Titania Sol Research Articles

Novel ternary nanocomposite (TiO2@Fe3O4-chitosan) system for nitrate removal from water: an adsorption cum photocatalytic approach.

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe3O4), and titanium dioxide (TiO2) and its application for the removal of nitrates from model-contaminated water. Fe3O4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol-gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV-vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe3O4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe3O4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1h from 100ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg-1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5h when using an inlet concentration of 100ppm, bed height 12cm, and flow rate 5.0mlmin-1. A representative fixed-bed column adsorption experiment conducted using CTA-F3 beads for the treatment of a real groundwater sample shows reasonable results for nitrate removal (71.7% efficiency) along with a significant removal rate for the other anions as well. Thus, the novel adsorbent/photocatalyst developed is suitable for the removal of nitrates from water due to the synergistic effect between Fe3O4, chitosan, and titanium dioxide.

Investigation of antibacterial property of functionalized polypropylene nonwoven fabrics by S–N Co-doped nano-TiO2 films

This study focused on the antibacterial and ultraviolet protection properties of the functionalized polypropylene nonwoven fabrics (PPNWF). Sulfur and nitrogen co-doped titanium dioxide (S–N–TiO2) sol was synthesized by sol–gel method and S–N–TiO2 films were coated on the surface of PPNWF with impregnating method. The tensile strength, mass per unit area, thickness, whiteness, and glossiness of the prepared simples were investigated. The ultraviolet protection properties of the samples were assessed by ultraviolet transmittance spectrum and Ultraviolet Protection Facto. The results show that ultraviolet protection properties, tensile strength, and mass per unit area of the functionalized fabrics increase whereas its whiteness and glossiness decrease. The structural analysis and chemical composition of S–N–TiO2 were made by X-ray diffraction and X-ray photoelectron spectroscopy, which indicate the successful doping of S and N into TiO2. The results of Fourier transform infrared spectrometer and scanning electron microscopy show that S–N–TiO2 nano-films have been well dispersed on the surface of the PPNWF, which is beneficial to the ultraviolet protection property and antibacterial activity of the samples. The antibacterial activities were evaluated by shake flask method. It is found that the S–N–TiO2 nano-films coated PPNWF (S–N–TiO2/PPNWF) exhibit excellent antibacterial activities against both Staphylococcus aureus and Escherichia coli, and the antibacterial rate of 96.8% and 98.4% against Staphylococcus aureus and Escherichia coli, respectively. After 50 cycles of consecutive laundering, the antibacterial rates remain over 85.48% and 84.4% for Staphylococcus aureus and Escherichia coli, respectively. It indicates that the antibacterial performance of the S–N–TiO2/PPNWF fabrics is also durable.

Low-temperature synthesis of peptized TiO2 hydrosols with tunable surface charges for enhanced photocatalytic activity

Peptized titania sols offer numerous advantages, including uniform distribution, small particle size, good dispersibility in aqueous solutions, and strong interfacial adsorption capabilities. In this study, a novel insight into the systematic analysis of key parameters influencing the characteristics of peptized titania sols synthesized from the hydrolysis-peptization of titanium iso-propoxide (TIP) is presented. The article focuses on electrostatic stabilization, surface area dependent on various modifying conditions including H+/Ti molar ratio, solvent, pH, particle size distribution, peptizing temperature and ageing. The study also establishes the mobility of charges, facilitating charge accumulation on particle surfaces under different conditions. This resulting in enhancing electrostatic potential development in the solution, as indicated by the zeta potential value. Furthermore, the synthesized sols were used to investigate its photocatalytic performance by Methyl Violet and Rhodamine 6G organic dye degradation and other characterizations were performed to validate its properties.

Insights into the calcination temperature and loading amount of the catalyst support (TiO2) in the fibrous ceramic-based catalytic filter element prepared by microwave drying

The fibrous ceramic-based catalytic filter element (CFE) is a promising multifunctional material capable of simultaneously removing dust and NOx from hot gases. In this study, various calcination temperatures and titanium sols with different solid contents were used to prepare CFEs based on microwave drying, and their influences on the catalytic performance were experimentally investigated. The results showed that both the calcination temperature and the solid content of the titanium sol had important impacts on the catalytic activity. As the calcination temperature increased, the particle size, crystallite size, and average pore diameter of the loaded catalyst support (TiO2) increased, while the specific surface area decreased, ultimately resulting in a decline in the catalytic activity. However, a suitable calcination temperature ranging from 300 to 400 °C was required to achieve a good combination between the catalyst and the fibrous ceramic and a relatively uniform mesoporous structure. Furthermore, the increase in the solid content gave rise to a corresponding increase in the TiO2 loading amount, which increased the pressure drop and reaction surface area of the CFE. Excessive vanadium content caused by insufficient catalyst support induced side reactions of NH3 oxidation under high-temperature conditions, thereby reducing catalytic activity. Therefore, the preferred calcination temperature and solid content were set at approximately 300–400 °C and 8 wt%, respectively. The final prepared CFE demonstrated superior catalytic performance and adaptable gas velocity properties.

Construction of V2O5-WO3/TiO2 nanocones catalyst layer on SiC ceramic membrane for efficient removal of NO and dust

In this work, TiO2 nanocones grown on SiC membrane was used as the support of V2O5-WO3 species to prepare V2O5-WO3/TiO2@SiC (VWTi(C-X)@SiC) catalytic membrane for dust filtration and NH3-SCR denitration. On account of the large specific surface area, abundant surface acid sites and prominent redox property, the optimized VWTi(C-550)@SiC catalytic membrane shows >90% NO removal efficiency at the temperature of 280–360 °C, which are much higher than VWTi(P-550)/SiC catalytic membrane (TiO2 nanoparticles prepared by traditional vacuum coating titanium sol method was used as the support of V2O5-WO3 species, NO conversion <80% at whole tested temperature). Additionally, VWTi(C-550)@SiC displays superior stability during the SO2 + H2O resistance and 300 h long-term test at 300 °C, and exhibits an excellent dust filtration performance (2.5 μm SiO2 particles interception rate exceeded 99.99%) under all test conditions. More importantly, the structure of nanocones decrease the influence of tensile stresses due to the different thermal expansion coefficients of TiO2 and SiC membranes, which significantly suppress the fall of VWTi catalyst layer from the surface of SiC during pulse-jet cleaning. Among above results, it can be concluded that the optimized VWTi(C-550)@SiC catalytic membrane shows a prosperous application prospect for the simultaneously dust filtration and NH3-SCR denitration of medium–high temperature flue gas.

Titanium dioxide effect on the decolourisation of organic dyes Remazol Black B using electrocoagulation in situ-Fe2O3

ABSTRACT In this research, combination of TiO2 pillared clay with electrocoagulation in situ-Fe2O3 provides excellent performance to remove dyes water waste Remazol Black B(RBB). The best TiO2:clay ratio is 1:6, with highest degradation performance 89.8% in 30 minutes photodegradation process under UV light 254 nm. The excellent performance of pillared clay causes mesoporous pore that can be achieved by pillarisation of the clay layer using titanium dioxide sol which was made by diluting TiCl4 in ethanol solution. Besides, the excellent electrocoagulation performance was conducted by dual compartment system using 10ppm of RBB in the alkaline system containing 1 g NaCl as an electrolyte at potential apply+6 V with 98% degradation efficiency in 3 hours running compared to the 78% in single compartment system towards the formation of in situ-Fe2O3 that is directly driven by formation of intermediate species Fe(OH)3. This optimum decolourisation efficiency was gained at 0.1 A, pH 7.2 and 2 cm of inter-electrode distance. The power consumption was very low with the excellent and fast degradation performance towards organic dyes Remazol Black B, where this tandem cell can produce 100 mL clean water using 0.0052 kWh energy with cheaper cost operation.

Microwave‐Assisted Synthesis of SrTiO3 Nanocuboids without TiCl4

Strontium titanate (STO) nanocuboids are a novel support for Pt nanoparticle catalysts (Pt/STO). The first of many steps in commercializing Pt/STO will be developing a scalable, environmentally sustainable, and cost‐effective STO nanocuboid synthesis. Herein, Sr–Ti–OH mixtures are synthesized from various Sr2+ and Ti4+ reagents and treated by convection‐ and microwave‐assisted heating to obtain STO nanoparticles. These experiments clarify how phase composition of the prehydrothermal Sr–Ti–OH mixture and choice of heating method affect final nanoparticle morphology. In Sr–Ti–OH mixtures synthesized with TiCl4, STO is the most stable phase and precipitates prior to heating, while titania sol–gels are the most stable phase when other Ti4+ sources are used. STO nanocrystals always form when Sr–Ti–OH mixtures are treated by convection heating, though nanocuboids are only observed if STO precipitates from the Sr–Ti–OH mixture. Microwave‐assisted hydrothermal treatment more rapidly heats the precursor solution, and thus, STO nanocuboids can form from a variety of Sr–Ti–OH mixtures regardless of mixture composition. Two microwave syntheses of STO nanocuboids are reported: one which uses TiCl4 as a Ti4+ source, and another that uses titanium(IV) bis(ammonium lactato) dihydroxide ([NH4CH3CH(O)CO2]2Ti(OH)2), a water‐stable Ti4+ complex.

Water-Based Photocatalytic Sol–Gel TiO2 Coatings: Synthesis and Durability

The environmental impact of industrial technologies and related remediation methods are major research trend lines. Unfortunately, in the development of materials for wastewater treatment or air purification, hazardous reactants are often employed, reducing the overall beneficial contribution of such technology on the environment. We here synthesize stable titanium dioxide (TiO2) sols using a green route, with titanium tetraisopropoxide (TTIP) as precursor, water as solvent and acetic acid acting as catalyst, chelating agent and peptizing agent. The sol was deposited on glass by dip-coating and then analyzed using XRD, SEM and spectrophotometry. Wastewater purification ability was evaluated in the photocatalytic degradation of two organic dyes (Rhodamine B and Methylene Blue). Results on RhB showed &gt; 85% degradation in 6 h maintained along a series of 7 tests, confirming good efficiency and reusability, and 100% in 3 h on MB; efficiency mostly depended on calcination temperature and layer thickness. High photodegradation efficiency was found in nonannealed samples, suggesting TiO2 nanoparticles crystallization during sol–gel production. Yet, such samples showed a gradual decrease in photoactivity in repeated tests, probably due to a partial release of TiO2 particles in solution, while on calcined samples a good adhesion was obtained, leading to a more durable photoactive layer.

Industrial applications of sol-gel derived coatings.

Sol-gel derived coatings have many practical applications in different industries. In this paper, HI-GARD® hard coat, multi-layer antireflective coatings, and an anti-glare coating with organic particles are described. Optical and mechanical performances of these coatings are discussed in addition to adhesion properties. The HI-GARD® hard coat was dip or spin coated from a sol by hydrolyzing alkoxysilanes with water in an acidic condition. The hard coat acts as a protective coating for optical lenses with excellent optical properties with a Bayer ratio of 4.8 and an adhesion of 5B. The multi-layer antireflective coatings were prepared by incorporating titanium oxide sol into the HI-GARD® hard coat solution to obtain different layers by spin-coating with tunable refractive index. These two-layer or three-layer antireflective coatings increase transmittance by at least 3% compared to an uncoated glass substrate. Anti-glare coatings were spray-coated at room temperature on glass substrates by embedding cationic or anionic polystyrene particles in an acid-hydrolyzed silane sol. The anti-glare coating with organic particles can provide a significant glare reduction with a haze value of up to 13% for display surface without sparkling. In addition to these transparent coatings, non-transparent sol-gel derived coatings such as a sol-gel non-stick coating for cookware and bakeware, and two zinc-silicate protective coatings hydrolyzed from a silane with addition of zinc dusts for corrosion protection are also discussed briefly. The schematic structures of the hard coat on CR-39® substrate, three-layer AR coatings on glass substrate, and organic particle embedded anti-glare coatings on glass substrate, and their respective transmittance or reflective curves.

Preparation and Photocatalytic Performance of Hollow Spherical TiO2/Cu2O Composites

The anatase phase titanium dioxide sols were prepared by hydrothermal method using titanium sulfate as the titanium source. Copper acetate monohydrate was used as the copper source, cubic phase Cu2O with matched bandgap TiO2 was introduced to synthesize hollow spherical nano-TiO2/Cu2O composites by precipitation method. The powder samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area testing (BET), X-ray electron spectroscopy (XPS) and ultraviolet and visible spectrophotometry (UV–Vis) diffuse reflectance spectroscopy analysis using methyl orange (MO) solution as indicator. The results showed that the introduction of Cu2O did not affect the physical phase of TiO2. Titanium dioxide was a shuttle-shaped nanorod with an average particle size less than 20[Formula: see text]nm, Cu2O was a sphere with an average particle size greater than 400 nm. TiO2 loading results in smaller particle size, larger specific surface area, thinner spherical walls, increased hollowness, and improved adsorption and photocatalytic properties of spherical Cu2O. The optimum Ti content of TiO2/Cu2O nanocomposite was 4.0 wt.%, the maximum specific surface area of TiO2/Cu2O sample was 90.57 m2/g with particle size less than 150 nm. When TiO2/Cu2O sample with Ti content of 4.0[Formula: see text]wt.% was used as photocatalyst, the adsorption effect was 66.2% under the dark reaction at 60[Formula: see text]min, the degradation effect was 91.2% under visible light irradiation at 120[Formula: see text]min. The adsorption and photocatalytic performance were excellent when the TiO2/Cu2O sample with Ti content of 4.0[Formula: see text]wt.% was used as the photocatalyst. This work provides an effective method for photocatalytic treatment of waste liquids.

Transition metal nitride/oxide-based multilayer PVD coating with sol–gel derived ormosil passivation layer as an efficient solar absorber: Studies on high temperature stability and performance evaluation

We describe a hybrid multilayer solar absorber coating consisting of physical vapor deposited (PVD) Ti interlayer, aluminum titanium nitride (AlTiN) main absorber layer, aluminum titanium oxynitride (AlTiON) semi-absorber layer, aluminum titanium oxide (AlTiO) anti-reflection layer and sol–gel deposited ormosil passivation layer. The ormosil layer, which is essentially organically modified silica, also acts like an anti-reflection coating, thus, increasing the absorptance (α) of the multilayer stack to ∼ 0.950 (c.f., α = 0.930 for the PVD coating on stainless steel substrate) along with an emittance (ε) of 0.17@82 °C. Generally, pure inorganic sol–gel coatings like silica contain defects, which allow gases and corrosive substances to penetrate the coating/substrate interface, thereby, deteriorating the performance of the coating under extreme environments. However, the presence of an organic moiety in the inorganic network results in a dense microstructure with improved mechanical flexibility and hardness. We discuss in detail the effect of ormosil layer on the performance of the PVD deposited solar absorber coating. We report that the unique and stable microstructure of the ormosil layer helps in increasing the thermal stability of the underneath PVD coated solar absorber coating, particularly suitable for applications in concentrating solar collectors useful for solar steam generation.

Preparation and Application of Class A1 Flame Retardant Composite Material with Waterproof Properties

ABSTRACT The Class A1 flame retardant eco-material with excellent comprehensive properties is strongly needed to replace the low-level flame retardant products for potential applications in the building industry. In this work, modified titanium sol with the re-dispersible latex powder (VAE) is compounded to prepare non-combustible flame retardant composites. The optimal content of polylactic acid (PLA) is determined as 10 wt%. The results reveal that the addition of modified titanium sol has simultaneous improvements in flame resistance, water resistance, and mechanical properties of the composite material. The composites with 8 wt% modified titanium sol show low gross heat of combustion (0.646 MJ·kg−1) and low water absorption (4.26%), satisfying the enterprise standards. Besides, the flexural strength of the composites exhibited the maximum at 18.8 MPa. Structure observation discloses that the modified titanium sol promotes the formation of a three-dimensional network structure in the material and further forms a dense protective layer during combustion to inhibit burning. Overall results suggest that the composites with modified titanium sol as the Class A1 flame retardant composite will shed light on their promising applications in the construction industry.

Fabrication of Al2O3 supported TiO2 membranes for photocatalytic applications

A facile sol–gel spin coating process to synthesise mesoporous nanocrystalline Al2O3 supported TiO2 photocatalytic membranes performance has been reported. Titania sol containing lauryl lactyl lactate surfactant as a pore forming agent was employed to improve the porous structure of TiO2 materials. The sol was spin coated on Al2O3 support to synthesise TiO2/Al2O3 membranes. The composite membranes were dried and calcined. The above procedure was repeated for three times. The fabricated TiO2 composite membrane has been utilised for the photocatalytic degradation of methylene blue dye as a model pollutant. The highest percentage degradation of about 99.25% was observed at pH 12. Such membranes can be employed very efficiently in waste water treatment systems, separation of gases and liquid mixtures, treating microorganisms and also for self-antifouling action.

Microwave-assisted preparation of porous fibrous ceramic-based catalytic filter elements for the simultaneous removal of NO and dust from high-temperature gases

Different drying conditions and three types of porous fibrous ceramics with different contents and dispersions of the silica-based binder were used to prepare catalytic filter elements (CFEs) for the simultaneous removal of NOx and dust, and their effects on the catalytic performances were also investigated. The results indicated that the content and dispersion of the silica-based binder had a significant effect on the catalytic activity of the CFE. The removal of useless binder in the pores and the inhibition of binder agglomeration could improve the NO conversion. Compared with traditional electric heating blast drying, microwave drying effectively inhibited the migration of titanium sol so that the catalyst in the prepared CFE had good uniformity and dispersion. Meanwhile, microwave drying changed the morphology, crystal grain, and pore structure of the catalyst support (TiO2), ultimately increasing the specific surface area. Furthermore, this study also determined that the optimal average output power for microwave drying was 385 W. With a filtration velocity of 1 m/min, NO and NH3 inlet concentrations of 600 ppm, and an O2 content of 5 vol%, the prepared CFE achieved more than 98% NO conversion in the temperature range of 250 to 350 °C, and its highest conversion of 100% was achieved at 275–325 °C.

Self-cleaning, photocatalytic films on aluminum plates for multi-pollutant air remediation: promoting adhesion and activity by SiO2 interlayers

In recent years, nanoparticles have come under close scrutiny for their possible health and environmental issues, making them less attractive for photocatalytic applications in air or water purification. Replacing free nano-powders with active and stable films is thus a fundamental step towards developing effective photocatalytic devices. Aluminum represents a cheap and technologically-relevant substrate, but its photocatalytic applications have been hampered by adhesion issues and metal ion diffusion within the photocatalytic layer. In this work, the use of silica interlayers is investigated as a strategy to promote adhesion, efficiency and reusability of TiO2 films deposited on aluminum plates. Films were prepared from stable titania sols to avoid the use of nano-powders. Aluminum substrates with different surface morphology were investigated and the role of the silica interlayer thickness was studied. Films were extensively characterized, studying their structure, morphology, optical properties, adhesion and hardness. Self-cleaning properties were studied with respect to their superhydrophilicity and ability to resist fouling via alkylsilanes. Photocatalytic degradation tests were carried out using both volatile organic compounds and NO x , also in recycle tests. The presence of the silica interlayer proved crucial to promote the film robustness and photocatalytic activity. The substrate morphology determined the optimal interlayer thickness, especially in terms of the film reusability.

Experimental investigation of a unique solar photoelectrochemical hydrogen generating reactor for clean fuels

A new photoanode configuration utilizes the maximum light over daytime at any angle of the delivered rays due to its meshy dome design. This specific dome design of the photoanode is unique and helps increase the illumination electrode area, and the mesh type of configuration makes the rays reach inside the dome body better to increase the received sunlight at any angle of the solar rays. The mesh dome photoanode is manufactured of stainless steel and coated with titanium dioxide sol–gel solution using the dip-coating method. This photoanode is immersed in 0.1 M potassium dioxide solution with titanium mesh dome cathode and examined under the solar simulator at vertical light and 45° tilted light conditions. The present experimental measurements indicate that the highest hydrogen mass generation rate produced under the vertical light condition is 5.58 µg/s occuring at the photocurrent density of 1.62 mA/cm2. Moreover, the exergy and energy efficiencies that could be achieved at the vertical light condition are 0.81% and 1.17%, respectively. The enhancement of the hydrogen mass production rates that happens at tilted light conditions is varied between 75% and 80% of the enhancement by vertical light conditions. According to the experimental results, this photoanode design is effective during the daytime considering the angle of sun rays.

Hydrophobically modified cotton fabric assisted separation of oil-water mixture.

Superhydrophobic-superoleophilic fabrics were prepared and evaluated for oil-water mixture separation efficiencies. The nano-TiO2 and nano-SiO2 based coatings were done on the surface of the cotton fabric to create nanoscale roughness over the surface which was further modified by low energy material 1, 1, 3, 3-Hexamethyldisilazane (HMDS) and, polydimethylsiloxane (PDMS). Particle size and stability of prepared sol were characterized by particle size analysis and zeta potential. Coated cotton fabric samples were characterized by contact angle, contact angle hesteresis and surface free energy for its hydrophobic nature. Surface morphology was studied by scanning electron microscopy (SEM). The coated fabrics were found to be hydrophobic with low surface free energy values. The maximum contact angle was found to be 133° and lowest contact angle hysteresis was 5°. SEM confirmed the appearance of nanoscale surface roughness after coating of sols on cotton fabric. The average particle size and zeta potential values of silica sol was 61 nm and 137 mv whereas for titania sol it was found 344 nm and 200 mv, respectively. The oil-water separation efficiency of coated fabric was also observed by a different oil-water mixture. The coatings were found to be hydrophobic in nature and seem to be very useful for oil-water mixture separation.

Slot-Die Process of a Sol–Gel Photocatalytic Porous Coating for Large-Area Fabrication of Functional Architectural Glass

The slot-die process is an appealing technology for the fabrication of coatings on large-area substrates. However, its application on the production of photocatalytic coatings based on sol–gel formulations remains virtually unexplored. Thus, assessing the suitable formulation of the sol and operational parameters that allow one to yield high-efficacy photocatalyst coatings is a current challenge. This work aims to analyze the transferability of titania sol formulation optimized for dip-coating processes to slot-die technology. In this sense, firstly, the sol formulation is optimized by analyzing the influence of several types of surfactants on the microstructural features and photoactivity of TiO2 coatings’ growth on glass substrates. All formulations rendered a meaningful porosity and nanoscopic anatase crystallites (11–15 nm) with optical band gap values close to the expectation (3.25–3.31 eV). Accordingly, the performance of the photocatalytic dye degradation was closely related to the porosity and crystallite size led by each titania sol, and no meaningful differences were found between the results provided by the coatings developed by dip-coating and the slot-die method, which demonstrates the capability of the latter for its application on a large-scale fabrication of photocatalytic coatings.

Synthesis, Structure, Optic and Photocatalytic Properties of Anatase/Brookite Nanocomposites

Anatase/brookite nanocomposites were fabricated by the classical method of hydrolysis, additionally using hydrothermal treatment of preformed titanium dioxide sol with tetrabutyl orthotitanate. The influence of hydrothermal processing the buffer solution of TiO2 synthesis on the average particle sizes, specific surface area, pore sizes distributions, optical and photocatalytic properties investigated by X-ray diffraction, low-temperature nitrogen adsorption and UV-Vis spectroscopy. It has been determined that the hydrothermal treatment of pre-prepared titania sol as hydrolysis product leads to rutile formation after annealing at 400°C. Respective model of forming anatase/brookite/rutile nanocomposites was proposed. The changes of bang gap energy of TiO2 were observed and explained by effect of change phase composition and particles size of nanocomposite particles. Methylene blue (MB) photo-oxidation reactions using titanium dioxide nanocomposite were analyzed. Maximal photocatalytic activity of MB oxidation was detected for material with the ratio of the titania phases (anatase : brookite : rutile – 2 : 2 : 1). Synergistic effect between crystallinity, phase ratio, morphology of oxide material, band gap and photocatalytic activity in the anatase/brookite nanocomposites was established.

A double anti-fouling mechanism established by self-assembly of TiO2 on F127 chains for improving the hydrophilicity of PES membrane based on RTIPS method

Novel polyethersulfone (PES) membranes with porous top surface and sponge-like structure based on reverse thermally induced phase separation (RTIPS) method modified by titania sol (TiO2 sol) and triblock copolymer (F127) were developed. The highlight of this work was that the self-assembly of TiO2 on F127 was obtained during the RTIPS membrane formation process. Properties of PES/TiO2/F127 membranes, which varied with TiO2 sol, F127 and coagulation water bath temperature, were investigated by cloud point, SEM, EDX, AFM, TGA, XPS, FRR, contact angle and so on. SEM morphologies revealed that homogeneous porous top surface as well as sponge-like structure appeared in the membrane prepared by RTIPS process, while dense skin surface and finger-like cross-section obtained from the membranes by NIPS method. As a result, the pure water flux, rm and porosity of the membranes by RTIPS method were higher than that by NIPS method. EDX results indicated that the agglomeration of titanium dioxide was avoided by sol gel process. The XPS data revealed that the self assembly of TiO2 on PEO segments in F127 alleviated the leakage of TiO2 from the modified membrane and then improved the hydrophilic stability of the membrane. The water contact angle illustrated that the addition of TiO2 and F127 improved the hydrophilicity of the membrane. Furthermore, the pure water flux recovery ratio of the modified membranes were higher (>79%) than that of pure PES membrane (61%). In a word, the permeability and anti-pollution performance of the PES/TiO2/F127 membrane could be improved by the addition of TiO2 sol and F127, moreover, RTIPS method was a superior method for membrane preparation.