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The controllable synthesis of rutile TiO2 single crystal particles with the preferential orientation of {111} facets still remains a scientific and technological challenge. Here, we developed a facile route for fabrication of rutile TiO2 nanorod crystals (RTiO2NRs) having high ratios of oxidative {111} to reductive {110} surfaces. RTiO2NRs were synthesized using a peroxo-titanium complex (PTC) approach, which was controlled by changing the Ti/H2O2 ratio. The thus obtained RTiO2NRs revealed a high tendency to agglomerate through orientation-dependent attachment along the {110} facets. This resulted in an increased {111}/{110} surface ratio and led to a markedly improved photocatalytic activity of RTiO2NR aggregates. The reported findings illustrate the rich potential of the herein proposed facile and energy-efficient synthesis of nanostructured rutile TiO2-based photocatalysts.

Developing highly efficient semiconductor metal oxide (SMOX) sensors capable of accurate and fast responses to environmental humidity is still a challenging task. In addition to a not so pronounced sensitivity to relative humidity change, most of the SMOXs cannot meet the criteria of real-time humidity sensing due to their long response/recovery time. The way to tackle this problem is to control adsorption/desorption processes, i.e., water-vapor molecular dynamics, over the sensor's active layer through the powder and pore morphology design. With this in mind, a KIT-5-mediated synthesis was used to achieve mesoporous tin (IV) oxide replica (SnO2-R) with controlled pore size and ordering through template inversion and compared with a sol-gel synthesized powder (SnO2-SG). Unlike SnO2-SG, SnO2-R possessed a high specific surface area and quite an open pore structure, similar to the KIT-5, as observed by TEM, BET and SWAXS analyses. According to TEM, SnO2-R consisted of fine-grained globular particles and some percent of exaggerated, grown twinned crystals. The distinctive morphology of the SnO2-R-based sensor, with its specific pore structure and an increased number of oxygen-related defects associated with the powder preparation process and detected at the sensor surface by XPS analysis, contributed to excellent humidity sensing performances at room temperature, comprised of a low hysteresis error (3.7%), sensitivity of 406.8 kΩ/RH% and swift response/recovery speed (4 s/6 s). [ABSTRACT FROM AUTHOR]

In this study, we report the influence of vanadium oxide (VO), as a photosensitive component, on the photoactivity of TiO2 nanotubes (TNTs). A series of TNTs of varying tube diameter were synthesized by the anodization of titanium foils at different voltages, while vanadium oxide was deposited on TNTs by wet chemical deposition. An improvement in the optical properties of nanotubes was observed after the deposition of vanadium oxide. An improvement in the optical properties (redshift in UV-Vis spectra) of TNTs and TNT/VO was noted. The photocatalytic activity was improved with increasing tube diameter, while it was weakened after the deposition of VO. Furthermore, photoactivity was investigated in photodiodes based on TNTs or TNT/VO and single crystals of CH3NH3PbI3. The photoelectric measurement revealed that different TNT diameters did not influence the I-V characteristic of the photodiodes, while the deposition of VO improved the photocurrent for smaller TNTs. [ABSTRACT FROM AUTHOR]

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Abstract: Nanostructural TiO2/modified multi-wall carbon nanotubes photocatalysts were prepared by hydrolysis of Ti(iso-OC3H7)4 providing chemical bonding of anatase TiO2 nanoparticles onto oxidized- or amino-functionalized multi-wall carbon nanotubes (MWCNT). The processes of functionalization of the MWCNT and the deposition of TiO2 influence the photocatalytic activity of the synthesized nanocomposites. The phase composition, crystallite size, and the structural and surface properties of the obtained TiO2/modified-MWCNT nanocomposite were analyzed from XRD, FEG-SEM, TEM/HRTEM and FTIR data, as well low temperature N2 adsorption. In the photocatalytic study, the TiO2/oxidized-MWCNT catalyst showed the highest and the TiO2/amino functionalized-MWCNT catalysts somewhat lower degradation rates, indicating that the enhancement of photocatalysis was supported by the more effective electron transfer properties of the oxygen- than amino-containing functional groups, which support the efficient charge transportation and separation of the photogenerated electron-hole pairs. [Copyright &y& Elsevier]

Unmodified farming carp (cyprinus carpio) scales were used as a biosorbent for the removal of Cd(II), Pb(II) and As(V) ions from aqueous solutions. The adsorption studies were conducted as a function of pH, contact time and temperature. The best sorption of cadmium, lead and arsenate ions was achieved for pH between 6.0 and 8.0. The adsorption data for cadmium, lead and arsenate at 20, 30 and 40 °C are fitted to Langmuir, Freundlich, Sips, Dubinin-Radushkevich (D-R), Jovanovic, Jovanovic-Freundlich (J-F), Temkin, Toth and Koble-Corrigan (K-C) isotherm models. Experimental data were used to model adsorption kinetics using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. The results showed that the adsorption of Cd(II), Pb(II) and As(V) ions onto carp scale followed the pseudo-second-order kinetic model. Thermodynamic parameters, including the Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) changes, indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 20-40 °C. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of the synthetic textile dye CI Basic Yellow 28 (BY28) in water, using a recently synthesized P160 TiO2-based catalyst, under Osram ultra-vitalux® lamp (300 W) light, was studied. The effects of the operational parameters, such as initial concentration of catalyst, initial dye concentration and pH, were studied. The salt effect (NaCl, Na2CO3, Na2SO4 and NaNO3) was also investigated. It was found that the optimal concentration of catalyst is 2.0 g L-1. A pseudo first-order kinetic model was illustrated using the Langmuir--Hinshelwood mechanism and the adsorption equilibrium constant and the rate constant of the surface reaction were calculated (KBY = 6.126 L mg-1 and kC = 0.272 mg L min-1, respectively). The photodegradation rate was higher in weak acidic than in high acidic and alkaline conditions. The presence of CO32- ions increased the photodegradation rate while Cl-, SO4-2 and NO3- decreased the reaction rate. The rate of photodegradation of BY28 was measured using UV--Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: A method for the preparation of efficient TiO2/multi-wall carbon nanotubes nanocomposite photocatalysts by precipitation of anatase TiO2 nanoparticles onto differently oxidized carbon nanotubes is presented. The precursor compound titanium(IV) bromide was hydrolyzed producing pure anatase phase TiO2 nanoparticles decorated on the surface of the oxidized carbon nanotubes. The oxidative treatment of the carbon nanotubes influenced the type, quantity and distribution of oxygen-containing functional groups, which had a significant influence on the electron transfer properties, i.e., the photocatalytic activity of the synthesized nanocomposites. The results of C.I. Reactive Orange 16 photodegradation in the presence of all the synthesized nanocomposites showed their better photocatalytic activity in comparison to the commercial photocatalyst Degussa P-25. [Copyright &y& Elsevier]

A novel adsorbents, 6-arm amino polyethylene glycol functionalized multiwall carbon nanotubes (PEG/MWCNT) loaded with α -FeOOH (Fe/PEG/MWCNT), and hybrid α -FeOOH/ α -MnO 2 nano-deposit (Fe-Mn/PEG/MWCNT) were used for As(V) removal. In a batch test, the influence of pH, contact time, initial ion concentration and temperature on adsorption efficiency was studied. Time-dependent adsorption was best described by pseudo-second-order kinetic model and Weber–Morris model which predicted intra-particle diffusion as a rate-controlling step of overall process. Competitive kinetic study in the presence of interfering ions shows low detrimental effect on both capacity and kinetic of As(V) removal. Thermodynamic parameters showed that the adsorption was spontaneous and endothermic processes. Influences of the pH, iron oxide loading and interfering ions were modeled by using Visual MINTEQ software. High adsorption capacities: 49.39 and 59.78 mg g −1 were obtained for Fe/- and Fe–Mn/PEG/MWCNT, respectively, and multi-cycle reusability indicated high applicability of obtained material. Two step removal process, in a batch study, was successfully performed by using PEG/MWCNT for cations removal in the first step, and Fe or Fe–Mn/PEG/MWCNT for As(V) removal in the second. [ABSTRACT FROM AUTHOR]

The photocatalytic efficiency of a recently synthesized TiO2 powder, denoted P160, for the degradation of the Dye C.I. Reactive Orange 16 in natural and artificial seawater was investigated in comparison to its efficiency in deionized water and the efficiency of a standard TiO2 powder, Degusa P25. It was shown that the photocatalytic efficiency of P160 was slightly higher than that of P25, probably due to slightly higher specific surface area, higher pore volume and larger pores of the powder P160. The efficiency of both photo-catalysts in natural and artificial seawater was significantly lower than in deionized water. The overall rate of dye degradation for both types of photo-catalysts was slightly higher in artificial seawater than in natural seawater, which shows the influence of organic compounds naturally present in seawater on the photocatalysts activity. A saturation Langmuir-type relationship between the initial degradation rate and the initial dye concentration indicated that adsorption plays a role in the photocatalytic reaction. The photodegradation rate constant, k, which represents the maximum reaction rate, had similar values for P25 and P160 in all types of water due to the similar properties of the photocatalysts. [ABSTRACT FROM AUTHOR]

Multi-wall carbon nanotubes (MWCNTs) was functionalized with 6-arm amino polyethylene glycol (PEG), and synthesized PEG-MWCNTs was used as adsorbent in order to study adsorption characteristics with respect to Cd(II), Pb(II) and As(V) ions. In batch tests, the influence of contact time, initial metal ion concentration and temperature on the ion adsorption on PEG-MWCNTs was studied. Adsorption of Cd(II), Pb(II) and As(V) on PEG-MWCNTs strongly depends on pH. Time dependent adsorption can be described by intra-particular Weber-Morris kinetic model, and adsorption process was modelled by Koble-Corrigan isotherm, respectively. The maximum adsorption capacities of Cd(II), Pb(II) and As(V) on PEG-MWCNTs, for initial concentration of 10 mg dm-3 and at pH=4, were 77.6, 47.5 and 13 mg g-1 at 25°C, respectively. The competitive adsorption studies showed that the adsorption affinity of ions towards PEG-MWCNTs showed largest adsorption of Cd(II) at pH 8, following by Pb(II) at pH 6, and As(V) at pH 4. Thermodynamic parameters showed that the adsorption of Cd(II), Pb(II) and As(V) ions was spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

The controllable synthesis of rutile TiO 2 single crystal particles with the preferential orientation of {111} facets still remains a scientific and technological challenge. Here, we developed a facile route for fabrication of rutile TiO 2 nanorod crystals (RTiO 2 NRs) having high ratios of oxidative {111} to reductive {110} surfaces. RTiO 2 NRs were synthesized using a peroxo-titanium complex (PTC) approach, which was controlled by changing the Ti/H 2 O 2 ratio. The thus obtained RTiO 2 NRs revealed a high tendency to agglomerate through orientation-dependent attachment along the {110} facets. This resulted in an increased {111}/{110} surface ratio and led to a markedly improved photocatalytic activity of RTiO 2 NR aggregates. The reported findings illustrate the rich potential of the herein proposed facile and energy-efficient synthesis of nanostructured rutile TiO 2 -based photocatalysts.