Methylene Blue Degradation Test Research Articles

Zinc oxide nanoparticles immobilized on polymeric porous matrix for water remediation

This work proposes a novel approach to producing composite membranes by immobilizing and blending ZnO nanoparticles within a polymer matrix. The focus is investigating how different immobilization techniques impact membrane performance in critical technological applications, including membrane fouling mitigation and photocatalytic degradation. Lab-synthesized ZnO nanostructures were immobilized within a natural cellulose acetate (CA) matrix using a spray coating technique. To ensure comprehensive exploration, CA membranes with 12% and 15% wt polymer concentrations, which demonstrated superior overall performance in previous studies, were cast and prepared. The membranes underwent phase inversion, and a specially prepared ZnO solution was sprayed onto the membrane surface, creating a unique blend of polymer and nanoparticles. This comparative study highlights distinctions between nanomaterial immobilization techniques (mixing and spray coating) while maintaining identical polymer content. Such insights are crucial for both industrial applications and laboratory-scale research. The photocatalytic degradation of the reactive and toxic dye methylene blue (MB) served as a model reaction, employing a UV light module. Results unequivocally demonstrated that, irrespective of the immobilization technique employed, the combination of CA and ZnO nanoparticles significantly enhanced the photocatalytic activity of the membrane in degrading methylene blue (MB). Specifically, the dye concentration decreased from 25 to approximately 8 mg/L for both the spray coating and bulk immobilization methods, resulting in 62% and 69% dye degradation, respectively. These findings underscore the versatility of different immobilization techniques in various aspects of membrane technology. The CA-ZnO composite exhibited efficacy in photocatalytic MB degradation tests, offering promising alternatives for designing polymeric membranes tailored for contaminant removal, particularly in treating textile dye-contaminated aqueous solutions. The exploration of diverse immobilization techniques for nanocomposites presents an exciting avenue for optimization in different membrane technological processes.

Enhanced photocatalytic antibacterial activity of Au-coated Ni–Ti–O nanotubes for biomedical applications

Nickel-titanium (NiTi) alloy is a smart material exhibiting superelasticity, contributing to low stiffness and facilitating integration with bone structures. However, NiTi alloy's bioactivity and antibacterial activity limit its dental applications. In this study, we fabricated nickel titanium oxide (Ni–Ti–O) nanotubes with the potential for bioactivity and photocatalytic properties on the surface of NiTi alloy. Specifically, we applied a coating of gold (Au) nanoparticles to the surface of Ni–Ti–O nanotubes, in order to leverage the antibacterial activity through the photocatalytic effect under 470 nm visible light. Field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) observations revealed that Au was deposited mainly at the top surface of Ni–Ti–O nanotubes (diameter: 12.76 ± 2.91 nm, height: 721.12 ± 50.25 nm). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS) analyses revealed that the Ni–Ti–O nanotubes were NiTiO3 crystalline phases with low crystallinity. Therefore, based on the methylene blue (MB) degradation test, the photocatalytic effect was only achieved under visible light at 470 nm, facilitated by the presence of Au. The antibacterial colony forming unit test and enzymatic activity tests demonstrated that Au-coated Ni–Ti–O nanotubes displayed excellent antibacterial activity under 470 nm visible light irradiation, which was also attributed to photocatalytic effect. Consequently, the combination of Au-coated Ni–Ti–O nanotubes and visible light-based photofunctionalization holds promise for expressing antibacterial properties in dental applications.

Effect of carbon nanotube incorporation on the photocatalytic activity of TiO2 nanotubes

Arrays of titanium dioxide (TiO2) nanotubes were prepared on commercially pure titanium (Ti) foils by anodic oxidation in a 0.5 M hydrofluoric acid (HF)-based electrolyte with multiwalled carbon nanotubes (MWCNTs) up to 0.035 g/l. The samples were annealed at 450°C for 1 h after anodic oxidation to form a crystalline anatase structure. The effect of MWCNT addition on the morphology and photocatalytic activity of the nanostructures was characterized by scanning electron microscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and methylene blue degradation tests. The results showed that MWCNTs were successfully incorporated into the titanium dioxide nanotube structure and significantly affected its photocatalytic activity. The best photocatalytic performance was achieved with the use of 0.025 g/l MWCNTs in the electrolyte composition. However, when the MWCNT content in the electrolyte increased, the electron–hole recombination rate and photon absorption ability of the structure deteriorated, resulting in a decreased photocatalytic activity.

A machine learning approach for the estimation of photocatalytic activity of ALD ZnO thin films on fabric substrates

Research in the field of photocatalytic wastewater treatment is striving to enhance catalyst materials to achieve high-performance systems. A promising approach to this goal has been immobilizing photocatalytic materials on fibrous substrates via atomic layer deposition (ALD). Nevertheless, both the ALD process and the assessment of photocatalytic performance involve a multitude of parameters necessitating thorough investigation. In this study, we employ popular machine-learning algorithms, including Support Vector Regression (SVR) and Artificial Neural Networks (ANN), to predict the photocatalytic activity of ALD-coated textiles. The photocatalytic activity is evaluated through methylene blue and methyl orange degradation tests. Machine learning algorithms are tested and trained using the k-fold cross-validation technique. The findings demonstrate that the ANN and SVR methods utilized in this research can predict catalytic activity with mean absolute percentage errors (MAPE) of 2.35 and 3.25, respectively. This study illuminates that, within the defined range of process parameters, the photocatalytic activity of ALD-coated textiles can be precisely estimated with suitable machine-learning algorithms.

Silver Nanoparticles’ Biogenic Synthesis Using Caralluma subulata Aqueous Extract and Application for Dye Degradation and Antimicrobials Activities

The issue of organic contaminants in water resulting from industrial, agricultural, and home activities makes it necessary to effectively address the problems of water scarcity. Using modern technologies that can effectively remove pollutants from wastewater is the way to address this key problem. The use of nanoparticles (NPs) has been advocated due to their unique physical and chemical characteristics and advantageous applications. NPs’ surface stability and synthesis routes are core concerns for environmental remediation and biological applications. In this work, we demonstrated the biogenic synthesis of silver NPs (Ag-CS NPs) by using Caralluma subulata (CS) aqueous extract as a reducing and capping/template agent. The synthesized Ag-CS NPs were characterized by UV-visible absorbance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, powdered X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and Zeta potential. The performance of Ag-CS NPs was evaluated on methylene blue (MB) dye degradation and antibacterial activity tests against bacterial and fungal isolates. The results showed that Ag-CS NPs (0.05%, 20.0 μL) reduced MB by 95.52% within 28 min in the presence of NaBH4 (10.0 mM, 0.980 μL). The degradation of MB followed pseudo zero-order chemical kinetics (R2 = 0.9380), with the reaction rate constant 0.0508 mol L−1 min−1. In addition, Ag-CS NPs were applied as antibacterial agents against 19 bacterial isolates. Ag-CS NPs showed inhibition in both Gram-positive and Gram-negative bacterial, as well as fungal isolates. As a greener ecofriendly approach, multifunctional Ag-CS NPs make a promising candidate for the remediation of contaminated water, as well as for important bioapplications.

Antimicrobial Properties of TiNbSn Alloys Anodized in a Sulfuric Acid Electrolyte.

TiNbSn alloy is a high-performance titanium alloy which is biosafe, strong, and has a low Young's modulus. TiNbSn alloy has been clinically applied as a material for orthopedic prosthesis. Anodized TiNbSn alloys with acetic and sulfuric acid electrolytes have excellent biocompatibility for osseointegration. Herein, TiNbSn alloy was anodized in a sulfuric acid electrolyte to determine the antimicrobial activity. The photocatalytic activities of the anodic oxide alloys were investigated based on their electronic band structure and crystallinity. In addition, the cytotoxicity of the anodized TiNbSn alloy was evaluated using cell lines of the osteoblast and fibroblast lineages. The antimicrobial activity of the anodic oxide alloy was assessed according to the ISO 27447 using methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli. The anodic oxide comprised rutile and anatase titanium dioxide (TiO2) and exhibited a porous microstructure. A well-crystallized rutile TiO2 phase was observed in the anodized TiNbSn alloy. The methylene blue degradation tests under ultraviolet illumination exhibited photocatalytic activity. In antimicrobial tests, the anodized TiNbSn alloy exhibited robust antimicrobial activities under ultraviolet illumination for all bacterial species, regardless of drug resistance. Therefore, the anodized TiNbSn alloy can be used as a functional biomaterial with low Young's modulus and excellent antimicrobial activity.

Enhanced photocatalytic activity of TiO2 nanostructures produced by anodic oxidation of pre-deformed Cp–Ti

ABSTRACT Arrays of TiO2 nanotubes were prepared on pre-deformed commercially pure titanium (Cp–Ti) foils by anodic oxidation in 1 vol.-% HF-based electrolyte. Prior to the anodic oxidation, the samples were deformed by uniaxial tension and cold rolling at room temperature in three different strain levels. Following the anodic oxidation, the samples were annealed at 450°C to obtain crystalline anatase structure. Effects of the deformation on the produced nano structures were investigated by characterisation studies and photocatalytic activity tests including methylene blue degradation test, photoluminescence, and UV–Vis diffuse reflectance spectra analyses. The results showed that the induced strain has a remarkable effect on the nanotube morphology. It also led to a decrease in the crystallite size in the uniaxial tensioned and cold rolled titanium foils. As a result of the morphological and structural changes, the photocatalytic activity of the samples increased with cold rolling strain, and uniaxial tension strains up to a critical level.

Visible-light-driven hierarchical porous CeO2 derived from wood for effective photocatalytic degradation of methylene blue

To improve the photodegradation efficiency of organic dyes under visible light, a novel bio-inspired photocatalyst was designed herein based on the theory of wood-bionics. Graded porous cerium oxide with wood structure (W–CeO2) was prepared by using larch wood splinters as the template. W–CeO2 maintains the structure of the wood. W–CeO2 showed many advantages such as low consumption, high performance, and long-term stability for application as a photocatalyst. In this study, the morphological features, crystalline structure, specific surface area, chemical composition, carrier separation efficiency and optical properties of the as-developed photocatalyst were investigated comprehensively. The results show that W–CeO2 completely replicated the multi-scale hierarchical pore structure of the wood template. Compared with cerium oxide prepared by the traditional hydrothermal method (0-CeO2), the specific surface area of W–CeO2 was doubled, and the average pore diameter was reduced by 73% to 5.38 nm. Moreover, W–CeO2 showed the characteristics of anisotropy, circular electron diffraction pattern, reduced crystallinity, and higher charge separation efficiency. W–CeO2 also possessed higher electronic activity, greater active oxygen content, and lower electron-hole recombination efficiency. Methylene blue (MB) dye was used as the target pollutant to test the photocatalytic performance of W–CeO2. The MB degradation test results show that using wood as a template greatly improved the catalytic efficiency of the catalyst. The main free radicals involved in the reaction were determined by adding 1,4-benzoquinone (BQ) and tert-butanol (TBA) for comparative experiments. The results of this work can provide new insights into the construction of bio-inspired materials for promoting the photocatalytic reaction of organic dyes and indicate that W–CeO2 photocatalyst is a promising candidate for wastewater treatment application.

Aligned Porous Structure of (Ba,Ca)(Ti,Zr)O3 Piezoelectric Ceramics for Enhanced Catalytic Activity

The effect of pore orientation and pore volume on the dielectric and piezoelectric properties as well as the piezocatalytic activity of lead‐free porous (Ba,Ca)(Ti,Zr)O3 (BCTZ) are investigated. The pore orientation in BCTZ is controlled using a freeze‐casting method. Two types of porous BCTZ samples, i.e., A‐BCTZ and B‐BCTZ, are prepared by cutting them in parallel and perpendicular directions, respectively, to the longitudinal pore direction. The samples with 30% porosity indicate that the permittivity of A‐BCTZ is 648, less than 1/3 of that of B‐BCTZ (2059). A‐BCTZ also exhibits the highest hydrostatic voltage coefficient (gh, 9.26 × 10−3 Vm N−1), which is approximately 1.7 times higher than B‐BCTZ and 50 times higher than the dense BCTZ sample. Photo–piezocatalytic effect is investigated by a methylene blue (MB) degradation test under UV light while applying ultrasonic wave, and the catalytic activity of the poled porous BCTZs shows much higher than the dense BCTZ by their large specific surface area. Thus, porous piezoelectric materials are promising as a semipermanently available catalyst to replace nanoparticles whose specific surface area is reduced likely by agglomeration.

Ag3PO4-TiO2-Carbon nanofiber Composite: An efficient Visible-light photocatalyst obtained from electrospinning and hydrothermal methods

In this contribution, we synthesized Ag3PO4-TiO2 NPs assembled carbon nanofibers (Ag3PO4-TiO2-CNFs) photocatalyst by the combination of electrospinning and hydrothermal processes. The photocatalyst was characterized by various techniques such as SEM, TEM, XRD, UV, PL, etc. The morphological examination by SEM and TEM revealed a uniform distribution of the Ag3PO4 NPs over the TiO2-CNFs surface. Compared to TiO2 NFs, the loading of Ag3PO4 NPs into the TiO2-CNFs composite enhances its absorbance to the visible light region and offers a route with low resistance for charge separation. The photocatalytic performance of the Ag3PO4-TiO2-CNFs composite was studied by a methylene blue (MB) degradation test under visible light irradiation. It was observed that the Ag3PO4-TiO2-CNFs composite exhibited significantly enhanced photocatalytic performance as compared to the pristine Ag3PO4 NPs and TiO2 NFs. The Ag3PO4-TiO2-CNFs composite eliminated the entire MB dye within 10 min of visible light irradiation. Also, the reusability test indicated that the photocatalyst possesses excellent stability. The high photocatalytic activity is attributed to the increased surface area, enhanced visible light response, accelerated charge separation, and dye adsorption property of the composite material. Furthermore, the photocatalyst showed good antibacterial property against Escherichia coli (E. coli) bacteria. The excellent dyes removal ability and the good antibacterial property of the as-prepared Ag3PO4-TiO2-CNFs photocatalyst show the potentiality of the material in wastewater treatment.

Influence of aging on the physicochemical behavior of photocatalytic asphalt cements subjected to the natural environment

This investigation evaluates aging characteristics and photocatalytic performance of asphalt cements modified with titanium dioxide (TiO2) at different percentages (3, 5, and 7% by weight of the asphalt binder). Conventional and photocatalytic asphalt cements were used to manufacture specimens of hot mix asphalt (HMA) compacted in the laboratory with a Gyratory Compactor and subjected to environmental conditioning for 6, 12, or 18 months in which they were exposed to temperature changes, rain, and sunlight. FTIR (Fourier-Transform Infrared Spectroscopy), MSCR (Multiple Stress Creep and Recovery), and degradation of methylene blue (MB) tests were carried out to evaluate the influence of aging on the chemical and mechanical properties. Besides, the photocatalytic efficiency of asphalt cements extracted from aged asphalt concrete specimens by the reflux method was also studied. FTIR results indicated that photocatalytic asphalt cements exhibit greater aging resistance over time than conventional asphalt binders. MSCR results showed that mechanical properties represented by deformation recovery and non-recoverable creep compliance parameters improved with TiO2 content and environmental conditioning time. On the other hand, the MB degradation tests indicated that the photocatalytic efficiency of modified asphalt cements increases with the TiO2 content and remains between 20 and 25% for all environmental conditions assessed in this study.

Improved photoelectrocatalytic activity of anodic TiO2 nanotubes by boron in situ doping coupled with geometrical optimization: Application of a potent photoanode in the purification of dye wastewater

A comparative study on the photoelectrocatalytic activity of anodic TiO2 nanotubes (TNTs) and boron-doped TiO2 nanotubes (BTNTs) was performed through fabricating them in two distinguished fluoride-containing electrolytes, namely NH4F and NH4BF4. Furthermore, by applying anodization voltage (in the range of 40–60 V) as a regulating factor, an analogy was drawn between morphologies, optical properties, photoelectrochemical features, and photoelectrocatalytic activities of both TNTs and BTNTs. The results revealed that using NH4BF4 not only led to the introduction of boron into TiO2 lattices but also resulted in shorter nanotubes owing to their less corrosive effect compared with NH4F. Furthermore, anodization voltage had a significant impact on the optical properties; with increasing the voltage to 60 V, a red shift occurred in the band edge of both TNTs (from 3.05 to 2.8 eV) and BTNTs (from 2.9 to 2.6 eV). Particularly, via anodization at 60 V in NH4BF4 instead of NH4F, the photocurrent density and photoconversion efficiency increased from 0.19 to 0.67 Ma cm−2 and from 0.12 to 0.270%, respectively. Moreover, methylene blue degradation tests showed that BTNTs had an outstanding photoelectrocatalytic activity in comparison to TNTs; in this regard, the sample synthesized at 60 V in NH4BF4 rather than NH4F enhanced PEC degradation efficiency from 79 to 100% under UV irradiation. Finally, the kinetics investigation confirmed that all photoelectrocatalytic reactions in both groups followed the first-order kinetics.

Development of Eco-Friendly and Self-Cleaning Lime-Pozzolan Plasters for Bio-Construction and Cultural Heritage

Nowadays, the design and use of multi-functional mortars has increased significantly, with interesting applications in the green building and cultural heritage conservation sectors. A key point for a correct adoption of these innovative materials is their behavior along time and their resistance to the weathering. The objective of this project was to define the performance and durability of innovative mortars, in order to use them correctly and to avoid irreparable damage over time. For the development of this project, lime–metakaolin and hydraulic lime–metakaolin based mortars (hereinafter called A, B), as well as A and B with the addition of nano-TiO2 and perlite (hereinafter referred to as A+, B+), have been tested. The focus of the work was to carry out preliminary tests to evaluate the performance and durability characteristics of these mortars, verifying their behavior over time through exposure to artificial aging cycles, including thermal shock cycles in saline solution aerosols, freeze cycles in vapor aerosol, and aging by heat treatment at high temperatures. Before and after each artificial aging cycle, weight measurements, and macroscopic and microscopic observations were performed in order to evaluate possible structural changes. The characteristics of the mortars were assessed by determination of the apparent volume mass, mechanical properties, such as compressive and bending strength, water absorption, whereas their self-cleaning capacity was measured by methylene blue degradation test under UV and solar irradiation. The results obtained show degradation effects in the mortar samples due to aging after each test, and indicated that mortars with perlite and nano-TiO2 are the best-performing ones, both from the durability and energetic point of view, rendering them suitable for applications in the green building sector and the conservation of cultural heritage.

Preparation and photocatalytic activity of g-C3N4/TiO2 heterojunctions under solar light illumination

The solar light sensitive g-C3N4/TiO2 heterojunction photocatalysts containing 20, 50, 80, and 90 wt% graphitic carbon nitride (g-C3N4) were prepared by growing Titania (TiO2) nanoparticles on the surfaces of g-C3N4 particles via one step hydrothermal process. The hydrothermal reactions were allowed to take place at 110 °C at autogenous pressure for 1 h. Raman spectroscopy analyses confirmed that an interface developed between the surfaces of TiO2 and g-C3N4 nanoparticles. The photocatalyst containing 80 wt% g-C3N4 was subsequently heat treated 1 h at temperatures between 350 and 500 °C to improve the photocatalytic efficiency. Structural and optical properties of the prepared g-C3N4/TiO2 heterojunction nanocomposites were compared with those of the pristine TiO2 and pristine g-C3N4 powders. Photocatalytic activity of all the nanocomposites and the pristine TiO2 and g-C3N4 powders were assessed by the Methylene Blue (MB) degradation test under solar light illumination. g-C3N4/TiO2 heterojunction photocatalysts exhibited better photocatalytic activity for the degradation of MB than both pristine TiO2 and g-C3N4. The photocatalytic efficiency of the g-C3N4/TiO2 heterojunction photocatalyst heat treated at 400 °C for 1 h is 1.45 times better than that of the pristine TiO2 powder, 2.20 times better than that of the pristine g-C3N4 powder, and 1.24 times better than that of the commercially available TiO2 powder (Degussa P25). The improvement in photocatalytic efficiency was related to i) the generation of reactive oxidation species induced by photogenerated electrons, ii) the reduced recombination rate for electron-hole pairs, and iii) large specific surface area.

Synthesis OF AG/TIO2 nanocomposite via plasma liquid interactions and degradation methylene blue

A novel method employing atmospheric pressure discharge plasma has been developed to reduce supported Ag nanoparticles (Ag NPs) and deposited on TiO2 powder without the use of any environmentally and biologically hazardous reducing chemicals. Ag/TiO2 nanocomposite was prepared by the atmospheric direct current plasma in water solution. Trisodium citrate and CMC was used as a capping agent for Ag nanoparticles. The nanocomposites were characterized using UV–Vis spectroscopy, X-ray diffraction, scanning electron microscopy. The results showed that Ag NPs with an average diameter of 20–35.5 nm were uniformly distributed on the powders surface. The presence of nanosilver particles in TiO2 matrix is clearly visible. The bandgap of TiO2/Ag was confirmed (2.65–2.85 eV) through UV–vis DRS, which was lower than TiO2 (3.8 eV). The photocatalytic effect was conducted by methylene blue degradation test. The photocatalytic activity of a series of 2 wt. % Ag/TiO2 composites was evaluated in the degradation of MB (used as a model pollutant) in aqueous solution under solar light. The 2.0 mol % of Ag-doped TiO2 shows 96% degradation of methylene blue (MB) within 50 min under visible light irradiation and exhibit highest photocatalytic performance.

Highly efficient photocatalytic methylene blue degradation over Sn(O,S)/TiO2 photocatalyst fabricated via powder atomic layer deposition of SnO and subsequent sulfurization

In this work, tin oxysulfide coated TiO2 nanoparticles for photocatalytic pollutant degradation were fabricated via a two-step vacuum process which involves powder atomic layer deposition (PALD) of SnO on TiO2 nanoparticles followed by sulfurization annealing. The physical and chemical properties of the Sn(O,S)/TiO2 nanoparticles were characterized and compared with TiO2 and SnO/TiO2. From the methylene blue (MB) degradation test, the photocatalytic activities of Sn(O,S)/TiO2 were examined. The Sn(O,S)/TiO2 showed ~ 6.7 and 16-fold improved MB degradation rate constants of 0.002 and 0.114 min−1 compared to the pristine TiO2 under visible light and Xe lamp irradiations, respectively. This may be attributed to the synergetic effects of enhancing the electron-hole charge separation and light absorption characteristics.

TiO2 based nanopowder coatings over stainless steel plates for UV‐C photocatalytic degradation of methylene blue

AbstractImmobilizing the photocatalyst in a water treatment process design is essential; however, the immobilization method may affect the photoactivity of the photocatalyst. In this work, photocatalyst powders were successfully coated on 316 L stainless steel plates by a novel brush coating method. Three combinations of photocatalyst mixtures (pure TiO2 anatase, anatase doped with WO3, or TiO2 rutile) were and annealed at different temperatures between 460‐540°C. The ~ 10 μm thick coatings demonstrated full plate coverage and strong adhesion and adequate durability. Surface roughness increased with annealing temperature. The doping and annealing process enabled band gap reduction to the visible light spectrum for all coatings, with the smallest band gap being 2.48 eV (1 eV = 1.6 × 10−19 J). Subsequent methylene blue degradation tests under UV‐C showed that the coatings annealed in 460°C exhibited the best performance and with the highest degradation rate constant of 5.59 hours−1.

A novel template-free wet chemical synthesis method for economical production of zinc oxide microrods under atmospheric pressure

This work reports a template-free wet chemical synthesis method for economical production of zinc oxide (ZnO) microrods by using an inexpensive polypropylene beaker as a reactor under atmospheric pressure. The morphology and crystal structure of the as-prepared ZnO microrods were investigated by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Raman scattering. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), Ultraviolet–visible (UV/Vis) spectroscopy and methylene blue photocatalytic degradation test were also conducted to study their physical and chemical properties. The results show that the as-prepared ZnO microrods have a hexagonal crystal structure. Under the optimal synthesis condition, they have a diameter of 0.8–2.6 μm and a length of 10–40 μm. Compared with commercial ZnO powders, the as-prepared ZnO microrods have a higher whiteness. Meanwhile, the as-prepared ZnO microrods have very low photocatalytic activity, indicating that they have good photostability and are unlikely to cause the photodegradation of polymers such as binders. As a result, they will be an excellent and economical white pigment with great potential in coating applications.

The relationship between local structure and photo-Fenton catalytic ability of glasses and glass-ceramics prepared from Japanese slag

Local structure and the photo-Fenton reactivity of iron-containing glasses and glass-ceramics prepared from Japanese domestic waste slag were investigated. The largest rate constant (k) of (2.8 ± 0.08) × 10−2 min−1 was recorded for the methylene blue degradation test by using H2O2 with a heat-treated ‘model slag’. The 57Fe Mossbauer spectrum was composed of a paramagnetic doublet with isomer shift of 0.18 ± 0.01 mm s−1 attributed to distorted FeIIIO4 tetrahedra. These results indicate that the paramagnetic Fe3+ provided strong photo-Fenton catalytic ability, and that waste slag can thus be recycled as an effective visible-light activated photocatalyst.

One-pot synthesis of Au/N-TiO2 photocatalysts for environmental applications: Enhancement of dyes and NOx photodegradation

Au/N-TiO2 photocatalysts with enhanced photoactivity thanks to nitrogen doping and gold nanoparticles (AuNPs) controlled deposition onto titania have been obtained by means of a simple and innovative one-pot synthesis promoting synergetic activity between these two approaches. The activity of the materials under study was evaluated by methylene blue and NOx degradation tests as models of environmental remediation processes for water purification and air depollution. The use of a deposition-precipitation method employing urea allows obtaining Au/N-TiO2 photocatalysts containing 0.3 at.% of nitrogen and 0.5 wt% of gold. The results obtained confirmed that the presence of both, nitrogen and AuNPs, enhanced the TiO2 photoactivity increasing the photodegradation of the dye and NOx in a factor of 4.5 and 1.7, respectively. In particular, the AuNPs enabled the photoactivity under visible light and improved substantially the selectivity of the NO degradation process. The photocatalysts here proposed maintain their properties as they are integrated into a silica matrix producing a product with potential use for the coating of different substrates, such as building materials for application in urban areas and fabrics or foams for the photocatalytic filters production.