Zirconium Hydroxide Research Articles

Preparation of a BTA–UIO–GO nanocomposite to endow coating systems with active inhibition and passive anticorrosion performances

Zirconium ions (Zr4+) react with hydroxide ions (OH−) to form a zirconium hydroxide (Zr(OH)4) passive film to protect the metal.

Dual-purpose high-efficiency air filter paper loaded with reactive zirconium hydroxide for the filtration aerosols and degradation of chemical warfare agents.

Traditional air filter papers can only filter toxic aerosols without the function of decontamination. If the poison stagnating in the paper is desorbed, it may pose a secondary threat to personnel and make it more difficult to dispose of the scrapped paper. Using an alkali-free glass fiber as the base material and zirconium hydroxide as the decontaminant, a self-decontaminating air filter paper that can degrade HD and VX simultaneously was successfully prepared by an intra-pulp addition method, with high filtration efficiency, low pressure drop and moderate tensile strength. The physicochemical properties were characterized by FE-SEM, EDX, XRD and TGA, and the results indicated that Zr(OH)4 was dispersed uniformly in the paper and filled in the interstices of the glass fiber. The preparation of the composite material had no impact on the structure of fibers and Zr(OH)4. The preparation technology of the self-decontaminating air filter paper was optimized. It was found that the paper with a fiber grammage of 50 g m−2, the adhesive of 2% and a Zr(OH)4 retention rate of 175.0 wt% could completely degrade HD and VX, whose conversion rate exceeded 99.0%, and had a tensile strength of 0.1193 kN m−1, a filtration efficiency of 99.995%, and a pressure drop of 313.6 Pa. Using GC-MS to detect the decontamination products, it was speculated that HD mainly underwent hydrolysis and elimination reactions, VX mainly underwent hydrolysis and polymerization reactions, and their products were non-toxic or low-toxic. The reaction kinetics of HD and VX on the paper was investigated and the half-lives were 2.6 h and 16.2 min, respectively, which demonstrated an outstanding degradation performance. This work manifested for the first time that the air filter paper can be optimized as an efficient self-decontaminating material, which will open up new possibilities for the design and manufacture of multifunctional protective materials.

Synthesis of 2-mercaptopropionic acid/hydrous zirconium oxide composite and its application for removal of Pb(II) from water samples: Central composite design for optimization

In this study, 2-mercaptopropionic acid was incorporated into hydrous zirconium oxide matrix to prepare 2-mercaptopropionic acid/ hydrous zirconium oxide (MPA/HZO) composite and applied to eliminate Pb(II) from aqueous environment. MPA/HZO was characterized by FTIR, TGA-DTA and SEM with EDX. Response surface methodology (RSM) was utilized for optimizing the independent variables affecting the uptake of Pb(II)). The maximum efficiency was reached at an equilibrating time of 40 min. At the optimum conditions (pH:6.8; contact time: 40 min; adsorbent dose: 0.016 g; initial concentration: 60 mg/L), 99.37% Pb(II) was successfully eliminated. Nonlinear regression analysis was applied for the investigation of isotherm and kinetic equations. Langmuir isotherm model with R2 > 0.99 was best fit model to demonstrate the adsorption of Pb(II) onto MPA/HZO. The maximum Langmuir adsorption capacity (qm) was 128.50 mg/g. Pseudo-second order kinetic model with R2 > 0.999 illustrated its best fitting to the kinetic data.

Transfer hydrogenation of furfural to furfuryl alcohol over modified Zr-based catalysts using primary alcohols as H-donors

Catalytic transfer hydrogenation is gaining increasing attention as a promising alternative to conventional hydrogenation with H2. In present work, a series of modified Zr-based catalysts were synthesized and tested for furfural catalytic transfer hydrogenation into furfuryl alcohol (FA). The results indicated that more than 13 % of furfural conversion and furfuryl alcohol yield could be achieved with modified zirconium hydroxide (mZrH) at 140 °C when compared with zirconium hydroxide (ZrH) using ethanol as H-donor and solvent in continuous flow regime, and the activity could be further enhanced by increasing the reaction temperature or Ru loading on the catalyst. The best result of 92 % furfural conversion with ∼99 % FA selectivity was obtained at 150 °C with 6% Ru/mZrH as catalyst, and the productivity of FA is 5.5 mmol g−1 h−1 which is 2 times higher than that reported with ZrH in batch. Moreover, long-term stability study of the catalysts indicated that 6% Ru/mZrH not only performs a better activity, but also a better stability than 6% Ru/ZrH. Characterizations of the catalysts by BET, XRD, EA, IR, SEM-EDS, XPS and CO2 adsorption indicated that zirconium hydroxide (ZrH) was successfully modified with hydroxylamine, leading to significantly change of its morphology and basic sites. And the deactivation of the catalysts was due to both the leaching of Ru and the deposition of side-products on its surface.

Performance analysis of hydrated Zr(IV) oxide nanoparticle-impregnated anion exchange resin for selective phosphate removal

The superior removal selectivity of hydrated zirconium oxide nanoparticle-impregnated porous anion exchange resin (ZAE) highlights its use as phosphate removal adsorbent. However, most research examines selective phosphate removal performance using randomly determined single content of hydrated zirconium oxide, and thus the use of the ZAE in real applications remains limited. Therefore, this study aimed to investigate the selective phosphate removal performance of ZAE with different content of hydrated zirconium oxide nanoparticle (HZO NP, represented by zirconium content) by considering various conditions. A molybdate intermediate method was devised to fabricate ZAE with high loaded HZO by weakening the Donnan exclusion to HZO precursors produced from the fixed positively charged host. Consequently, the resultant ZAE was characterized by 17.8 wt% of zirconium. ZAE exhibited an increased selectivity to phosphate against competing ions in the synthetic and simulated real water matrices for both batch and fixed-bed modes as the zirconium content of ZAE increased. High performance was retained, and regeneration led to possible reusability. The linear correlation between selective phosphate removal performances and zirconium content indicates that the zirconium content is a fundamental factor determining the ZAE phosphate adsorption removal. The HZO NPs within ZAE slow adsorption kinetics by blocking AE pores and provide specific adsorption sites for phosphate removal by inner-sphere complexation.

Facile synthesis of WOx/ZrO2 catalysts using WO3·H2O precipitate as synthetic precursor of active tungsten species

Zirconia-supported tungsten oxide (WOx/ZrO2) catalysts were successfully synthesized using a suspension containing amorphous hydrous zirconia precipitates [ZrOx(OH)4-2x·yH2O]n and tungstate monohydrate (WO3·H2O) precipitates. The procedure involved the dissolution of the WO3·H2O precipitate during the aging process with the release of oxyanion [WO4]2- species, interaction of this species with the surface of the [ZrOx(OH)4-2x·yH2O]n precipitate and, formation of active WOx species after thermal treatment. Non-bridging hydroxyl (OH−) groups present in the [ZrOx(OH)4-2x·yH2O]n precipitate act as an active agent for the WO3·H2O dissolution. N2 physisorption, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), temperature-programmed reduction using hydrogen (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD), Fourier-transform infrared (FTIR) spectroscopy of adsorbed pyridine, and Raman spectroscopy were used to elucidate the catalyst structure–performance relationship. The catalytic activity was evaluated for the oxidative desulfurization (ODS) of a model fuel containing dibenzothiophene (DBT). For a fixed WO3·H2O content, longer aging times improved the catalyst activity, reaching a maximum when WO3·H2O was completely dissolved. The increase in surface area and formation of more active Zr-WOx clusters and polytungstates are observed for the highest active catalysts. A synergetic effect between local Lewis and Brønsted acid sites seems to have contributed to the observed superior activity. The proposed strategy provides an efficient approach to produce active WOx/ZrO2 catalysts and may be applicable for designing other heterogeneous catalytic systems.

Catalytic behavior of the WOx-ZrO2 system in the clean selective oxidation of diphenyl sulfide (DPS)

WOx-ZrO2 (ZWx) based catalysts were prepared by equilibrium adsorption in basic condition (pH 10) with W content of 10.5, 19.7 and 27.0 wt.%, using hydrous zirconia [ZrO2(383)] as support. In order to determine the soluble fraction of W species which did not interact with the surface, samples were leached with NH3, dried and re-calcined [ZWx(NH3)y]. The W content was determined by spectrophotometric method, before and after the leaching. All catalysts were characterized by textural analysis (BET), X-ray diffraction (XRD) and Raman spectroscopy; the acidic strength was determined by potentiometric titration with n-butylamine.The catalytic behavior was analyzed for the selective oxidation of diphenyl sulfide (DPS) to diphenyl sulfoxide (DPSO) or diphenyl sulfone (DPSO2) using H2O2 as oxidizing agent. High conversion of DPS (∼100 %) and selectivity to DPSO2 (>90 %) at 60 min of reaction time were obtained for the ZWx series of catalysts. The ZWx(NH3)y series (W content: 3.65, 6.50 and 7.50 wt.%, respectively) also showed high selectivity to diphenyl sulfone but the maximum conversion (∼100 %) was achieved with reaction times longer (30 min) than those of the ZWx (10 min) samples.Polytungstate species strongly interacting with the support, identified by Raman spectroscopy in both series of samples, are considered the active phases.

Utilization of gel-type polystyrene host for immobilization of nano-sized hydrated zirconium oxides: A new strategy for enhanced phosphate removal

The urgent need for eutrophication control motivated the development of many novel adsorbents for enhanced phosphate polishing removal. Among these, zirconium-based nanomaterial was regarded as an effective kind because of its ability to bind phosphate specifically via inner-sphere complexation. In this study, we proposed a new strategy to improve the efficiency of zirconium oxides (HZO) nanoparticles by immobilizing them onto a gel-type anion exchange resin covalently attached with ammonium groups, denoted as HZO@N201. A previously developed macro-porous polymeric nanocomposite HZO@D201 was used for comparison. The immobilized nanoparticles in HZO@N201 were well dispersed in the gel matrix, manifesting smaller particle size and richer surface hydroxyl groups in comparison to HZO@D201. As a result of the structural merits in collective, HZO@N201 not only exhibited superior phosphate adsorptive capacity and affinity towards phosphate to HZO@D201, but also facilitate phosphate diffusion, based on isotherm, pH and kinetic tests. Mechanistic study by XPS and 31P SS-NMR substantiated the selective phosphate adsorption pathway as the formation of inner-sphere complexes by HZO@N201, which exhibited enhanced reactivity than HZO@D201. Lastly, fixed-bed runs of HZO@N201 was conducted, achieving an effective treatable volume of 2000 BV, which was 600 BV more than HZO@D201. Additional adsorption-regeneration cycle confirmed its reusability and potential for practical application. We believe the gel-type polymeric host could facilitate the formation and dispersion of smaller sized nanoparticles, exposing more surface hydroxyl groups highly accessible to phosphate. The results of this paper offer insights to a new strategy for immobilization of functional nanoparticles aiming at enhanced adsorptive removal of phosphate.

Zirconium Oxalates: Zr(OH)2(C2O4), (H11O5)2[Zr2(C2O4)5(H2O)4], and MM'[Zr(C2O4)3]·xH2O with M and M' = Ammonium, Alkali Metal, and Hydroxonium Ion H2n+1O n + (n = 2, 3, 4).

Crystallized powder of dihydroxide zirconium oxalate Zr(OH)2(C2O4) (ZrOx) was obtained by precipitation and the structure determined from powder X-ray data. The three-dimensional (3D) framework observed in (ZrOx) results from the interconnection of zirconium hydroxide chains 1∞[Zr(OH)2]2+ and zirconium oxalate chains 1∞[{Zr(C2O4)}2+]. Single crystals of (H11O5)2[Zr2(C2O4)5(H2O)4] (H2Zr2O5) were obtained by evaporation. The structure contains dimeric anions [Zr2(C2O4)5(H2O)4]2– connected through hydrogen bonds to hydroxonium ions (H11O5)+ to create a 3D supramolecular framework. The addition of ammonium or alkali nitrate led to the formation of single crystals of Na2[Zr(C2O4)3]·2H2O (Na2ZrOx3), M(H7O3)[Zr(C2O4)3]·H2O, M = K (KHZrOx3), M = NH4 (NH4HZrOx3), M(H5O2)0.5(H9O4)0.5[Zr(C2O4)3], M = Rb (RbHZrOx3), and M = Cs (CsHZrOx3). For the five compounds, the structure contains ribbons 1∞[{ZrOx3}2–] formed by entities Zr(C2O4)4 sharing two oxalates. In (Na2ZrOx3), the shared oxalates are in cis positions and the chain 1∞[Zr–Ox] is stepped with a Zr–Zr–Zr angle of 98.27(1)°. In the other compounds, the shared oxalates are in trans positions and the chains 1∞[Zr–Ox] are corrugated with Zr–Zr–Zr angles in the range 140.34(1)–141.07(1)°. In the compounds (MHZrOx3), the cohesion between the ribbons is ensured by the alkaline or ammonium cations and the hydroxonium ions (H7O3)+ for M = K, NH4, (H5O2)+, and (H9O4)+ for M = Rb and Cs. During the thermal decomposition of the alkaline-free zirconium oxalates (ZrOx), (H2Zr2Ox5), and (NH4HZrOx3), the formed amorphous zirconia is accompanied by carbon; the oxidation of carbon at about 540 °C to carbon dioxide is concomitant with the crystallization of the stabilized tetragonal zirconia.

Zirconium Hydroxide Cross-linked Nanocomposite Hydrogel with High Mechanical Strength and Fast Electro-Response

Electro-responsive hydrogel actuators have attracted considerable interest because of their low power usage and accurately modulated capability. However, they still have disadvantages such as their...

Efficient and selective removal of copper from aqueous solution by nanosized hydrated zirconium oxides loaded in vermiculite

Novel nanosized hydrated zirconium oxide (ZrO(OH)2) loaded in vermiculite (VMT) was successfully prepared and used to remove Cu2+ from aqueous solution. The adsorbent was characterized by XRF, XRD, SEM and TEM. The adsorption process of Cu2+ could reach equilibrium within 30 min and its kinetic data could be well described by pseudo-second-order model. The isotherm data could be described better by Langmuir model and the calculated maximum adsorption capacity was 96.23 mg/g. The adsorption of Cu2+ on nanosized ZrO(OH)2 loaded in vermiculite (NZV) was intensively affected by solution pH and different electrolytes. NaClO4 inhibited the adsorption of Cu2+, while NaCl and NaNO3 promoted the Cu2+ adsorption on NZV. The adsorption enhancement by NaNO3 was much significant than that of NaCl due to more ternary complexes forming among Cu2+, NO3- and the surface of NZV. The adsorption speed and capacity of Cu2+ were apparently reduced in the presence of Ni2+ in solution, while Cu2+ showed a higher affinity to adsorbent than Ni2+. The selective adsorption of Cu2+ in Cu-Ni mixed solution could be easily achieved in the presence of 0.8 mol/L of NaNO3, leading to 100% removal of Cu2+ and around 5% removal of Ni2+.

Zr(OH)4/GO Nanocomposite for the Degradation of Nerve Agent Soman (GD) in High-Humidity Environments.

Zirconium hydroxide, Zr(OH)4 is known to be highly effective for the degradation of chemical nerve agents. Due to the strong interaction force between Zr(OH)4 and the adsorbed water, however, Zr(OH)4 rapidly loses its activity for nerve agents under high-humidity environments, limiting real-world applications. Here, we report a nanocomposite material of Zr(OH)4 and graphene oxide (GO) which showed enhanced stability in humid environments. Zr(OH)4/GO nanocomposite was prepared via a dropwise method, resulting in a well-dispersed and embedded GO in Zr(OH)4 nanocomposite. The nitrogen (N2) isotherm analysis showed that the pore structure of Zr(OH)4/GO nanocomposite is heterogeneous, and its meso-porosity increased from 0.050 to 0.251 cm3/g, compared with pristine Zr(OH)4 prepared. Notably, the composite material showed a better performance for nerve agent soman (GD) degradation hydrolysis under high-humidity air conditions (80% relative humidity) and even in aqueous solution. The soman (GD) degradation by the nanocomposite follows the catalytic reaction with a first-order half-life of 60 min. Water adsorption isotherm analysis and diffuse reflectance infrared Fourier transform (DRIFT) spectra provide direct evidence that the interaction between Zr(OH)4 and the adsorbed water is reduced in Zr(OH)4/GO nanocomposite, indicating that the active sites of Zr(OH)4 for the soman (GD) degradation, such as surface hydroxyl groups are almost available even in high-humidity environments.

Thermodynamics of high‐temperature aluminum, zirconium, and yttrium hydroxide and oxyhydroxide vapor species

AbstractThermodynamic parameters are reported for gaseous hydroxides and oxyhydroxides of Al, Zr, and Y. The structures and vibrational frequencies are calculated using density functional theory with the B3LYP functional. This yields entropies at 298.15 K and heat capacities. The enthalpies are calculated from appropriate reactions and the CCSD(T) (Coupled Cluster, Singles, Doubles, and perturbative Triples) approach. The hydroxide groups are treated as hindered rotors for all species. The results are compared to the limited experimental and theoretical calculations for these species. Finally, the data are put into a database for a free‐energy minimizer and the vapor pressures for each species are compared.

Interfacial integration of zirconium components with amino-modified lignin for selective and efficient phosphate capture

Water pollution is becoming increasingly serious, and one of the main culprits is the excessive phosphate in aquatic systems. Herein, a flexibly prepared, environment-friendly sustainable and highly efficient bio-sorbent (AL-DETA@Zr) for phosphate capture was developed by diethylenetriamine-modified lignin integrated with zirconium hydroxide. The related properties and functional group changes of AL-DETA@Zr were investigated by multiple characterizations such as XRD, SEM, TGA, FTIR and XPS. According to a batch adsorption experiments, AL-DETA@Zr showed excellent thermal stability, fast adsorption rate for phosphate, and maximum sorption capacity of 167.7 mg/g. It was shown from the temperature experiments that the sorption process of phosphate over AL-DETA@Zr is endothermic and spontaneous. More importantly, it exhibited outstanding selective adsorption toward phosphate and anti-interference capability for co-existing anions. After three consecutive cycles, the sorption performance of AL-DETA@Zr did not decrease significantly, demonstrative of its excellent reusability under testing conditions. The mechanism of phosphate capture onto AL-DETA@Zr could be mainly ascribed to electrostatic attraction and ligand exchange. Accordingly, as-prepared AL-DETA@Zr would be a promising choice to remedy the excess phosphate in wastewater, due to its environment-friendly, high efficiency, excellent phosphate selectivity and mechanical stability.

Effects of chelating agents on the sol-gel synthesis of nano-zirconia: Comparison of the Pechini and sugar-based methods

This study focused on the comparison of the Pechini and sugar-based combustion synthesis methods to produce nano-zirconia. Zirconium hydroxide was utilized as metal precursor and citric acid, sucrose, and fructose were used as chelating agents, followed by calcination at 500, 600, and 700°C in air, respectively. Characterization was conducted by thermal analysis, specific surface area measurement, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning and transmission electron microscopy. When sucrose and citric acid were used as chelating agents during synthesis, mixtures of monoclinic and tetragonal phases were formed after calcination at 600 and 700°C. In the fructose samples, the tetragonal structure was the unique characterized phase. The tetragonal parameters in the fructose samples were determined using the diffraction data and the lattice parameter ratio was proven to increase with the temperature increase. Compared with the citrate and sucrose samples, the largest specific surface area (27 m2·g−1) and smallest particle size (39.1 nm) were obtained for the fructose sample after calcination at 700°C. The study revealed the formation of single-phase stabilized tetragonal zirconia using fructose as chelating agent after calcination at 500°C, and the presence and formation mechanism of stabilized tetragonal phase were also discussed on the basis of the X-ray and electron diffraction studies.

MEMBRANES MODIFIED BY NANOCOMPOSITES OF HYDRATED ZIRCONIUM DIOXIDE AND OXIDIZED GRAPHENE

Organo-inorganic membranes were obtained by impregnating ultrafiltration membranes with a composite modifier - zirconium (IV) hydroxide, containing oxidized graphene (0.5 wt.%). The modifier was precipitated in the active layer of the membrane, thus forming a "secondary active layer". The layer thickness calculated according to the Kozeny-Carman equation is 0.66-1.38 μm. A thinner layer is formed in the membrane with smaller pore size. The diffusion coefficients of Li+ and Na+ ions were found. The effect of the modifier on the retention ability relative to hardness ions (10-14%) and to protein compounds (95-98%) during filtration is determined. Mathematical modeling of the dependence of the permeate flux via time showed that the presence of ion exchanger particles in the polymer active layer prevents the accumulation of organic substances in the pores. Therefore, only the outer surface of the membrane is contaminated, and the precipitate can be easily removed mechanically. It was shown that insertion of a carbon component into pores of the membranes, in addition to the inorganic ion-exchangers, is advisable only in the case of a finely porous active layer. In particular, the performance of the initial polymer membrane (20 dm3/m3.h)) and the selectivity to the calibration substance with a molecular weight of 40 kDa (99%) serve as expediency criteria. In comparison with a membrane modified only with inorganic ion exchanger, selectivity is increased, the rate of filtration of protein solutions is higher, and resistance to contamination by organic substances is achieved. The results are discussed from the view of the hydrophobic-hydrophilic properties of oxidized graphene.

Development of a 225Ac/213Bi Generator with Two Inorganic Sorbents. Processes Involving Radionuclides of the 225Ac Subfamily

Scheme of a two-column 225Ac/213Bi generator using inorganic sorbents based on hydrated titanium oxide (JSC “Termoxid”) and hydrated zirconium oxide modified with nickel-potassium ferrocyanide (Termoxid, T-35) is suggested. 213Bi is obtained via a prolonged washing-out of 221Fr from the first column with T-5 sorbent containing 225Ac and its retention in the second column with T-35 for the decay and accumulation of 213Bi, which is extracted afterwards with a 1 M HCl solution. The direct-flow and circulatory schemes were tested, and the properties of the generator toward radionuclides of the 225Ac subfamily were determined in a wide range of flow rates and eluent volumes. It is assumed that the sorbents of the T-5 and T-35 brands are suitable for creating a 225Ac/213Bi generator with activity of hundreds of 225Ac mCi.

Insight into suppression performance and mechanisms of ultrafine powders on wood dust deflagration under equivalent concentration

Flame propagation characteristics of wood dust deflagration and suppression mechanism of ultrafine powders are investigated systematically. The deflagration reaction intensity of wood dust increases firstly and then decreases with the increase in dust cloud concentration. This is due to factors such as oxygen supply, positive feedback among flame characteristic parameters. Thus, there is an equivalent dust concentration for greatest deflagration intensity. Nano-sized ultrafine zirconium hydroxide (Zr(OH)4) and silicon dioxide (SiO2) powder are introduced to suppress wood dust deflagration at the equivalent concentration. It is found that Zr(OH)4 has a suppression effect of endothermic decomposition to generate zirconia (ZrO2), dilution of oxygen and absorption of free radicals; while SiO2 exerts suppression effect due to its high melting point and heat absorption. The suppression performance of Zr(OH)4 is better than that of SiO2. This is because that Zr(OH)4 and ZrO2 have a catalytic carbonization effect. It can not only improve thermal stability of wood particles by catalyzing production of high-temperature resistant residuals, but also promote the formation of catalytic sites to reduce crystallite size of carbon layer on wood particles surface, weakening heat and mass transfer between particles.

Highly Dispersed Ni Catalyst on Metal-Organic Framework-Derived Porous Hydrous Zirconia for CO2 Methanation.

We report the preparation of porous hydrous zirconia by treatment of zirconium-based metal-organic framework (MOF) UiO-66 with a strong base. Microporosity of the original MOF was partially retained in the resultant porous hydrous zirconia. NiII centers were then adsorbed onto the OH-rich hydrous zirconia and in situ converted to highly dispersed Ni0 for CO2 hydrogenation to CH4. The activated catalyst after an induction period showed a turnover frequency of 345 h-1 or a space-time yield of 5851 mmol·gNi-1·h-1 with a CH4 selectivity of over 99%. The catalyst was tested for 100 h on stream, showing only a 4% decrease in activity, and was found to convert atmospheric CO2 to CH4 via CO2 collection through Na2CO3/NaHCO3 cycling. Thermal decomposition of NaHCO3 released CO2 for hydrogenation to CH4, and the resultant Na2CO3 absorbed CO2 from air to form NaHCO3. This work highlights the opportunity in using MOFs as precursors to prepare highly porous metal oxide/hydroxide supports for solid-gas phase catalysis.

Removal of F− from Water Using Templated Mesoporous Carbon Modified with Hydrated Zirconium Oxide

Three types of MgO-templated mesoporous carbon possessing different specific surface area and pore size distribution were modified with hydrated zirconium oxide (ZrO2·xH2O) to prepare fluoride anion (F−) adsorbents. ZrO2·xH2O was synthesized through the auto-hydrolysis of zirconium oxychloride (ZrOCl2) in water under the coexistence of mesoporous carbon. X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS) indicated that the mesoporous carbon surfaces were coated with mainly amorphous ZrO2·xH2O. Capabilities of aqueous F− removal of the prepared adsorbents and the unmodified mesoporous carbons were compared. The F− uptake by the prepared adsorbents was larger than that observed using unmodified carbons, indicating that the F− adsorption capacity was improved through the ZrO2·xH2O coating. Moreover, the adsorption capability was found to depend on the pore size of the mesoporous carbons. The F− uptake decreased as pH of F− solution increased. Protonation and deprotonation of ZrO2 were found to affect the F− adsorption.