Highly active non-metals doped mixed-phase TiO 2 for photocatalytic oxidation of ibuprofen under visible light

Facile Synthesis of Band Gap-Tunable Kappa-Carrageenan-Mediated C,S-Doped TiO2 Nanoparticles for Enhanced Dye Degradation

Semiconducting nanoparticles (SNPs) have garnered significant attention for their role in photocatalysis technology, offering a cost-effective and highly efficient method for breaking down organic dyes. Of particular significance within SNP-based photocatalysis are tunable band gap TiO2 nanoparticles (NPs), which demonstrate remarkable enhancement in photocatalytic efficiency. In the present work, we introduce an approach for the synthesis of TiO2 NPs using kappa-carrageenan (κ-carrageenan), not just as a reducing and stabilizing agent but as a dopant for the resulting TiO2 NPs. During the synthesis of TiO2 NPs in the presence of sulfate-rich carrageenan, the process predominantly leaves residual sulfur and carbon. The presence of residual carbon, in conjunction with sulfur doping, as indicated by fast FTIR spectra, XPS, and EDX, leads to a significant reduction in the band gap of the resulting composite to 2.71 eV. The reduction of composite band gap yields remarkable degradation of methylene blue (99.97%) and methyl orange (97.84%). This work presents an eco-friendly and highly effective solution for the swift removal of environmentally harmful organic dyes.

Synthesis of mesoporous Ag/α-Fe2O3/TiO2 heterostructures with enhanced and accelerated photo/-catalytic reduction of 4-nitrophenol

4-Nitrophenol (4-NP) is reported to originate disadvantageous effects on the human body collected from industrial pollutants; therefore, the detoxification of 4-NP in aqueous contamination is strongly recommended. In this study, the heterojunction mesoporous α-Fe₂O₃/TiO₂ modulated with diverse Ag percentages has been constructed via a sol-gel route in the occurrence of a soft template P123. The formation of biphasic crystalline TiO₂ anatase and brookite phases has been successfully achieved with the average 10 nm particle sizes. The photo/-catalytic reduction of 4-NP has been performed utilizing NaBH₄ as a reducing agent with and without visible illumination. All Ag/Fe₂O₃/TiO₂ nanocomposites exhibited significantly higher photo/-catalytic reduction efficiency than pure Fe₂O₃, TiO₂ NPs, and Fe₂O₃/TiO₂ nanocomposite. 2.5% Ag/Fe₂O₃/TiO₂ nanocomposite was considered the highest and superior photocatalytic reduction efficiency, and it almost achieved 98% after 9 min. Interestingly, the photocatalytic reduction of 4-NP was accelerated 9 times higher than the catalytic reduction over 2.5% Ag/Fe₂O₃/TiO₂; its rate constant value was 709 and 706 times larger than pure TiO₂ and Fe₂O₃ NPs, respectively. The enhanced photocatalytic reduction ability of Ag/Fe₂O₃/TiO₂ nanocomposite might be referred to as significantly providing visible light absorption and a large surface area, and it can upgrade the effective separation and mobility of electron holes. The stability of the synthesized catalysts exhibited that the obtained catalysts can undergo a slight decrease in reduction efficiency after five successive cycles. This approach highlights a novel route for constructing ternary nanocomposite systems with high photo/-catalytic ability.

Heterophase Polymorph of TiO2 (Anatase, Rutile, Brookite, TiO2 (B)) for Efficient Photocatalyst: Fabrication and Activity

TiO₂ exists naturally in three crystalline forms: Anatase, rutile, brookite, and TiO₂ (B). These polymorphs exhibit different properties and consequently different photocatalytic performances. This paper aims to clarify the differences between titanium dioxide polymorphs, and the differences in homophase, biphase, and triphase properties in various photocatalytic applications. However, homophase TiO₂ has various disadvantages such as high recombination rates and low adsorption capacity. Meanwhile, TiO₂ heterophase can effectively stimulate electron transfer from one phase to another causing superior photocatalytic performance. Various studies have reported the biphase of polymorph TiO₂ such as anatase/rutile, anatase/brookite, rutile/brookite, and anatase/TiO₂ (B). In addition, this paper also presents the triphase of the TiO₂ polymorph. This review is mainly focused on information regarding the heterophase of the TiO₂ polymorph, fabrication of heterophase synthesis, and its application as a photocatalyst.

Catalytic Photodegradation of Cyclic Sulfur Compounds in a Model Fuel Using a Bench-scale Falling-film Reactor Irradiated by a Visible Light

A homemade N doped-TiO2 nanoparticle were used to degrade dibenzothiophene (DBT) in a model fuel flowing on a bench-scale glass-made falling film reactor irradiated by a xenon lamp that emitted visible light. The photocatalyst was immobilized on the glass sheet. EDS, SEM, and FT-IR techniques were utilized to identify the morphology of the N doped-TiO2 nanoparticles. Different operating parameters (e.g., N loading (0, 4, 5, and 6 wt%), light intensity (20, 40, and 60 W/m2), and pH (4, 7, and 10)) were investigated for their effect on the DBT degradation.  The effect of the N loading on the wettability of the nano-TiO2 particles was also investigated. Experimental results revealed that the N loading did not affect the wettability characteristics of the nano TiO2 particles. Moreover, results showed that DBT conversion positively depends on N loading, light intensity (hv), and pH increase. The estimated optimal operating parameters were 5 wt% N loading, pH = 10, and hv = 40 W/m2 to ensure the best photo-oxidation efficiency of 91.4% after 120 min of operation. The outcomes of the present work confirmed the effective efficiency of the N-doped TiO2 nanoparticles irradiated by visible light for DBT degradation. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Semiconductors Application Forms and Doping Benefits to Wastewater Treatment: A Comparison of TiO2, WO3, and g-C3N4

Photocatalysis has been vastly applied for the removal of contaminants of emerging concern (CECs) and other micropollutants, with the aim of future water reclamation. As a process based upon photon irradiation, materials that may be activated through natural light sources are highly pursued, to facilitate their application and reduce costs. TiO2 is a reference material, and it has been greatly optimized. However, in its typical configuration, it is known to be mainly active under ultraviolet radiation. Thus, multiple alternative visible light driven (VLD) materials have been intensively studied recently. WO3 and g-C3N4 are currently attractive VLD catalysts, with WO3 possessing similarities with TiO2 as a metal oxide, allowing correlations between the knowledge regarding the reference catalyst, and g-C3N4 having an interesting and distinct non-metallic polymeric structure with the benefit of easy production. In this review, recent developments towards CECs degradation in TiO2 based photocatalysis are discussed, as reference catalyst, alongside the selected alternative materials, WO3 and g-C3N4. The aim here is to evaluate the different techniques more commonly explored to enhance catalyst photo-activity, specifically doping with multiple elements and the formation of composite materials. Moreover, the possible combination of photocatalysis and ozonation is also explored, as a promising route to potentialize their individual efficiencies and overcome typical drawbacks.

Effective removal of pharmaceutical contaminants ibuprofen and sulfamethoxazole from water by Corn starch nanoparticles: An ecotoxicological assessment

Pharmaceutical pollutants, a vital type of emerging contaminants, have attracted researchers to study their removal from water. In this research, Corn starch nanoparticles (CSNP) have been synthesized and characterized using various analytical techniques. The synthesized CSNP was used for the biosorption of two pharmaceutical drugs, ibuprofen (IBU) and sulfamethoxazole (SUL). The influence of various experimental conditions was optimized through batch study with the removal efficiency of 86.33 % (IBU) and 85.80 % (SUL) at pH 2 and 3, initial concentration of 10 mg/L, 0.01 g of CSNP dosage. The biosorption of IBU follows Temkin, and SUL follows Langmuir isotherm models. The toxicological assessment was performed using the seeds of Vigna mungo (VM) and Vigna radiata (VR) and zebrafish to evaluate the toxic effects of pollutants on these organisms. The LC₅₀ of IBU and SUL on zebrafish before the biosorption process was 209.50 mg/L and 338.84 mg/L. After biosorption, the LC₅₀ values increase to 1435.82 mg/L for IBU and 1317.04 mg/L for SUL. Thus, CSNP is an efficient biosorbent for removing the pharmaceutical pollutants to protect ecological systems.

Photocatalytic Efficiency of Titanium Dioxide for Dyes and Heavy Metals Removal from Wastewater

The hazardous toxicity of dye materials, even in low concentrations, harms ecological systems. It releases a large number of contaminants into the water, resulting as waste water. Dyes prevent the process of photosynthesis by obstructing light passage, lowers the oxygen levels dissolved in the water. Also, a good number of the dyes and heavy metals are carcinogenic and mutagenic to human beings. Heterogeneous photocatalysis is a promising technology for removing organic, inorganic, and microbial pollutants from water and wastewater. It is preferable to other conventional wastewater treatment approaches due to its benefit, such as low cost, environmental friendliness, ability to proceed at ambient temperature and pressure conditions, and to completely degrade pollutants into environmentally safe products with suitable measures. The titanium oxide (TiO2) is one of the most promising material that has gained enormous importance in the field of energy and environmental applications. The unique physicochemical properties of TiO2 make it one of the best candidates among existing photocatalysts. This review provides an overview of strategies employed to augment its catalytic performance as well as the impact of different operational parameters on the removal proficiency of various organic and inorganic pollutants in water and wastewater treatment. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

TiO2-La2O3 as Photocatalysts in the Degradation of Naproxen

The indiscriminate use of naproxen as an anti-inflammatory has been the leading cause of pollution in sewage effluents. Conversely, titanium dioxide is one of the most promising photocatalyst for the degradation of pollutants. Ti-La mixed oxides containing 0, 1, 3, 5, and 10 wt.% of lanthanum were synthetized by sol-gel and tested as photocatalysts in the degradation of naproxen (NPX). The materials were further characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), scanning electron microscopy (SEM), UV-Vis and Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The XRD patterns resembled that of anatase titania. The Eg values, determined from the UV-Vis spectra, vary from 2.07 to 3.2 eV corresponded to pure titania. The photocatalytic activity of these materials showed a degradation of naproxen from 93.6 to 99.8 wt.% after 4 h under UV irradiation.

Nanophotocatalysis for the Removal of Pharmaceutical Residues from Water Bodies: State of Art and Recent Trends

Background:

The occurrence of pharmaceuticals in surface and drinking water is ubiquitous and is a major concern of researchers. These compounds cause a destructive impact on aquatic and terrestrial life forms, and the removal of these compounds from the environment is a challenging issue. Existent conventional wastewater treatment processes are generally inefficacious because of their low degradation efficiency and inadequate techniques associated with the disposal of adsorbed pollutants during comparatively effective methods like the adsorption process.

Remediation Method:

Semiconductor-mediated photocatalysis is an attractive technology for the efficient removal of pharmaceutical compounds. Among various semiconductors, TiO2 and ZnObased photocatalysts gained much interest during the last years because of their efficiency in decomposing and mineralizing the lethal organic pollutants with the utilization of UV-visible light. Incessant efforts are being undertaken for tuning the physicochemical, optical, and electronic properties of these photocatalysts to strengthen their overall photocatalytic performance with good recycling efficiency.

Results:

This review attempts to showcase the recent progress in the rational design and fabrication of nanosized TiO2 and ZnO photocatalysts for the removal of pollutants derived from the pharmaceutical industry and hospital wastes.

Conclusion:

Photocatalysis involving TiO2 and ZnO provides a positive impact on pollution management and could be successfully applied to remove pharmaceuticals from wastewater streams. Structure modifications, the introduction of heteroatoms, and the integration of polymers with these nano photocatalysts offer leapfrogging opportunities for broader applications in the field of photocatalysis.

Preparation of a Photosensitive Composite Carbon Fiber for Spilled Oil Cleaning

This paper deals with preparing a functional composite carbon fiber with a large surface area for spilled oil cleaning. The composite fiber consisted of photosensitive oxide particles and polymer-derived carbon. It was made by co-spinning the polymer and metallic compounds. After heat treatment at high temperatures, an activated carbon fiber containing oxide particles was obtained. The particles were found distributed in the fiber and at the surface of the fiber. The composite fiber was found sensitive to sunlight. Fiber mats made of the composite fiber possessed a high surface area for oil absorption and removal. Cobalt(II) titanate particles were obtained from the reaction of titanium dioxide and cobalt oxide. The reaction happened in situ through the hydrolysis of metallic compounds in the spun fiber. The titanium dioxide and cobalt(II) titanate particle-containing fibers demonstrated the photoactivity in the visible light spectrum. It was concluded that particle-containing composite carbon fiber mats can be prepared successfully by co-electrospinning. Due to the oleophilic property and the high active surface area, the composites are suitable for spilled oil cleaning through fast absorption.

Effect of Calcination Conditions on the Properties and Photoactivity of TiO2 Modified with Biuret

A simple wet impregnation-calcination method was used to obtain a series of novel non-metal doped TiO2 photocatalysts. Biuret was applied as C and N source, while raw titanium dioxide derived from sulfate technology process was used as TiO2 and S source. The influence of the modification with biuret and the effect of the atmosphere (air or argon) and temperature (500–800 °C) of calcination on the physicochemical properties and photocatalytic activity of the photocatalysts towards ketoprofen decomposition under simulated solar light was investigated. Moreover, selected photocatalysts were applied for ketoprofen photodecomposition under visible and UV irradiation. Crucial features affecting the photocatalytic activity were the anatase to rutile phase ratio, anatase crystallites size and non-metals content. The obtained photocatalysts revealed improved activity in the photocatalytic ketoprofen decomposition compared to the crude TiO2. The best photoactivity under all irradiation types exhibited the photocatalyst calcined in the air atmosphere at 600 °C, composed of 96.4% of anatase with 23 nm crystallites, and containing 0.11 wt% of C, 0.05 wt% of N and 0.77 wt% of S.

Photocatalytic Properties of a Novel Keratin char-TiO2 Composite Films Made through the Calcination of Wool Keratin Coatings Containing TiO2 Precursors

In this study, the photocatalytic properties of novel keratin char-TiO2 composite films, made through the calcination of wool keratin coatings containing TiO2 precursors at 400 °C, were investigated for the photodegradation of organic contaminants under visible light irradiation. Its structural characteristics and photocatalytic performance were systematically examined. It was shown that a self-cleaning hydrophobic keratin char-TiO2 composite film containing meso- and micro-pores was formed after the keratin—TiO2 precursors coating was calcined. In comparison with calcinated TiO2 films, the keratin char-TiO2 composite films doped with the elements of C, N, and S from keratins resulted in decreased crystallinity and a larger water contact angle. The bandgap of the char-TiO2 composite films increased slightly from 3.26 to 3.32 eV, and its separation of photogenerated charge carriers was inhibited to a certain degree. However, it exhibited higher photodegradation efficiency to methyl blue (MB) effluents than the pure calcinated TiO2 films. This was mainly because of its special porous structure, large water contact angle, and high adsorption energy towards organic pollutants, confirmed by the density functional theory calculations. The main active species were 1O2 radicals in the MB photodegradation process.

Influence of rGO and Preparation Method on the Physicochemical and Photocatalytic Properties of TiO2/Reduced Graphene Oxide Photocatalysts

In this study, a series of TiO2/rGO photocatalysts were obtained with a two-step procedure: a solvothermal method and calcination at 300–900 °C in an argon atmosphere. It was noted that the presence of rGO in photocatalysts had an important role in the changes in crystallite size and specific surface area. In TiO2/rGO samples, different surface functional groups, such as C−Cgraph, C−Caliph, C−OH, C=O, and CO(O), were found. It was observed that rGO modification suppressed the anatase-to-rutile phase transformation. The photocatalytic activity of the obtained nanomaterials was investigated through the decomposition of methylene blue under UV and artificial solar light irradiation. It was found that the adsorption degree played an important role in methylene blue decomposition. The experimental results revealed that TiO2/rGO samples exhibited superior removal efficiency after calcination for methylene blue compared toTiO2 without rGO, as well as a commercial photocatalyst KRONOClean 7000. It was noted that photocatalytic activity increased with the increase in the calcination temperature. The highest activity was observed for the sample calcined at 700 °C, which consisted of 76% anatase and 24% rutile. This study clearly demonstrated that TiO2/rGO samples calcined in argon can be used as efficient photocatalysts for the application of methylene blue decomposition.

Combined Adsorption and Photocatalytic Degradation for Ciprofloxacin Removal Using Sugarcane Bagasse/N,S-TiO2 Powder Composite

N,S-TiO2 deposited on three kinds of pre-treated sugarcane bagasse was synthesized via a sol–gel method. The obtained composites were characterized by various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). UV-visible induced degradation of ciprofloxacin was investigated. The influence of some experimental parameters such as contact time, pH, dosage, and initial concentration on the efficiency of ciprofloxacin elimination was also evaluated. The highest efficiency was observed for the alkaline pre-treated sugarcane bagasse combined with N,S-TiO2, about 86% under optimal conditions (contact time 150-min irradiation, pH 5.5–6, dosage 0.5 g L−1, and the initial concentration CIP 30 ppm). There may be a rapid ciprofloxacin transition from the adsorption site to the photocatalytic site, and the alkaline pre-treated sugarcane bagasse/N,S-TiO2 prevented the recombining of holes and electrons of the photocatalyst. Furthermore, the alkaline pretreatment sugarcane bagasse/N,S-TiO2 composite material was sustainable, with only a 10% reduction after reusing the material three times. The presence of sugarcane bagasse made the material easy to recover from the liquid phase.

Green Synthesis of Flower-Shaped Copper Oxide and Nickel Oxide Nanoparticles via Capparis decidua Leaf Extract for Synergic Adsorption-Photocatalytic Degradation of Pesticides

Green manufacturing of catalysts enables sustainable advanced oxidation processes and water treatment processes for removing trace contaminants such as pesticides. An environmentally friendly biosynthesis process produced high-surface-area CuO and NiO nanocatalysts using phytochemicals in the Capparis decidua leaf extract, which served as a reductant and influenced catalyst shape. Capparis decidua is a bushy shrub, widely distributed in dry and arid regions of Africa, Pakistan, India, Egypt, Jordan, Sudan, Saudi Arabia. The synthesized CuO and NiO nanoparticles were characterized by UV-vis spectroscopy (UV-vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) and thermo-gravimetric analysis/differential thermal analysis (TGA/DTA). The produced nanoparticles were spherical and flower-like in shape and have a characteristic face-centered cubic structure of CuO and NiO. Biosynthesized catalysts were photoactive and degraded recalcitrant pesticide Lambda-cyhalothrin (L-CHT). Photocatalytic degradation of L-CHT was affected by the initial L-CHT concentration, solution pH levels between 5 and 9, and photocatalyst concentration. The L-CHT removal percentage attained by CuO photocatalyst (~99%) was higher than for NiO photocatalyst (~89%). The degradation of L-CHT follows a pseudo-first-order kinetic model, and the apparent rate constant (kapp) decreased from 0.033 min−1 for CuO to 0.0084 min−1 for NiO photocatalyst. The novel flower-shaped nanoparticles demonstrated high stability in water and recyclability for removing L-CHT pesticide contamination in water.

Facile fabrication of hybrid titanium(IV) isopropoxide/pozzolan nanosheets (TnS-Pz) of high photocatalytic activity: characterization and application for Cr(VI) reduction in an aqueous solution

This paper presents the synthesis of a hybrid material through the use of natural pozzolan and titanium(IV) isopropoxide using the sol-gel method and its application in the photocatalytic hexavalent chromium reduction. The characterization data indicated a mesoporous material possessing a surface area of 271.7 m² g^-1. The morphology studies (SEM and TEM) showed nanosheet hybrid structures. The analysis of DRUV, FTIR, XRD, and Mössbauer spectroscopy provides a different electronic structure of the synthetized material when compared with the originals, proving the hybridization process between pozzolan and titanium(IV) isopropoxide. The photocatalytic reduction of Cr(VI) to Cr(III) using the hybrid material showed a better performance than conventional photocatalysts (precursor and TiO₂-P25). Operational conditions such as chromium initial concentration (0.02-0.20 mM), solution pH (3-6), and type of scavenger (citric or tartaric acid) were evaluated in order to determine the best experimental conditions for the Cr(VI) photoreduction. At their optimum (catalyst load of 15 mg L^-1, tartaric acid as scavenger, [scavenger]₀/[Cr(VI)]₀ M ratio = 3:1, pH 3, and 25 °C), the total photoreduction of 0.20 mM Cr(VI) was achieved in 180 min. The novel hybrid materials synthesized from pozzolan and titanium(IV) isopropoxide showed to be a potential catalyst for the Cr(VI) reduction in aqueous solution. Graphical abstract.

Nickel ferrite nanoenabled graphene oxide (NiFe2O4@GO) as photoactive nanocomposites for water treatment

Nanocomposite materials can enhance the capabilities of water treatment processes such as photocatalysis. In this work, novel light-driven nanocatalysts were synthesized by using nickel ferrite (NiFe₂O₄) to nanoenable graphene oxide (GO) substrates. GO is an emerging 2D nanomaterial with high conductivity and adsorption properties. Moreover, the electric properties of GO improve photocatalytic performance by promoting charge carrier separation. Results of the characterization of the nickel ferrite nanoenabled graphene oxide (NiFe₂O₄@GO) nanocomposites demonstrate that homogeneous and stable photocatalysts were produced. The as-synthesized nanocatalysts enabled complete decolorization of the colored water matrix in short irradiation times of 150 min using minimal catalyst loading at 0.5 g L^-1. The selective hook and destroy mechanism reduced the competitive effect of co-existing ions in solution. Furthermore, the use of specific scavengers helped to elucidate the degradation mechanisms of organic dye methylene blue by NiFe₂O₄@GO nanocomposites.

C-,N- and S-Doped TiO2 Photocatalysts: A Review

This article presents an overview of the reports on the doping of TiO2 with carbon, nitrogen, and sulfur, including single, co-, and tri-doping. A comparison of the properties of the photocatalysts synthesized from various precursors of TiO2 and C, N, or S dopants is summarized. Selected methods of synthesis of the non-metal doped TiO2 are also described. Furthermore, the influence of the preparation conditions on the doping mode (interstitial or substitutional) with reference to various types of the modified TiO2 is summarized. The mechanisms of photocatalysis for the different modes of the non-metal doping are also discussed. Moreover, selected applications of the non-metal doped TiO2 photocatalysts are shown, including the removal of organic compounds from water/wastewater, air purification, production of hydrogen, lithium storage, inactivation of bacteria, or carbon dioxide reduction.

Mitigation of environmentally-related hazardous pollutants from water matrices using nanostructured materials - A review

An unprecedented rise in population growth and rapid worldwide industrial development are associated with the increasing discharge of a range of toxic and baleful compounds. These toxic pollutants including dyes, endocrine-disrupters, heavy metals, personal care products, and pharmaceuticals are destructing nature's balance and intensifying environmental toxicity at a disquieting rate. Therefore, finding better, novel and more environmentally sound approaches for wastewater remediation are of great importance. Nanoscale materials have opened up some new horizons in various fields of science and technology. Among a range of treatment technologies, nanostructured materials have recently received incredible interest as an emerging platform for wastewater remediation owing to their exceptional surface-area-to-volume ratio, unique electrical and chemical properties, quantum size effects, high scalability, and tunable surface functionalities. An array of nanomaterials including noble metal-based nanostructures, transition metal oxide nanomaterials, carbon-based nanomaterials, carbon nanotubes, and graphene/graphene oxide nanomaterials to their novel nanocomposites and nanoconjugates have been attempted as the promising catalysts to overcome environmental dilemmas. In this review, we summarized recent advances in nanostructured materials that are particularly engineered for the remediation of environmental contaminants. The toxicity of various classes of relevant tailored nanomaterials towards human health and the ecosystem along with perspectives is also presented. In our opinion, an overview of the up-to-date advancements on this emerging topic may provide new ideas and thoughts for engineering low-cost and highly-efficient nanostructured materials for the abatement of recalcitrant pollutants for a sustainable environment.

Doping TiO2 with CuSO4 enhances visible light photocatalytic activity for organic pollutant degradation

Photocatalysis is one of the most promising advanced oxidation processes due to the capability of solid catalyst to continuously produce oxidant species under light irradiation. The use of conventional UV lamps is high cost intensive, which undermines the possible implementation in developing countries. Visible light active photocatalysts can overcome these challenges and find a market opportunity for competitive technology implementation. This work proposes the synthesis of visible light active catalyst following a facile sol-gel synthesis that introduces CuSO₄ as dopant in TiO₂. Results present complete abatement of methylene blue in 120 min of treatment under 50 mW cm^-2 of blue light (λ = 450 nm), while commercial P25 TiO₂ presented null abatement under identical conditions. Synthesis parameters including dopant level and calcination temperature allowed defining optimum synthesis conditions based on material characteristics modification and catalytic activity enhancement. A doping level of 0.21 mol% CuSO₄ was identified as optimum condition to enable visible light photocatalysis of doped TiO₂ catalysts calcined at 300 °C. Finally, operational parameters were evaluated defining a wide range of pH operation under 3.0 g L^-1 of catalyst dose to treat up to 20 g L^-1 of highly recalcitrant phenothiazine dye. These optimum conditions allowed complete dye removal under visible light after 120 min of treatment.

MOF-derived TiO2 modified with g-C3N4 nanosheets for enhanced visible-light photocatalytic performance

A g-C₃N₄/TiO₂ heterojunction was prepared for the first time using a mechanical agitation method assisted by a template method and a two-step calcination method.

Morphology- and Crystalline Composition-Governed Activity of Titania-Based Photocatalysts: Overview and Perspective

Titania photocatalysts have been intensively examined for both mechanism study and possible commercial applications for more than 30 years. Although various reports have already been published on titania, including comprehensive review papers, the morphology-governed activity, especially for novel nanostructures, has not been reviewed recently. Therefore, this paper presents novel, attractive, and prospective titania photocatalysts, including zero-, one-, two-, and three-dimensional titania structures. The 1D, 2D, and 3D titania structures have been mainly designed for possible applications, e.g., (i) continuous use without the necessity of particulate titania separation, (ii) efficient light harvesting (e.g., inverse opals), (iii) enhanced activity (fast charge carriers’ separation, e.g., 1D nanoplates and 2D nanotubes). It should be pointed out that these structures might be also useful for mechanism investigation, e.g., (i) 3D titania aerogels with gold either incorporated inside the 3D network or supported in the porosity, and (ii) titania mesocrystals with gold deposited either on basal or lateral surfaces, for the clarification of plasmonic photocatalysis. Moreover, 0D nanostructures of special composition and morphology, e.g., magnetic(core)–titania(shell), mixed-phase titania (anatase/rutile/brookite), and faceted titania NPs have been presented, due to their exceptional properties, including easy separation in the magnetic field, high activity, and mechanism clarification, respectively. Although anatase has been usually thought as the most active phase of titania, the co-existence of other crystalline phases accelerates the photocatalytic activity significantly, and thus mixed-phase titania (e.g., famous P25) exhibits high photocatalytic activity for both oxidation and reduction reactions. It is believed that this review might be useful for the architecture design of novel nanomaterials for broad and diverse applications, including environmental purification, energy conversion, synthesis and preparation of “intelligent” surfaces with self-cleaning, antifogging, and antiseptic properties.

A Comparative Study of Microcystin-LR Degradation by UV-A, Solar and Visible Light Irradiation Using Bare and C/N/S-Modified Titania

In an endeavor to tackle environmental problems, the photodegradation of microcystin-LR (MC-LR), one of the most common and toxic cyanotoxins, produced by the cyanobacteria blooms, was examined using nanostructured TiO2 photocatalysts (anatase, brookite, anatase–brookite, and C/N/S co-modified anatase–brookite) under UV-A, solar and visible light irradiation. The tailoring of TiO2 properties to hinder the electron–hole recombination and improve MC-LR adsorption on TiO2 surface was achieved by altering the preparation pH value. The highest photocatalytic efficiency was 97% and 99% with degradation rate of 0.002 mmol L−1 min−1 and 0.0007 mmol L−1 min−1 under UV and solar irradiation, respectively, using a bare TiO2 photocatalyst prepared at pH 10 with anatase to brookite ratio of ca. 1:2.5. However, the bare TiO2 samples were hardly active under visible light irradiation (25%) due to a large band gap. Upon UV, solar and vis irradiation, the complete MC-LR degradation (100%) was obtained in the presence of C/N/S co-modified TiO2 with a degradation rate constant of 0.26 min−1, 0.11 min−1 and 0.04 min−1, respectively. It was proposed that the remarkable activity of co-modified TiO2 might originate from its mixed-phase composition, mesoporous structure, and non-metal co-modification.

Solar light active silver/iron oxide/zinc oxide heterostructure for photodegradation of ciprofloxacin, transformation products and antibacterial activity

This paper reports on the multitasking potential of a silver/iron oxide/zinc oxide (Ag/Fe₂O₃/ZnO) heterostructure, which was used for the photocatalytic decomposition of ciprofloxacin (CPX) and bacterial disinfection. The Ag/Fe₂O₃/ZnO heterostructure was successfully prepared using a facile precipitation method, and characterization results showed interesting structural, morphological, compositional and luminescent properties. The morphological results of the prepared heterostructure confirmed the deposition of Ag nanoparticles onto the surface of ZnO nanoplates and Fe₂O₃ nanorods. Treatment studies showed that the Ag/Fe₂O₃/ZnO heterostructure had superior solar light driven photocatalytic activity towards CPX degradation (76.4%) compared to bare Fe₂O₃ nanorods (43.2%) and ZnO nanoplates (63.1%), Ag/Fe₂O₃ (28.2%) and Ag/ZnO (64.5%) under optimized conditions (initial CPX concentration: 10 mg/L; pH 4; catalyst loading: 0.3 g/L). Reactive species study confirmed the roles of e^-, h⁺, OH and O₂^- in the photocatalytic degradation process. This photocatalytic behaviour of the Ag/Fe₂O₃/ZnO heterostructure could be attributed to the improved full solar spectrum harvesting capacity, separation of charge carriers and migration of e^-/h⁺ across the heterostructure interface. In addition, the Ag/Fe₂O₃/ZnO heterostructure also showed good antibacterial activity against Escherichia coli (E. coli) under both dark and visible light conditions. This might be due to generation of reactive oxygen species during the reaction. To the best of our knowledge, this is the first study till date on the utilization of Ag/Fe₂O₃/ZnO heterostructure for the photocatalytic degradation of CPX and E. coli bacteria disinfection. Therefore, this work offers an attractive path to design ZnO-based ternary heterostructures for solar-driven applications in wastewater remediation.

Photocatalytic degradation of ibuprofen in water using TiO2 and ZnO under artificial UV and solar irradiation

The degradation of anti-inflammatory and antipyretic drug (Ibuprofen; IBP) has been described in this study by using photocatalytic-based advanced oxidation processes. The catalysts (TiO₂ and ZnO) were activated by irradiation of artificial UV lamp and solar rays for the generation of highly oxidizing species which resulted in the degradation of IBP to intermediates and finally to carbon dioxide and water. In solar reactor, quartz and borosilicate tubes were installed for absorption of required ultraviolet rays and curved chrome plates were used to reflect and concentrate rays on the tubes containing feed mixture. The liquid chromatography, Total organic carbon (TOC), and Chemical oxygen demand (COD) tests were employed to determine the degradation rates and demineralization of solution samples. At catalyst dosing of 1-1.5 g/L, TiO₂ -based experiments showed high degradation rate under acidic conditions. Similarly, for ZnO catalyst, 1 g/L dozing rate was found to be effective under neutral conditions (pH = 7.0). UV lamp-based photocatalysis had higher degradation rate as compared to that of solar reactor. Moreover, better absorption of solar rays by quartz tubes resulted in higher degradation than that in borosilicate tubes. For UV lamp photocatalysis, the TOC and COD reduction was higher. With improved catalyst doping and better solar reactor design, solar-based IBP degradation could be more promising than UV-based catalysis. PRACTITIONER POINTS: TiO₂ and ZnO were employed to generate oxidizing agents for comparative photocatalytic degradation. Degradation rate of Ibuprofen with TiO₂ was much higher compared to ZnO. Quartz material was found more effective as radiation absorbing material than borosilicate glass for solar photo catalysis. Influence of catalyst loading (TiO₂ and ZnO) and pH conditions on degradation rate and mineralization of IBP was examined. IBP is a carcinogenic and endocrine disrupting drug so its degradation in water can protect ecological and human life.

Photodegradation of Microcystin-LR Using Visible Light-Activated C/N-co-Modified Mesoporous TiO₂ Photocatalyst

Microcystin-LR (MC-LR), a potent hepatotoxin produced by the cyanobacteria, is of increasing concern worldwide because of severe and persistent impacts on humans and animals by inhalation and consumption of contaminated waters and food. In this work, MC-LR was removed completely from aqueous solution using visible-light-active C/N-co-modified mesoporous anatase/brookite TiO₂ photocatalyst. The co-modified TiO₂ nanoparticles were synthesized by a one-pot hydrothermal process, and then calcined at different temperatures (300, 400, and 500 °C). All the obtained TiO₂ powders were analyzed by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), specific surface area (SSA) measurements, ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) analysis. It was found that all samples contained mixed-phase TiO₂ (anatase and brookite), and the content of brookite decreased with an increase in calcination temperature, as well as the specific surface area and the content of non-metal elements. The effects of initial pH value, the TiO₂ content, and MC-LR concentration on the photocatalytic activity were also studied. It was found that the photocatalytic activity of the obtained TiO₂ photocatalysts declined with increasing temperature. The complete degradation (100%) of MC-LR (10 mg L^-1) was observed within 3 h, using as-synthesized co-modified TiO₂ (0.4 g L^-1) at pH 4 under visible light. Based on the obtained results, the mechanism of MC-LR degradation has been proposed.

Visible photodegradation of ibuprofen and 2,4-D in simulated waste water using sustainable metal free-hybrids based on carbon nitride and biochar

Rational designing of metal-free carbon nitride based photocatalysts can lead to an excellent optical response and a higher photocatalytic activity driven by visible and solar light. This combines green photocatalytic technology with greener materials prepared by facile approaches for environmental remediation. Herein we report utilization of star photocatalyst g-C₃N₄ (CN) to form highly efficient hetero-assemblies along with acidified g-C₃N₄ (ACN), polyaniline (PANI), reduced graphene oxide (RGO) and biochar. By use of these organic semiconductors we synthesize g-C₃N₄/ACN/RGO@Biochar (GARB), g-C₃N₄/PANI/RGO@Biochar (GPRB) and ACN/PANI/RGO@Biochar (APRB) nano-assemblies with different optical response and band edge positions for a better charge flow and reduced recombination of carriers. These synthesized catalysts were used for visible light powered degradation of 2,4-Dichlorophenoxy acetic acid (2,4-D) and ibuprofen (IBN). APRB performs the best and degrades 99.7% and 98.4% of 2,4-D and IBN (20 mg L^-1) under Xe lamp exposure in 50 min and retention of high activity in natural sunlight. Optical analysis, photoelectrochemical response and radical quenching studies show both hydroxyl and superoxide radical anions as major reactive species and a Z-scheme photocatalytic mechanism. RGO acts as an electron mediator and protects higher positioned bands of PANI and ACN in APRB for a remarkable photocatalytic activity for a metal free material. The degradation pathway was analyzed by LC-MS analysis and 42% and 40% total organic carbon was removed in 2 h for 2,4-D and IBN degradation respectively. The toxicity of degraded products was analyzed by analyzing viability of human peripheral blood cells with retaining of 99.1% cells.

Roles of Vanadium and Nitrogen in Photocatalytic Activity of VN-Codoped TiO2 Photocatalyst

In the present manuscript, we explore the VN-codoped TiO₂ system intended to understand the role played by each dopant in synergistic enhancement in performance of TiO₂ photocatalyst. The photocatalytic decomposition of organic pollutants in aqueous solution under visible light was used as a probe reaction to evaluate the performance of VN-codoped TiO₂ samples with different V and N concentrations. An optical measurement of VN-codoped TiO₂ shows considerable improved visible light absorption with increase in V-concentration as compared to increase in N concentration, which was due to the effective narrowing of the band gap by V-doping. The energy levels formed by N-dopants act as the trapping centers for photogenerated holes to suppress recombination process as indicated by PL and TRPL results. It is also observed that at high V-concentrations recombination centers are created in the form of oxygen vacancies as indicated by XPS and PL. In VN-codoped TiO₂ , addition of N partially fills these oxygen vacancies to reduce the number of recombination centers and prolong the lifetime of charge carriers. Thus, V improves the visible light absorption while N reduces the recombination of electron-hole pairs, thus creating the synergistic effect to produce three times better performance than pure TiO₂ .