Degradation Ratio Of Methylene Blue Research Articles

Exploring the hetero-catalytic proficiencies of pristine and carbon-doped titania nanocatalysts in dye degradation and their synergetic profiles against bacteria

Herein, carbon-doped titania nanostructures (C/TNTs) were prepared via a facile hydrothermal route using different carbon sources, i.e., carbon sheets (CSs), acetylene black (AB), graphene oxide (GO), and reduced graphene oxide (rGO), as doping agents. The morphological characteristics, crystalline nature, nanometric size, and phase purity were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and powder X-ray diffraction (XRD), which revealed a tube-like morphology with a ∼30 nm size, anatase nature, and titanium-oxygen structure, respectively. The as-synthesized nanostructured materials were investigated as photocatalysts under sunlight irradiation for the degradation of methylene blue (MB), a model dye, and for the inactivation of Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive), which are representative microorganisms. Compared with that of a bare titania nanocatalyst (60 %), the photocatalytic degradation efficiency of the as-prepared C/TNT nanostructures was remarkably high (approximately 74 to 94 %) when utilizing a 10 mg of catalyst under sunlight for 40 min. Moreover, these nanocatalysts exhibit exceptional antibacterial properties by restraining the growth of bacteria. The antibacterial analysis demonstrated that the C/TNT nanocatalysts had a significant impact on all bacteria as opposed to bare TNTs. These results revealed that doping with carbon enhanced the photocatalytic activity of TNTs under sunlight irradiation against MB dye as well as selected microbes, especially the rGO/TNT nanocatalyst, which exhibited superior photocatalytic and antibacterial activity. In addition, the rGO/TNTs have good recycling ability, with an MB degradation ratio of more than 81 % after five cycles. We hope that this high activity of the C/TNT nanocatalyst under sunlight irradiation for organic dye degradation and bacterial inactivation implies that hydrothermal synthesis allows for the preparation of efficient and low-cost carbon-doped photocatalysts for a wide range of environmental applications.

Fabrication of iron doped titanium dioxide photocatalytic nanocomposite supported by water-quenched blast furnace slag and photocatalytic degradation of wastewater

Metallurgical solid waste blast furnace water quenched slag (WBFS) was employed as carrier materials to prepare Fe–TiO2/WBFS composite photocatalyst using a sol-gel method for improving both the photocatalytic activity and the high-value utilization of metallurgical solid waste. The Fe3+ doping technology was adopted to increase the utilization of solar energy. The influencing factors and photocatalytic activity were systematically evaluated by thermogravimetry/differential thermal analyser (TG-DSC), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy-energy spectrometer (SEM-EDS), X-ray photoelectric spectroscopy (XPS), UV–Vis absorption spectrum and photoluminescence spectra technology through the degradation rate of methylene blue (MB) solution. The results showed that the Fe3+ ions were successfully incorporated into the TiO2 lattice, which had no effect on the crystalline phase of TiO2 and expanded the spectral response range of TiO2 from the ultraviolet region to the visible light region. When the calcination temperature was at 450 °C and the number of Fe–TiO2 sol loading cycles was two times, the photocatalytic activity of Fe–TiO2/WBFS presented the strongest, and the degradation ratio of MB reach the maximum value of 98.9 %. A uniform and dense anatase TiO2 thin film was wrapped on the surface of WBFS. The photocatalytic activity first improved and then weakened with an increase of calcination temperature, Fe3+ doping amounts and the loading cycles of sol. The TiO2 film changed from thin to thick and uneven to uniform, until cracking and spalling phenomenon finally occurred with an increase of Fe–TiO2 sol loading cycle from 1 to 3 times. When the Fe–TiO2/WBFS was reused for four times, the degradation rate of MB could still show 67.4 %, being far higher than that of TiO2/WBFS of 25.4 %.

Built-in electric field accelerates photogenerated carrier separation in vanadium-oxygen doped C3N4 for flash degradation of methylene blue: Experimental and molecular simulations

Flash photodegradation of organic pollutants at high concentrations is an urgent need for industrial organic wastewater treatment. Situ high-energy wet ball milling is adopted to fabricate the vanadium-oxygen doped carbon nitride catalysts to implement the flash degradation of methylene blue (MB). The experimental results indicated that the photocatalyst degradation ratio of MB was higher than 90% in 3 min under visible-light irradiation 300 W, catalyst dosage 0.2 g/L and MB concentration of 100 mg/L. MB removal rate was nearly 20 times higher than that of primitive carbon nitride. Vanadium-oxygen doping was beneficial to the reduction of band gap less than 2.0 eV and the formation of built-in electric field. It is notable notice that both valence band and conduction band of catalyst were tuned to be in positive potential region, benefiting for holes (h+) formation to boost the flash degradation of contaminants. Strong electrophilic attack of h+ caused the bonds of C-S+=C and CN-C broken, triggering the aromatic ring opened to decompose into smaller molecules.

Improving peroxymonosulfate activation mediated by oxygen vacancy-abundant BaTiO3/Co3O4 composites: The vital roles of BaTiO3

Co3O4-based catalysts are considered as promising heterogeneous catalysts for peroxymonosulfate (PMS) activation, but the poor Co2+/Co3+ redox cycle restricts their environmental application. In this study, BaTiO3/Co3O4 (BT/Co3O4) composites with abundant oxygen vacancies (OVs) were synthesized via a sol-gel method with BT as the OVs donor, and used to activate PMS for organic dye degradation. Co3O4+PMS system degraded only 13.8% of methylene blue (MB) within 20 min, whereas the MB degradation ratio reached 100% for BT/Co3O4+PMS system. The enhanced performance can be attributed to the presence of abundant OVs in BT/Co3O4 composites, which significantly promoted electron transfer and improved the Co3+/Co2+ redox cycle, therefore accelerating PMS activation. The BT/Co3O4+PMS system degraded MB via radical and non-radical pathways, in which singlet oxygen (1O2) played a leading role. In addition, the BT/Co3O4+PMS system exhibited wide pH adaptability and excellent tolerance for inorganic ion interference. This study provides a new strategy for introducing OVs into catalytic materials to substantially enhance the catalytic activity.

Competitive coordination strategy for preparing TiO2/C nanocomposite with adsorption-photocatalytic synergistic effect

The synergistic adsorption-photodegradation effect has been used to form TiO2-based photocatalyst but is limited by the multi-step preparation strategy. The present study employed the “one-pot” method to form the precursor via a competitive coordination strategy. Ca2+/Ti4+-alginate coordination complex was prepared and further carbonized to C-TiO2/CaCO3 nanocomposites for methylene blue (MB) removal. The resultant materials were characterized by FT-IR, XRD, XPS, UV–Vis DRS, TG-DTA, BET, and SEM-EDS techniques, and their synergistic adsorption-photodegradation performance on MB was also studied under simulated sunlight. Results indicated that the anatase-rutile phase of TiO2 in the nanocomposite transformed to the anatase phase by adding CaCl2. The C-TiO2/CaCO3 nanocomposite presented higher specific surface area, pore volume, and mean pore size and consequently showed enhanced adsorption capacity. Low bandgap energy determined an excellent photocatalytic activity, and the degradation ratio of MB reached 96.46% within 10 min. The cycling photodegradation of MB indicated high cycling stability. The C-TiO2/CaCO3 composites made by this simple method have synergistic adsorption-photodegradation performance and can be reused after regeneration, opening up a sustainable opportunity for wastewater treatment.

Study on negative pressure assisted hydrodynamic cavitation (NPA-HC) degradation of methylene blue in dye wastewater

Hydrodynamic cavitation (HC), as a new AOP, has been tried to treat some organic dye wastewater. In traditional HC equipment only positive pressure from water pump was used, which results in a low degradation extent. In this paper, the negative pressure from water pump is used to intensify the whole HC effect for enhancing the decolorization and mineralization of methylene blue (MB) in wastewater. Some influence factors (orifice plate hole number, inlet pressure, initial concentration and solution temperature) on MB degradation efficiency are studied. The determined results of Total Organic Carbon (TOC) and Liquid Chromatograph-Mass Spectrometer (LC-MS) were used to identify MB mineralization extent and confirm the intermediate products during MB degradation, respectively. The results showed that, under the conditions of low temperature, high inlet pressure and moderate dye concentration, the negative pressure assisting hydrodynamic cavitation (NPA-HC) system displayed a significantly enhanced MB degradation effect. The most efficient combination of 25 hole negative pressure assisted 3 hole positive pressure is obtained. At 30 °C in 10 mg/L MB solution, the degradation ratios are 27.43% (in NPA-HC) and 97.48% (in NPA-HC+H2O2 (MB/H2O2 = 1.0:7.5 in molar ratio)), respectively. And that, in single positive pressure HC system the MB degradation ratio is only 16.23%. This study provides a feasible method for intensifying organic dye HC degradation and enlarging wastewater treatment scale.

Preparation and photo fenton-like activities of CuO/nanocellulose composite

A combination between the nanostructured photocatalyst and cellulose-based materials promotes a new functionality of cellulose towards the development of new bio-hybrid materials for water treatment and renewable energy applications. In this study, nanocellulose (CNC) was synthesized from sugarcane bagasse (SCB) biomass via formic /peroxyformic acid process treatment and acid hydrolysis at an atmospheric pressure. The resulting CNC of sugarcane bagasse were characterized by crystallinity index, chemical structure and morphology. X-ray diffraction (XRD) analysis revealed that the crystallinity increased with successive treatments. Images generated by TEM showed that CNC was rod-like in morphology, average diameter and length of 10 nm and 410 nm, respectively. The obtained CNC was used as a biotemplate for the synthesis of copper oxide (CuO) nanostructures through in - situ solution casting method. The photo-Fenton catalytic activity was evaluated via the degradation of methylene blue under sunlight irradiation with H2O2 as a oxidizing agent. The methylene blue degradation ratio of CuO/ CNC composite could achieve 98% in 150 min. The addition of H2O2 enhanced photocatalytic activities of the CuO/CNC. H2O2 not only prevented the recombination of charge carriers by accepting the photogenerated electrons and holes effectively but also produced additional OH.

Development and numerical modelling of a novel UV/H2O2 rotating flow reactor for water treatment.

The ultraviolet photochemical degradation process is widely applied in wastewater treatment due to its low cost, high efficiency and sustainability. In this study, a novel rotating flow reactor was developed for UV-initiated photochemical reactions. The reactor was run in a continuous flow mode, and the tangential installation of the inlet and outlet on the annular reactor improved reaction rates. Numerical modelling, which combined solute transport, radiation transfer and photochemical kinetic degradation processes, was conducted to evaluate improvement compared to current reactor designs. Methylene Blue (MB) decomposition efficiency from the modelling results and the experimental data agreed well with each other. The model results showed that a rotational motion of fluid was well developed inside the designed reactor for a wide range of inflow rates; the generation of ·OH radicals significantly depended on UV irradiation dose, and thus the degradation ratio of MB showed a strong correlation with the UV irradiation distribution. In addition, the comprehensive numerical modelling showed promising potential for the simulation of UV/H2O2 processes in rotating flow reactors.

Shewanella oneidensis MR‐1 in situ biosynthesis of Ag nanoparticles on TiO 2 nanotubes with enhanced photocatalytic performance

Biogenetic nanocomposites research provides valuable methods for the green synthesis of nanomaterials. As a dissimilatory metal-reducing bacterium, Shewanella oneidensis MR-1 is used to reduce Ag+ to Ag nanoparticles (Ag NPs) (diameter about 10 nm) under anaerobic conditions, resulting in the in-situ formation of Ag NPs immobilised on TiO2 nanotubes (TNTs) (Ag/TNTs nanocomposites). The loading amount of Ag nanocrystals on the TNT surface can be controlled easily through adjusting the AgNO3 concentration and further influence visible-light absorption efficiency of Ag/TNTs nanocomposites by decreasing the Ag loading amount. Ag/TNTs nanocomposites show superior photocatalytic efficiency under simulated sunlight than single TiO2 nanomaterials. Moreover, the photocatalytic capacity of Ag/TNTs nanocomposites synergistic by S. oneidensis MR-1 is further enhanced and the degradation ratio of methylene blue reaches 92.3% within 30 min which attributed to a synergistic effect.

Enhanced photocatalytic performance of NaNbO3 nanorods by loading Al2O3 nanoparticles

Herein, we report the fabrication of UV-active NaNbO3/Al2O3 (30 wt.%) ferroelectric heterojunction photocatalyst with enhanced photoelectrochemical activity to Methylene Blue (MB). Pure NaNbO3 nanorods (NRs) were synthesized by a facile hydrothermal process and NaNbO3/Al2O3 composite was prepared by an ultrasonic vibration method. The heterostructures showed a remarkable increase in photocurrent density and the MB degradation ratio reached 88% in the initial 15 min and eventually reached 98.6% in 75 min. The high photocatalytic efficiency is attributed to the ferroelectric polarization of NaNbO3 with the forming of heterojunction electric fields assisted by Al2O3. These properties demonstrate that NaNbO3/Al2O3 ferroelectric heterojunction photocatalyst shows promising photoactivity and provides an effective method to improve the photocatalytic properties of other ferroelectrics.

Fabrication of ZnO nanoparticles adorned nitrogen-doped carbon balls and their application in photodegradation of organic dyes

In the present study, a novel ZnO nanoparticles adorned nitrogen-doped carbon balls (ZnO@CBs) were successfully synthesized from polybenzoxazine and ZnO nanoparticles through a simple carbonization method. The typical wurtzite hexagonal zinc oxide phase in ZnO@CBs and degree of graphitization were revealed by the X-ray diffraction pattern. The field emission scanning electron microscopy confirmed that the synthesized carbon materials have well dispersed ball-like structure, wherein, the ZnO nanoparticles are distributed evenly on the carbon balls (CBs). The synthesized ZnO@CBs with different wt.% (20, 40, 60 and 80) and bare ZnO nanoparticles were investigated for methylene blue (MB) dye degradation experiment. The synthesized ZnO@CBs exhibited high activity in the degradation of MB. Among the different wt.% of ZnO@CBs, 60 wt.% of ZnO@CBs showed the highest MB degradation ratio (99%) with a fast degradation rate (1.65% min−1) under the following optimum conditions: 20 mg of ZnO@CBs in 50 mL of MB solution at room temperature.

Ag6Si2O7/CNTs with highly efficient and stable visible light photocatalytic activity

A novel Ag6Si2O7/CNTs composite photocatalyst was prepared by in-situ precipitation and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS) and photoluminescence spectroscopy (PLS). Photoelectric property and photocatalytic activity were evaluated by photocurrent (PC) and methylene blue (MB) degradation. Photocatalytic activity of Ag6Si2O7/CNTs firstly increased and then decreased with the increasing CNTs content. The degradation ratio of MB by Ag6Si2O7/CNTs with the CNTs content of 0.1% attained 95.2% under visible light irradiation only for 5 min and still retained 93.8% after three recycling runs.

Facile Preparation of Rod-like MnO Nanomixtures via Hydrothermal Approach and Highly Efficient Removal of Methylene Blue for Wastewater Treatment.

In the present study, nanoscale rod-shaped manganese oxide (MnO) mixtures were successfully prepared from graphitic carbon nitride (C3N4) and potassium permanganate (KMnO4) through a hydrothermal method. The as-prepared MnO nanomixtures exhibited high activity in the adsorption and degradation of methylene blue (MB). The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, the effects of the dose of MnO nanomixtures, pH of the solution, initial concentration of MB, and the temperature of MB removal in dye adsorption and degradation experiments was investigated. The degradation mechanism of MB upon treatment with MnO nanomixtures and H2O2 was studied and discussed. The results showed that a maximum adsorption capacity of 154 mg g−1 was obtained for a 60 mg L−1 MB solution at pH 9.0 and 25 °C, and the highest MB degradation ratio reached 99.8% under the following optimum conditions: 50 mL of MB solution (20 mg L−1) at room temperature and pH ≈ 8.0 with 7 mg of C, N-doped MnO and 0.5 mL of H2O2.

One-step hydrothermal synthesis of N/Ti3+ co-doping multiphasic TiO2/BiOBr heterojunctions towards enhanced sonocatalytic performance

N/Ti3+ co-doping multiphasic TiO2/BiOBr heterojunctions (NT-TBx) were prepared by one-step in situ hydrothermal processes. The crystal phase, morphology, component, and optical properties of the heterojunctions were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, and Ultraviolet–visible diffuse reflectance spectroscopy techniques, respectively. The as-prepared samples exhibit better sonocatalytic activity for the degradation methylene blue, Rhodamine B, and p-Nitrophenol aqueous solution compared with pristine TiO2 and N/Ti3+ co-doping multiphasic TiO2. Especially, the highest degradation ratio of methylene blue was achieved for NT-TB0.3 up to 98.2% after 50 min under ultrasonic irradiation. The high sonocatalytic activity has been kept after four cycles with the tiny decline, indicating the excellent stability of the as-prepared samples. The improvement of sonocatalytic activity could be attributed to the formation of doping level and multiphasic TiO2/BiOBr heterojunctions, which account for the absorption of long wavelength light and the electron-hole pair separation, respectively. Furthermore, superoxide radical (O2−) was demonstrated to be the main reactive species for the degradation of methylene blue under ultrasonic irradiation. This study provides a facile fabrication procedure for N/Ti3+ co-doping multiphasic TiO2/BiOBr heterojunctions and demonstrates an efficient route to promote the application of TiO2 in addressing environment-related issues.

The magnetic and photocatalytic properties of nanocomposites SrFe12O19/ZnFe2O4

Magnetic composites SrFe12O19/ZnFe2O4 were successfully synthesized by one-pot coprecipitation method. The as-prepared samples with different molar ratio of SrFe12O19 to ZnFe2O4 were characterized and analysed. XRD and SEM results show that the composites are highly crystalline with few impurities. Raman spectrum confirms the interactions between two phases in the composites. UV–vis spectra and photoluminescence spectra show the optical property of the samples. The magnetic properties analysis reveals that the coercivity of composites decrease evidently with the increase of the ZnFe2O4 phase. Furthermore, photocatalytic performance of the samples were investigated by the degradation of methylene blue (MB) under visible light irradiation. The maximum degradation ratio of MB with Sample-A was 90%. The recycling tests confirm that the photocatalytic activity was above 50% after three cycles. These all prove that the composite SrFe12O19 and ZnFe2O4 not only improve the magnetic and photocatalytic properties, but also effectively avoid secondary pollution of treated water.

Hierarchical structured ZnFe2O4@SiO2@TiO2 composite for enhanced visible-light photocatalytic activity

The preparation and application of magnetic photocatalyst has become an important subject in removal of organic pollutant. In this study, ZnFe2O4@SiO2@TiO2 (hereafter ZST) photocatalysts were facilely synthesized via a sol-gel method. The load amount of TiO2 particles could be tailored by controlling TBOT dosage in ZST composites. The photocatalytic activity was evaluated by the degradation of methylene blue (MB). Under visible light irradiation, the ZST40 catalyst displayed superior photocatalytic performance. The degradation ratio of MB was up to 95.1% in 2 h, which demonstrated that the catalyst with larger specific surface area and mesoporous structure had a better catalytic performance in degrading MB. In addition, the ZST catalyst exhibited excellent chemical stability and recyclability after eight recycling runs. We anticipate that controllable synthesis of ZST photocatalysts has promising applications in environment treatment.

Dual application of Shewanella oneidensis MR-1 in green biosynthesis of Pd nanoparticles supported on TiO2 nanotubes and assisted photocatalytic degradation of methylene blue.

Biosynthesised nanocomposites have attracted growing interests attributed to their 'green' synthesis nature in recent years. Shewanella oneidensis MR-1, a dissimilatory metal-reducing bacterium, was used to reduce palladium (II) nitrate to palladium (0) nanoparticles (Pd NPs) under anaerobic conditions, resulting in the in situ formation of Pd NPs immobilised on TiO2 nanotubes (TNTs) (Pd/TNTs nanocomposites). The Pd/TNTs nanocomposites were characterised by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray, and electron spin resonance, respectively. The results indicated that Pd NPs are successfully grown on the TNTs without aggregation. Photocatalytic degradation of methylene blue (MB) by Pd/TNTs nanocomposites under simulated sunlight was also investigated. Pd/TNTs nanocomposites had photocatalytic efficiency superior to that of single TiO2 nanomaterials. The photocatalytic activity of Pd/TNTs nanocomposites can be enhanced by S. oneidensis MR-1. The results showed that after only 10 min, the degradation ratio of MB reached 98.7% by Pd/TNTs nanocomposites when simultaneously assisted with S. oneidensis MR-1.

Studies on growth mechanism and physical properties of hydrothermally synthesized CdS with novel hierarchical superstructures and their photocatalytic activity

A simple, facile and organic-free hydrothermal method was utilized to synthesize cadmium sulfide (CdS) superstructures. The cadmium chloride and thiourea used as a Cd2+ and S2− ion sources for the growth of CdS superstructures. The reaction was carried out at different time and temperatures. The X-ray diffraction studies confirmed that the obtained products were highly crystalline with hexagonal phase. Scanning and transmission electron microscopy images reveal a monodisperse dendrite-like CdS superstructure. It consisted of a central long trunk with secondary branches, lying parallel to each other and making a certain angle with the central trunk, and small ternary branches grew out of the secondary branches. The selected area electron diffraction altogether with high-resolution electron microscopy patterns depicted that the leaves of dendrite were single crystalline in nature and preferentially grown along (111) direction. The UV-vis absorbance and photoluminescence study illustrated that the hierarchically grown CdS superstructures revealed the good quality of optical properties. A probable growth mechanism for the formation of CdS dendritic superstructures was also discussed and demonstrated by experimental results. The photocatalytic activity of CdS superstructures was studied with the photodegradation of methylene blue (MB) in an aqueous solution, under the visible light irradiation. The results showed that the degradation ratio of MB could reach 94.93% in 220 min. Based on the results, the possible mechanism of the photocatalytic reaction of MB with CdS dendrites is useful for visible light photocatalytic applications.

Hydrothermal synthesis of CdS/CoWO4 heterojunctions with enhanced visible light properties toward organic pollutants degradation

Effective solar energy harvesting and charge carrier separation are two key factors of the photocatalysis system. In this work, the heterojunction photocatalyst of CdS/CoWO4 was fabricated by a facile hydrothermal method. Compared with the pristine CdS and CoWO4, the CdS/CoWO4 heterojunction photocatalyst showed enhanced photocatalytic activity for the methylene blue (MB) degradation under visible light irradiation. Particularly, the sample with molar ratio of CdS:CoWO4 (sample C2) controlled at 3:5 showed the highest MB degradation ratio (83%) in 1h among all samples, which is about 3 times over the pure CdS and 8 times over pure CoWO4, respectively. The greatly enhanced photocatalytic activity (3–8 times) of CdS/CoWO4 is due to the efficient separation of electron-hole pairs by the heterojunction structure and strong visible light absorption of CdS. This work provides a new insight into the application of tungstate-based heterojunction photocatalysts in environmental remediation.

Cooperative luminescence mediated near infrared photocatalysis of CaF2:Yb@BiVO4 composites

It is a challenge to develop efficient photocatalyst that can be activated by photons with long wavelength. In our previous work, a near infrared (NIR) driven photocatalyst (e.g., NaYF4:Yb,Tm@TiO2) was designed, for which, however, a two-step energy transfer was involved for photocatalysis so that the ultimate photocatalytic capability is low. In this work, we designed and prepared a new type of NIR photocatalyst composed of cooperative luminescence agent CaF2:Yb and semiconductor BiVO4, in which a one-step energy transfer occurs to realize NIR photocatalysis. Steady-state and dynamic fluorescence spectroscopy analysis revealed that cooperative energy transfer of a Yb3+-dimer to BiVO4 leads to the indirect excitation of semiconductor BiVO4 by NIR light. The degradation of methylene blue (MB) compound by CaF2:1%Yb3+@BiVO4 particles upon NIR radiation and its corresponding controlled experiments demonstrated the NIR light responsive photocatalytic capability. It is noteworthy that nearly 80% degradation ratio of MB was achieved with 7h of NIR light irradiation, indicating a relatively high photocatalytic activity, compared with that of our previously reported system NaYF4:Yb,Tm@TiO2, for which ∼65% of degradation ratio of MB was obtained within 14h of NIR irradiation. Recycling experiments of photocatalysis indicate that our present CaF2:Yb@BiVO4 composite has good photochemical stability in spite of a long time of NIR irradiation.