TiO2 based nano-photocatalysis immobilized on cellulose substrates

Design of TiO2-Surfactin Hybrid Systems with Multifunctional Properties

In recent years, multifunctional inorganic-organic hybrid materials have been widely investigated in order to determine their potential synergetic, antagonist, or independent effects in terms of reactivity. The aim of this study was to design and characterize a new hybrid material by coupling well-known photocatalytic TiO2 nanoparticles with sodium surfactin (SS), a biosurfactant showing high binding affinity for metal cations as well as the ability to interact with and disrupt microorganisms' cell membranes. We used both chemical and colloidal synthesis methodologies and investigated how different TiO2:SS weight ratios affected colloidal, physicochemical, and functional properties. We discovered a clear breaking point between TiO2 and SS single-component trends and identified different ranges of applicability by considering different functional properties such as photocatalytic, heavy metal sorption capacity, and antibacterial properties. At low SS contents, the photocatalytic properties of TiO2 are preserved (conversion of organic dye = 99% after 40 min), and the hybrid system can be used in advanced oxidation processes, taking advantage of the additional antimicrobial SS properties. At high SS contents, the TiO2 photoactivity is inhibited, and the hybrid can be usefully exploited as a UV blocker in cosmetics, avoiding undesired oxidative effects (UV adsorption in the range between 300-400 nm). Around the breaking point (TiO2:SS 1:1), the hybrid material preserves the high surface area of TiO2 (specific surface area around 180 m2/g) and demonstrates NOx depletion of up to 100% in 80 min, together with improved adhesion of hybrid antibacterial coating. The last design demonstrated the best results for the concurrent removal of inorganic, organic, and biological pollutants in water/soil remediation applications.

Physicochemical and Photocatalytic Properties of 3D-Printed TiO2/Chitin/Cellulose Composite with Ordered Porous Structures

In this study, we printed three-dimensional (3D) titanium dioxide (TiO₂)/chitin/cellulose composite photocatalysts with ordered interconnected porous structures. Chitin microparticles were mixed with cellulose in the N-methylmorpholine-N-oxide (NMMO) solution to prepare the printing "ink". TiO₂ nanoparticles were embedded on the chitin/cellulose composite in the NMMO removal process by water before the freeze-drying process to build the 3D cellulosic photocatalysts with well-defined porous structures. The 3D-printed TiO₂/chitin/cellulose composites were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Disperse Spectroscopy (EDS). The XRD and FTIR analyses showed that chitin had an interference effect on the crystal regeneration of cellulose and resulted in a large amount of amorphous phase. The SEM images show that the printed cellulosic strands had a hollow structure, and the EDS analysis showed that TiO₂ nanoparticles were embedded on the chitin/cellulose composite surfaces. In the photocatalytic degradation process of methylene blue (MB) dye in an aqueous solution, the TiO₂/chitin/cellulose 3D composite photocatalysts demonstrated efficient MB degradation activities with excellent reusability and stability, in which the chitin content performed the function of adjusting the MB degradation efficiency.

Investigation of Photocatalyst Composites for Pollutant Degradation in a Microslit Reactor Utilizing High Throughput Screening Techniques

The high-throughput screening investigations on TiO2 based photocatalyst composites presented here have been carried out in a 60-fold parallel photoreactor. Additional catalyst testing was performed in a microslit reactor system with immobilized catalysts. For further enhancing the photocatalytic activity of TiO2 (P25), composites of P25 and, for example, Bi2 O3 , CeO2 , g-C3 N4 , WO3 or ZnO were formulated in different nominal molar ratios. The catalysts' performances were assessed by their conversion of 17α-ethinyl estradiol (EE2) in aqueous solutions, determined by LC-MS. Findings show rapid EE2 conversions in short residence times. The extensive testing of catalysts led to the conclusion that the photocatalytic conversion is rather a function of residence time than a function of the materials utilized. This makes adequate process development seem more important than material development. The novelty of this contribution lies in the unique combination of testing a wide range of composite catalysts in a unique microreactor geometry.

Application of titanium dioxide immobilized on a cellulosic material for the photocatalytic degradation of Acid Black 24 dye in a continuous flow cascade reactor

The aim of this work is the study of the photocatalytic degradation of Acid Black 24 dye (AB24), in a continuous flow cascade reactor, using titanium dioxide (TiO2) immobilized on a cellulosic material. The results obtained demonstrated a synergistic effect of the two phenomena adsorption and photocatalysis. The effects of various parameters that affect the dye removal efficiency were investigated. The best photocatalytic degradation yield of AB24 molecules is obtained in acidic medium because of the strong attraction between the positively charged catalyst and the anionic dye molecules. The optimum times for obtaining the best yields depend on the initial concentration of the dye, the volume of the treated solution, and the feed rate of the reactor. In addition, reusing the catalytic material several times is technically possible; this can decrease the cost of treatment for a possible industrial scale application.

Multifunctional hybrid membranes for photocatalytic and adsorptive removal of water contaminants of emerging concern

This work focuses on the combination of multifunctional photocatalytic and adsorbent materials in a unique polymeric membrane. For this purpose, Au/TiO₂ and Y₂(CO₃)₃ nanoparticles were immobilised onto a poly (vinylidene fluoride-hexafluoropropylene), (PVDF-HFP) membrane, and the physical-chemical characterisation of these materials was performed, as well as pollutant removal efficiency. An efficient TiO₂ functionalisation with gold nanoparticles was achieved, endowing these particles with the capability to absorb visible radiation absorption. A favourable porous structure was obtained for the membranes, with an average pore size of 4 μm, and the nanoparticles immobilisation did not alter the chemical properties of the polymeric membrane. The produced hybrid materials, including both the Au/TiO₂ and Y₂(CO₃)₃ nanoparticles, presented an efficiency of 57% in the degradation of norfloxacin (5 mg/L) under ultraviolet radiation for 120 min, 80% under visible radiation for 300 min, and 58% in arsenic adsorption for 240 min. These membranes represent a new multifunctional platform for removing several pollutants, which may allow their incorporation in more efficient and less energy-consuming water treatment processes favouring its application, even in low energy resources countries.

Chlorella vulgaris meets TiO2 NPs: Effective sorbent/photocatalytic hybrid materials for water treatment application

A new class of bio-nano hybrid catalyst useable in downstream wastewater treatment was developed. We combined the sorption potentialities of Chlorella vulgaris microalgae with the photocatalytic properties of TiO₂ NPs in order to investigate unexplored synergistic effects that could push the algal remediation technology toward a more promising cost-effective balance. We exploited non-living C. vulgaris, which keeps the biosorption properties of the living microalgae, but greatly enhancing the overall processability. C. vulgaris biomass was coupled with TiO₂ NPs and the nanosols were then dried by means of a spray freeze drying (SFD) process able to produce highly reactive granules. A widespread physicochemical characterization supported the preparation and the performance evaluation, so highlighting the key-role of C. vulgaris/TiO₂ interaction at the colloidal state. Heavy metal adsorption, tested for copper ions, and photocatalytic activity, assessed for Rhodamine B (RhB) photodegradation, were evaluated as key performances. The results pointed out a positive synergistic effect for hybrid samples consistent with the enhancement of metal biosorption which ranges from 103 mg g^-1, for pristine C. vulgaris, to about 4000 mg g^-1, when the biomass was coupled with the inorganic nanophase. The photocatalytic activity was well preserved with a complete RhB conversion after 1 h and even advanced in presence of SiO₂NPs into the inorganic counterpart, so increasing the kinetic constant from 8.70 to 10.7 10^-2 min^-1. The results pave the way for the integration of these sorbent/photocatalytic hybrid materials into water remediation systems in an innovative sustainable design perspective.

Ceramized Fabrics and Their Integration in a Semi-Pilot Plant for the Photodegradation of Water Pollutants

The use of nano-photocatalysts for the water/wastewater purifications, particularly in developing regions, offers promising advantages over conventional technologies. TiO2-based photocatalysts deposited on fabrics represent an efficient solution for obtaining heterogeneous photocatalysts, which are easily adaptable in the already installed water treatment plants or air purification systems. Despite the huge effort spent to develop and characterize novel nano-photocatalysts, which are especially active under solar light, knowledge gaps still persist for their full-scale application, starting from the reactor design and scale-up and the evaluation of the photocatalytic efficiency in pre-pilot scenarios. In this study, we offered easily scalable solutions for adapting TiO2-based photocatalysts, which are deposited on different kinds of fabrics and implemented in a 6 L semi-pilot plant, using the photodegradation of Rhodamine B (RhB) as a model of water pollution. We took advantage of a multi-variable optimization approach to identify the best design options in terms of photodegradation efficiency and turnover frequency (TOF). Surprisingly, in the condition of use, the irradiation with a light-emitting diode (LED) visible lamp appeared as a valid alternative to the use of UV LED. The identification of the best design options in the semi-pilot plant allowed scaling up the technology in a 100 L pilot plant suitable for the treatment of industrial wastewater.

Use of Titanium Dioxide (TiO2) Nanoparticles as Reinforcement Agent of Polysaccharide-Based Materials

In recent years, a strong interest has emerged in polysaccharide-hybrid composites and their potential applications, which have interesting functional and technological properties. This review summarizes and discusses the reported advantages and limitations of the functionalization of conventional and nonconventional polysaccharides by adding TiO2 nanoparticles as a reinforcement agent. Their effects on the mechanical, thermal, and UV-barrier properties as well as their water-resistance are discussed. In general, the polysaccharide–TiO2 hybrid materials showed improved physicochemical properties in a TiO2 content-dependent response. It showed antimicrobial activity against bacteria (gram-negative and gram-positive), yeasts, and molds with enhanced UV-protective effects for food and non-food packaging purposes. The reported applications of functionalized polysaccharide–TiO2 composites include photocatalysts (dye removal from aqueous media and water purification), biomedical (wound-healing material, drug delivery systems, biosensor, and tissue engineering), food preservation (fruits and meat), cosmetics (sunscreen and bleaching tooth treatment), textile (cotton fabric self-cleaning), and dye-sensitized solar cells. Furthermore, the polysaccharide–TiO2 showed high biocompatibility without adverse effects on different cell lines, indicating that their use in food, pharmaceutical, and biomedical applications is safe. However, it is necessary to evaluate the structural changes promoted by the storage conditions (time and temperature) on the physicochemical properties of polysaccharide–TiO2 hybrid composites to guarantee their stability during a determined time.

Functionalized Cellulose for the Controlled Synthesis of Novel Carbon-Ti Nanocomposites: Physicochemical and Photocatalytic Properties

Carbon-Ti nanocomposites were prepared by a controlled two-step method using microcrystalline cellulose as a raw material. The synthesis procedure involves the solubilization of cellulose by an acid treatment (H3PO4 or HNO3) and the impregnation with the Ti precursor followed of a carbonization step at 500 or 800 °C. The type of acid treatment leads to a different functionalization of cellulose with phosphorus- or oxygen-containing surface groups, which are able to control the load, dispersion and crystalline phase of Ti during the composite preparation. Thus, phosphorus functionalities lead to amorphous carbon-Ti composites at 500 °C, while TiP2O7 crystals are formed when prepared at 800 °C. On the contrary, oxygenated groups induce the formation of TiO2 rutile at an unusually low temperature (500 °C), while an increase of carbonization temperature promotes a progressive crystal growth. The removal of Orange G (OG) azo dye in aqueous solution, as target pollutant, was used to determine the adsorptive and photocatalytic efficiencies, with all composites being more active than the benchmark TiO2 material (Degussa P25). Carbon-Ti nanocomposites with a developed micro-mesoporosity, reduced band gap and TiO2 rutile phase were the most active in the photodegradation of OG under ultraviolet irradiation.

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.

The influence of titanium dioxide nanoparticles on their cellular response to macrophage cells

As the most widely application of nanomaterials in biology and medicine, their interaction with biological system and the afterwards cellular responses would be addressed. Here, the agglomerate states of two kinds of TiO₂ NPs in culture medium were characterized and the cluster specific cellular responses in RAW264.7 cells were investigated. Owing to the smaller aggregates and more positively charged surface, 21 nm TiO₂ NPs exhibited higher cytotoxicity, which correlated with their ability to cause damage to mitochondria. While for 35 nm TiO₂ NPs, higher level of cell autophagy and stronger pro-inflammatory immune response were observed, which are responsible for their lower cytotoxicity. These results suggest that physiochemical properties of TiO₂ NPs in culture medium are important factor affecting their cellular response to RAW264.7 cells.

Natural sunlight driven highly efficient photocatalysis for simultaneous degradation of rhodamine B and methyl orange using I/C codoped TiO2 photocatalyst

Increasing the efficiency of dye degradation is a critical issue for the application for photocatalysis. It is one of the greatest challenges to enhance the utilization of photo generated carriers in semiconductor, especially for sunlight irradiation. In this study, I/C-codoped TiO₂ was synthesized by a simple solvothermal-calcination method. The codoping interstitial carbon and substitutional iodine not only widened the light absorption range of the TiO₂ photocatalysts, but also enhanced the separation of photo-induced carriers. The photocatalytic activities of RhB and MO degradation over the 4-I/C-TiO₂ photocatalyst could reach 98.2% and 94.2% after 25 min visible light irradiation (λ ≥ 400 nm), respectively. Notably, 4-I/C-TiO₂ showed good activity for MO and RhB mixed degradation and could also accomplish the photocatalytic degradation in the above mixed system under natural sunlight irradiation. According to the dark catalytic experiment, I/C-codoping could effectively accelerate the formation of hydroxyl radicals from the generated H₂O₂, which was formed for the enhanced photocatalytic activity of dye degradation. The gained knowledge may provide some insights into the photocatalytic degradation over the codoped TiO₂ catalyst.

Conversion of "Waste Plastic" into Photocatalytic Nanofoams for Environmental Remediation

Plastic debris is a major environmental concern, and to find effective ways to reuse polystyrene (PS) presents major challenges. Here, it is demonstrated that polystyrene foams impregnated with SnO₂ are easily generated from plastic debris and can be applied to photocatalytic degradation of dyes. SnO₂ nanoparticles were synthesized by a polymeric precursor method, yielding specific surface areas of 15 m²/g after heat treatment to 700 °C. Crystallinity, size, and shape of the SnO₂ particles were assessed by X-ray diffraction (XRD) and transmission electron microscopy (TEM), demonstrating the preparation of crystalline spherical nanoparticles with sizes around 20 nm. When incorporated into PS foams, which were generated using a thermally induced phase separation (TIPS) process, the specific surface area increased to 48 m²/g. These PS/SnO₂ nanofoams showed very good efficiency for photodegradation of rhodamine B, under UV irradiation, achieving up to 98.2% removal. In addition the PS/SnO₂ nanofoams are shown to retain photocatalytic activity for up to five reuse cycles.

Bacterial Biofilm Characterization and Microscopic Evaluation of the Antibacterial Properties of a Photocatalytic Coating Protecting Building Material

Use of photocatalytic paint-like coatings may be a way to protect building materials from microbial colonization. Numerous studies have shown the antimicrobial efficiency of TiO 2 photocatalysis on various microorganisms. However, few have focused on easy-to-apply solutions and on photocatalysis under low irradiance. This paper focuses on (a) the antibacterial properties of a semi-transparent coating formulated using TiO 2 particles and (b) the microscopic investigations of bacterial biofilm development on TiO 2 -coated building materials under accelerated growth conditions. Results showed significant antibacterial activity after few hours of testing. The efficiency seemed limited by the confinement of the TiO 2 particles inside the coating binder. However, a pre-irradiation with UV light can improve efficiency. In addition, a significant effect against the formation of a bacterial biofilm was also observed. The epifluorescence approach, in which fluorescence is produced by reflect rather than transmitted light, could be applied in further studies of microbial growth on coatings and building materials.

An overview on cellulose-based material in tailoring bio-hybrid nanostructured photocatalysts for water treatment and renewable energy applications

A combination between the nanostructured photocatalyst and cellulose-based materials promotes a new functionality of cellulose towards the development of new bio-hybrid materials for various applications especially in water treatment and renewable energy. The excellent compatibility and association between nanostructured photocatalyst and cellulose-based materials was induced by bio-combability and high hydrophilicity of the cellulose components. The electron rich hydroxyl group of celluloses helps to promote superior interaction with photocatalyst. The formation of bio-hybrid nanostructured are attaining huge interest nowadays due to the synergistic properties of individual cellulose-based material and photocatalyst nanoparticles. Therefore, in this review we introduce some cellulose-based material and discusses its compatibility with nanostructured photocatalyst in terms of physical and chemical properties. In addition, we gather information and evidence on the fabrication techniques of cellulose-based hybrid nanostructured photocatalyst and its recent application in the field of water treatment and renewable energy.

Cellulose as a Scaffold for Self-Assembly: From Basic Research to Real Applications

Cellulose has received a tremendous amount of attention both in academia and industry owing to its unique structural features, impressive physical-chemical properties, and wide applications. This natural polymer is originally used for packaging, paper, lightweight composites, and so forth and is now being developed for various new areas, such as antibacterial treatment, catalysis, water purification and separation, and biological and environmental analysis. In the current article, we summarize the recent developments in the self-assembly of cellulose with various species including metal ions and metal and metal oxide nanoparticles. Then we highlight several key application areas of cellulose-based composites by reviewing the recent representative literature in each area. A significant part of this review demonstrates some exciting innovations for a wide range of practical applications of cellulose-based composites. Some challenges are also discussed with a view toward future developments.

A panel of in vitro tests to evaluate genotoxic and morphological neoplastic transformation potential on Balb/3T3 cells by pristine and remediated titania and zirconia nanoparticles

The FP7 Sanowork project was aimed to minimise occupational hazard and exposure to engineered nanomaterials (ENM) through the surface modification in order to prevent possible health effects. In this frame, a number of nanoparticles (NP) have been selected, among which zirconium (ZrO2) and titanium (TiO2) dioxide. In this study, we tested ZrO2 NP and TiO2 NP either in their pristine (uncoated) form, or modified with citrate and/or silica on their surface. As benchmark material, Aeroxide® P25 was used. We assessed cytotoxicity, genotoxicity and induction of morphological neoplastic transformation of NP by using a panel of in vitro assays in an established mammalian cell line of murine origin (Balb/3T3). Cell viability was evaluated by means of colony-forming efficiency assay (CFE). Genotoxicity was investigated by cytokinesis-block micronucleus cytome assay (CBMN cyt) and comet assay, and by the use of the restriction enzymes EndoIII and Fpg, oxidatively damaged DNA was detected; finally, the morphological neoplastic transformation of NP was assayed in vitro by cell transformation assay (CTA). Our results show that the surface remediation has not been effective in modifying cyto- and genotoxic properties of the nanomaterials tested; indeed, in the case of remediation of zirconia and titania with citrate, there is a tendency to emphasise the toxic effects. The use of a panel of assays, such as those we have employed, allowing the evaluation of multiple endpoints, including cell transformation, seems particularly advisable especially in the case of long-term exposure effects in the same cell type.

Comparative efficiency of TiO2 nanoparticles in suspension vs. immobilization into P(VDF–TrFE) porous membranes

Optimized photocatalytic membranes based on TiO₂ and NaY immobilized into P(VDF–TrFE) have been developed showing a degradation efficiency of 96%.

Hybrid cotton–anatase prepared under mild conditions with high photocatalytic activity under sunlight

Cotton fibres were coated with nanolayers of TiO₂, anatase, using a new approach based on a non-hydrolytic sol–gel process followed by a mild hydrothermal treatment at a temperature lower than 140 °C.

TiO₂ Nanosols Applied Directly on Textiles Using Different Purification Treatments

Self-cleaning applications using TiO₂ coatings on various supporting media have been attracting increasing interest in recent years. This work discusses the issue of self-cleaning textile production on an industrial scale. A method for producing self-cleaning textiles starting from a commercial colloidal nanosuspension (nanosol) of TiO₂ is described. Three different treatments were developed for purifying and neutralizing the commercial TiO₂ nanosol: washing by ultrafiltration; purifying with an anion exchange resin; and neutralizing in an aqueous solution of ammonium bicarbonate. The different purified TiO₂ nanosols were characterized in terms of particle size distribution (using dynamic light scattering), electrical conductivity, and ζ potential (using electrophoretic light scattering). The TiO₂-coated textiles’ functional properties were judged on their photodegradation of rhodamine B (RhB), used as a stain model. The photocatalytic performance of the differently treated TiO₂-coated textiles was compared, revealing the advantages of purification with an anion exchange resin. The study demonstrated the feasibility of applying commercial TiO₂ nanosol directly on textile surfaces, overcoming problems of existing methods that limit the industrial scalability of the process.

Impact and effectiveness of risk mitigation strategies on the insurability of nanomaterial production: evidences from industrial case studies

Workers involved in producing nanomaterials or using nanomaterials in manufacturing plants are likely to have earlier and higher exposure to manufactured/engineered nanomaterials (ENM) than the general population. This is because both the volume handled and the probability of the effluence of 'free' nanoparticles from the handled volume are much higher during a production process than at any other stage in the lifecycle of nanomaterials and nanotechnology-enabled products. Risk assessment (RA) techniques using control banding (CB) as a framework for risk transfer represents a robust theory but further progress on implementing the model is required so that risk can be transferred to insurance companies. Following a review of RA in general and hazard measurement in particular, we subject a Structural Alert Scheme methodology to three industrial case studies using ZrO2 , TiO2 , and multi-walled carbon nanotubes (MWCNT). The materials are tested in a pristine state and in a remediated (coated) state, and the respective emission and hazard rates are tested alongside the material performance as originally designed. To our knowledge, this is the first such implementation of a CB RA in conjunction with an ENM performance test and offers both manufacturers and underwriters an insight into future applications.