Solar Photocatalytic Degradation of Sulfamethoxazole by TiO2 Modified with Noble Metals

Clinical implementation of a paediatric 3D-printed combination of Sulfamethoxazole and Trimethoprim

Adherence to treatment is one of the major challenges in chronic diseases. Inappropriate dosage forms or bad taste are the main factor for non-adherence, especially in paediatric patients. 3D printed medicines could be tailored to specific patients to make medicines more acceptable, however the clinical implementation in hospitals is still limited. This study addresses the challenge of developing pharma-inks (mixtures of drugs and excipients) for semi-solid extrusion (SSE) to produce chewable tablets of Sulfamethoxazole (SMX) and Trimethoprim (TMP) for paediatric oncology patients in a hospital setting. SMX and TMP pharma-inks were stable and printable on demand for more than 3 months. The chewable tablets were also stable, and the drug dissolution profiles were comparable to those of the commercial formulations, indicating potential bioequivalence. Human sensory evaluations confirmed that the formulation improved palatability compared to traditional suspensions. 3D-printed SMX/TMP formulations are an alternative to traditional formulations for paediatric patients in hospital settings, enhancing acceptability and adherence while enabling personalized dosing.

The photo-based treatment technology simultaneously removes resistant bacteria and resistant genes from wastewater

Because of the recent widespread usage of antibiotics, the acquisition and dissemination of antibiotic-resistance genes (ARGs) were prevalent in the majority of habitats. Generally, the biological wastewater treatment processes used in wastewater treatment plants have a limited efficiencies of antibiotics resistant bacteria (ARB) disinfection and ARGs degradation and even promote the proliferation of ARGs. Problematically, ARB and ARGs in effluent pose potential risks if they are not further treated. Photocatalytic oxidation is considered a promising disinfection technology, where the photocatalytic process generates many free radicals that enhance the interaction between light and deoxyribonucleic acid (DNA) for ARB elimination and subsequent degradation of ARGs. This review aims to illustrate the progress of photocatalytic oxidation technology for removing antibiotics resistant (AR) from wastewater in recent years. We discuss the sources and transfer of ARGs in wastewater. The overall removal efficiencies of ultraviolet radiation (UV)/chlorination, UV/ozone, UV/H2O2, and UV/sulfate-radical based system for ARB and ARGs, as well as the experimental parameters and removal mechanisms, are systematically discussed. The contribution of photocatalytic materials based on TiO2 and g-C3N4 to the inactivation of ARB and degradation of ARGs is highlighted, producing many free radicals to attack ARB and ARGs while effectively limiting the horizontal gene transfer (HGT) in wastewater. Finally, based on the reviewed studies, future research directions are proposed to realize specific photocatalytic oxidation technology applications and overcome current challenges.

Degradation pathways of sulfamethoxazole under phototransformation processes: A data base of the major transformation products for their environmental monitoring

Sulfamethoxazole (SMX) is frequently detected in wastewater and aquatic environments worldwide at concentrations from ng L-1 to μg L-1. Unfortunately, SMX is not completely removed in municipal wastewater treatment plants (WWTPs), thus, SMX and their transformation products (TPs) are discharged into aquatic environments, where can be transformed by phototransformation reactions. In this study, the phototransformation of SMX as well as generation of their major TPs under photolysis and photocatalysis processes was reviewed. SMX can be totally removed under photolysis and photocatalysis processes in aqueous solutions using simulated or natural radiation. Degradation pathways such as isomerization, hydroxylation, fragmentation, nitration, and substitution reactions were identified during the generation of the major TPs of SMX. Particularly, 26 TPs were considered for the creation of a data base of the major TPs of SMX generated under phototransformation processes. These 26 compounds could be used as reference during the SMX monitoring both wastewater and water bodies, using analytic methodologies such as target analysis and suspect screening. A data base of the major TPs of pharmaceuticals active compounds (PhACs) as SMX could help to implementation of best environmental monitoring programs for the study of the environmental risks both PhACs and their TPs with highest occurrence in aquatic environments.

Persulfate assisted photocatalytic and antibacterial activity of TiO2-CuO coupled with graphene oxide and reduced graphene oxide

Photocatalysts of TiO2-CuO coupled with 30% graphene oxide (GO) were hydrothermally fabricated, which varied the TiO2 to CuO weight ratios to 1:4, 1:2, 1:1, 2:1 and 4:1 and reduced to form TiO2-CuO/reduced graphene oxide (rGO) photocatalysts. They were characterized using XRD, TEM, SEM, XPS, Raman, and DRS technologies. TiO2-CuO composites and TiO2-CuO/GO degrade methylene blue when persulfate ions are present. Persulfate concentration ranged from 1, 2, 4 to 8 mmol/dm-3 in which the highest activity of 4.4 × 10-2 and 7.35 × 10-2 min-1 was obtained with 4 mmol/dm-3 for TiO2-CuO (1:4) and TiO2-CuO/GO (1:1), respectively. The presence of EDTA and isopropyl alcohol reduced the photodegradation. TiO2-CuO coupled with rGO coagulates methylene blue in the presence of persulfate ions and such coagulation is independent of light. The catalyst dosage and the concentration of the dye were varied for the best-performing samples. The antibacterial activity of the synthesized samples was evaluated against the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonia. Ti:Cu (1:2)-GO and Ti:Cu (1:4)-GO had the highest antibacterial activity against K. pneumoniae (16.08 ± 0.14 mm), P. aeruginosa (22.33 ± 0.58 mm), E. coli (16.17 ± 0.29 mm) and S. aureus (16.08 ± 0.88).

Facile aqueous synthesis and comparative evaluation of TiO2-semiconductor and TiO2-metal nanohybrid photocatalysts in antibiotics degradation under visible light

Advanced oxidation processes using TiO2-based nanomaterials are sustainable technologies that hold great promise for the degradation of many types of pollutants including pharmaceutical residues. A wide variety of heterostructures coupling TiO2 with visible-light active nanomaterials have been explored to shift its photocatalytic properties to harness sun irradiation but a systematic comparison between them is lacking in the current literature. Furthermore, the high number of proposed nanostructures with different size, morphology, and surface area, and the often complex synthesis processes hamper the transition of these materials into commercial and effective solutions for environmental remediation. Herein, we have designed a facile and cost-effective method to synthesize two heterostructured photocatalysts representative of two main families of novel structures proposed, hybrids of TiO2 with metal (Au) and semiconductor (CeO2) nanomaterials. The photocatalysts have been extensively characterized to ensure a good comparability in terms of co-catalyst doping characteristics, morphology and surface area. The photocatalytic degradation of ciprofloxacin and sulfamethoxazole as target pollutants, two antibiotics of high concern polluting water sources, has been evaluated and CeO2/TiO2 exhibited the highest activity, achieving complete antibiotic degradation at very low photocatalyst concentrations. Our study provides new insights into the development of inexpensive heterostructured photocatalysts and suggests that the non-stoichiometry and characteristic d and f electronic orbital configuration of CeO2 have a significantly improved role in the enhancement of the photocatalytic reaction.

Strategy for improvement of molecular oxygen activation capacity of PPECu by chlorine doping for water decontamination

The activation of molecular oxygen and generation of reactive oxygen species (ROS) play important roles in the efficient removal of contaminants from aqueous ecosystems. Herein, using a simple and rapid solvothermal process, we developed a chlorine-doped phenylethynylcopper (Cl/PPECu) photocatalyst and applied it to visible light degradation of sulfamethazine (SMT) in aqueous media. The Cl/PPECu was optimized to have a 2.52 times higher steady-state concentration of O2•- (3.62 × 10-5 M) and a 28.87 times higher degradation rate constant (0.2252 min-1) for SMT compared to pure PPECu. Further, the effectiveness of Cl/PPECu in treating sulfonamide antibiotics (SAs) in real water systems was verified through an investigation involving natural water bodies, SAs, and ambient sunlight. The energy band structure, DFT calculation and correlation heat map indicated that the addition of chlorine modulated the local electronic structure of PPECu, leading to an improvement in the electron-hole separation, enhanced the O2 activation, and promoted the generation of ROSs. This study not only puts forward innovative ideas for the eco-compatible remediation of environmental pollution using PPECu, but also sheds new light on the activation of oxygen through elemental doping.

Current perspectives of metal-based nanomaterials as photocatalytic antimicrobial agents and their therapeutic modes of action: A review

Efforts to restrict the emergence and progression of multidrug-resistant bacterial strains should heavily involve the scientific community, including government bodies, researchers, and industries, in developing new and effective photocatalytic antimicrobial agents. Such changes warrant the modernization and upscaling of materials synthesis laboratories to support and expedite the mass production of materials at the industrial scale for the benefit of humankind and the environment. Despite the massive volume of publications reporting the potential usage of different types of metal-based nanomaterials as antimicrobial agents, reviews uncovering the similarities and differences among the various products remain lacking. This review details the basic and unique properties of metal-based nanoparticles, their use as photocatalytic antimicrobial agents, and their therapeutic modes of action. It shall be noted that compared to traditional antibiotics, the mode of action of photocatalytic metal-based nanomaterials for killing microorganisms are completely different, despite displaying promising performance against antibiotic-resistant bacteria. Besides, this review uncovers the differences in the mode of actions of metal oxide nanoparticles against different types of bacteria, as well as towards viruses. Last but not least, this review comprehensively describes previous published clinical trials and medical usages involving contemporary photocatalytic antimicrobial agents.

Fabrication, characterization, and performance evaluation of Bi2WO6/TiO2/Fe3O4 photocatalyst responding to visible light for enhancing bisphenol A degradation

A novel magnetic Bi₂WO₆/TiO₂/Fe₃O₄ photocatalyst was synthesized by a hydrothermal approach. The pattern, structure, elemental composition, light-absorbing properties, and magnetism of Bi₂WO₆/TiO₂/Fe₃O₄ were characterized and analyzed. The performance, influencing factors, and mechanism of Bi₂WO₆/TiO₂/Fe₃O₄ towards bisphenol A (BPA) degradation were investigated and deduced. BPA removal up to 95% was achieved with the addition of 1.25 g/L Bi/Ti/Fe2 (molar ratio of Bi₂WO₆:TiO₂:Fe₃O₄ = 2:1:0.17) in the solution containing 10 mg/L BPA at pH 5.6. The performance of Bi/Ti/Fe2 was stable for five cycles at least after extracted from the reacted solution by magnet. Photoexcited h⁺, •OH, and •O₂^- formed in the reaction mainly contributed to BPA degradation. The Bi/Ti/Fe2 composite was composed of a three-layer petal structure from outside to inside to be Bi₂WO₆, TiO₂, and Fe₃O₄. This structure was conducive in forming a heterojunction between TiO₂ and Bi₂WO₆, inhibiting the merging of photoexcited e^- and h⁺, and improving the photocatalytic efficiency.

Photocatalytic degradation of sulfamethoxazole using TiO2-based materials - Perspectives for the development of a sustainable water treatment technology

Heterogeneous photocatalysis using titanium dioxide-based materials is considered a promising and innovative solution to the water pollution problem. However, due to the limitations concerning the use of the developed materials and the applied photodegradation conditions, the research on photoremediation using TiO₂ often stays behind the lab door. The challenge is to convert the basic research into a successful innovation, leading to the implementation of this process into wastewater treatment. For this purpose, the most active materials and optimal photodegradation conditions must be chosen. This article collects and compares the studies on photocatalytic degradation of an emerging pollutant - sulfamethoxazole, an antibacterial drug - and attempts to find the best approaches to be successfully applied on an industrial scale. Various types of TiO₂-based photocatalysts are compared, including different nanoforms, doped or polymer-based composites, composites with graphene, activated carbon, dyes or natural compounds, as well as possible supporting materials for TiO₂. The paper covers the impact of the irradiation source (natural sunlight, LED, mercury or xenon lamps) and water matrix on the photodegradation process, considering the ecological and economic sustainability of the process. Emphasis is put on the stability, ease of separation and reuse of the photocatalyst, power and safety of the irradiation source, identification of photodegradation intermediates and toxicity assays. The main approaches are critically discussed, main challenges and perspectives for an effective photocatalytic water treatment technology are pointed out.

Pt-N Co-Modified TiO2 Nanotube Electrode Photoelectrocatalytic Degradation of Oxytetracycline in Simulated Wastewater

Using photodeposition and plasma, Pt-N co-modified TiO₂ nanotube electrodes were created. Several techniques, such as SEM, XRD, UV-VIS-DRS, XPS, and PL, were used to analyze the electrode shape, crystalline structure, light absorption range, elemental composition, and photogenerated carrier recombination efficiency. Using the electrochemical workstation, EIS and I-t were utilized to examine the electrochemical characteristics. The results indicated that the diameter of the TiO₂ nanotube tubes was around 90 nm, and that the photodeposition duration affected the amount of Pt particles deposited. The deposited Pt particles efficiently reduced the photogenerated carrier complexation rate of the N-TiO₂ nanotube electrode, contributing to the separation of electron-hole pairs and light utilization. Electrochemical studies indicated that Pt-N co-modified TiO₂ increased the electrode's oxidation and electrical conductivity, as well as its photoelectrocatalytic capacity. Oxytetracycline degradation in simulated wastewater by a Pt-N co-modified TiO₂ nanotube electrode revealed the exceptional PEC activity, and the oxytetracycline degradation processes followed primary kinetics. •O₂^- and •OH played a significant role in the photoelectrocatalytic degradation of oxytetracycline, resulting in a novel method for oxytetracycline degradation.

Supported TiO2 in Ceramic Materials for the Photocatalytic Degradation of Contaminants of Emerging Concern in Liquid Effluents: A Review

The application of TiO₂ as a slurry catalyst for the degradation of contaminants of emerging concern (CEC) in liquid effluents has some drawbacks due to the difficulties in the catalyst reutilization. Thus, sophisticated and expensive separation methods are required after the reaction step. Alternatively, several types of materials have been used to support powder catalysts, so that fixed or fluidized bed reactors may be used. In this context, the objective of this work is to systematize and analyze the results of research inherent to the application of ceramic materials as support of TiO₂ in the photocatalytic CEC removal from liquid effluents. Firstly, an overview is given about the treatment processes able to degrade CEC. In particular, the photocatalysts supported in ceramic materials are analyzed, namely the immobilization techniques applied to support TiO₂ in these materials. Finally, a critical review of the literature dedicated to photocatalysis with supported TiO₂ is presented, where the performance of the catalyst is considered as well as the main drivers and barriers for implementing this process. A focal point in the future is to investigate the possibility of depurating effluents and promote water reuse in safe conditions, and the supported TiO₂ in ceramic materials may play a role in this scope.

Editorial Catalysts: Special Issue on Recent Advances in TiO2 Photocatalysts

The development of civilization and the massive use of traditional energy sources has led to progressive environmental degradation that requires immediate action [...]

Application of TiO2-Based Photocatalysts to Antibiotics Degradation: Cases of Sulfamethoxazole, Trimethoprim and Ciprofloxacin

The extensive application of antibiotics in human and veterinary medicine has led to their widespread occurrence in a natural aquatic environment. Global health crisis is associated with the fast development of antimicrobial resistance, as more and more infectious diseases cannot be treated more than once. Sulfamethoxazole, trimethoprim and ciprofloxacin are the most commonly detected antibiotics in water systems worldwide. The persistent and toxic nature of these antibiotics makes their elimination by conventional treatment methods at wastewater treatment plants almost impossible. The application of advanced oxidation processes and heterogeneous photocatalysis over TiO2-based materials is a promising solution. This highly efficient technology has the potential to be sustainable, cost-efficient and energy-efficient. A comprehensive review on the application of various TiO2-based photocatalysts for the degradation of sulfamethoxazole, trimethoprim and ciprofloxacin is focused on highlighting their photocatalytic performance under various reaction conditions (different amounts of pollutant and photocatalyst, pH, light source, reaction media, presence of inorganic ions, natural organic matter, oxidants). Mineralization efficiency and ecotoxicity of final products have been also considered. Further research needs have been presented based on the literature findings. Among them, design and development of highly efficient under sunlight, stable, recyclable and cost-effective TiO2-based materials; usage of real wastewaters for photocatalytic tests; and compulsory assessment of products ecotoxicity are the most important research tasks in order to meet requirements for industrial application.

Photocatalytic degradation of sulfamethoxazole using TiO2 in simulated seawater: Evidence for direct formation of reactive halogen species and halogenated by-products

Nowadays photoactivation mechanism of titanium dioxide nanoparticles (TiO₂ NPs) and reactive species involved in saline waters is not sufficiently established. In this study, TiO₂ photocatalytic process under simulated solar irradiation was evaluated in synthetic seawater and compared with deionized water, using sulfamethoxazole (SMX) as model organic compound. For a TiO₂ concentration of 100 mg L^-1, SMX degradation resulted two times slower in seawater than in deionized water by the determination of their pseudo-first order rate constants of 0.020 min^-1 and 0.041 min^-1, respectively. Selected scavenging experiments revealed no significant contribution of hydroxyl radicals (OH) on the degradation process in seawater, while these radicals contributed to circa 60% on the SMX depletion in deionized water. Instead, the involvement of reactive halogen species (RHS) as main contributors for the SMX degradation in seawater could be established. A mechanism for the RHS generation was proposed, whose initiation reactions involve halides with the TiO₂ photogenerated holes, yielding chlorine and bromine radicals (Cl and Br) that may later generate other RHS. Production of RHS was further confirmed by the identification of SMX transformation products (TPs) and their evolution over time, carried out by liquid chromatography-mass spectrometry (LC-MS). SMX transformation was conducted through halogenation, dimerization and oxidation pathways, involving mainly RHS. Most of the detected transformation products accumulated over time (up to 360 min of irradiation). These findings bring concerns about the viability of photocatalytic water treatments using TiO₂ NPs in saline waters, as RHS could be yielded resulting in the generation and accumulation of halogenated organic byproducts.

Synthesis of Superior Visible-Light-Driven Nanophotocatalyst Using High Surface Area TiO2 Nanoparticles Decorated with CuxO Particles

This work provides an alternate unique simple methodology to design and synthesize chemically modified nanophotocatalyst based on high surface area TiO2 nanoparticles that can be used efficiently for the photodegradation of organic pollutants under normal visible light rather than complicated UV irradiation. In this study, dual visible light and UV-driven nanophotocatalysts were synthesized via wet chemistry procedures using high surface area TiO2 nanoparticles functionalized with (3-Aminopropyl) trimethoxysilane and attached chemically to the CuXO to improve the charge separation and maintain the non-charge recombination. The successful modification of the TiO2 nanoparticles and the formation of the TiO2-NH2-CuxO nanophotocatalyst were confirmed using different characterization techniques, and the results revealed the synthesis of high surface area TiO2 nanoparticles, and their chemical modification with an amino group and further decoration with copper to produce TiO2-NH2-CuxO nanophotocatalyst. The photocatalytic activity of TiO2 and TiO2-NH2-CuxO nanophotocatalyst were evaluated using methylene blue (MB) dye; as an example of organic pollutants. The resulting TiO2-NH2-CuxO nanophotocatalyst exhibited superior photocatalytic activity for the degradation of MB dye under visible light irradiation, due to the reduction in the energy bandgap. The degradation of the MB dye using the TiO2-NH2-CuxO nanophotocatalyst was investigated using LC-MS, and the results revealed that the hydroxyl free radical is mainly responsible for the cleavage and the degradation of the MB dye.

Mechanistic pathways for the degradation of SMX drug and floatation of degraded products using F-Pt co-doped TiO2 photocatalysts

This work presents smart pathways to enhance the photocatalytic activity of TiO2 via co-doping with fluorine (F) and platinum (Pt) to form F-Pt co-doped TiO2 photocatalysts and investigates the unique and unusual fluorination of the floated products. Our investigations indicate that the crystalline structure of the photocatalysts was a mixture of anatase and brookite phases and that the nanoparticles of the synthesized nanocomposites had nanometric sizes (4-25 nm). The F-Pt co-doped TiO2 nano-photocatalysts demonstrated degradation of sulfamethoxazole (SMX) drug of >93% within 90 min under direct solar light and 58% degradation within 360 min under a solar simulator. Thus, co-doping TiO2 with F and Pt atoms to form F-Pt co-doped TiO2 nanocomposite is an efficient pathway to achieve high photocatalytic performance escorted with the formation of floating metal-fluoropolymer, unlike pristine TiO2 which has less photocatalytic degradation and no generation of a floating polymer. Our photocatalytic protocol demonstrates that the degradation of SMX started with redox reactions of oxygen and water absorbed on the surface of the prepared nanocomposites to form superoxide anions (O2˙-) and hydroxy radicals (˙OH) which have oxidation superpower. The resultant products were subsequently fluorinated by fluoride radical ions and floated as metal-fluoropolymer.

Sulfamethoxazole and Trimethoprim Degradation by Fenton and Fenton-Like Processes

In this work, the degradation of sulfamethoxazole (SMX) and trimethoprim (TMP) via Fenton and Fenton-like processes was evaluated using Mn2+ as supporting catalyst in the Fenton reaction. The optimum conditions of degradation were also evaluated. Besides that, the effect of independent factors pH, [H2O2], [Fe2+], [Mn2+] and reaction time (t) on the efficiency of the SMX and TMP degradation were assessed. Box–Behnken was the experimental design adopted, delineating the relative concentration (C/Co) of antibiotics after treatments as response variable. The inferences were conducted using variance analysis, Pareto chart, response surface methodology, and desirability function. Due to the lack of adjustment of the SMX degradation model, there are no more inferences about it. The significant variables (p ≤ 0.05) on TMP degradation were: reaction time quadratic and linear effect, [Fe2+] linear effect, [Mn2+] linear effect, interaction pH vs. [Mn2+]. The Mn2+ addition aided TMP degradation in environments with lower pH values. However, the addition may harm the efficiency of the antibiotic degradation at higher pH. The optimum condition for TMP degradation in the conventional process (without the addition of Mn2+) is: pH 5, [H2O2] equal to 4.41 mmol L−1, [Fe2+] equal to 0.81 mmol L−1 and 90 min reaction time.

Industrial Textile Wastewater Ozone Treatment: Catalyst Selection

One of the recent trends in textile wastewater treatment has become catalytic ozonation. The necessity of effective color removal in a short treatment time is a standard during industrial implementation. At the same time, efficient chemical oxygen demand (COD), total organic carbon (TOC), and toxic by-product removal are highly expected. This study presents the results of a catalytic ozonation treatment. Three types of catalysts: a metal oxide (TiO2 as P25 by Degussa), activated carbon (nano-powder by Sigma, AC), and metal particles (platinum, 1% wt. supported on AC matrix by Sigma, Pt–AC) have been applied. The investigations were conducted for real industrial wastewater originated in textile dyeing with Reactive Black 5 dye (RB5). The experiments ran for the raw wastewater (without pretreatment), exposed blocking of the catalytic action by all used catalysts. The catalytic effect could be observed when catalytic ozonation was used as a polishing step after electrocoagulation (EC). Although the catalytic effect could be observe for all catalysts then, especially in the removal of colorless by-products, the AC was exposed as the most effective. This contributed to 35% and 40% of TOC and COD removal. While only 18% and 23% of TOC and COD were removed in the same process without AC. The decrease in toxicity was 30%. The results of the study revealed the complexity of the issue and resulted in an extensive discussion devoted to the basis of the catalytic activity of each catalyst.

Comparison of radical-driven technologies applied for paraben mixture degradation: mechanism, biodegradability, toxicity and cost assessment

Parabens (esters of p-hydroxybenzoic acid) are xenobiosis belonging to endocrine disruptors and commonly used as a preservative in cosmetics, food, pharmaceutical, and personal care products. Their wide use is leading to their appearance in water and wastewater in the range from ng/L to mg/L. In fact, the toxicity of benzylparaben is comparable to bisphenol A. Therefore, it is important to find not only effective but also ecofriendly methods for their removal from aqueous environment since the traditional wastewater treatment approaches are ineffective. Herein, for the first time, such extended comparison of several radical-driven technologies for paraben mixture degradation is presented. The detailed evaluation included (1) comparison of ozone and hydroxyl peroxide processes; (2) comparison of catalytic and photocatalytic processes (including photocatalytic ozonation); (3) characterisation of catalysts using SEM, XRD, DRS, XPS techniques and BET isotherm; (4) mineralisation, biodegradability and toxicity assessment; and (5) cost assessment. O₃, H₂O₂/Fe²⁺, H₂O₂/UVC, O₃/H₂O₂, O₃/UVA, O₃/H₂O₂/UVA, UVA/catalyst, O₃/catalyst and O₃/UVA/catalyst were selected from advanced oxidation processes to degrade parabens as well as to decrease its toxicity towards Aliivibrio fischeri, Corbicula fluminea and Lepidium sativum. Research was focused on the photocatalytic process involving visible light (UVA and natural sunlight) and TiO₂ catalysts modified by different metals (Ag, Pt, Pd, Au). Photocatalytic oxidation showed the lowest efficiency, while in combining ozone with catalysis and photocatalysis process, degradation efficiency and toxicity removal were improved. Photocatalytic ozonation slightly improved degradation efficiency but appreciably decreased transferred ozone dose (TOD). Results indicate that the degradation pathway is different, or different transformation products (TPs) could be formed, despite that the hydroxyl radicals are the main oxidant. Graphical abstract.

Morphology, Photocatalytic and Antimicrobial Properties of TiO2 Modified with Mono- and Bimetallic Copper, Platinum and Silver Nanoparticles

Noble metal nanoparticles (NMNPs) enhanced TiO₂ response and extended its activity under visible light. Photocatalytic activity of TiO₂ modified with noble metal nanoparticles strongly depends on the physicochemical properties of NMNPs. Among others, the differences in the size of NMNPs seems to be one of the most important factors. In this view, the effect of the metal’s nanoparticles size, type and amount on TiO₂ photocatalytic and biocidal activity was investigated. TiO₂ modified with mono- and bimetallic nanoparticles of Pt, Cu and Ag were prepared using chemical and thermal reduction methods. Obtained nanocomposites were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and diffuse-reflectance spectroscopy (DR/UV-Vis) techniques. The photocatalytic activity was examined in 2-propanol oxidation and hydrogen generation processes. The mechanism of modified TiO₂ excitation was evaluated in action spectrum measurements during phenol oxidation. A possibility of using less energy-consuming light sources as a set of light-emitting diodes (LEDs) selected based on action spectrum results was examined. It was found that the differences in NMNPs size were the result of the reduction method. Moreover, coupling with a second metal strongly affected and differentiated the photocatalytic and biocidal activity of the obtained TiO₂-based photocatalysts.