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Hiromasa Nishikiori - One of the best experts on this subject based on the ideXlab platform.
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water retentivity of Allophane titania nanocomposite films
Applied Catalysis B-environmental, 2020Co-Authors: Hiromasa Nishikiori, Mizuki Watanabe, Miku Nakase, Ayaka Kikuchi, Tomohiko Yamakami, Katsuya TeshimaAbstract:Abstract The water absorptivity and retentivity of titania as well as the water adsorptivity can be enhanced by its photoinduced hydrophilic conversion. The hydrophilic natural clay mineral, Allophane, can further enhanced such properties. Titania and/or Allophane nanoparticle-dispersing titania films were layered on glass plates by a simple sol–gel process. The influences of the Allophane amount and thickness of the Allophane-dispersing layer of the nanocomposite films on the hydrophilicity, water absorptivity, and water retentivity were investigated by measuring the contact angle of a water droplet, FTIR spectroscopy, and UV–Vis spectroscopy using a dye molecular probe. The hydrophilicity was enhanced by the UV irradiation and the Allophane dispersion. The Allophane nanoparticles also effectively increased the water absorptivity and retentivity. The FTIR spectra of the adsorbed water and UV–Vis spectra of the deposited dye were more suitable for the hydrophilicity evaluation of the film’s inside and surface, respectively, because the water molecules can penetrate deeper into the inside of the film (water absorption) than the dye molecules. The temperature on the film surface successfully decreased with increases in the irradiation time and the thickness of the Allophane-dispersing layer due to the enhancement of the water retentivity of the film’s inside by the endothermal process of water vaporization.
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Water retentivity of Allophane–titania nanocomposite films
Applied Catalysis B: Environmental, 2020Co-Authors: Hiromasa Nishikiori, Mizuki Watanabe, Miku Nakase, Ayaka Kikuchi, Tomohiko Yamakami, Katsuya TeshimaAbstract:Abstract The water absorptivity and retentivity of titania as well as the water adsorptivity can be enhanced by its photoinduced hydrophilic conversion. The hydrophilic natural clay mineral, Allophane, can further enhanced such properties. Titania and/or Allophane nanoparticle-dispersing titania films were layered on glass plates by a simple sol–gel process. The influences of the Allophane amount and thickness of the Allophane-dispersing layer of the nanocomposite films on the hydrophilicity, water absorptivity, and water retentivity were investigated by measuring the contact angle of a water droplet, FTIR spectroscopy, and UV–Vis spectroscopy using a dye molecular probe. The hydrophilicity was enhanced by the UV irradiation and the Allophane dispersion. The Allophane nanoparticles also effectively increased the water absorptivity and retentivity. The FTIR spectra of the adsorbed water and UV–Vis spectra of the deposited dye were more suitable for the hydrophilicity evaluation of the film’s inside and surface, respectively, because the water molecules can penetrate deeper into the inside of the film (water absorption) than the dye molecules. The temperature on the film surface successfully decreased with increases in the irradiation time and the thickness of the Allophane-dispersing layer due to the enhancement of the water retentivity of the film’s inside by the endothermal process of water vaporization.
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influence of Allophane distribution on photocatalytic activity of Allophane titania composite films
Applied Clay Science, 2017Co-Authors: Hiromasa Nishikiori, Shingo Matsunaga, Naoyuki Furuichi, Hitoshi Takayama, Koji Morita, Katsuya Teshima, Hiromi YamashitaAbstract:Abstract Allophane–titania composite films were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane as a nano-sized adsorbent. The composites of the titania dispersing the Allophane particles in the whole film efficiently degraded trichloroethylene and acetaldehyde better than the normal titania and the titania dispersing the Allophane only on the film surface. The titania dispersing the Allophane particles in the whole film produced lower amounts of the intermediate products in certain stages than the titania. These results are due to the effective reactant transport from the Allophane to titania. Photocatalytic degradation of glucose and photoelectrochemical measurements using an electrolyte solution containing glucose indicated that oxidative degradation of the glucose enhanced the generation of electricity during UV irradiation. A higher short circuit current was observed using the film dispersing the Allophane on the surface layer with an ca. 50-nm thickness than the titania and those dispersing the Allophane only on the film surface. Allophane effectively adsorbed the glucose molecules and transported them to the titania, then the products were desorbed into the liquid phase. Therefore, the holes were efficiently transported and consumed by the glucose oxidation.
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Influence of Allophane distribution on photocatalytic activity of Allophane–titania composite films
Applied Clay Science, 2017Co-Authors: Hiromasa Nishikiori, Shingo Matsunaga, Naoyuki Furuichi, Hitoshi Takayama, Koji Morita, Katsuya Teshima, Hiromi YamashitaAbstract:Abstract Allophane–titania composite films were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane as a nano-sized adsorbent. The composites of the titania dispersing the Allophane particles in the whole film efficiently degraded trichloroethylene and acetaldehyde better than the normal titania and the titania dispersing the Allophane only on the film surface. The titania dispersing the Allophane particles in the whole film produced lower amounts of the intermediate products in certain stages than the titania. These results are due to the effective reactant transport from the Allophane to titania. Photocatalytic degradation of glucose and photoelectrochemical measurements using an electrolyte solution containing glucose indicated that oxidative degradation of the glucose enhanced the generation of electricity during UV irradiation. A higher short circuit current was observed using the film dispersing the Allophane on the surface layer with an ca. 50-nm thickness than the titania and those dispersing the Allophane only on the film surface. Allophane effectively adsorbed the glucose molecules and transported them to the titania, then the products were desorbed into the liquid phase. Therefore, the holes were efficiently transported and consumed by the glucose oxidation.
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Photoelectrochemical properties of dye-dispersing Allophane–titania composite electrodes
Applied Clay Science, 2015Co-Authors: Hiromasa Nishikiori, Koji Morita, Katsuya Teshima, Naohiro Kanada, Rudi Agus Setiawan, Tsuneo FujiiAbstract:Abstract Dye-dispersing Allophane–titania composite electrodes were prepared from titanium alkoxide sols containing dye and Allophane. The photoelectric conversion properties of the electrodes were investigated by photoelectrochemical measurements. The photocurrent values in the UV range decreased with an increase in the Allophane content, whereas those in the visible range were increased by adding 1.0% (Al/Ti ratio) Allophane. As a small amount of Allophane nanoparticles were highly dispersed in the titania electrodes, the dye molecules were dispersed in the electrodes without decreasing the efficiency of the electron injection from the dye to the titania conduction band. The dye molecules dispersed on the titania nanoparticle surface were capped with Allophane nanoparticles which prevented desorption. The dye molecules strongly interacted with the titania nanoparticle surface and efficiently injected the excited electrons into the titania conduction band.
Tsuneo Fujii - One of the best experts on this subject based on the ideXlab platform.
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Photoelectrochemical properties of dye-dispersing Allophane–titania composite electrodes
Applied Clay Science, 2015Co-Authors: Hiromasa Nishikiori, Koji Morita, Katsuya Teshima, Naohiro Kanada, Rudi Agus Setiawan, Tsuneo FujiiAbstract:Abstract Dye-dispersing Allophane–titania composite electrodes were prepared from titanium alkoxide sols containing dye and Allophane. The photoelectric conversion properties of the electrodes were investigated by photoelectrochemical measurements. The photocurrent values in the UV range decreased with an increase in the Allophane content, whereas those in the visible range were increased by adding 1.0% (Al/Ti ratio) Allophane. As a small amount of Allophane nanoparticles were highly dispersed in the titania electrodes, the dye molecules were dispersed in the electrodes without decreasing the efficiency of the electron injection from the dye to the titania conduction band. The dye molecules dispersed on the titania nanoparticle surface were capped with Allophane nanoparticles which prevented desorption. The dye molecules strongly interacted with the titania nanoparticle surface and efficiently injected the excited electrons into the titania conduction band.
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reaction in photofuel cells using Allophane titania nanocomposite electrodes
Applied Catalysis B-environmental, 2014Co-Authors: Hiromasa Nishikiori, Rudi Agus Setiawan, Shun Hashiguchi, Masaaki Ito, Tsuneo FujiiAbstract:Abstract Allophane–titania nanocomposite electrodes for photofuel cells were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane. The electrochemical measurements indicated that the oxidative degradation of starch in the solutions and suspensions enhanced the generation of electricity during UV irradiation. CO2 was observed as the degradation product. A higher photocurrent was observed using the Allophane–titania nanocomposite electrode adsorbing a greater amount of the starch molecules. Allophane increased the capacity of the electrode to adsorb the starch molecules, even from the suspensions. This brought the molecules close to the titania nanoparticles, on which their oxidation induced the generation of electricity.
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Reaction in photofuel cells using Allophane–titania nanocomposite electrodes
Applied Catalysis B: Environmental, 2014Co-Authors: Hiromasa Nishikiori, Rudi Agus Setiawan, Shun Hashiguchi, Masaaki Ito, Tsuneo FujiiAbstract:Abstract Allophane–titania nanocomposite electrodes for photofuel cells were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane. The electrochemical measurements indicated that the oxidative degradation of starch in the solutions and suspensions enhanced the generation of electricity during UV irradiation. CO2 was observed as the degradation product. A higher photocurrent was observed using the Allophane–titania nanocomposite electrode adsorbing a greater amount of the starch molecules. Allophane increased the capacity of the electrode to adsorb the starch molecules, even from the suspensions. This brought the molecules close to the titania nanoparticles, on which their oxidation induced the generation of electricity.
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photofuel cells using Allophane titania nanocomposites
Chemistry Letters, 2012Co-Authors: Hiromasa Nishikiori, Rudi Agus Setiawan, Ayaka Kikuchi, Tomohiko Yamakami, Masaaki Ito, Tsuneo FujiiAbstract:Allophane–titania nanocomposite electrodes were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane. Electrochemical measurements indicated that the oxidative degrada...
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degradation of trichloroethylene using highly adsorptive Allophane tio2 nanocomposite
Applied Catalysis B-environmental, 2011Co-Authors: Hiromasa Nishikiori, Masaru Furukawa, Tsuneo FujiiAbstract:Abstract A highly adsorptive Allophane–TiO2 nanocomposite photocatalyst was prepared by dispersing nanoparticles of the natural clay mineral Allophane into a titanium alkoxide solution by the sol–gel method. During the photocatalytic degradation of trichloroethylene using the Allophane–TiO2 nanocomposite, emission of the intermediate product, phosgene, was drastically inhibited. Trichloroethylene was transformed into the intermediate products, phosgene and dichloroacetyl chloride, on the TiO2 during the UV irradiation. These compounds are rapidly adsorbed on the Allophane. The compounds then gradually degraded after diffusing to the TiO2.
Katsuya Teshima - One of the best experts on this subject based on the ideXlab platform.
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water retentivity of Allophane titania nanocomposite films
Applied Catalysis B-environmental, 2020Co-Authors: Hiromasa Nishikiori, Mizuki Watanabe, Miku Nakase, Ayaka Kikuchi, Tomohiko Yamakami, Katsuya TeshimaAbstract:Abstract The water absorptivity and retentivity of titania as well as the water adsorptivity can be enhanced by its photoinduced hydrophilic conversion. The hydrophilic natural clay mineral, Allophane, can further enhanced such properties. Titania and/or Allophane nanoparticle-dispersing titania films were layered on glass plates by a simple sol–gel process. The influences of the Allophane amount and thickness of the Allophane-dispersing layer of the nanocomposite films on the hydrophilicity, water absorptivity, and water retentivity were investigated by measuring the contact angle of a water droplet, FTIR spectroscopy, and UV–Vis spectroscopy using a dye molecular probe. The hydrophilicity was enhanced by the UV irradiation and the Allophane dispersion. The Allophane nanoparticles also effectively increased the water absorptivity and retentivity. The FTIR spectra of the adsorbed water and UV–Vis spectra of the deposited dye were more suitable for the hydrophilicity evaluation of the film’s inside and surface, respectively, because the water molecules can penetrate deeper into the inside of the film (water absorption) than the dye molecules. The temperature on the film surface successfully decreased with increases in the irradiation time and the thickness of the Allophane-dispersing layer due to the enhancement of the water retentivity of the film’s inside by the endothermal process of water vaporization.
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Water retentivity of Allophane–titania nanocomposite films
Applied Catalysis B: Environmental, 2020Co-Authors: Hiromasa Nishikiori, Mizuki Watanabe, Miku Nakase, Ayaka Kikuchi, Tomohiko Yamakami, Katsuya TeshimaAbstract:Abstract The water absorptivity and retentivity of titania as well as the water adsorptivity can be enhanced by its photoinduced hydrophilic conversion. The hydrophilic natural clay mineral, Allophane, can further enhanced such properties. Titania and/or Allophane nanoparticle-dispersing titania films were layered on glass plates by a simple sol–gel process. The influences of the Allophane amount and thickness of the Allophane-dispersing layer of the nanocomposite films on the hydrophilicity, water absorptivity, and water retentivity were investigated by measuring the contact angle of a water droplet, FTIR spectroscopy, and UV–Vis spectroscopy using a dye molecular probe. The hydrophilicity was enhanced by the UV irradiation and the Allophane dispersion. The Allophane nanoparticles also effectively increased the water absorptivity and retentivity. The FTIR spectra of the adsorbed water and UV–Vis spectra of the deposited dye were more suitable for the hydrophilicity evaluation of the film’s inside and surface, respectively, because the water molecules can penetrate deeper into the inside of the film (water absorption) than the dye molecules. The temperature on the film surface successfully decreased with increases in the irradiation time and the thickness of the Allophane-dispersing layer due to the enhancement of the water retentivity of the film’s inside by the endothermal process of water vaporization.
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influence of Allophane distribution on photocatalytic activity of Allophane titania composite films
Applied Clay Science, 2017Co-Authors: Hiromasa Nishikiori, Shingo Matsunaga, Naoyuki Furuichi, Hitoshi Takayama, Koji Morita, Katsuya Teshima, Hiromi YamashitaAbstract:Abstract Allophane–titania composite films were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane as a nano-sized adsorbent. The composites of the titania dispersing the Allophane particles in the whole film efficiently degraded trichloroethylene and acetaldehyde better than the normal titania and the titania dispersing the Allophane only on the film surface. The titania dispersing the Allophane particles in the whole film produced lower amounts of the intermediate products in certain stages than the titania. These results are due to the effective reactant transport from the Allophane to titania. Photocatalytic degradation of glucose and photoelectrochemical measurements using an electrolyte solution containing glucose indicated that oxidative degradation of the glucose enhanced the generation of electricity during UV irradiation. A higher short circuit current was observed using the film dispersing the Allophane on the surface layer with an ca. 50-nm thickness than the titania and those dispersing the Allophane only on the film surface. Allophane effectively adsorbed the glucose molecules and transported them to the titania, then the products were desorbed into the liquid phase. Therefore, the holes were efficiently transported and consumed by the glucose oxidation.
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Influence of Allophane distribution on photocatalytic activity of Allophane–titania composite films
Applied Clay Science, 2017Co-Authors: Hiromasa Nishikiori, Shingo Matsunaga, Naoyuki Furuichi, Hitoshi Takayama, Koji Morita, Katsuya Teshima, Hiromi YamashitaAbstract:Abstract Allophane–titania composite films were prepared from titanium alkoxide sols dispersing the natural clay mineral Allophane as a nano-sized adsorbent. The composites of the titania dispersing the Allophane particles in the whole film efficiently degraded trichloroethylene and acetaldehyde better than the normal titania and the titania dispersing the Allophane only on the film surface. The titania dispersing the Allophane particles in the whole film produced lower amounts of the intermediate products in certain stages than the titania. These results are due to the effective reactant transport from the Allophane to titania. Photocatalytic degradation of glucose and photoelectrochemical measurements using an electrolyte solution containing glucose indicated that oxidative degradation of the glucose enhanced the generation of electricity during UV irradiation. A higher short circuit current was observed using the film dispersing the Allophane on the surface layer with an ca. 50-nm thickness than the titania and those dispersing the Allophane only on the film surface. Allophane effectively adsorbed the glucose molecules and transported them to the titania, then the products were desorbed into the liquid phase. Therefore, the holes were efficiently transported and consumed by the glucose oxidation.
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Photoelectrochemical properties of dye-dispersing Allophane–titania composite electrodes
Applied Clay Science, 2015Co-Authors: Hiromasa Nishikiori, Koji Morita, Katsuya Teshima, Naohiro Kanada, Rudi Agus Setiawan, Tsuneo FujiiAbstract:Abstract Dye-dispersing Allophane–titania composite electrodes were prepared from titanium alkoxide sols containing dye and Allophane. The photoelectric conversion properties of the electrodes were investigated by photoelectrochemical measurements. The photocurrent values in the UV range decreased with an increase in the Allophane content, whereas those in the visible range were increased by adding 1.0% (Al/Ti ratio) Allophane. As a small amount of Allophane nanoparticles were highly dispersed in the titania electrodes, the dye molecules were dispersed in the electrodes without decreasing the efficiency of the electron injection from the dye to the titania conduction band. The dye molecules dispersed on the titania nanoparticle surface were capped with Allophane nanoparticles which prevented desorption. The dye molecules strongly interacted with the titania nanoparticle surface and efficiently injected the excited electrons into the titania conduction band.
Benny K.g. Theng - One of the best experts on this subject based on the ideXlab platform.
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The anti-inflammatory activity of natural Allophane
Applied Clay Science, 2014Co-Authors: Javiera Cervini-silva, Stephan Kaufhold, Antonio Nieto-camacho, Virginia Gómez-vidales, Benny K.g. ThengAbstract:Abstract This paper presents evidence of the novel anti-inflammatory properties of natural Allophane collected from New Zealand, Japan, and Ecuador. Allophanes were assessed by (i) the mouse-ear edema method using 12-O-tetradecanoylphorbol-13-acetate (TPA) as inflammatory agent; and (ii) the myeloperoxidase (MPO) enzymatic-activity method. After 4 h, applying 1 mg ear− 1 Allophane conveyed edema inhibition (EI; p ≤ 0.01) in up to 39%, while MPO content inhibition (CI) values surpassed 60%. Pearson's correlation analysis between EI and MPO data showed that edema was mediated by the migration of neutrophils at t = 4 h (p
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Catalytic wet peroxide oxidation of phenol over iron or copper oxide-supported Allophane clay materials: Influence of catalyst SiO2/Al2O3 ratio
Microporous and Mesoporous Materials, 2012Co-Authors: Elizabeth G. Garrido-ramirez, Benny K.g. Theng, Matte V. Sivaiah, Joël Barrault, Sabine Valange, Maria Soledad Ureta-zañartu, María De La Luz MoraAbstract:Allophane clay materials with SiO2/Al2O3 ratios of 1.0 (AlSi1) and 2.2 (AlSi2) were synthesized by a co-precipitation route and further impregnated with iron or copper species. The structure of the parent AlSi1 sample is similar to that of a typical Al-rich soil Allophane, while the parent AlSi2 material resembles the structure of a hydrous feldspathoid with a large interspherule surface, thereby exhibiting a high surface area. The ability of the various iron or copper-based Allophane samples to behave as efficient and stable catalysts in phenol oxidation using H2O2 was investigated in ambient conditions for the first time. Their structural and textural properties were determined by X-ray diffractometry, N2 adsorption-desorption at 77 K, electrophoretic mobility measurements, infrared spectroscopy, transmission and scanning electron microscopy, as well as by thermo-gravimetric analysis. The catalytic activity of the iron or copper oxide-supported Allophanes was markedly influenced by their SiO2/Al2O3 ratio and by their respective structure. The iron-based AlSi2 catalysts with tail-like structure and high surface area proved to be far more active than their corresponding AlSi1 counterparts. The highest catalytic efficiency in terms of total organic carbon abatement was obtained at 40 °C for the calcined iron oxide-supported AlSi2 Allophane sample, for which very low leaching level of iron species was noticed (0.37 mg L−1). By contrast, large differences in terms of catalytic efficiency (conversion rates) and stability were observed for the copper-based counterparts, thereby indicating that the iron oxide-supported Allophanes with a hydrous feldspathoid structure are highly active and stable in the catalytic wet peroxide oxidation of phenol
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ADENINE, ADENOSINE, RIBOSE AND 5'-AMP ADSORPTION TO Allophane
Clays and Clay Minerals, 2007Co-Authors: Hideo Hashizume, Benny K.g. ThengAbstract:We have investigated the adsorption of adenine, adenosine, ribose, and adenosine-5′-phosphate (5′-AMP) by Allophane at pH 4, 6 and 8. Adenine, adenosine and ribose gave similar isotherms, i.e. adsorption increased regularly with solution concentration and decreased in the order: pH 8 > pH 6 > pH 4. Allophane had a greater affinity for 5′-AMP than for adenine, adenosine or ribose. Further, the extent of adsorption for 5′-AMP increased in the order: pH 8 ≪ pH 6 ≈ pH 4. The adsorption of 5′-AMP at pH 4 and pH 6 was about 60 times greater than at pH 8. The strong adsorption of 5′-AMP accords with the well known high phosphate-retention capacity of Allophane and Allophane-rich soils. The experimental data may be rationalized in terms of the pH-dependent charge characteristics of the organic solutes and Allophane. The large propensity of Allophane to retain 5′-AMP is ascribed to ligand exchange between the phosphate of 5′-AMP and the hydroxyl of (HO)Al(OH2) groups, exposed at perforations on the wall of Allophane spherules, giving rise to a surface (chelation) complex. The high affinity of nucleotides for Allophane has implications for the possible role of Allophane in the abiotic formation of RNA-type polynucleotides although nucleotide ‘immobilization’ by surface complexation might hinder RNA oligomerization.
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Sorption of copper and cadmium by Allophane-humic complexes
Developments in Soil Science, 2002Co-Authors: Guodong Yuan, Benny K.g. Theng, H. J. Percival, Roger L. ParfittAbstract:We have investigated the sorption of Cu and Cd by Allophane and its complexes with a soil humic acid (HA), varying in carbon content from 14–123 g kg −1 . The sorption of Cu and Cd was measured at pH 5.0 and 5.5, using the batch technique and a single concentration (2mM) of Cu or Cd in the presence of LiClO 4 . The sorbed metals were partly desorbed by treatment with 0.1 M KNO 3 . Allophane sorbed 71 and 179 mmol Cu kg −1 at pH 5.0 and 5.5, respectively. By comparison, only 3 mmol kg −1 of Cd was sorbed at pH 5.0 and 9 mmol kg −1 at pH 5.5. Irrespective of pH, complex formation with HA led to a marked increase in Cu and Cd sorption. Indeed, sorption increased linearly with the amount of HA sorbed. Less than 20% of the sorbed Cu, and 49–94% of sorbed Cd, was desorbable by KNO 3 . Copper appears to be specifically sorbed by Allophane through coordination with exposed hydroxyl groups because sorption can occur even when Allophane was positively charged. Moreover, the sorption capacity for Cu increased with pH, and the majority of the sorbed Cu was not desorbable. In contrast, the sorption of Cd by Allophane largely occurs by electrostatic interactions. The relative contribution to metal sorption of Allophane and HA in Allophane-HA complexes was derived from the linear relationship between sorption and HA content of the complexes. The HA content at which there is an apparently equal (50/50) contribution of Allophane and HA to Cu sorption is 28 and 87 g C kg −1 Allophane at pH 5.0 and 5.5, respectively. Above these apparently “equal-contribution indicator” values the HA component in the complex contributes more to sorption than does the Allophane counterpart. For Cd the apparently “equal-contribution indicator” values are 1.9 and 5.2 g C kg −1 Allophane at pH 5.0 at pH 5.5, respectively. This observation has implications for soil management in terms of permissible loads for heavy metals and practical means of increasing the sorption capacity of soil.
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A 13C‐NMR study of the interactions of soil organic matter with aluminium and Allophane in podzols
European Journal of Soil Science, 1999Co-Authors: Roger L. Parfitt, Guodong Yuan, Benny K.g. ThengAbstract:Summary The stabilization of organic matter in soil by interaction with aluminium (Al) or Allophane is important in maintaining soil quality, and in retarding the decomposition of soil organic matter. Complexation of Al by soil organic matter may also ameliorate Al toxicity. Here we use 13C-NMR spectroscopy to assess the interaction of soil organic matter with both Al and Allophane in two poorly drained podzols containing only trace amounts of iron. The 13C-NMR spectrum of the subsoil of the Allophane-rich One Tree Point podzol shows an intense peak at 179 p.p.m., assigned to carbon in carboxylic acids. This peak shifts to 177 p.p.m. after removal of Allophane (11% of the soil mass) by treatment with HF. We infer that the carboxyl groups in the organic matter are bonded to structural Al on the surface of Allophane spherules. In the non-allophanic Te Kopuru podzol, on the other hand, the organic matter apparently interacts with Al ions in the soil solution. This soil also has more aromatic carbon and fewer carbons in carboxyl and carbohydrate structures than the allophanic sample. There is an indication that Allophane stabilizes carbohydrate groups as well as carboxyl groups.
Guodong Yuan - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and adsorption characteristics of hollow spherical Allophane nano-particles
Applied Clay Science, 2012Co-Authors: Fumitoshi Iyoda, Shuhei Hayashi, Shuichi Arakawa, Baiju John, Masami Okamoto, Hidetomo Hayashi, Guodong YuanAbstract:Abstract We synthesized three Allophanes from precursors by a hydrothermal reaction at 100 °C for 48 h. The precursors were formed from the solutions of Na 4 SiO 4 and AlCl 3 ⋅ 6H 2 O at different Si/Al molar ratios (0.5, 0.75, 1.0). The nanostructure of the synthetic Allophanes was compared with that of a natural Allophane from New Zealand by using X-ray diffractometry, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetry/differential thermal analysis, 29 Si and 27 Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), field emission electron microscopy, and pore-size distribution based on the Cranston–Inkley method. The propensity of the Allophanes to adsorb adenine and adenosine-5′-monophosphate (5′-AMP) was assessed by batch experiments. The adsorption data were fitted by the Freundlich equation and the adsorption parameters were discussed in relation to the properties of the natural and synthetic Allophanes. The adsorption capacity ( K f ) of the natural Allophane for 5′-AMP was three times that for adenine. The average K f value of the three synthetic Allophanes for 5′-AMP was more than twice that of the natural Allophane, possibly due to the higher purity of the synthetic Allophanes.
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Sorption of copper and cadmium by Allophane-humic complexes
Developments in Soil Science, 2002Co-Authors: Guodong Yuan, Benny K.g. Theng, H. J. Percival, Roger L. ParfittAbstract:We have investigated the sorption of Cu and Cd by Allophane and its complexes with a soil humic acid (HA), varying in carbon content from 14–123 g kg −1 . The sorption of Cu and Cd was measured at pH 5.0 and 5.5, using the batch technique and a single concentration (2mM) of Cu or Cd in the presence of LiClO 4 . The sorbed metals were partly desorbed by treatment with 0.1 M KNO 3 . Allophane sorbed 71 and 179 mmol Cu kg −1 at pH 5.0 and 5.5, respectively. By comparison, only 3 mmol kg −1 of Cd was sorbed at pH 5.0 and 9 mmol kg −1 at pH 5.5. Irrespective of pH, complex formation with HA led to a marked increase in Cu and Cd sorption. Indeed, sorption increased linearly with the amount of HA sorbed. Less than 20% of the sorbed Cu, and 49–94% of sorbed Cd, was desorbable by KNO 3 . Copper appears to be specifically sorbed by Allophane through coordination with exposed hydroxyl groups because sorption can occur even when Allophane was positively charged. Moreover, the sorption capacity for Cu increased with pH, and the majority of the sorbed Cu was not desorbable. In contrast, the sorption of Cd by Allophane largely occurs by electrostatic interactions. The relative contribution to metal sorption of Allophane and HA in Allophane-HA complexes was derived from the linear relationship between sorption and HA content of the complexes. The HA content at which there is an apparently equal (50/50) contribution of Allophane and HA to Cu sorption is 28 and 87 g C kg −1 Allophane at pH 5.0 and 5.5, respectively. Above these apparently “equal-contribution indicator” values the HA component in the complex contributes more to sorption than does the Allophane counterpart. For Cd the apparently “equal-contribution indicator” values are 1.9 and 5.2 g C kg −1 Allophane at pH 5.0 at pH 5.5, respectively. This observation has implications for soil management in terms of permissible loads for heavy metals and practical means of increasing the sorption capacity of soil.
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a 13c nmr study of the interactions of soil organic matter with aluminium and Allophane in podzols
European Journal of Soil Science, 1999Co-Authors: R.l. Parfitt, Guodong Yuan, B. K. G. ThengAbstract:Summary The stabilization of organic matter in soil by interaction with aluminium (Al) or Allophane is important in maintaining soil quality, and in retarding the decomposition of soil organic matter. Complexation of Al by soil organic matter may also ameliorate Al toxicity. Here we use 13C-NMR spectroscopy to assess the interaction of soil organic matter with both Al and Allophane in two poorly drained podzols containing only trace amounts of iron. The 13C-NMR spectrum of the subsoil of the Allophane-rich One Tree Point podzol shows an intense peak at 179 p.p.m., assigned to carbon in carboxylic acids. This peak shifts to 177 p.p.m. after removal of Allophane (11% of the soil mass) by treatment with HF. We infer that the carboxyl groups in the organic matter are bonded to structural Al on the surface of Allophane spherules. In the non-allophanic Te Kopuru podzol, on the other hand, the organic matter apparently interacts with Al ions in the soil solution. This soil also has more aromatic carbon and fewer carbons in carboxyl and carbohydrate structures than the allophanic sample. There is an indication that Allophane stabilizes carbohydrate groups as well as carboxyl groups.
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A 13C‐NMR study of the interactions of soil organic matter with aluminium and Allophane in podzols
European Journal of Soil Science, 1999Co-Authors: Roger L. Parfitt, Guodong Yuan, Benny K.g. ThengAbstract:Summary The stabilization of organic matter in soil by interaction with aluminium (Al) or Allophane is important in maintaining soil quality, and in retarding the decomposition of soil organic matter. Complexation of Al by soil organic matter may also ameliorate Al toxicity. Here we use 13C-NMR spectroscopy to assess the interaction of soil organic matter with both Al and Allophane in two poorly drained podzols containing only trace amounts of iron. The 13C-NMR spectrum of the subsoil of the Allophane-rich One Tree Point podzol shows an intense peak at 179 p.p.m., assigned to carbon in carboxylic acids. This peak shifts to 177 p.p.m. after removal of Allophane (11% of the soil mass) by treatment with HF. We infer that the carboxyl groups in the organic matter are bonded to structural Al on the surface of Allophane spherules. In the non-allophanic Te Kopuru podzol, on the other hand, the organic matter apparently interacts with Al ions in the soil solution. This soil also has more aromatic carbon and fewer carbons in carboxyl and carbohydrate structures than the allophanic sample. There is an indication that Allophane stabilizes carbohydrate groups as well as carboxyl groups.
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X-ray photoelectron spectroscopic characterization of Silica Springs Allophane
Clay Minerals, 1997Co-Authors: Cyril W. Childs, Benny K.g. Theng, K. Inoue, Haruhiko Seyama, Mitsuyuki Soma, Guodong YuanAbstract:A range of Allophane samples (atomic Al/Si bulk ratios 1.1-1.9) from Silica Springs, New Zealand, has been characterized by X-ray photoelectron spectroscopy (XPS). Binding energies of Si 2s, Si 2p, Al 2p, O 1s, C 1s, and N 1s electrons, together with the kinetic energies of Al KL 23 L 23 Auger electrons, at or near the surface of Allophane aggregates, have been derived The values for Al, Si and O electrons are similar to those for kaolinite but also to those for some framework silicates (feldspars) having 4-coordinate Al. Values for N electrons suggest that N occurs in organic structures. Comparison of XPS and bulk Al/Si ratios shows an enrichment of Al at or near the surface of Allophane aggregates. The same is true for C and N. Extraction with citrate-dithionite-bicarbonate (CDB) reagent leaves the surfaces depleted in Al. The CDB extracts have higher Al/Si ratios than the bulk Allophanes. Similarly, CDB treatment reduces the degree of surface enrichment of C and N. Small increases in the binding energies of Si electrons following CDB treatment suggest partial dissolution of the bulk structure though a concomitant removal of a separate phase or species cannot be ruled out. The results may be accounted for in terms of the structure previously suggested for the primary spherules of Silica Springs Allophane (Childs et al., 1990) though the composition of the spherules at or near the surface of the Allophane aggregates is different from those of the bulk.