TiO2 Hydrosol Research Articles

Polyimide/titanium dioxide self-cleaning nano-hybrid films with high photocatalytic properties

Self-cleaning films are considered an emerging paradigm of environmentally functional materials. Enhancing the photocatalytic activities of self-cleaning film is a viable strategy for improving its antifouling characteristics. In this work, a polyimide/titanium dioxide (TiO2) film (PI/TiO2) film was developed by casting a mixture of polyamic acid solution and TiO2 hydrosol with a subsequent thermal imidization. TiO2 with a concentration of 1, 3, and 5 ​wt% was successfully incorporated into the PI matrix and was equally distributed in nanometer size in the PI/TiO2 nano-hybrid films. The addition of TiO2 into the film significantly improved its catalytic performance as indicated by the photocatalytic degradation of methylene blue and resazurin solution, suggesting a good self-cleaning property for antifouling applications. In addition, the thermal and mechanical stability of the PI film were improved with the addition of TiO2. After eight cycles, the PI-TiO2 films also demonstrated excellent cycling stability. This study introduces a novel self-cleaning film family composed of PI/TiO2 nano-hybrid film and emphasizes the engineering potential of photocatalytic materials in the context of self-cleaning film.

Basic magnesium chloride whisker photocatalytic materials: Synthesis and toluene degradation efficiency

This study brings a novel magnesium oxychloride cement-based photocatalytic material. Basic magnesium chloride whisker (BMCW) was modified by nano-SiO2 to improve the loading capacity of TiO2 photocatalyst. Then, TiO2 was supported in BMCW/SiO2 to form the basic magnesium chloride whisker photocatalytic materials (BMCWPM). The effects of pH values and TiO2 supporting concentrations on physio-chemical properties and photocatalytic performance were investigated in detail. As TiO2 hydrosol pH value is about 7.55, the loaded BMCWPM has the best degradation efficiency on gaseous toluene. BMCWPM synthesized with 5 % TiO2 supporting concentration shows the best photocatalytic efficiency of unit TiO2, also shows an excellent photocatalytic cyclic stability, the photocatalytic degradation efficiency and reaction rate of gaseous toluene are exceeding 55 % and 22.7*10−7 mol/m2 min, respectively. This study provides a kind of photocatalytic material with high efficiency and durability, which is expected to apply in wall decoration materials for air purification.

Variation of self-cleaning performance of nano-TiO2 modified mortar caused by carbonation: From hydrates to carbonates

Evaluation and quantification of the effects of the carbonation process on photocatalytic activity are essential for the long-term functional assurance of nano TiO2 modified photocatalytic concrete. This work focuses on the photocatalytic self-cleaning performance variation of mortar containing different dosages of nano TiO2 hydrosol at different carbonization duration. The colourimetric analysis is used to evaluate the self-cleaning performances of carbonated mortar samples. The distribution areas of anatase TiO2, hydrates, and carbonates in the mortar surface are characterized by the Confocal Raman Microscopy. The data recorded during the 28 days of carbonation show that the self-cleaning performance of mortar surfaces features a recovery phenomenon during carbonation. The correlations between photocatalytic self-cleaning performance and the possible parameters are analysed. A predictive model is suggested to evaluate the influence of carbonation degree on the photocatalytic self-cleaning ability of nano TiO2 hydrosol modified mortar.

Self-cleaning and air purification performance of Portland cement paste with low dosages of nanodispersed TiO2 coatings

The strong agglomeration potential and poor re-dispersibility of nano TiO2 particles in powder form seriously affect the depollution and self-cleaning performances. The nano TiO2 particles in hydrosol form can be stably dispersed in aqueous solution, but the synthetic temperature influences the crystal pattern, stability, and hydrodynamic diameter of nano TiO2 particles. In this study, a stable and nano dispersed anatase TiO2 hydrosol is synthesized by hydrolysis of titanium isopropoxide, and the effects of synthetic temperature on physicochemical properties and stability of TiO2 hydrosol are discussed. The photocatalytic and self-cleaning performances of synthetic TiO2 hydrosol coating are characterized by the colour change rate of Rhodamine B and NOx conversion UV irradiation. Compared with a commercial nano TiO2 powder (Degussa P-25), the TiO2 hydrosol coating with very low dosages shows better photocatalytic and self-cleaning performances under the same experimental conditions.

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Nanodispersed TiO2 hydrosol modified Portland cement paste: The underlying role of hydration on self-cleaning mechanisms

The self-cleaning performance of photocatalytic cement paste is related to the dispersion of nano-TiO2 in the hardened matrix. This work aims to study the influences of Portland cement hydration on the self-cleaning behaviour of acidic anatase TiO2 hydrosol modified hardened Portland cement paste (HPCP), and the working mechanisms. The presence of TiO2 hydrosol results in the retardation of hydration at early age and better self-cleaning performance of HPCP. The additional surface defects of TiO2 in HPCP are the main reason of self-cleaning performance enhancement. The morphology and the pore size distribution of hydration products also contribute to the enhancement of self-cleaning performance by the surface electron capture effect, which are supported by the analyses of Confocal Raman Microscopy and Scanning Electron Microscope. A new mechanism is suggested to explain the role of photocatalytic property and cement hydration on the enhancement of self-cleaning performance of HPCP with different concentration of TiO2 hydrosol.

G‐C3N4/TiO2 Composite Film in the Fabrication of a Photocatalytic Air‐Purifying Pavements

The fabrication of a photocatalytic air‐purifying pavement with a facile loading route, long depolluting period, and excellent deNOx activity under weak solar irradiation is essential for ambient air purification. Herein, a promising methodology is developed relying on the exploitation of a graphitic carbon nitride/TiO2 (g‐C3N4/TiO2) composite hydrosol at room temperature. The TiO2 hydrosol can act as a source of photocatalyst and dispersant for g‐C3N4 during loading. The photoinduced hydrophilicity, adhesive force, and regeneration tests in the laboratory show the long‐term deNOx application potential of g‐C3N4/TiO2 coatings. Field studies indicate that the NO removal rate is 70.7% of g‐C3N4/TiO2‐coated pavement in the morning (07:00–10:00) and afternoon (17:00–19:00), at which times solar radiation is weakest. The deNOx efficiency is influenced by solar irradiation and traffic volume. The latter exerts a more significant influence on deNOx efficiency than the former. A desirable route in fabricating a photocatalytic air‐purifying pavement is provided and offers a promising photocatalyst suitable for outdoor environmental remediation.

Study of the Effect of Titanium Dioxide Hydrosol on the Photocatalytic and Mechanical Properties of Paper Sheets.

Different amounts of a stable aqueous TiO2 hydrosol were used to fabricate paper sheets having photocatalytic activity. The TiO2 hydrosol was prepared in aqueous medium using titanium butoxide as precursor and acetic acid as catalyst for the hydrolysis of titanium butoxide. An aging process at room temperature and atmospheric pressure was finally applied to obtain crystalline anatase TiO2 hydrosol. The effects of different TiO2 hydrosol loadings on the mechanical strength and barrier properties of modified paper sheets were investigated in detail. The photocatalytic behavior of TiO2-modified paper sheets was investigated as well using methylene blue (MB) as target pollutant.

Photocatalytic performance and dispersion stability of nanodispersed TiO2 hydrosol in electrolyte solutions with different cations

The existence of electrolytes in aquatic environment on the photocatalytic performance and coagulation of nanodispersed TiO2 hydrosol and the corresponding photocatalytic alteration were investigated by studying cations (Na+, K+, Ca 2+, Mg2+, and Al3+). The photocatalysis reactions of nano TiO2 with different dosages of electrolytes were measured by monitoring the degradation of Rhodamine B (RhB) under ultraviolet A (UV-A) irradiation over time. The results showed that the photocatalytic performance of TiO2 was improved by the presence of Al3+, while the performance was impaired by the other tested cations. The negative influences of divalent ions on the photocatalytic performance of TiO2 were more significant than monovalent ions. The TiO2 sol dispersed stable at nano scale at low concentration of electrolyte (<0.01 mol/L) with slight change of pH, and coagulated into micro sizes at high concentration of electrolytes (>0.1 mol/L) with larger increase or decrease of pH. The positive effects of Al3+ on the photodegradation rate of RhB might relate to the strong hydrolytic action of Al3+ in aquatic solutions. The photocatalytic processes of TiO2 in the presence of all ions followed the Langmuir-Hinshelwood model, and the reaction kinetic constant was increased with the decrease of pH caused by different cations. These work suggested a new perspective about the relationship between coagulation and photocatalytic performance of TiO2 hydrosols in electrolyte with hydrolysable cations, which demonstrated that TiO2 hydrosols may be suitable as photocatalysts in aquatic environments.

On Photocatalytic Activity of Systems of Titania/(Fe (II, III))-Type in Aqueous Suspensions

. The photocatalytic activity of three systems, promising for chemical water purification technologies, was experimentally compared, based on a combination of titanium dioxide/(Fe(II, III)), applying to the model oxidation reaction of methylorange organic dye in an aqueous medium. Herewith the cases of photocatalytic systems were investigated, which are based on: a) titania hydrosol obtained by hydrolysis of titanium isobutylate; b) a similar hydrosol with addition of Fe(III) ions; c) suspension of ilmenite powder based on FeTiO3. As a result of the investigation, the increase of the rate of destruction of methylorange by more than two times was found in the system with the introduction of a small amount of iron ions into initial suspension of the TiO2 hydrosol (at the obtaining a medium with the Fe3+ concentration up to 3.7 × 10–5 M). In the photocatalytic system, based on the suspension of pretreated (with suphation and calcination) ilmenite powder, enough high photocatalytic activity (the degree of methylorange decomposition up to 77 %) was measured but at a higher exposure than for the case of systems based on the TiO2 hydrosol. For the photocatalytic systems of the type being investigated, a possible mechanism of increasing their oxidative activity was briefly considered, which requires an additional physico-chemical analysis.

High-efficient biosorption of dye wastewater onto aerobic granular sludge and photocatalytic regeneration of biosorbent by acid TiO2 hydrosol.

In present study, aerobic granular sludge (AGS) was applied as a high-efficient biosorbent for dye wastewater treatment. The feasibility of acid TiO2 hydrosol as self-clean eluent for the regeneration of dye-loaded AGS and subsequently photo-catalytic degrade desorbed dyes was investigated. Acid TiO2 hydrosol was successfully synthesized and characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Batch sorption experiments suggested that methyl orange (MO) and crystal violet (CV) sorption onto AGS were both fitted well with Langmuir model, and the maximum adsorbed capacities of AGS for MO and CV were 741.6 and 323.6mg/g, respectively. Biosorbent regeneration experiment indicated that adsorbed dyes were successfully desorbed from dye-loaded AGS and subsequently degraded by a self-cleaning acid TiO2 hydrosol (pH at 2.0). It was found that the photodegradation times for MO and CV were 240 and 300min, respectively. Moreover, the AGS retained more than 50 and 70% of its original MO and CV adsorption capacity after the fourth cycle. The result implied that the integration of biosorption with self-cleaning desorption and photocatalytic degradation process could be applied as a feasible technique for dye wastewater practical treatment.

A sustainable and cost effective surface functionalization of cotton fabric using TiO2 hydrosol produced in a pilot scale: Condition optimization, sunlight-driven photocatalytic activity and practical applications

This paper aimed to develop a successful multi-functional finishing of cotton fabric with TiO2 hydrosol produced on a pilot-scale as a sustainable and cost-effective alternative to the market dominating nano TiO2 powders. The surface morphology, crystalline phase and photocatalytic activity of the finished fabric was evaluated and compared with those finished with two commercial nano TiO2 powders. The finished fabric was tested for its ability to decompose indoor formaldehyde and to self-clean three different stains under illumination. The results indicated that 130 °C is the optimal curing temperature to obtain the finished fabric with higher TiO2 loading and catalytic activity. Increasing the pH of the TiO2 hydrosol enhanced the TiO2 loading, however, led to a lower activity. The catalytic activity of the TiO2 hydrosol finished fabric was similar to or higher than that of finished fabric with nano TiO2 powders. The catalytic activity of the hydrosol finished fabric was found to be sunlight-driven and greatly dependent on weather conditions. This finished fabric shows excellent decomposition of indoor formaldehyde and self-cleaning performance on different stains under compact fluorescent or solar irradiation.

Assembly of 2D MXene nanosheets and TiO2 nanoparticles for fabricating mesoporous TiO2-MXene membranes

A simple and scalable method was proposed for the preparation of mesoporous membranes by assembling two-dimensional (2D) MXene nanosheets and TiO2 nanoparticles (NPs) on a macroporous support. MXene nanosheets were introduced into TiO2 hydrosol, and then the sol was transformed into gel for fabrication of mesoporous TiO2-MXene membranes. Characterization results confirmed that an assembled structure of TiO2-MXene nanosheets was formed, benefiting from the nanosheets as ‘floor tiles’, thereby successfully inhibited the sol infiltration to the porous support. As a result, the hydrosols could be directly coated on macroporous substrates (with only one single cycle of aging and calcination) such as a disc support with an average pore size of ~100 nm and a four-channel hollow fiber with an average pore size of ~ 00 nm. Filtration experiments revealed the resulted membranes, in particular of the hollow fiber TiO2-MXene membranes, had a narrow pore size distribution, desirable rejection characteristics of dextran and high water permeate flux. The 2D nanosheet assisted TiO2 NPs assembly proposed in this work promises a simple, feasible and scalable approach for fabricating high-performance mesoporous TiO2 membranes.

Tuning morphology and mechanical property of polyacrylamide/Laponite/titania dual nanocomposite hydrogels by titania

The tough polyacrylamide/Laponite/titania (TiO2) dual nanocomposite (NC) hydrogel was fabricated byin situradical polymerization of acrylamide (AAm) in the dispersion of Laponite and TiO2. TiO2nanoparticles were prepared by sol‐gel method and used as both the inorganic filler and multi‐functional crosslinking agent. The morphology of hydrogel was tuned as functions of the sodium hydroxide (NaOH) concentration and the ratio of Ti (mmol) to clay (g) (mmol Ti/g clay). SEM and HR‐TEM morphologies revealed that Laponite and TiO2tended to form a uniform and regular microstructure like peasecod in poly(acrylamide) (PAAm) matrix due to the synergistic effect between electrostatic interaction and covalent interaction when the concentration of NaOH used in TiO2hydrosol increased to 1 × 10−1mol/L. This homogeneous microstructure enhanced mechanical properties of hydrogel. The compression strength, modulus and fracture energy reached 2,107 kPa, 247 kPa, and 1,837 J/m2, respectively. The gels exhibited excellent fatigue resistance and good UV protective performance. It might have potential application in optical materials, wound dressing materials and tissue engineering scaffolds. POLYM. COMPOS., 40:E466–E475, 2019. © 2018 Society of Plastics Engineers

Swift sol–gel synthesis of mesoporous anatase-rich TiO2 aggregates via microwave and a lyophilization approach for improved light scattering in DSSCs

TiO2 aggregates (TAs) were prepared via combination of facile ‘microwave assisted sol–gel synthesis’ and ‘lyophilization based extraction.’ The rapid hydrolysis followed by peptization of titanium iso-propoxide was carried out under microwave irradiation to form TiO2 hydrosol at temperature as low as 90 °C in just 10 min. Further, lyophilization of the as-synthesized TiO2 hydrosol resulted in the formation of loosely packed TAs. The X-ray diffraction and Raman analysis confirmed the crystallinity of TAs with predominant anatase phase. The transmission electron microscopy images of TAs revealed the interlinked aggregated structure of ~10-nm-sized TiO2 nanoparticles. The scanning electron microscopy images further confirmed the agglomerated structure of TAs with the size ranging from 500 to 1000 nm, which composed of several TiO2 nanoparticles. In addition, the Brunauer–Emmett–Teller (BET) analysis of TAs revealed its mesoporous structure and high specific surface area of 95 m2/g. The photoanode films fabricated with TAs proved for its better dye intake and superior light scattering owing to its high surface area and comparable size with incident wavelength, respectively, which in turn significantly improves the light-harvesting ability. In comparison with standard P25 nanoparticle-based DSSCs, short circuit photocurrent density (Jsc) and photoconversion efficiency of TA-based DSSCs showed improvement up to ~35 % under simulated AM1.5 G illumination (100 mW/cm2).

Enhanced visible-light photocatalytic activity of a TiO2 hydrosol assisted by H2O2: Surface complexation and kinetic modeling

Although the complexation of H2O2 onto TiO2 particles can form a colored surface with enhanced visible-light photocatalytic activity, the properties and behavior of this complex (>Ti-OOH) have not been thoroughly characterized. In this study, rather than using TiO2 powder, a nanoscale TiO2 hydrosol was used because it is easily measured using spectrometric methods. The results indicated that the addition of H2O2 to the TiO2 hydrosol greatly enhanced the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Although the presence of O2 slightly affected the photocatalytic activity, the presence of dissolved H2O2 markedly enhanced the photocatalytic activity. Furthermore, the results demonstrated that the consumption of dissolved H2O2 may account for the decrease in MB degradation after repeated cycles. The kinetics of the formation of >Ti-OOH were examined using UV–vis spectroscopy and the stopped-flow spectral system, and the adsorption–desorption constant (714M−1) and the complex formation rate constants ((1.01±0.13)×104M−1s−1 and 14.1±1.2s−1) are reported for the first time. Based on the MB degradation and >Ti-OOH formation results, a kinetic model composed of well-known key reactions was established. By fitting the experimental data to the model, the forward and backward rate constants for the photo-excitation of >Ti-OOH were determined to be (3.5±0.9)×10−5s−1 and (6.1±2.0)×1013M−1s−1, respectively.

Low-toxic gelcasting of bulk porous silica with bi-modal pore structure and its application in TiO2 photocatalysts

Bulk porous silica with bi-modal pore structure was successfully prepared by low-toxic aqueous gelcasting using egg white and glutinous rice flour as foamers and industrial waste as silica raw material. Anatase TiO2 hydrosol with high photocatalytic activity was prepared by a water peptization method. The bulk porous silica-supported TiO2 catalysts as prepared by surface adsorption method showed excellent photocatalytic properties, with advantages of both porous silica supporter and TiO2 hydrosol, and did not require direct the use of nano TiO2 crystallites and can be readily and practically used in the degradation of pollutants, environmental remediation, and other applications.

Statistical optimization of Basic Blue 41 dye biosorption by Saccharomyces cerevisiae spent waste biomass and photo-catalytic regeneration using acid TiO2 hydrosol

Abtract Factorial experiments with five factors; stirring rate, process time and temperature, initial dye concentration and biosorbent dosage at three levels were conducted based on central composite design of experiments to investigate their effect on Basic Blue 41 dye biosorption onto bioethanol fermentation spent waste biomass of Saccharomyces cerevisiae . A highly statistically significant quadratic model at 95% confidence level ( p R 2 0.9612 a n d R adj 2 0.9386 ) was developed to charcterize the influence of these variables on biosorption effeciency. Response surface methodology was employed to optimize the process, recording maximum biosorption % of ≈94% (23.5 mg/g) under static condition, within 14 h at 20 °C using 0.6% biosorbent in an initial dye solution of 150 mg/L. Approximately 92% of adsorbed dye was desorbed by elution with self-clean acid TiO 2 hydrosol (pH 2) and the regenerated biosorbent was employed for four successive cycles. The photo-catalytic degradation of the desorbed dye under ultraviolet illumination (8 W) followed the pseudo first order kinetic model ( R 2 0.9687) with apparent rate constant K app of ≈0.0043 min −1 . The proposed integrating biosorption with self-clean desorption and photo-catalytic degradation process, resulted in no secondary pollution in the form of any concentrated wastes, thus has important environmental and economic aspects.

Modified colloidal sol–gel process for fabrication of titania nanofiltration membranes with organic additives

A modified colloidal sol–gel process with organic additives was proposed for the fabrication of TiO2 NF membranes with a MWCO of ~820Da and a water permeability of ~8L/(m2hbar). The properties of the TiO2 materials were greatly influenced by the modified route denoted Route B, but little difference was detected in the materials synthesized via the traditional route denoted Route A. For the TiO2 materials prepared using Route B, the DLS analysis showed that the particle size of the TiO2 hydrosol decreased as the amount of organics increased; the XRD patterns and TEM images confirmed the role of additives in restraining the TiO2 grain growth and A→R transformation. This behavior may be explained by the lower packing and ordering of the nanoparticles, which would inhibit rearrangement among the nanoparticles and slow both the grain growth and phase transformation. After comparing the N2 adsorption–desorption results, the TiO2 material with 90dwb% glycerin was optimized for forming NF membranes. Small organics were better for this process than larger ones. Finally, the TiO2 NF membranes were fabricated using Route B, and the resultant membranes showed better retention properties compared to those of the TiO2 membranes fabricated via Route A.

Non-UV Driven Self-Cleaning and Anti-Fogging Glasses Prepared by Ultrasonic Nebulization of TiO&lt;sub&gt;2&lt;/sub&gt; Hydrosol

Highly transparent glasses coated with TiO2 hydrosol and polyethylene glycol (PEG) have been successfully fabricated via ultrasonic nebulization technique. Experimental evidences have indicated that the obtained glass surfaces show excellent non-UV activated superhydrophilic wetting and antifogging performance. These properties are significantly affected by calcination temperature and the optimal value is 600 oC. In this paper, the effect of film thickness and the role of PEG in facilitating the pore formation and interacting with TiO2 are also discussed.