Visible-light Photocatalytic Degradation Of Tetracycline Research Articles

Ferrocenylselenoether and its cuprous cluster modified TiO2 as visible-light photocatalyst for the synergistic transformation of N-cyclic organics and Cr(vi).

In this study, fcSe@TiO2 and [Cu2I2(fcSe)2]n@TiO2 nanosystems based on ferrocenylselenoether and its cuprous cluster were developed and characterized by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX), and electron paramagnetic resonance (EPR). Under optimized conditions, 0.2 g L-1 catalyst, 20 mM H2O2, and initial pH 7, good synergistic visible light photocatalytic tetracycline degradation and Cr(vi) reduction were achieved, with 92.1% of tetracycline and 64.5% of Cr(vi) removal efficiency within 30 minutes. Mechanistic studies revealed that the reactive species ˙OH, ˙O2-, and h+ were produced in both systems through the mutual promotion of Fenton reactions and photogenerated charge separation. The [Cu2I2(fcSe)2]n@TiO2 system additionally produced 1O2 from Cu+ and ˙O2-. The advantages of the developed nanosystems include an acidic surface microenvironment provided by Se⋯H+, resourceful product formation, tolerance of complex environments, and excellent adaptability in refractory N-cyclic organics.

Oxygen-vacancy hydroxyapatite for visible-light photocatalytic degradation of tetracycline with online spectral monitoring

In this study, OV-HAp with abundant oxygen vacancies (OVs) were prepared by calcining carbonate-doped HAp (CHAp), and the effects of calcination temperature, time and atmosphere on the formation of OVs in OV-HAp and the influence of OVs concentration on its photoelectrochemical properties were investigated in detail. The results showed that the calcination temperature and atmosphere play a major role in the generation of OVs in OV-HAp. Through changing the temperature or atmosphere, the optical absorption range of OV-HAp can be broadened to the visible light and the band gap can be reduced to 1.6 eV. OV-HAp obtained by calcining CHAp at 600℃ for 5 h under H2 atmosphere (OV-HAp-H2) exhibited the highest efficiency for tetracycline (TC) photocatalytic degradation (65.4%). h+ and ·O2– were demonstrated to be the main active species in the degradation process by radical trapping experiments. Meanwhile, an integrated platform for photocatalytic degradation of TC with online spectral monitoring was constructed, and the feasibility of online spectral monitoring the TC degradation was tentatively explored. This work will provide a theoretical and technical basis for the development of HAp-based high-efficient photocatalysts, and this is favorable for promoting their use by a large scale for water pollutant removal. Moreover, it will also open a new path for online spectral monitoring and kinetic study of photocatalytic degradation of organic pollutants.

Quantitatively regulating the ketone structure of triazine-based covalent organic frameworks for efficient visible-light photocatalytic degradation of organic pollutants: Tunable performance and mechanisms.

As promising visible-light-responsive photocatalysts, triazine-based covalent organic frameworks (CTFs) still suffer from broad bandgap and high electron-hole recombination. As such, different contents of electron-rich ketone group were introduced to CTFs (X % keto-CTF), aiming to clarify the mechanism of quantitatively regulating ketone for enhanced visible-light photocatalytic performance of CTFs. As ketone content increased, the bandgap narrowed, electron-hole recombination decreased, charge transfer and quantum yield increased. As a result, keto-CTF outperformed other keto-CTFs in visible-light photocatalytic degradation of tetracycline, and apparent rate constant of TC (kobs) was 3.69 times higher than that of CTF. Importantly, ketone tuning induced varied types and concentrations of reactive species. Integrated with quantitative structure-activity relationships (QSARs) analysis and density functional theory (DFT) calculations, this study unravels how ketone content regulates bandgap structure of CTF, affects the contribution of varied reactive species, and quantitatively enhances the photocatalytic performance of CTFs. It also provides novel insights into the precise design and synthesis of CTFs-based catalyst structures for high-efficient visible-light photocatalytic degradation of organic pollutants.

Enhancement of Visible-Light Photocatalytic Degradation of Tetracycline by Co-Doped TiO2 Templated by Waste Tobacco Stem Silk.

In this study, Co-doped TiO2 was synthesized using waste tobacco stem silk (TSS) as a template via a one-pot impregnation method. These samples were characterized using various physicochemical techniques such as N2 adsorption/desorption analysis, diffuse reflectance UV-visible spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and electron paramagnetic resonance spectroscopy. The synthesized material was used for the photodegradation of tetracycline hydrochloride (TCH) under visible light (420-800 nm). No strong photodegradation activity was observed for mesoporous TiO2 synthesized using waste TSS as a template, mesoporous Co-doped TiO2, or TiO2. In contrast, Co-doped mesoporous TiO2 synthesized using waste TSS as a template exhibited significant photocatalytic degradation, with 86% removal of TCH. Moreover, owing to the unique chemical structure of Ti-O-Co, the energy gap of TiO2 decreased. The edge of the absorption band was redshifted, such that the photoexcitation energy for generating electron-hole pairs decreased. The electron-hole separation efficiency improved, rendering the microstructured biotemplated TiO2 a much more efficient catalyst for the visible-light degradation of TCH.

Fabrication of g-C3N4/N,Fe co-doped CQDs composites: in situ decoration of g-C3N4 with N-CQDs and Fe and efficient visible-light photocatalytic degradation of tetracycline

Herein, for the first time, g-C3N4/N,Fe co-doped carbon quantum dots (CN/N,Fe-CQDs) composites were fabricated by a two-step fabrication route. N,Fe-CQDs were obtained via facile pyrolysis of ammonium ferric citrate. Through thermal condensation of the synthesized N,Fe-CQDs and urea, CN/N,Fe-CQDs composites were successfully fabricated for highly efficient photocatalytic degradation of tetracycline (TC). The optimized CN/N,Fe-CQDs composite obtained the degradation efficiency of 81.0% after 40 min visible-light illumination, and its apparent rate constant was 3.41 times higher than that of pure g-C3N4. The remarkable enhancement of photodegradation activity is mainly attributed to the synergetic effect of N-CQDs and Fe co-decoration in CN/N,Fe-CQDs arising from the incorporation of N,Fe-CQDs into the g-C3N4 matrix, which could increase the specific surface area, wide visible-light absorption range, and accelerate separation and transfer of interfacial charge. The active species capture experiments and electron spin resonance technique testified that ‧O2 −, ‧OH, 1O2 and h+ were all involved in the degradation of TC in the photocatalytic process. According to the result of mass spectrometry, TC underwent hydroxylation, demethylation, N-demethylation, deamination, dehydroxylation, ring opening processes, and was ultimately mineralized into CO2 and H2O. This research can provide a new understanding of the roles played by non-metal and metal ions co-doped CQDs in photocatalytic system and open up a new way to develop highly efficient photocatalysts for TC degradation.

Ti3C2 MXene derived (001)TiO2/Ti3C2 heterojunctions for enhanced visible-light photocatalytic degradation of tetracycline

As a photocatalyst, titanium dioxide (TiO2) suffers from the wide band gap and the quick carrier recombination process, thus leading to the inefficient use of solar energy and poor catalytic performance. Herein, in this work, TiO2/Ti3C2 heterojunctions are designed to overcome these shortcomings via growing TiO2 in situ on the titanium element of Ti3C2 MXene. The TiO2/Ti3C2 heterojunctions not only broaden the range of light absorption, but also hugely extend the lifetime of photogenerated carriers. Besides, the anatase TiO2 with exposed (001) facets further enhances the catalytic properties. After optimizing the amount of TiO2/Ti3C2 heterojunctions by controlling reaction time, 20 mg catalysts can degrade 97.6% of 30 mL tetracycline solution (15 mg/L) in 90 min under visible light. Even after five cycles, the degradation ability of TiO2/Ti3C2 only changes from 97.6% to 94.3%. This paper offers another perspective on the synthesis of efficient and stable photocatalysts.

Fabrication of 0D/1D Bi2MoO6/Bi/TiO2 heterojunction with effective interfaces for boosted visible-light photocatalytic degradation of tetracycline

The efficient photo-induced charges transfer/separation plays a critical role in enhancing photocatalytic performance. Heterojunctions with low dimensional morphologies, such as nanosheets and nanobelts, can decrease the electron transfer distance, which can further promote charge transfer/separation. In this work, Bi2MoO6/Bi/TiO2 composites with low dimensional heterostructure as nanobelts decorated by quantum dots were successfully prepared by solvothermal method, and their photocatalytic activity was evaluated by the degradation of tetracycline under visible light irradiation. Compared with pristine TiO2 (35.56%) and Bi2MoO6 (44.14%), the photocatalyitic degradation performance under visbile light irradiation of composite TBM0.05–5 (82.73%) are grealy improved. The k (under visible light irradiation) is about 8.49 and 8.64 times that of pure TiO2 and Bi2MoO6 respectively. The boosted photocatalytic activity can be attributed to the new charge transfer pathway formed by heterojunction, short transfer distance provided by the low dimensional morphology and plasmonic Bi acted as electron trap. The good stability and general applicability were also confirmed by recycling and universality experiments. Moreover, the superiority of composite with low dimensional heterostructure as nanobelts decorated by quantum dots was also proved by comparing to composites with other morphologies. This novel Bi2MoO6/Bi/TiO2 photocatalyst may provide inspirations for antibiotic degradation and wastewater treatment.

Bi2O2CO3/Bi2O3 Z-scheme photocatalyst with oxygen vacancies and Bi for enhanced visible-light photocatalytic degradation of tetracycline

A novel Z-scheme heterojunction photocatalyst Bi-BOC/BO-OVs was successfully prepared. OVs and metal Bi enhanced light response and separation of photoinduced carriers. Thus, catalyst showed superior catalytic activity in simulated water matrices.

Self-organization of unimolecular micelles in beam stream for functional mesoporous metal oxide nanofibers

The use of linear amphiphilic block copolymers as templates is an important method for the preparation of mesoporous materials. However, the obtained assemblies are usually sensitive to synthetic conditions, which impedes the preparation of such mesoporous materials in certain environments. Herein, we report a universal strategy applying an amphiphilic multi-arm triblock copolymer in the preparation of mesoporous metal oxide nanofibers (NFs) using one metal oxide (TiO2, ZrO2, WO3, CeO2), or two (TiO2/WO3, TiO2/ZrO2, TiO2/CeO2) and three (TiO2/WO3/CuO) metal oxides as composites. The template consists of modified β-cyclodextrin as the center of the macromolecule which is attached sequentially to a block of polystyrene, poly(acrylic acid), and poly(ethylene oxide). Under electrospinning conditions, stable unimolecular micelles are formed and effectively co-assemble with metal ions to form fibrous nanostructures. As indicated by various characterization methods, the synthesized TiO2 and its derived composite NFs maintain a straight and continuous fibrous structure after calcination, and TiO2 NFs exhibit uniform mesopores of 10.8 nm in diameter and a large Brunauer-Emmett-Teller surface area of 143.3 m2 g−1. Benefiting from the characteristic structure, still present after modification, Pt-decorated mesoporous TiO2 NFs display excellent ability in the visible-light photocatalytic degradation of tetracycline, which is superior to the commercial P25 catalyst. This study reveals a promising strategy for the preparation of fibrous mesoporous metal oxides.

Enhancing visible-light photocatalytic degradation of tetracycline by ZnFe2O4 loaded on UiO-66-NH2 under activated persulfate

Enhancing visible-light photocatalytic degradation of tetracycline by ZnFe2O4 loaded on UiO-66-NH2 under activated persulfate

Construction of two-dimensional BiOI on carboxyl-rich MIL-121 for visible-light photocatalytic degradation of tetracycline

A series of BiOI/MIL-121(Al) hybrid photocatalysts has been prepared by a facile hydrothermal method. Two-dimensional BiOI sheets are intimately anchored on rod-like MIL-121 due to the electrostatic and coordination effects between Bi3+ and carboxyl. The BiOI/MIL-121(Al) hybrid exhibits favorable performances for visible-light-driven degradation of tetracycline. The degradation performance of the optimal sample BM-20 is more than twice as that of pure BiOI. Apart from the close contacts between BiOI and MIL-121, the hydrogen bond induced by carboxyl in MIL-121 promotes the adsorption of tetracycline, which is also conducive to the photocatalytic degradation process. Moreover, results show that photo-induced holes and superoxide radicals are both the main active species for the photocatalytic degradation of tetracycline over BiOI/MIL-121 composites. This work would inspire the materials design with specific functional groups for efficient (photo)catalytic reaction.

Surface engineering induced superstructure Ta2O5−x mesocrystals for enhanced visible light photocatalytic antibiotic degradation

Mesocrystals are types of fascinating multifunctional materials in fabricating rapid charge transport pathways, and surface engineering could be considered as a significant influencing factor in boosting charge separation for efficient photocatalytic application. In this work, surface engineered Ta2O5−x mesocrystals were synthesized by facile alkali treatment strategy for enhanced visible light photocatalytic tetracycline degradation. The highly enhanced photocatalytic activity could be attributed to the highly increased surface areas and surface hydroxyl groups to compare with those of commercial Ta2O5 and pristine Ta2O5−x mesocrystals, which could provide more surface reactive sites and high electron density center for trapping photo-generated holes. Besides, possible tetracycline transformation pathways over surface engineered Ta2O5−x mesocrystals and visible light photocatalytic mechanism were also proposed in this work. Current work also provides a facile strategy for regulating surface property of ultrawide bandgaps semiconductors for enhanced visible light photocatalytic performance.

Nanodiamonds anchored on porous ZnSnO3 cubes as an efficient composite photocatalyst with improved visible-light photocatalytic degradation of tetracycline

Using sunlight to degrade organic pollutants is a promising and environmentally friendly wastewater treatment strategy. Herein, nanodiamonds (NDs) anchored on ZnSnO3 (ZSO) cubes to form NDs/ZSO composite photocatalyst was successfully prepared via one-step calcination route. Analysis of experimental and characterization results shows that the NDs are uniformly dispersed on the surface of the ZSO cubes to form the stable heterojunction, which not only increases the light absorption, but also promotes the separation of photogenerated electrons and holes, thus improving the photocatalytic performance. In addition, the contact angle test demonstrates that the introduction of NDs with oxygen-containing functional groups is helpful to promote the hydrophilicity of ZSO, and then to improve the contact probability of organic pollutants and enhance photocatalytic degradation activity. The optimal 4% NDs/ZSO composite displays the first-rank photocatalytic efficiency in tetracycline (TC) degradation under visible light and the degradation rate is up to 90%, which is 4.73 times higher than pristine ZSO. Furthermore, the active species capture experiments and electron spin resonance (ESR) techniques were adopted to investigate the photocatalytic reaction mechanism. Liquid chromatography-mass spectrometry (LC-MS) was employed to analyze the degradation intermediate products in photocatalytic process. This study provides a simple strategy for the preparation of highly efficient and stable NDs-based composite photocatalysts.

Ultrathin carbon-coated Zr3+-ZrO2 nanostructures for efficient visible light photocatalytic antibiotic elimination

Broadband solar light absorption and visible light photocatalysis of surface modified ultrawide bandgap semiconductors are receiving wide attentions because of their more negative conduction band potential and positive valence band potential for refractory organics degradation. Here, we reported a novel modified solvothermal strategy by the introduction of distilled water into small molecular alcohols to synthesize crystallized carbon-coated Zr3+-ZrO2 composites for enhanced visible light absorption and visible light photocatalytic tetracycline degradation, in which the distilled water favored for the crystallization of Zr3+-ZrO2 and the formed ultrathin carbon layers derived from the polymerization of small molecular alcohols were contributing to the generation of Zr3+ species and well dispersion of Zr3+ self-doped ZrO2 nanoparticles. The experimental results also showed that carbon-coated Zr3+-ZrO2 composites exhibited enhanced visible light absorption, long-lived charges, efficient visible light photocatalytic performance and good recyclable stability. Besides, possible photocatalytic mechanism and antibiotic degradation pathways over carbon-coated Zr3+-ZrO2 composites under visible light irradiation were also proposed in detail.

Structure-controlled three-dimensional BiOI/MoS2 microspheres for boosting visible-light photocatalytic degradation of tetracycline

Three-dimensional (3D) photocatalytic heterostructures have attracted intense interest, due to their interlayer synergy and high quantum yield. Bismuth oxyiodide (BiOI) is considered as a useful semiconductor material due to its narrow bandgap, good visible-light absorption and tendency to form anisotropic heterostructures. Herein, we propose a facile design strategy for structure-controlled nano-flower-like BiOI/MoS2 microspheres with uniform size and enhanced capacity to photodegrade tetracycline (TC) and methyl orange (MO). These 3D BiOI/MoS2 microspheres were outstanding catalysts of visible-light-driven contaminant degradation, as shown by their ability to degrade TC and MO three times and four times faster, respectively, than pure BiOI. This excellent photocatalytic performance of 3D BiOI/MoS2 microspheres is attributable to synergistic effects resulting from their unique defect-rich structure, specifically the loading of MoS2 onto the surface of defect-rich BiOI suppressing recombination of photogenerated electron–hole pairs. Moreover, the abundant active edge-sites and unique physicochemical properties of MoS2 nanosheets enables them to inhibit photogenerated electron–hole recombination. In this study, a novel route for synthesis of structure-controlled nano-flower-like BiOI/MoS2 microspheres was developed, which will increase the application of these useful materials for addressing environmental pollution. An important direction in future research will be to develop large-scale, controllable synthesis and interfacial microstructural control of these heterostructured photocatalysts.

Realizing improved defect-mediated charge separation by assembling C–TiO2-X nanodots into nanostructured microspheres

Nanostructured C–TiO2-X microspheres were prepared by facile modified solvothermal method and employed as an efficient visible light photocatalyst for photocatalytic antibiotic elimination. The acetone as well as distilled water not only induced the high crystallization of nanostructured C–TiO2-X microspheres, the formation of C–TiO2-X nanodots, and oxygen vacancies, but also boosted the assembling of C–TiO2-X nanodots into nanostructured microspheres. The photocatalytic performance of nanostructured C–TiO2-X microspheres was evaluated by photocatalytic antibiotic degradation under visible light and Xe lamp irradiation. The prepared C–TiO2-X microspheres showed highly improved visible light absorption, charge separation, and visible light photocatalytic activity. The visible light photocatalytic activity of nanostructured C–TiO2-x-180 microspheres was approximately 3.14 times of commercial TiO2, which could be attributed to the construction of unique nanostructures, oxygen vacancies, and carbon doping for efficient solar light harvesting and utilization, the diffusion of degraded products, and charge separation. Besides, the detailed energy band structures, active species for visible light photocatalytic tetracycline degradation, and visible light photocatalytic mechanism of nanostructured C–TiO2-X microspheres were also proposed in the work.

Excellent photocatalytic degradation of tetracycline over black anatase-TiO2 under visible light

As an emerging semiconductor different from regular white TiO2, black TiO2 has attracted intensive attention on visible light driven photocatalysis for degrading dyes, but rarely for degradation of antibiotics. In this study, black anatase-TiO2 was demonstrated to be an effective catalyst for tetracycline (TC) visible light photodegradation. 66.2% removal efficiency of TC was achieved over black TiO2 under visible light illumination, while white TiO2 and N-doped TiO2 exhibited 43.4% and 59.6% removal efficiencies, respectively. Furthermore, only ⋅O2− radicals played an important role in TC photodegradation over white TiO2, whereas both ⋅O2− and h+ were responsible for the degradation over black TiO2 and N-doped TiO2. Different from white TiO2 for visible light photocatalytic TC degradation that follows photosensitization, the visible light photodegrataion over black TiO2 is due to photoexcitation.

Efficient visible light photocatalytic antibiotic elimination performance induced by nanostructured Ag/AgCl@Ti3+-TiO2 mesocrystals

Efficient visible light photocatalytic elimination of pharmaceutical factory wastewater is one of widely concerned and greatly significant attempts in dealing with increasingly serious environmental pollution problems. In this work, hybrid Ag/AgCl nanoparticles were successfully introduced into Ti3+ self-doped TiO2 mesocrystals via precipitation and photo-reduction methods for efficient visible light photocatalytic antibiotic elimination. Some characterization measurements, such as XRD, SEM, TEM, XPS, UV–vis DRS spectra, fluorescence emission spectra, time-resolved fluorescence spectra, FT-IR spectra, and electrochemical measurements, were applied to investigate the physico-chemical properties of nanostructured Ag/AgCl@Ti3+-TiO2 mesocrystals. The experiment results showed that nanostructured Ag/AgCl@Ti3+-TiO2-60 composites presented the best visible light photocatalytic performance for tetracycline degradation, which was approximately 3.52 times of Ti3+-TiO2 mesocrystals and 22.43 times of commercial TiO2. Trapping experiments of active species and DMPO spin-trapping ESR experiments further confirmed that the visible light photocatalytic tetracycline degradation by Ag/AgCl@Ti3+-TiO2 mesocrystals were mainly due to the continuous attacks of photo-generated holes, OH and O2− radicals on tetracycline molecules. Besides, nanostructured Ag/AgCl@Ti3TiO composites were also employed in visible light photocatalytic industrial para-ester wastewater degradation. Finally, possible tetracycline transformation pathways and visible light photocatalytic tetracycline degradation mechanism over plasmonic Ag/AgCl@Ti3+-TiO2 composites were also proposed. Current work indicates that defective semiconductor mesocrystals and their composites have huge prospects in the refractory organic elimination.

Fabrication of perylene imide-modified NH2-UiO-66 for enhanced visible-light photocatalytic degradation of tetracycline

A series of perylene imide-modified NH2-UiO-66 (PIU) photocatalysts, used for tetracycline-hydrochloride (TC·HCl) photocatalytic degradation, have been successfully prepared via the amidation reaction between 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and amino groups on NH2-UiO-66 (UiO). PTCDA converted into perylene imide (PI) on the surface of UiO after amidation. Such covalent linkage provides a platform for PI as an electron acceptor to transfer electrons from UiO, leading to the improved separation efficiency of electron-hole pairs. In the TC·HCl photocatalytic degradation, the performance of PIU was enhanced significantly compared with that of pristine UiO. The apparent rate constant and the total removal rate on the optimized PIU (7PIU) are about 73 and 4 times higher than pristine UiO. After three reuses, 7PIU remains a good photocatalytic activity. Furthermore, the main reactive species and the electron transfer process are discussed. This study might provide a new strategy for the design of effective MOF-based photocatalysts and demonstrates the potential of imide-modified MOFs for pollution removal.

Prominent co-catalytic effect of CoP nanoparticles anchored on high-crystalline g-C3N4 nanosheets for enhanced visible-light photocatalytic degradation of tetracycline in wastewater

Graphitic carbon nitride (g-C3N4) has been regarded as an emerging and promising semiconductor photocatalyst for the solar hydrogen production and organic pollution removal. However, pure g-C3N4 typically exhibits moderate photocatalytic activity. And the amorphous structures and the rapid recombination of the electron-hole pairs are the two main challenges for the improved photocatalytic performance of the single bulk g-C3N4. In this work, we reported the CoP as a co-catalyst modified high-crystalline g-C3N4 (HCCN) to form an stable and highly efficient CoP/HCCN composite via a simple solvothermal method. As expected, the as-prepared composites showed impressive photocatalytic performance toward the tetracycline (TC) degradation. In particular, 5 wt% CoP/HCCN exhibited the optimum photocatalytic efficiency (96.7%, 120 min) and its corresponding degradation rate constant is 10.2 times than HCCN. Additionally, the role of coexisting ions in simulated practical TC wastewater was explored. The enhanced photocatalytic performance mainly derives from two factors: (i) the formation of HCCN to reduce structural defects; (ii) CoP as the cocatalyst on the HCCN surface to accelerate the separation of the photo-generated electrons-hole pairs and strengthen the surface photoreaction of the samples. Our work opens up a new window to the construction of highly effective HCCN-based composite photocatalysts for solar light-driven wastewater treatment.