the expected results, it is disclosed that uncalcined ZrW exhibits higher catalytic activity and stability than calcined ZrW. Modifications in the products distribution were observed as glycolic acid formation at the expense of lactic acid formation upon ZrW calcination. Even more surprising, the catalytic activity of W free amorphous zirconium oxyhydroxide ZrO2-x(OH)2x is similar to uncalcined ZrW, with lactic acid as the main product while ZrO2 does not have any catalytic activity. These results suggest that the active phase of these catalysts might combine the couple Zr4+ and OH− species while the role of W species would be of secondary importance.

Hydrothermal Fabrication of Zirconium Oxyhydroxide Capped Chitosan/Kaolin Framework for Highly Selective Nitrate and Phosphate Retention

In recent years, hydrothermal technology has been paid more attention because of its unique advantages like large surface area and high porous nature. In the present study, chitosan (CS) embedded k...

Fabrication of Chitosan‐Reinforced ZrxAl1‐xOOH Nanocomposites and Their Arsenite and Fluoride Depollution Densities from Single/Binary Systems

AbstractThe unique and versatile adsorbents zirconium oxyhydroxide (ZrOOH), aluminum oxyhydroxide (AlOOH), zirconium‐aluminum oxyhydroxide (ZrxAl1‐xOOH) and chitosan‐supported zirconium‐aluminum oxyhydroxide (CS@ZrxAl1‐xOOH) were synthesized via a simple co‐precipitation method. CS was used as a pillar‐like support to reinforce the ZrxAl1‐xOOH, the resulting material was capable of simultaneously adsorbing both F− and AsO33− because the functional groups of CS facilitated the formation of both ZrOOH and AlOOH nanoparticles. Interestingly, ZrxAl1‐xOOH and CS@ ZrxAl1‐xOOH had better F− adsorption capacities at pH<7, whereas better AsO33− removal was observed at pH>9. The Langmuir maximum adsorption capacity of CS@ZrxAl1‐xOOH was 0.655 and 0.983 mmol g−1 for AsO33− and F−, respectively and the performance was superior to that of previously reported metallic oxide and chitosan‐based sorbents. In addition, the presence of coexisting anions revealed that the CS@ZrxAl1‐xOOH material selectively removed AsO33− over F− in a binary batch system. The adsorption kinetics of the adsorbents were well fit to the pseudo‐second‐order model. Due to the simultaneous and quick uptake capacity and cost‐effectiveness, CS@ZrxAl1‐xOOH nanocomposite have potential application in environmental cleanup.

Higher Brønsted acidity of WOx/ZrO2 catalysts prepared using a high-surface-area zirconium oxyhydroxide

The precipitated zirconium oxyhydroxide, ZrOH(H), was used as a support for tungstate loading, where its specific surface area was 1.5-fold higher than that of the analogous sample obtained commercially, ZrOH(L). Due to this difference, crystalline WO3 and ZrO2 (tetragonal and monoclinic) were formed at a higher calcination temperature by 150K for WZrOH(H) than for WZrOH(L) when tungstate was loaded. For WOx/ZrO2 with different W surface densities produced by calcination at 723–1173K, pyridine-IR experiment and Raman spectroscopy revealed that more Brønsted acid sites were present for WZrOH(H) calcined at 1023 and 1073K than for WZrOH(L) calcined at 873K while distorted Zr-stabilized WO3 nanoparticles were found for these samples. Thus, the former samples showed the superior activity to the latter in the dehydration of formic acid. The linear relationship between the catalytic performance and Brønsted acidity was observed, explaining that WOx/ZrO2 with more Brønsted acid sites is more active in the dehydration reaction. Consequently, the enhanced Brønsted acidity and catalytic activity of WZrOH(H) resulted from the use of zirconium oxyhydroxide with a high surface area for tungstate loading.

Sorbents based on xerogels of zirconium, aluminum and manganese oxyhydroxides

Sorbents based on xerogels of zirconium, aluminum and manganese oxyhydroxides

Formation of nanocrystals in the ZrO2–H2O system

Formation of zirconia nanocrystals in the course of thermal treatment of an X-ray amorphous zirconium oxyhydroxide was studied. It was shown that the formation of tetragonal and monoclinic polymorphs of ZrO2 in the temperature range from 500 to 700°C occurs owing to dehydration and crystallization of amorphous hydroxide. An increase of the temperature up to 800°C and higher activates mass transfer processes and, as a result, activates the nanoparticle growth and increases the fraction of the phase based on monoclinic modification of ZrO2 due to mass transfer from the nanoparticles with the non-equilibrium tetragonal structure. Herewith, formed ZrO2 nanocrystals with monoclinic structure have a broad size distribution of crystallites, and the average crystallite size after thermal treatment at 1200°C for 20 min is about 42 nm.

Zirconium and aluminum oxyhydroxides particles formation during sol–gel process

Abstract The hydrolysis kinetics of aluminum and zirconium oxychloride salts in the presence of carbamide was investigated. The determined rate constant varies in the range of 0.0027–0.0038 min −1 and is independent on initial mixture composition. The effect of initial components molar ratio and concentration on formation of sol particles was established. As a result, zirconium and aluminum oxyhydroxide 25–44 nm particles were obtained during sol–gel synthesis. It was found that particle size strongly depends on synthesis conditions. In addition, synthesis conditions determine porosity of final sample and allow to obtain highly porous material at certain conditions. The formation of porous oxyhydroxides structure via particles aggregation with formation of aggregates 60 nm ÷ 1–10 μm was confirmed. The specific surface area of samples varies from 85 to 540 m 2 /g depending on composition and synthesis conditions The carbamide effect on zirconium oxyhydroxide gelation process was studied.

Thermal behavior of the composite xerogels of zirconium oxyhydroxide and silicic acid

Gels were prepared via sol–gel method by addition of zirconium oxychloride solution into sodium metasilicate (SZ) and sodium metasilicate solution into zirconium oxychloride (ZS) at varying final pH. Si/Zr molar ratio equaled 1/1. Synthesized gels were dried with calcium chloride until they reached a constant mass. SEM and nitrogen adsorption analysis have shown that SZ gels have surface area 175–200 m2 g−1, consist of 20–30 nm grains. ZS samples have surface area about 1 m2 g−1, consist of grains smaller than 10 nm. Thermal and X-ray phase analysis have shown that transition of amorphous ZrO2 to crystalline form shifts from 430 to 850–870 °C for SZ gels. Unlike zirconia gels phase transitions that proceed in order: “amorphous (430 °C)—tetragonal (800 °C)—monoclinic (1,000 °C) phases”, the monoclinic phase in ZS gels appears immediately after transition from amorphous to crystalline state; the tetragonal phase in SZ samples is stable until 1,000 °C.

Finely dispersed phases of MO(OH)2 (M = Zr, Hf) oxyhydroxides

We discuss studies of new finely dispersed phases of zirconium and hafnium oxyhydroxides MO(OH)2 (M = Zr, Hf) by means of X-ray diffraction, NMR, Raman scattering, IR spectroscopy, electronic microscopy and thermal analysis. It is demonstrated that these compounds and their precursors (lithium salts obtained by citrating) are isostructural. Hafnium oxyhydroxide is thermally more stable than its zirconium analog and decomposes at approximately 260°C.

The corrosion behaviour of Zr-based bulk metallic glasses in 0.5 M NaCl solution

The corrosion behaviour of eutectic Zr 50Cu 40Al 10 and hypoeutectic Zr 70Cu 6Al 8Ni 16 bulk metallic glasses (BMGs) was studied by electrochemical measurements, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Zr 50Cu 40Al 10 BMG was highly susceptible to pitting corrosion in naturally aerated 0.5 M NaCl solution at 30 °C. In contrast, Zr 70Cu 6Al 8Ni 16 BMG passivated spontaneously under the same condition. EDX results for Zr 50Cu 40Al 10 indicated that enrichment of Cu, Cl and O occurred in the pitted region, while for Zr 70Cu 6Al 8Ni 16 BMG, no significant difference was found in the surface composition from the specimens before and after immersion in the solution. XPS analysis including angle-resolved measurements for Zr 70Cu 6Al 8Ni 16 BMG revealed that zirconium cation (Zr 4+) was highly concentrated in both air-formed and passive films. Furthermore, the concentration of Zr 4+ ions after immersion for 24 h or more showed tendency to increase with decreasing take-off angle, indicating that the exterior part of the passive film consisted exclusively of zirconium oxyhydroxide. The high corrosion resistance of Zr 70Cu 6Al 8Ni 16 BMG was attributed to the formation of homogeneous and stable passive film enriched with zirconium.

Improving bacteria viability in metal oxide hosts via an alginate-based hybrid approach

A two-step process relying on cell encapsulation in alginate beads followed by inorganic gelation from colloidal metal oxides was successfully applied to the immobilization of Escherichia coli bacteria in the presence of boehmite and zirconium oxyhydroxide particles. In the case of the Al-based gel, the alginate bead obtained at low biopolymer content provides an efficient barrier against the encapsulation stress. In contrast, an increase in the alginate concentration together with the phosphate-induced mineralization of the biopolymer bead is found necessary to maintain the viability of entrapped bacteria in Zr-based gels. Diffusion studies using model molecular and colloidal species put in evidence that positively charged Zr-oligomers and ZrO2 nanoparticles may be involved in the cytotoxicity of the precursor solution. This optimization of the encapsulation process allows the first observation of E. coligrowth within such metal oxide–alginate hybrid gels. Results presented in this work give a clear evidence that sol–gel based cell encapsulation can now be envisioned within a wide variety of metal oxide hosts through the optimization of the pre-encapsulation environment.

Bacteria encapsulation in colloidal inorganic matrices: Is it a general method?

Zirconium oxyhydroxide nanoparticles prepared by an aqueous route were evaluated for Escherichia coli bacteria encapsulation. A low viability rate was measured 24 hours after immobilization that could be attributed to nanoparticle cytotoxicity. Moreover, the presence of glycerol, a long-term cell-preserving molecule, hindered gel formation, probably due to its adsorption on the nanoparticle surface. A comparison with boehmite and ferrihydrite gels previously synthesized following a similar aqueous colloidal route suggests that the generalization of this method will rely on a careful control of the nanoparticle surface reactivity and may require surface chemical modification.

Synthesis of biodiesel over zirconia-supported isopoly and heteropoly tungstate catalysts

The liquid-phase synthesis of biodiesel by transesterification of sunflower oil with methanol is carried out by using zirconia-supported isopoly and heteropoly tungstates (HPAs) as catalysts. The isopoly and heteropoly tungstate catalysts were prepared by suspending zirconium oxyhydroxide in water/methanol solution of ammonium metatungstate/silicotungstic acid, phosphotungstic acid (WO3/HPA loading, 15%) followed by drying and calcination at 750 °C. The catalysts were characterized by XRD, Raman spectroscopy, IR spectroscopy, NH3-TPD and FTIR pyridine adsorption spectroscopy. XRD results indicate that the presence of isopoly and heteropoly tungstates stabilizes ZrO2 in tetragonal phase. Raman and IR spectra of the catalysts show that tungstate species exist as zirconia-anchored octahedral mono-oxotungstate. The acidity measurements by NH3-TPD and FTIR pyridine adsorption spectroscopy show that zirconia-supported phosphotungstate has the highest total acidity and zirconia-supported isopoly tungstate has the highest Brønsted acidity. The zirconia-supported isopoly tungstate shows superior catalytic performance compared to zirconia-supported heteropoly tungstate catalysts. Under the reaction conditions of 200 °C and methanol/oil molar ratio 15, 15% WO3/ZrO2 calcined at 750 °C gave 97% conversion of oil. This catalyst also efficiently catalyzes methanolysis of other vegetable oils like mustard oil and sesame oil. The deactivated catalyst could be regenerated by calcination without appreciable loss in activity.

Sorption of phosphate ions on iron(III), zirconium(IV), and chromium(III) oxyhydroxides from aqueous electrolyte solutions

The adsorption of phosphate ions from aqueous solutions with an ionic strength of 0.5 on iron(III), zirconium(IV), and chromium(III) oxyhydroxide hydrogels has been studied as influenced by chloride and sulfate ions. Despite the high concentrations of chloride and sulfate ions, they do not inhibit phosphate adsorption on the hydrogels; they only slightly change the isotherm shape. In the range of equilibrium phosphate concentrations equal to 30–50 mmol/l, all isotherms for iron and zirconium oxyhydroxide gels signify the appearance of a second adsorption layer (two-step isotherms). Both steps are satisfactorily fitted by the Langmuir equation. The maximum adsorptions and adsorption constants have been calculated. For chromium oxyhydroxide gels, the intraduction of an electrolyte dramatically decreases the equilibration rate.

Thermal behaviour and catalytic properties towards propene combustion of zirconia modified by different first row transition metals

Zirconium oxyhydroxide was synthesized in the presence of different transition metals from the first row (Cr, Mn, Fe, Co, Ni, Cu) and calcined at two different temperatures 450 °C and 700 °C. Differential Thermal Analysis exhibits a delay in zirconia crystallization with high specific surface areas when the transition metal is associated with zirconium. Transition metals improved zirconia catalytic activity and selectivity in propene deep oxidation to CO 2 and H 2O. Catalytic activity enhancement was explained by the stabilization (total or partial) of zirconia tetragonal phase (evidenced by ambient and temperature programmed XRD studies) which leads to higher amount of anionic vacancies. The existence of reduction peaks (Temperature Programmed Reduction with hydrogen) in the temperature range of catalytic activity explained the better catalytic performances of Cr, Mn, Co and Cu samples compared to Fe- and Ni-based ones.