H3PO4 Aqueous Solution Research Articles

Osteoconductive TiO<sub>2</sub> Coating on Titanium Using Anodizing in High Content Phosphoric Acid

In this study, anodizing of Ti in the various concentration of H3PO4 aqueous solutions gave TiO2 films, and the osteoconductivity was examined using in vivo testing. In the anodizing treatment, anodizing potential of < 200 V was applied to the Ti substrate in H3PO4 aqueous solutions with the concentration of 0.1 to 14 M at 298 K. The coatings were evaluated using SEM, XRD, FT-IR and XPS. In in vivo testing, the coated samples were implanted in the rats’ tibia for 14 d to evaluate the osteoconductivity. In H3PO4 aqueous solutions with any concentration, anatase-type TiO2 films were obtained on the Ti substrate by anodizing. The crystallinity of anodized TiO2 films depended on the concentration of H3PO4 and sparking. In less than 2 M H3PO4, anatase with high crystallinity was formed. On the other hand, anodizing with sparking in more than 4 M H3PO4, gave low crystallinity anatase film. In in vivo testing, osteoconductivity of the coatings with low crystallinity anatase was much higher than that with high crystallinity.

Anodic Oxide Coatings on Ti Alloys and their Osteoconductivity

Titanium and Ti alloys are widely used as substitutional materials for natural bone because of their good biocompatibility, high strength, and high corrosion resistance. In our previous studies, TiO2 coating on Ti with Ra (arithmetical means of roughness) < 0.1 μm formed by anodizing had much higher osteoconductivity than that of pure Ti. It can be expected that TiO2 coating with fine surface can improve the osteoconductivity of Ti alloys. In this study, the effects on the osteoconductivity of TiO2 coatings on different kinds of Ti alloys were investigated by in vivo study. TiO2 coatings with Ra < 0.1 μm were formed on 4 kinds of Ti alloys (Ti-6Al-4V (Ti64), Ti-6Al-7Nb (Ti67), Ti-29Nb-13Ta-4.6Zr (TNTZ), Ti-13Cr-1Fe-3Al (TCFA)) using anodizing in H3PO4 aqueous solution. Surface properties of these coatings were evaluated using SEM, XRD, and XPS. In in vivo study, samples were implanted in rats’ tibia for 14 days, and then removed. Cross section of the sample was observed with optical microscope and bone-implant contact ratio (RB-I) at the interface between body tissue and bone was used as a parameter of osteoconductivity. Anatase type TiO2 coatings with Ra < 0.1 μm were uniformly formed on all of the Ti alloys by anodizing at low voltage. These oxide coatings contained the ions of other alloy elements. TiO2 coatings on Ti64 and Ti67 indicated high osteoconductivity similar to that of TiO2 coating on pure Ti. On the contrary, TiO2 coating on TNTZ and TCFA showed low osteoconductivity. It was thought that ions of alloy elements brought bad influence on the osteoconductivity of TiO2.

Formation of Amorphous TiO<sub>2</sub> Film on Ti Using Anodizing in Concentrated H<sub>3</sub>PO<sub>4</sub> Aqueous Solution and Its Osteoconductivity

Anodizing of Ti specimens were performed in concentrated H3PO4 aqueous solutions with a purpose to incorporate a large amount of phosphate ion into anodized coatings, and their osteoconductivity was evaluated in in vivo test. Ti specimens were anodized in 0.1­11M H3PO4 aqueous solutions up to 200V at a rate of 0.1V s11. Anodized coatings were evaluated with SEM, TEM, XRD, XPS, and laser microscope. Anodized specimens were implanted in rats’ tibia for 14 d, and then extracted. When anodized in concentrated (22M) H3PO4 aqueous solutions under spark discharge, crystallized anatase transformed to amorphous anatase by containing a large amount of PO4 in crystal lattice of TiO2. The amorphous anatase coatings had better osteoconductivity than the crystallized anatase coatings. It is not exactly clear what was the intrinsic factor for the high osteoconductivity, but the crystallinity of anatase and/or PO4 in the film is considered to be responsible for the difference in bone-forming ability of TiO2 films. [doi:10.2320/matertrans.M2011234]

チタン表面へのミクロレベルの表面粗さを制御した陽極酸化皮膜の作製と骨伝導性

The aim of this study was to elucidate the relationship between the surface roughness and osteoconductivity of anodized titanium surfaces. Before anodizing, titanium substrates with different surface roughness were prepared by wet-polishing. These substrates were anodized at various voltages in H3PO4 ,H 2SO4, and NaOH aqueous solutions, and their surface roughness was controlled simultaneously at the micron level. Surface roughness of these coatings was expressed with the arithmetical means (Ra). The osteoconductivity of anodized samples was evaluated by in vivo tests. In in vivo tests, samples were implanted in rats’ tibia for 14 d. Anatase type TiO2 films were formed on all of the anodized samples for in vivo tests. It was newly found that TiO2 film with small Ra value exhibited high osteoconductivity than that with high Ra value, especially when Ra value was 0:3 was not improved by anodizing, showing the same low osteoconductivity of as-polished samples. These tendencies were observed for all of the TiO2 films regardless of the type of electrolytes. [doi:10.2320/matertrans.M2011049]

Development of activated carbon from vine shoots by physical and chemical activation methods. Some insight into activation mechanisms

Activated carbons (ACs) are prepared from vine shoots (VS) by the method of physical activation in air, CO2 and steam atmospheres and by the method of chemical activation with H3PO4, ZnCl2 and KOH aqueous solutions. The ACs were characterized texturally by N2 adsorption at −196 °C, mercury porosimetry, and density measurements. The method of chemical activation has been proved to be more effective than the method of physical activation to prepare ACs with a well-developed porosity. ACs with high micro- and mesopore volumes are prepared with ZnCl2 and H3PO4. Using ZnCl2, the volume of micropores is 0.62 cm3 g−1 and the volume of mesopores is 0.81 cm3 g−1. A greater development of macroporosity is obtained by KOH activation. The volume of macropores is as high as 1.13 cm3 g−1 for the resulting AC. Yield of the process of preparation of the ACs is low for the method of chemical activation. Some insights into the performance of the activating agents in the activation process are provided.

Photocatalytic Activity of TiO<sub>2</sub> Loaded on HZSM-5 Zeolite Treated with Phosphoric Acid

HZSM-5 zeolite was prepared by treating of NaZSM-5 with phosphoric acid and used as support for TiO2 prepared by sol-gel method. Adsorption and photocatalytic activity of the zeolite, adsorption ability of the loaded TiO2, and the optimum TiO2 loading amount were studied. The maximum methyl orange adsorption rate was less than 1% in the range of HZSM-5 dosage from 0.01 g up to 0.07 g. After 30 min of irradiation, the photocatalytic activity of HZSM-5 under UV irradiation was only between 1.5% and 2.7%. Methyl orange reached its adsorption equilibrium after 20 min under stirring. Total adsorption on the supported material was less than 2% after adsorption equilibrium. The TiO2 loaded on HZSM-5 treated with 0.2 mol/l phosphoric acid presented the optimum activity. The TiO2/HZSM-5 photocatalyst loaded on HZSM-5 treated with 0.2 mol/l aqueous H3PO4 solution could remove 93% of the initial methyl orange after 2 h.

Osteoconductivity of Anodized Titanium with Controlled Micron-Level Surface Roughness

The aim of this study was to elucidate the relationship between the surface roughness and osteoconductivity of anodized titanium surfaces. Before anodizing, titanium substrates with different surface roughness were prepared by wet-polishing. These substrates were anodized at various voltages in H3PO4, H2SO4, and NaOH aqueous solutions, and their surface roughness was controlled simultaneously at the micron level. Surface roughness of these coatings was expressed with the arithmetical means (Ra). The osteoconductivity of anodized samples was evaluated by in vivo tests. In in vivo tests, samples were implanted in rats’ tibia for 14 d. Anatase type TiO2 films were formed on all of the anodized samples for in vivo tests. It was newly found that TiO2 film with small Ra value exhibited high osteoconductivity than that with high Ra value, especially when Ra value was <0.3 μm. In addition, the osteoconductivity of anodized samples with Ra/μm >0.3 was not improved by anodizing, showing the same low osteoconductivity of as-polished samples. These tendencies were observed for all of the TiO2 films regardless of the type of electrolytes.

Preparation of Calcium Hydroxyapatite Nanoparticles Using Microreactor and Their Characteristics of Protein Adsorption

The calcium hydroxyapatite Ca(10)(PO(4))(6)(OH)(2) (Hap) nanoparticles were prepared by using microreactor and employed these Hap nanoparticles to clarify the adsorption behavior of proteins. The size of Hap particles produced by the microreactor reduced in the order of a hardness of the reaction conditions for mixing Ca(OH)(2) and H(3)PO(4) aqueous solutions, such as flow rates of both solutions and temperature. Finally, the size of the smallest Hap nanoparticle became 2 × 15 nm(2), similar to that of BSA molecule (4 × 14 nm(2)). It is noteworthy that the smallest Hap nanoparticles still possesses rodlike shape, suggesting that particles are grown along c-axis even though the reactants mixed very rapidly in narrow channels of the microreactors. The X-ray diffraction patterns of the Hap nanoparticles revealed that the crystallinity of the materials produced by the microreactor is low. The FTIR measurement indicated that the Hap nanoparticles produced by microreactor were carbonate-substituted type B Hap, where the carbonate ions replace the phosphate ions in the crystal lattice. All the adsorption isotherms of acidic bovine serum albumin (BSA), neutral myoglobin (MGB), and basic lysozyme (LSZ) onto Hap nanoparticles from 1 × 10(-4) mol/dm(3) KCl solution were the Langmuirian type. The saturated amounts of adsorbed BSA (n(S)(BSA)) for the Hap nanoparticles produced by microreactor were decreased with decrease in the mean particle length, and finally it reduced to zero for the smallest Hap nanoparticles. Similar results were observed for the adsorption of LSZ; the saturated amounts of adsorbed LSZ (n(S)(LSZ)) also reduced to zero for the smallest Hap nanoparticles. However, in the case of MGB, the saturated mounts of adsorbed MGB (n(S)(MGB)) are also depressed with decreased in their particle size, but about half of MGB molecules still adsorbed onto the smallest Hap nanoparticles. This difference in the protein adsorption behavior was explained by the difference in the size and flexibility of three kinds of proteins. The reduction of n(S)(BSA) is due to the decrease in the fraction of C sites on the side face of each Hap nanoparticle; i.e., there is not enough area left on the nanoparticle surface to adsorb large BSA molecules even though the BSA molecules are soft and their conformations are alterable. The reduction of n(S)(LSZ) was explained by the reduction of P sites. Further, rigidity of the LSZ molecules was given another possibility of the depression of n(S)(LSZ) for the Hap nanoparticles. However, MGB molecules with small and soft structure were adsorbed on the Hap nanoparticle surface by changing their conformation. We could control the amounts of adsorbed proteins by changing the particle size of Hap in the nanometer range and kinds of proteins. These obtained results may be useful for developing biomimetic materials for bone grafts and successful surgical devices in the biochemical field.

Synthesis and hyperthermia property of hydroxyapatite–ferrite hybrid particles by ultrasonic spray pyrolysis

Biocompatible hybrid particles composed of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and ferrite (γ-Fe2O3 and Fe3O4) were synthesized using a two-step procedure. First, the ferrite particles were synthesized by co-precipitation. Second, the suspension, which was composed of ferrite particles by a co-precipitation method, Ca(NO3)2, and H3PO4 aqueous solution with surfactant, was nebulized into mist ultrasonically. Then the mist was pyrolyzed at 1000°C to synthesize HAp–ferrite hybrid particles. The molar ratio of Fe ion and HAp was (Fe2+ and Fe3+)/HAp=6. The synthesized hybrid particle was round and dimpled, and the average diameter of a secondary particle was 740nm. The cross section of the synthesized hybrid particles revealed two phases: HAp and ferrite. The ferrite was coated with HAp. The synthesized hybrid particles show a saturation magnetization of 11.8emu/g. The net saturation magnetization of the ferrite component was calculated as 32.5emu/g. The temperature increase in the AC-magnetic field (370kHz, 1.77kA/m) was 9°C with 3.4g (the ferrite component was 1.0g). These results show that synthesized hybrid particles are biocompatible and might be useful for magnetic transport and hyperthermia studies.

Absorption of ammonia on tantalum hydroxide synthesized by a hydrofluoric acid method

Ammonia is strongly absorbed on tantalum hydroxide prepared by ammonia neutralization of TaF7 2− or TaF6 − complexes. FTIR analysis of tantalum hydroxide shows a characteristic peak around 1,400 cm−1, attributed to NH4 +. TG and FTIR analyses show that the NH4 + decomposes at about 500 °C. The correct chemical formula of tantalum hydroxide prepared by ammonia neutralization of TaF7 2− or TaF6 − is thus TaO x (OH)5-x (NH4) x . This conclusion is also confirmed by TG and FTIR analysis of tantalum hydroxide treated with various concentrations of inorganic acid at room temperature. The NH4 + in tantalum hydroxide can be exchanged completely in aqueous HNO3 solution, and the weight loss of the resulting sample is ended at about 415 °C by TG analysis. The NH4 + can also be exchanged completely with aqueous H2SO4 solution; however, SO4 2− is weakly absorbed on the tantalum hydroxide. Finally, the NH4 + can be exchanged partially with aqueous H3PO4 solution; however, PO4 3− is strongly absorbed on the tantalum hydroxide.

Simultaneous determination of eight components in Polygonum orientale by ultra performance liquid chromatography(UPLC) method

In this study, a UPLC-PDA method for simultaneous determination of catechin(1), isoorientin(2), orientin(3), quercetin-3-O-(2"-O-alpha-rhamnopyranosyl)-beta-glucarono-pyranoside(4), taxifoliol(5), luteolin(6), quercitrin(7) and kaempferol-3-O-beta-D-glucoside(8) in Polygonum orientale in Guizhou province was developed. Analysis was performed at 45 degrees C, on ACQUITY UPLC BEH C18 column (2.1 mm x 150 mm, 1.7 microm), eluted with a gradient program of acetonitrile-0.1% H3PO4 aqueous solution as the mobile phases. The flow rate was of 0.30 mL x min(-1), and the detection wavelength was 260 nm. The method validation proved that the linearity, instrument precision, repeatability, intermediate precision and accuracy accorded with the requirement for anassay. The established method had been used for determination above eight components in twenty lots of P. orientale in different places and harvest time in Guizhou province, and the results showed that the chemical composition was basically the same in herbs, but there were some difference in content of the tested components. the contents of the tested ingredients were relatively high and stable in the sample collected in August.

Temperature Inhomogeneity during Multibubble Sonoluminescence

When a liquid is subjected to high-intensity ultrasound, bubbles are formed, grow, and implosively collapse. This phenomenon of acoustic cavitation generates both chemical reactions (i.e., sonochemistry) and the emission of light (i.e., sonoluminescence, SL). It is generally agreed that both sonochemistry and sonoluminescence result from the intense compressional heating of gas and vapor inside the collapsing bubbles, and the extraordinary temperatures and pressures thus created. The emission of light can occur either from a cloud of cavitating bubbles (i.e., multibubble sonoluminescence, MBSL), or in a carefully controlled standing wave acoustic field from a single isolated bubble (i.e., single-bubble sonoluminescence, SBSL). MBSL is more closely related to sonochemistry, and quantification of the conditions generated during MBSL can lead to a better understanding of sonochemistry. Measurement of atomic and molecular emission from volatile species during MBSL revealed effective temperatures of thousands of Kelvins created during bubble collapse. Little is known, however, about the origin of emission derived from nonvolatile species during MBSL. This emission is directly relevant to the observed sonochemistry of dissolved reactants. Extensive emission bands and lines have been observed both from aqueous and non-aqueous liquids during MBSL, and can be used as spectroscopic thermometers to quantify the conditions generated inside the collapsing bubbles. For example, the Swan bands of C2 , [8,14] excited-state metal atoms (e.g., Fe, Cr, Mo), and even excited state Ar emission have been used to measure the intracavity temperatures. Other nonspectroscopic methods have also been used to measure the temperatures of cavitating bubbles. No prior study, however, has reported simultaneous measurement of temperature from two or more independent emitting species, which would permit one to probe the homogeneity of the temperature profile generated in bubble clouds from spatial variance during acoustic cavitation. By examining the MBSL from aqueous H3PO4 solutions, we have observed ultrabright sonoluminescence, found strong molecular emissions from both OHC and POC radicals, and have succeeded in using both simultaneously as spectroscopic thermometers. There is a dramatic temperature inhomogeneity that is dependent on the location within the bubble cloud and is consistent with two distinct kinds of cavitating bubbles: those that collapse symmetrically and those that do not. H3PO4 is a strongly hydrogen-bonded liquid; it has a relatively high viscosity and low vapor pressure (ca. 2.4 Torr for 85%H3PO4). Interestingly, the vapor of H3PO4 consists of water molecules alone; there are no acid molecules present in the vapor over most concentrated H3PO4 samples, even at high temperatures. Thus, in the gas phase of H3PO4 , the only volatile component inside the bubbles is water vapor; the phosphoric acid molecules can be considered as nonvolatile species during MBSL. Ultrabright sonoluminescence from 85% H3PO4 saturated with noble gases can be observed by naked eye, even in a well-lit room, as shown in Figure 1.

Preparation of hydroxyapatite–ferrite composite particles by ultrasonic spray pyrolysis

Abstract Bio-compatible composite particles composed of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and ferrite (maghemite (γ-Fe2O3) or magnetite (Fe3O4)) were synthesized by two-step synthesis. In this work, co-precipitation method using aqueous solution of FeSO4 and FeCl3 was employed to synthesize γ-Fe2O3 and Fe3O4 particles. It was found that the resultant phase was changed by the molar ratio of FeSO4 and FeCl3, and optimal molar ratio to suppress the coexistence of α-FeOOH was FeSO4/FeCl3 = 2. The suspension composed of crushed ferrite particles, Ca(NO3)2 and H3PO4 aqueous solution with surfactant ultrasonically nebulized into mist and the mist was pyrolyzed at 500 °C to synthesize HAp–ferrite composite particles. The shape of the synthesized composite particle was round with dimple, and the particle size was around 0.5–3 μm in diameter. The composite particle showed saturation magnetization of 0.833 emu/g. Net saturation magnetization of the ferrite component was calculated to be 46.4 or 48.0 emu/g under the assumption that the ferrite was composed of γ-Fe2O3 or Fe3O4, respectively.

MORPHOLOGY CONTROL OF CERIUM PHOSPHATES VIA SOLUTION PROCESSES FOR NEW SUNSCREEN APPLICATION

Plate-like hydrated cerium phosphate, Ce2(PO4)2HPO4 · H2O , ca. 3 μm in diameter, was obtained by the hydrothermal reaction of Ce(SO4)2 in H3PO4 aqueous solution at 150–200°C. Ce2(PO4)2HPO4 · H2O transformed to CeP2O7–CePO4 mixture around 700°C while maintaining the plate-like morphology. Plate-like CePO4 and CeP2 O 7 were also synthesized as single phase by heating plate-like Ce2(PO4)2HPO4 · H2O at 700°C with cerium hydroxide and NH4H2PO4 , respectively. Plate-like cerium phosphates showed excellent comfort, absorption ability of UV-ray and lower oxidation catalytic activity than undoped ceria. The UV-shielding ability was in the order Ce2(PO4)2HPO4 · H2O &gt; CeP2O7 &gt; CeP2O7–CePO4 mixture &gt; CePO4 &gt; K0.8Li0.266Ti1.734O4.

SYNTHESIS OF PLATE-LIKE CERIUM PHOSPHATES AND THEIR PHOTOCHEMICAL PROPERTIES VIA SOFT CHEMICAL REACTIONS

Plate-like cerium phosphates have attracted attention because of their unique UV-shielding ability with low photocatalytic activity and excellent comfort when applied on skin. Plate-like hydrated cerium phosphate, Ce2(PO4)2HPO4·H2O, ca 3 μm in diameter, was obtained by the hydrothermal reaction of Ce(SO4)2 in H3PO4 aqueous solution at 200 °C for 3 h. Ce2(PO4)2HPO4·H2O transformed to CeP2O7-CePO4, mixture around 700 °C with the transcription of plate-like morphology. Plate-like CePO4 and CeP2O7 were also synthesized as single phase by heating plate-like Ce2(PO4)2HPO4·H2O with cerium hydroxide and NH4H2PO4, respectively. Plate-like cerium phosphates showed excellent comfort, absorption ability of UV-light and lower oxidation catalytic activity than undoped ceria. The UV-shielding ability of them was in the order Ce2(PO4)2HPO4·H2O > CeP2O7 > CeP2O7-CePO4 mixture > CePO4 > K0.8Li0.266Ti1.734O4.

Osteoconductive HAp and TiO2Coatings on Titanium using Hydro-process

AbstractHydroxyapatite (Ca10(PO4)6(OH)2, HAp) and titanium dioxide (TiO2, titania) are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants using hydro-processes and investigated thein vivoperformance. HAp coatings were formed on cp-titanium plates or rods by the thermal substrate method in an aqueous solution included 0.3 mM Ca(H2PO4)2and 0.7 mM CaCl2. In the formation of carbonate apatite coating, CaHCO3was added to the solution, and in HAp/gelatin and HAp/collagen composite coatings, acid-soluble collagen (Type I) was added. The coating experiments were conducted at 313-433 K and pH = 8 for 15 or 30 min. Titania films were formed on the titanium implants by anodizing at &lt; 100 V in 0.1 M H2SO4, H3PO4, and NaOH aqueous solutions at 298 K. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. And the surface roughness of titania coatings was measured. In in vivo evaluations, the coated rod specimens were implanted in rats femoral for 2 weeks, the osteoconduction on them was evaluated. Two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, RB-I, which was used for the evaluation of new bone formation, was significantly depended on the compound formed on titanium implants, and also the coating processes.

Deactivation of vanadia-based commercial SCR catalysts by polyphosphoric acids

Commercial vanadia-based SCR monoliths have been exposed to flue gases in a pilot-scale setup into which phosphoric acid has been added and the deactivation has been followed during the exposure time. Separate measurements by SMPS showed that the phosphoric acid formed polyphosphoric acid aerosols, which were characterized by particle number concentrations in the order of 1×1014#/m3 at 350°C and diameters <0.1μm. Three full-length monoliths have been exposed to flue gases doped with 10, 100 and 1000ppmv H3PO4 for 819, 38 and 24h, respectively. At the end of the exposure the relative activities were equal to 65, 42 and 0%, respectively. After exposure, samples of the spent monoliths have been characterized by ICP-OES, Hg-porosimetry, SEM–EDX and in situ EPR. The results showed that the polyphosphoric acids chemically deactivate the vanadia-based catalysts by decreasing the redox properties of the catalyst surface and by titrating the number of V(V) active species. When plate-shaped commercial catalysts have been wet impregnated with different aqueous solutions of H3PO4 obtaining P/V ratios in the range 1.5–5, the relative activity for the doped catalysts in the whole P/V range was 0.85–0.90 at 350°C. These results show that the presence of phosphor compounds in the flue gas may be much more harmful than indicated by simple wet chemical impregnation by phosphoric acid. The reason has been found in the nature of the polyphosphoric acid aerosol formed in the combustion process, which cannot be reproduced by the wet impregnation process.

OPTIMIZATION OF HYDROTHERMAL SYNTHESIS OF PLATE-LIKE HYDRATED CERIUM PHOSPHATES AND THEIR PHOTOCHEMICAL PROPERTIES

Plate-like hydrated cerium phosphate, Ce2(PO4)2HPO4•H2O, has attracted attention because of its unique UV-shielding ability with excellent comfort when applied on the skin. Optimization of preparation conditions of hydrated cerium phosphate is required to obtain medium size plate-like particles of 5-50 μm in diameter which provide good comfort for human skin. Plate-like hydrated cerium phosphate, ca 20 μm in diameter, was obtained by the hydrothermal reaction of Ce(SO4)2 in H3PO4 aqueous solution at 200oC for 3 h. The sample showed excellent comfort, absorption ability of light less than 450 nm of wavelength and lower oxidation catalytic activity than undoped ceria.

Effect of pretreatment method of activated carbon on the catalytic reduction of NO by carbon over CuO

The influence of pretreatment method of activated carbon (AC) made from coconut shell, on the NO reduction by AC over CuO was studied, in which AC was used as a reducing agent and pretreated by air oxidation or wet oxidation in the HNO3(N), H2O2(H), H2SO4(S) or H3PO4(P) aqueous solution. The results show that over the CuO catalyst, the reductive activity of air oxidized AC for NO increases with a rise of the air oxidation temperature of AC, and the order of the reductive activity of wet oxidized AC for NO is AC-H>AC-N>AC-S>AC-P. The surface chemical properties of these ACs were studied by XRD, TPD, Boehm titration and so on. The dispersion of CuO on AC can be improved by treating AC with the HNO3 or H2O2 aqueous solution. AC treated with H2O2 is an effective reducing agent for the reduction of NO over CuO, and the temperature of complete reduction of NO by AC-H is 270°C, which is 120°C lower than that by original AC. Both the high concentration of acidic oxygen groups and moderate amount of basic sites on AC-H help to increase the conversion of NO reduced by AC-H.

Phase development and photocatalytic ability of gel-derived P-doped TiO2

P-doped titanium dioxide (TiO2) nanoparticles were synthesized using a sol-gel method. The ethanol solution of Ti(OC2H5)4 was mixed with an aqueous solution of H3PO4 to undergo hydrolysis and polycondensation at 90 °C for 4 h. The resultant solids were centrifugally filtered, dried, and then calcined at different temperatures, followed by chemical and physical characterization. At an atomic ratio of P/Ti = 0.03, the formed P-doped TiO2 can preserve its anatase structure at 900 °C for 3 h, with no formation of other phases. Further increasing the P/Ti atomic ratio in the P-doped TiO2 may stabilize the anatase–TiO2 at even higher temperatures but may lead to the formation of TiP2O7 or (TiO)2P2O7. A test of photocatalysis showed that the P-doped TiO2 nanoparticles, with a P/Ti ratio = 0.03 and after being calcined at temperatures between 400 and 800 °C, can decompose ⩾98 mol.% of the methylene blue (MB) after 30 min of irradiation by 365-nm ultraviolet light, while P25 particles can only decompose 71 mol% of the MB.