Kinetic modeling of the photocatalytic degradation of acetaminophen and its main transformation products.

In this study, a kinetic model of the heterogeneous photocatalytic degradation of acetaminophen and its main transformation products is presented. Kinetic photocatalytic modeling and photon absorption rate modeling were included. Monte Carlo method was used to model the photon absorption process. Experiments were carried out in a reactor operated in batch mode and TiO2 nanotubes were used as photocatalyst irradiated with 254 nm UVC. Kinetic parameters were estimated from the experiments data by applying a non-linear regression procedure. Intrinsic expressions to the kinetics of acetaminophen degradation and its main transformation products were derived. Model, kinetics and photon absorption formulations and parameters proved to be affordable for describing the photocatalytic degradation of acetaminophen, but improvements should be done for better description of formation and oxidation kinetics of main transformation products. The model should be tested with other pharmaceuticals and emergent pollutants to calibrate it and evaluate its applicability in a wide range of compounds.

Atrazine degradation through a heterogeneous dual-effect process using Fe-TiO2-allophane catalysts under sunlight.

This study investigated the novel application of Fe-TiO2-allophane catalysts with 6.0 % w/w of iron oxide and two TiO2 proportions (10 % and 30 % w/w) for degrading atrazine (ATZ) using the heterogeneous dual-effect (HDE) process under sunlight. Comparative analyses with Fe-allophane and TiO2-allophane catalysts were conducted in both photocatalysis (PC) and HDE processes. FTIR spectra reveal the unique hydrous feldspathoids structure of allophane, showing evidence of new bond formation between Si-O groups of allophane clays and iron hydroxyl species, as well as Si-O-Ti bonds that intensified with higher TiO2 content. The catalysts exhibited an anatase structure. In Fe-TiO2-allophane catalysts, iron oxide was incorporated through the substitution of Ti4+ by Fe3+ in the anatase crystal lattice and precipitation on the surface of allophane clays, forming small iron oxide particles. Allophane clays reduced the agglomeration and particle size of TiO2, resulting in an enhanced specific surface area and pore volume for all catalysts. Iron oxide incorporation decreased the band gap, broadening the photoresponse to visible light. In the PC process, TiO2-allophane achieves 90 % ATZ degradation, attributed to radical species from the UV component of sunlight. In the HDE process, Fe-TiO2-allophane catalysts exhibit synergistic effects, particularly with 30 % w/w TiO2, achieving 100 % ATZ degradation and 85 % COD removal, with shorter reaction time as TiO2 percentage increased. The HDE process was performed under less acidic conditions, achieving complete ATZ degradation after 6 h without iron leaching. Consequently, Fe-TiO2-allophane catalysts are proposed as a promising alternative for degrading emerging pollutants under environmentally friendly conditions.

Sol-Gel Synthesis of TiO2 with Pectin and Their Efficiency in Solar Cells Sensitized by Quantum Dots.

In this study, titanium oxide TiO2 nanoparticles were produced using the sol-gel approach of green synthesis with pectin as the reducing agent. The synthetized TiO2 nanoparticles with pectin were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), visible light absorption (UV-Vis) and the BET method. The structure and morphology of the TiO2 powder were described with SEM, revealing uniform monodisperse grains with a distribution of 80% regarding sizes < 250 nm; the resulting crystal phase of synthetized TiO2 was identified as an anatase and rutile phase with a crystallinity size estimated between 27 and 40 nm. Also, the surface area was determined by nitrogen adsorption-desorption using the Brown-Emmet-Teller method, with a surface area calculated as 19.56 m2/g, typical of an IV type isotherm, indicating mesoporous NPs. UV-Vis spectra showed that sol-gel synthesis reduced the band gap from the 3.2 eV common value to 2.22 eV after estimating the optical band gap energy using the adsorption coefficient; this translates to a possible extended photo response to the visible region, improving photoactivity. In addition, the power conversion of the photoelectrode was compared based on similar assembly techniques of TiO2 electrode deposition. Quantum dot crystals were deposited ionically on the electrode surface, as two different paste formulations based on a pectin emulsifier were studied for layer deposition. The results confirm that the TiO2 paste with TiO2-synthesized powder maintained good connections between the nanocrystalline mesoporous grains and the deposited layers, with an efficiency of 1.23% with the transparent paste and 2.27% with the opaque paste. These results suggest that pectin could be used as a low-cost, functional sol-gel catalysis agent for the synthesis of controlled NPs of metal oxide. It demonstrates interesting optical properties, such as an increase in photo response, suggesting further applications to photocatalysts and biomedical features.

Formation of Olive-like TiO2 Nanospheres in a Polymeric Mesh by Sol-Gel Method.

Olive-like TiO2 (titanium dioxide), nanospheres compounds were synthesized. Polysaccharide (1-3 linked ß-D galactapyranose and 1.4-linked 3.6 anyhdro-α-L-galactopyranose and titanium isopropoxide (IV) was used as a precursor in its formation. The powder sample was evaluated by scanning tunneling microscope, X-ray diffraction pattern, power spectral density, fast Fourier transform, differential thermal analysis, continuous wavelet transform, and isotropy texture analysis. The results demonstrate that these nanospheres can successfully be synthesized in a solution using a polysaccharide network by means of the sol-gel method. The synthesized olive-like TiO2 nanospheres have diameters ranging from 50 nm to 500 nm. The synthesis parameters, such as temperature, time, and concentration of the polysaccharide, were controlled in solution.

Illuminating Pathways to Dynamic Nanotribology: Light-Mediated Active Control of Interfacial Friction with Nanosuspensions.

Active control of nanotribological properties is a challenge. Materials responsive to external stimuli may catalyze this paradigm shift. Recently, the nanofriction of a thin film is modulated by light, ushering in phototribology. This frontier is expanded here, by investigating photoactive nanoparticles in lubricants to confer similar functionality to passive surfaces. Quartz-crystal microbalance (QCM) is employed to assess the phototribological behavior of aqueous suspensions of titanium dioxide nanoparticles. A comparison of dark and illuminated conditions provides the first demonstration of tuning the interfacial friction in solid-nanosuspension interfaces by light. Cyclic tests reveal reversible transitions between higher (dark) and lower friction (illuminated) regimes. These transitions are underpinned by transient states with surface charge variations, as confirmed by Zeta potential measurements. The accumulated surface charge increases repulsion within the system and favors sliding. Upon cessation of illumination, the system returns to its prior equilibrium state. These findings impact not only nanotribology but nanofluidics and nanorheology. Furthermore, the results underscore the need to consider light-induced effects in other scenarios, including the calculation of activity coefficients of photoactive suspensions. This multifaceted study introduces a new dimension to in operando frictional tuning, beckoning a myriad of applications and fundamental insights at the nanoscale.

Photocatalytic Degradation of Naproxen: Intermediates and Total Reaction Mechanism.

Photochemical and photocatalytic oxidation of naproxen (NPX) with UV-A light and commercial TiO2 under constant flow of oxygen have been investigated. Adsorption experiments indicated that 90% of the solute remained in the solution. Combined chemical analysis of samples on the photochemical degradation indicated that NPX in an aqueous solution (20 ppm) is efficiently transformed into other species but only 18% of the reactant is mineralized into CO2 and water after three hours of reaction. Performing the photocatalytic oxidation in the presence of TiO2, more than 80% of the organic compounds are mineralized by reactive oxidation species (ROS) within four hours of reaction. Analysis of reaction mixtures by a combination of analytical techniques indicated that naproxen is transformed into several aromatic naphthalene derivatives. These latter compounds are eventually transformed into polyhydroxylated aromatic compounds that are strongly adsorbed onto the TiO2 surface and are quickly oxidized into low-molecular-weight acids by an electron transfer mechanism. Based on this and previous studies on NPX photocatalytic oxidation, a unified and complete degradation mechanism is presented.

MnO2/TiO2-Catalyzed ozonolysis: enhancing Pentachlorophenol degradation and understanding intermediates.

Pentachlorophenol is a pesticide widely known for its harmful effects on sewage, causing harm to the environment. In previous studies, our group identified adsorption as a crucial factor in catalytic ozonation processes, and subsequent observations revealed the catalyst's role in reducing toxicity during degradation. In this research, we quantified organochlorine intermediates and low molecular weight organic acids generated under optimal pH conditions (pH 9), with and without the catalyst. Additionally, we assessed the reactivity of these intermediates through theoretical calculations. Our findings indicate that the catalyst reduces the duration of intermediates. Additionally, the presence of CO2 suggests enhanced mineralization of pentachlorophenol, a process notably facilitated by the catalyst. Theoretical calculations, such as Fukui analysis, offer insights into potential pathways for the dechlorination of aromatic molecules by radicals like OH, indicating the significance of this pathway.

Characterization of modified titanium surfaces by anodisation and immersion tests.

This paper explores the features of both nanoporous and compact TiO2 films formed by titanium anodisation in two experimental conditions, given that they have completely different morphologies and properties than those found by our previous studies. After anodisation, samples have been subjected for 20 days to immersion tests in different media (H2O, H3PO4, and KOH). Surface morphology, phase composition and wettability of anodised films were investigated using FESEM, FTIR, Raman spectroscopy, contact angle measurements and XPS, and the hydrophilicity of modified surfaces was investigated by immersion tests. Nanoporous films exhibited hydrophobic surfaces, but contact angle values gradually decreased after immersing films in H2O, H3PO4 and KOH media, respectively. However, compact films produced superhydrophilic surfaces, both before and after immersion tests, with the exception of immersing the film in a H3PO4 medium due to film removal by acid attack. As for compact films, an unusual morphology revealed by the presence of cone-shaped particles might be responsible for the adsorption of -OH groups arranged so as to favour anatase phase formation.

Assessment of thermohydraulic performance and entropy generation in an evacuated tube solar collector employing pure water and nanofluids as working fluids.

This study conducts a numerical comparison of the thermal performance of three distinct working fluids (pure water, TiO2, and SiO2 water-based nanofluids) within an evacuated tube solar collector using Computational Fluid Dynamics. The study evaluates thermohydraulic performance alongside global and local entropy generation rates, while considering variations in solar radiation values and inlet mass flow rates. Results indicate that nanofluids demonstrate superior performance under low solar radiation, exhibiting higher outlet temperatures, velocities, thermal efficiency, and exergy efficiency compared to pure water. However, at the higher solar radiation level, the efficiency of SiO2 water-based nanofluid diminishes due to its impact on specific heat. Furthermore, the entropy generation analysis reveals significant reductions with TiO2 water-based nanofluid in all the phenomena considered (up to 79 %). The SiO2 nanofluid performance aligns closely with pure water under high radiation value. This investigation offers valuable insights into the utilization of nanofluids in solar collectors across diverse operating conditions, emphasizing their pivotal role in enhancing overall performance.

Enhancing Methylene Blue Removal through Adsorption and Photocatalysis-A Study on the GO/ZnTiO3/TiO2 Composite.

This study focuses on synthesizing and characterizing a graphene oxide/ZnTiO3/TiO2 (GO/ZTO/TO) composite to efficiently remove methylene blue (MB) from water, presenting a novel solution to address industrial dye pollution. GO and ZTO/TO were synthesized by the modified Hummers and sol-gel methods, respectively, while GO/ZTO/TO was prepared using a hydrothermal process. The structural and surface properties of the composite were characterized using various analytical techniques confirming the integration of the constituent materials and suitability for dye adsorption. The study revealed that GO/ZTO/TO exhibits an adsorption capacity of 78 mg g-1 for MB, with only a 15% reduction in adsorption efficiency until the fifth reuse cycle. Furthermore, the study suggests optimal adsorption near neutral pH and enhanced performance at elevated temperatures, indicating an endothermic reaction. The adsorption behavior fits the Langmuir isotherm, implying monolayer adsorption on homogeneous surfaces, and follows pseudo-second-order kinetics, highlighting chemical interactions at the surface as the rate-limiting step. The photocatalytic degradation of MB by GO/ZTO/TO follows pseudo-first-order kinetics, with a higher rate constant than that of GO alone, demonstrating the enhanced photocatalytic activity of the composite. In conclusion, GO/ZTO/TO emerges as a promising and sustainable approach for water purification, through an adsorption process and subsequent photocatalytic degradation.

Solid CaCO3 Formation in Glioblastoma Multiforme and its Treatment with Ultra-Nanoparticulated NPt-Bionanocatalysts.

BACKGROUND: Glioblastoma multiforme (GBM), the most prevalent form of central nervous system (CNS) cancer, stands as a highly aggressive glioma deemed virtually incurable according to the World Health Organization (WHO) standards, with survival rates typically falling between 6 to 18 months. Despite concerted efforts, advancements in survival rates have been elusive. Recent cutting-edge research has unveiled bionanocatalysts with 1% Pt, demonstrating unparalleled selectivity in cleaving C-C, C-N, and C-O bonds within DNA in malignant cells. The application of these nanoparticles has yielded promising outcomes. OBJECTIVE: The objective of this study is to employ bionanocatalysts for the treatment of Glioblastoma Multiforme (GBM) in a patient, followed by the evaluation of obtained tissues through electronic microscopy. METHODS: Bionanocatalysts were synthesized using established protocols. These catalysts were then surgically implanted into the GBM tissue through stereotaxic procedures. Subsequently, tissue samples were extracted from the patient and meticulously examined using Scanning Electron Microscopy (SEM). RESULTS AND DISCUSSION: Detailed examination of biopsies via SEM unveiled a complex network of small capillaries branching from a central vessel, accompanied by a significant presence of solid carbonate formations. Remarkably, the patient subjected to this innovative approach exhibited a three-year extension in survival, highlighting the potential efficacy of bionanocatalysts in combating GBM and its metastases. CONCLUSION: Bionanocatalysts demonstrate promise as a viable treatment option for severe cases of GBM. Additionally, the identification of solid calcium carbonate formations may serve as a diagnostic marker not only for GBM but also for other CNS pathologies.

Preliminary insights on the development of a continuous-flow solar system for the photocatalytic degradation of contaminants of emerging concern in water.

The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0 mg/L, except DXM (0.8 mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120 min. After 15 min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318 µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.

Pd:In-Doped TiO2 as a Bifunctional Catalyst for the Photoelectrochemical Oxidation of Paracetamol and Simultaneous Green Hydrogen Production.

The integration of clean energy generation with wastewater treatment holds promise for addressing both environmental and energy concerns. Focusing on photocatalytic hydrogen production and wastewater treatment, this study introduces PdIn/TiO2 catalysts for the simultaneous removal of the pharmaceutical contaminant paracetamol (PTM) and hydrogen production. Physicochemical characterization showed a high distribution of Pd and In on the support as well as a high interaction with it. The Pd and In deposition enhance the light absorption capability and significantly improve the hydrogen evolution reaction (HER) in the absence and presence of paracetamol compared to TiO2. On the other hand, the photoelectroxidation of PTM at TiO2 and PdIn/TiO2 follows the full mineralization path and, accordingly, is limited by the adsorption of intermediate species on the electrode surface. Thus, PdIn-doped TiO2 stands out as a promising photoelectrocatalyst, showcasing enhanced physicochemical properties and superior photoelectrocatalytic performance. This underscores its potential for both environmental remediation and sustainable hydrogen production.

VIS-active TiO2 films decorated by expanded graphite: impact of the exfoliation time on the photocatalytic behaviour.

TiO2/C nanocomposite films were applied on water treatment. Expanded graphite nanosheets (EG) were obtained by UVC-assisted liquid-phase exfoliation technique, without the addition of acids, surfactants, or aggressive oxidizing agents, which characterizes the process as an eco-friendly method. The carbon nanosheets were synthesized directly from graphite bulk at different times and deposited on TiO2 films surface by airbrush spray coating method, forming a TiO2/C heterojunction. The increase in the exfoliation time promoted a more efficient photocatalytic dye removal under visible light. Morphological modifications, changes in the electronic structure, and wide range of light absorption were observed from the TiO2/C heterojunction formation. The results showed that hybrid TiO2/C supported photocatalyst is a promise alternative for practical photocatalytic applications under sunlight.

Photocatalytic effect of N-TiO2 conjugated with folic acid against biofilm-forming resistant bacteria.

Antibiotic resistance challenges the treatment of bacterial biofilm-related infections, but the use of nanoparticles as a treatment is a promising strategy to overcome bacterial infections. This study applied nitrogen-doped titanium dioxide (N-TiO2) conjugated with folic acid (FA) on biofilm-forming resistant bacteria. The photocatalytic effect of TiO2 nanoparticles (NPs) was studied under ultraviolet (UV), visible light, and dark conditions at 60, 120, and 180 min against planktonic cells and biofilms of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. TiO2 NPs were in the anatase phase, spherical shaped with sizes of 10-13 nm, and effectively doped and conjugated with N and FA. The FA-conjugated nanoparticles (N-TiO2-FA and FA-TiO2) were shown to have a bactericidal effect on all bacteria between 60 and 180 min under UV and visible light conditions. Concerning biofilms, N-TiO2-FA was shown to have a highly disruptive effect on all bacterial biofilms under UV irradiation at 180 min. Meanwhile, the nanoparticles did not show DNA damaging potential and they had no cytostatic effect, indicating that these NPs are biocompatible. In sum, nanoparticle conjugation with FA promoted photocatalytic effectiveness, revealing the promise this nanomaterial holds as a biocompatible antimicrobial agent.

Synthesis and Characterization of a Photocatalytic Material Based on Raspberry-like SiO2@TiO2 Nanoparticles Supported on Graphene Oxide.

A raspberry-like SiO2@TiO2 new material supported on functionalized graphene oxide was prepared to reduce titania's band gap value. The material was characterized through different analytical methods such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). The band gap value was studied via UV-Vis absorption spectra and determined through the Kubelka-Munk equation. A theoretical study was also carried out to analyze the interaction between the species.

Photocatalytic and antifouling performance of titania-coated alumina membranes produced using a facile sol-gel dip-coating approach.

Photocatalytic membranes (PM) have been investigated as an antifouling strategy for membrane separation processes. Coating ceramic membranes with photocatalytic layers can provide a highly active surface capable of degrading foulants and smaller molecules improving the membrane's performance when the surface is irradiated by a suitable light. Nevertheless, the coating process often leads to pore blockage due to the formation or deposition of thick layers of photocatalyst on membrane surfaces, which modifies the original membranes' average pore size and reduces membrane permeability. A facile sol-gel dip coating process was used to produce PM without modifying the original surface morphology of alumina microfiltration membranes. A 3.7-fold increase in permeate volume after 90 minutes of permeation of an acetaminophen solution in continuous filtration mode under UV light (λ = 365 nm LED, 10W) using titania as photocatalyst compared to the bare alumina membrane without irradiation. Furthermore, fouling modeling proved a reduction in the fouling constant, while fouling mechanisms were not modified. Raman analysis showed 100% anatase formed on the membrane surface. Although membranes could remove up to 87% TOC for oily wastewater filtration, antifouling capabilities for this type of effluent were not observed for the photocatalytic membranes mainly due to fouling inside the pores and light attenuation due to the thick fouling layer on the membrane surface.

Ketorolac removal through photoelectrocatalysis using TiO2 nanotubes in water system.

Ketorolac, a highly persistent NSAID of environmental concern, was significantly removed from water (80% removal) through photoelectrocatalysis where titanium dioxide nanotubes prepared by Ti foil electrochemical anodization at 30 V were used as photoanodes. Fifteen milligrams per liter of ketorolac solutions in a 0.05 M Na2SO4 aqueous medium was subjected to irradiation from a 365-nm light with an intensity of 1 mWcm-2 and under an applied potential of 1.3 V (vs. Hg/Hg2SO4/sat.K2SO4) at pH 6.0. When each process (photo and electrocatalysis) was carried out separately, less than 20% drug removal was achieved as monitored through UV-vis spectrophotometry. Through scavenging experiments, direct oxidation on the photogenerated holes and oxidation by hydroxyl radical formation were found to play a key role on ketorolac's degradation. Chemical oxygen demand (COD) analyses also showed a significant COD decreased (68%) since the initial COD value was 31.3 mg O2/L and the final COD value was 10.1 mg O2/L. A 48% mineralization was also achieved, as shown by total organic carbon (TOC) analyses. These results showed that electrodes based on titania nanotubes are a promising alternative material for simultaneous photocatalytic and electrocatalytic processes in water remediation.

Multivariate optimization of methylene blue dye degradation using electro-Fenton process with self-doped TiO2 nanotube anode.

This paper reports the optimization of the electro-Fenton (EF) process using different anode materials for the degradation of Methylene Blue (MB) dye as a model compound. The cathode used was an air-diffusion PTFE, while three different anode materials (Pt, DSA, and self-doped TiO2 nanotubes - SD-TNT) were tested individually. A full factorial design (FFD) with a central point combined with response surface methodology (RSM) was employed to optimize the experimental variables, including solution pH, applied current, and anode material. The optimized EF conditions involved a pH of 4.0, a current of 100 mA, and an SD-TNT anode for 120 min of electrolysis. Under these conditions, the MB solution achieved complete decolorization and 45% of total organic carbon (TOC) removal after 120 min of EF treatment. The findings indicate that the hydroxyl radical (•OH) plays a crucial role as the primary oxidizing agent in the EF process. The decay of MB followed pseudo-first-order kinetics, reflecting a consistent formation of •OH radicals that effectively attacked the MB dye and its subproducts during mineralization. Moreover, the EF process exhibited superior performance in terms of energy consumption (EC) and mineralization current efficiency (ECM) in the initial treatment stages, while the presence of recalcitrant by-products and loss of anode self-doping impacted performance in the later stages. The optimized EF conditions and the understanding gained from this study contribute to the advancement of sustainable wastewater treatment strategies for the removal of organic dyes.

TiO2/MWCNT/Nafion-Modified Glassy Carbon Electrode as a Sensitive Voltammetric Sensor for the Determination of Hydrogen Peroxide.

In this work we describe a straightforward approach for creating a nanocomposite comprising multiwalled carbon nanotubes (MWCNTs) and titanium dioxide (TiO2) using the hydrothermal technique, which is then characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA) to assess its properties. Nafion is employed as a reticular agent for the nanocomposite on the glassy carbon electrode (GCE), creating the MWCNT/TiO2/Nafion/GCE system. The electrochemical behavior of the system was evaluated using cyclic voltammetry, revealing its remarkable electrocatalytic activity for detecting hydrogen peroxide in water. The developed sensor showcased a broad linear response range of 14.00 to 120.00 µM, with a low detection limit of 4.00 µM. This electrochemical sensor provides a simple and highly sensitive method for detecting hydrogen peroxide in aqueous solutions and shows promising potential for various real-world applications, particularly in H2O2 monitoring.