Visible Light Photodegradation Of Rhodamine Research Articles

Facile modification of TiO2 nanoparticles with H2O2 + NH4F for enhanced visible light photodegradation of rhodamine B and methylene blue

We report a facile modification method to increase the visible light activity of TiO2 samples. We use titanium isopropoxide (TTIP) as the raw Ti source, hydrolyzing in acidic and alkaline solutions, respectively, to fabricate different TiO2 samples as raw TiO2 together with P25-TiO2. Only hydrogen peroxide and ammonia fluoride are used for this facile modification method, and three TiO2 samples are modified for the visible light degradation. This method could promote the transformation of crystalline TiO2 from rutile to anatase, increase the specific surface area, and the bandgap of samples shift to lower energy (2.2 – 3.0 eV) after the modification. For the visible light photodegradation tests, all the three modified samples show a higher visible light photodegradation efficiency. The highest kinetic constant of Rhodamine B and methylene blue degradation is 7 and 2 times that of P25, respectively. Additionally, TiO2 fabricated by TTIP in alkaline solution and its as-modified sample show the highest adsorption of methylene blue dye, whose adsorption rate reaches 9 times that of P25. Thus, the present facile modification can effectively improve the photocatalytic ability of TiO2 under visible light.

Improvement in Structure and Visible Light Catalytic Performance of g-C3N4 Fabricated at a Higher Temperature

A highly-efficient graphitic carbon nitride (g-C3N4) photocatalyst for visible light photodegradation of rhodamine B (RhB) and methyl orange (MO) simulating dyeing wastewater was synthesized by the thermal polycondensation of melamine. The photocatalysts were characterized by TG-DTG-DSC, XRD, EA, XPS, FT-IR, SEM, TEM, BET, PL and UV-vis DRS. The results showed that the photocatalytic performance of g-C3N4 at a higher calcination temperature was significantly enhanced, and its photocatalytic activities for the photodegradation of RhB and MO were remarkably improved by 64.91% and 41.83%, respectively, which was mainly attributed to the satisfactory crystallinity, stable graphene-like structure, large surface area, and excellent optical properties. It was found that •O2− radicals and •OH radicals were the main active species for the photodegradation process by the free radicals trapping experiments and ESR analysis. The photodegradation mechanism of g-C3N4 was proposed predicated using the characterization results.

Coating metal-organic frameworks on plasmonic Ag/AgCl nanowire for boosting visible light photodegradation of organic pollutants.

Photoactive metal–organic frameworks, MIL-100(Fe), with controllable thickness are coated on plasmonic Ag/AgCl nanowire, for boosting visible light photodegradation of rhodamine B and tetracycline hydrochloride. The morphology and composition of the obtained nano-heterostructure were investigated in detail by SEM imaging, TEM imaging, XRD patterns, FT-IR spectra, N2 adsorption–desorption curves and TGA patterns. Photoelectric performance test suggested that a Z-scheme photocatalysis system for efficient transfer of photogenerated charge carriers was established between MIL-100(Fe) and plasmonic Ag/AgCl nanowire.

Valorization of phosphate waste rocks to Ag3PO4/hydroxyapatite for photocatalytic degradation of Rhodamine B under visible light irradiation.

A silver phosphate/hydroxyapatite (Ag3PO4/HA) composite was produced from phosphate waste rocks, firstly by the valorization of these wastes to HA and then by the treatment of this prepared HA with a silver nitrate solution. A type of response surface methodology, Box-Behnken experimental design, was used to find optimum synthesis parameters (silver to HA weight ratios, calcination temperature and calcination time). The visible light photodegradation of Rhodamine B in aqueous solution was used as the experimental response. The analysis of variance for the results showed that silver weight ratio is the most influential parameter on photoactivity of the synthesized photocatalyst. The optimum conditions were predicted to give an RhB degradation yield of 98.609%/4 hours under visible light conditions. In this context, a Ag/HA weight ratio of 14%, a calcination temperature of 300 °C, and a calcination time of 30 min were found to be the optimum conditions. Samples synthesized under the optimum condition were characterized by the use of X-ray diffraction, X-ray fluorescence spectrometer, Fourier transform infrared spectrum analysis, scanning electron microscopy, transmission electron microscopy and ultraviolet-visible diffuse reflection spectroscopy. By comparison with pure HA, the characterization results clearly showed the successful synthesis of the Ag3PO4/HA composite.

Coal tar pitch as natural carbon quantum dots decorated on TiO2 for visible light photodegradation of rhodamine B

Carbon quantum dots (CQDs) modified semiconductor photocatalysts for visible light photodegradation of organic contaminant has attracted increasing attention, but the tedious preparation procedure of CQDs hinders their large-scale application. Coal tar pitch (CTP) is a rich by-product isolated from the coke industry. The molecule of CTP consists of polycyclic aromatic hydrocarbon nucleus and alkyl side chains or heteroatom functional groups attached to the edge of the nucleus, which is similar in structure to CQDs and should be considered as natural CQDs. Based on this perception, we first propose the use of CTP as a natural alternative for CQDs, and prepare effective CTP/TiO2 composite photocatalysts by a simple green one-step solvothermal method. With Rhodamine B (RhB) as target pollutant, the as-prepared CTP/TiO2 composite photocatalysts have higher photocatalytic activity than pure TiO2 under visible light irradiation. The apparent degradation rate constant of the CTP/TiO2 composite photocatalyst with optimum CTP content is 23 times higher than that of pure TiO2. The main active species involved in the photocatalytic degradation of RhB are holes (h+) and hydroxyl radicals (·OH). The usage of cheap raw materials and facile synthesis method paves the way for the large-scale preparation of effective CTP/TiO2 composite photocatalysts.

Bi2MoO6/BiFeO3 heterojunction nanofibers: Enhanced photocatalytic activity, charge separation mechanism and magnetic separability

Uniform Bi2MoO6 nanosheets were grown in a high dispersed fashion on electrospun BiFeO3 nanofibers via a solvothermal technique. The loading amount of Bi2MoO6 in the Bi2MoO6/BiFeO3 heterojunction nanofibers could be controlled by adjusting the precursor concentrations in the solvothermal process. The XPS analysis, energy band position calculation and trapping experiments all proved that the Bi2MoO6/BiFeO3 heterojunction is a Z-scheme heterojunction. The Z-scheme Bi2MoO6/BiFeO3 heterojunction had a much higher photocatalytic activity in the visible-light photodegradation of Rhodamine B (RhB) and tetracycline hydrochloride (TC) than pure BiFeO3 nanofibers or pure Bi2MoO6 nanosheets. The enhanced photocatalytic activity was attributed to the formation of Z-scheme Bi2MoO6/BiFeO3 heterojunctions, which could be beneficial to the separation of photogenerated electron-hole pairs. Moreover, the Bi2MoO6/BiFeO3 heterojunction nanofibers could be easily separated under an external magnetic field via the ferromagnetic BiFeO3. After several cycles, the photocatalytic activity of the Bi2MoO6/BiFeO3 heterojunction no longer significantly decreased suggesting that the Bi2MoO6/BiFeO3 heterojunction is stable. These Z-scheme Bi2MoO6/BiFeO3 heterojunction nanofibers with highly visible-light photocatalytic activity, excellent chemical stability and magnetic separability could be useful in many practical applications.

Morphology effect on photocatalytic activity in Bi3Fe0.5Nb1.5O9

In this work, the Aurivillius-phase ferroelectric Bi3Fe0.5Nb1.5O9 were synthesized by hydrothermal (BFNO-H) and solid state methods (BFNO-S), respectively. The BFNO-H shows a hierarchical morphology, which is stacked by intersecting single-crystal nanosheets with {001} and {110} exposed facets, while the BFNO-S shows disorganized micron-scale morphology. BFNO-H shows a much stronger photodegradation activity (10.4 times and 9.8 times) than BFNO-S in the visible-light photodegradation of rhodamine B (RhB) and salicylic acid. The higher photodegradation activity of BFNO-H was firstly ascribed to the hierarchical structure and the larger specific surface area (16.586 m2 g−1) because a large specific surface area can increase reactive sites and shorten photogenerated carrier migration distance. However, after being normalized by the specific surface area, BFNO-H still performs better than BFNO-S, implying that the specific surface area is not the only factor that determines the photocatalytic activity. Considering that the built-in electric field originating from spontaneous polarization in Bi3Fe0.5Nb1.5O9 has existed in both ab plane and c direction, it matches well with the {001} and {110} exposed facets of BFNO-H nanosheets. This appropriate matching in BFNO-H nanosheets may improve the separation and transmission of photogenerated electron–hole pairs and further enhance its photocatalytic activity. Moreover, the trapping experiments reveals that holes (h+) are the main active species and hole-derived oxidation is the main redox reaction during photodegradation of organic pollutions.

Facile synthesis of g-C3N4/montmorillonite composite with enhanced visible light photodegradation of rhodamine B and tetracycline

A novel g-C3N4/montmorillonite (CN/M) composite with enhanced visible light photocatalytic activity was synthesized via a facile two-step process including wet-chemical and calcination method. The microstructure, interfacial and optical properties of the obtained CN/M composites were characterized by scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), surface area measurement (BET) and UV-visible diffused reflectance spectroscopy (UV-vis DRS). It is indicated that a tight interfacial combination between g-C3N4 nanosheets and montmorillonite layers was formed in the composite photocatalysts. Compared with the other reference samples, the as-received CN/M composites possess significantly enhanced photocatalytic activity towards rhodamine B and tetracycline. The optimal mass ratio of g-C3N4 with respect to montmorillonite is determined to be 31.86wt% and the corresponding reaction constant rate is almost 3.0 times that of the pure g-C3N4 under visible light. The enhanced photocatalytic activity of the g-C3N4/montmorillonite composite could be attributed not only to its relatively higher surface area and enhanced light-adsorption ability under visible light but also the synergistic effect arising from the tight combination between g-C3N4 and montmorillonite due to the electrostatic interaction, which leads to efficient separation of the photo-generated charge carriers.

Highly Active TiO<sub>2</sub>-MoS<sub>2</sub> Composite for Visible Light Photocatalytic Applications

Efficient visible light active TiO2-Molybdenum sulphide (TiO2-MoS2) composites were prepared by solvothermal methodfrom titanium isopropoxide and commercial MoS2 using N-methyl 2-pyrrolidone (NMP) and isopropanol (IPA) solvent mixture. Extended absorption band edge and enhanced visible light absorbance are supplemented intothe TiO2-MoS2 composites by this method. While TiO2 shows ~48% visible light photodegradation of rhodamine B (RhB) the TiO2-MoS2(0.24) exhibits~74% of degradation. In addition to the visible light enhancement, very high surface area and reduced charge transfer resistance at the interfaces are attributed to the enhanced activity of the composite.

Amorphous TiO2 doped with carbon for visible light photodegradation of rhodamine B and 4-chlorophenol

Visible light photocatalytic activity of amorphous TiO2 doped with carbon is prepared by a facile sol-gel route for the first time. The most active sample with mesostructure of amorphous phase, high surface area (273m2g−1) and large pore volume (0.33cm3g−1) is identified by X-ray diffractometer, Raman spectrometer, transmission electron microscope and N2 adsorption–desorption isotherms. In addition, the most active sample is characterized by Fourier transform-infrared spectrometer, X-ray photoelectron spectrometer, UV–vis diffuse reflectance spectrometer and luminescence spectrometer. The results show that the most active sample with oxygenic groups has a narrower bandgap and lower recombination of electron–hole, due to the carbon doping and phase of amorphous. Effective photodegradation capability and stability of rhodamine B and colorless 4-chlorophenol are verified by photocatalytic tests under visible light irradiation. A possible mechanism of amorphous TiO2 doped with carbon for visible light photocatalysis is proposed. The findings of this paper will provide new insights to design visible light-induced photocatalyst based on amorphous TiO2 for organic removal.

Visible Light Photodegradation of Rhodamine B Dye by Two Forms of Carbon-Covered Alumina Supported TiO2/Polysulfone Membranes

Two types of polysulfone (PS) membranes (one on a nonwoven fabric and the other without the fabric) with nanosized carbon-covered alumina supported TiO2 (CCA/TiO2) uniformly dispersed in 15 wt % PS casting solution were prepared. TiO2 nanoparticles were added in order to enhance the visible light photodegradation potential of the PS membranes. The influence of CCA/TiO2 nanoparticles on the PS membranes was investigated using Raman, XRD, SEM, TGA, and TGA-FTIR characterization, and their mechanical strength was determined with an Instron tensile tester. The Raman and XRD results exposed the probability of interactions between the polymer and the CCA/TiO2 nanoparticles, the SEM suggested that these membranes had a high degree of porosity, and this might have resulted in an increase in the permeate flux. The membranes were subsequently tested for the capability to photodegrade Rhodamine B under visible light illumination. The PS/CCA/TiO2 (with fabric) membrane photodegraded 82.4% of the dye, while the PS/CCA...

Synthesis and characterization of carbon-covered alumina (CCA) supported TiO2 nanocatalysts with enhanced visible light photodegradation of Rhodamine B

The anatase phase of titania (TiO2) nano-photocatalysts was prepared using a modified sol gel process and thereafter embedded on carbon-covered alumina supports. The carbon-covered alumina (CCA) supports were prepared via the adsorption of toluene 2,4-diisocyanate (TDI) on the surface of the alumina. TDI was used as the carbon source for the first time for the carbon-covered alumina support system. The adsorption of TDI on alumina is irreversible; hence, the resulting organic moiety can undergo pyrolysis at high temperatures resulting in the formation of a carbon coating on the surface of the alumina. The TiO2 catalysts were impregnated on the CCA supports. X-ray diffraction analysis indicated that the carbon deposited on the alumina was not crystalline and also showed the successful impregnation of TiO2 on the CCA supports. In the Raman spectra, it could be deduced that the carbon was rather a conjugated olefinic or polycyclic hydrocarbons which can be considered as molecular units of a graphitic plane. The Raman analysis of the catalysed CCAs showed the presence of both the anatase titania and D and G band associated with the carbon of the CCAs. The scanning electron microscope micrographs indicated that the alumina was coated by a carbon layer and the energy dispersive X-ray spectra showed the presence of Al, O and C in the CCA samples, with the addition of Ti for the catalyst impregnated supports. The Brunauer Emmet and Teller surface area analysis showed that the incorporating of carbon on the alumina surface resulted in an increase in surface area, while the impregnation with TiO2 resulted in a further increase in surface area. However, a decrease in the pore volume and diameter was observed. The photocatalytic activity of the nanocatalysts was studied for the degradation of Rhodamine B dye. The CCA-TiO2 nanocatalysts were found to be more photocatalytically active under both visible and UV light irradiation compared to the free TIO2 nanocatalysts.

Synthesis and Photocatalytic Properties of Fe-Doped TiO<sub>2</sub> Nanobelts

Fe-doped anatase TiO2nanobelts were prepared using layered titanate nanobelts as precursor by two-step hydrothermal process. Various measurement techniques were employed to investigate the morphology and structure of products. The results show that Fe-doped TiO2still remain nanobelt-like and structure as pure TiO2nanobelts. Fe-cations doped in TiO2nanobelts lead to the red-shift of the absorption edge of TiO2nanobelts. The visible-light photodegradation of Rhodamine B on the products exhibits that Fe-doped products with low Fe-content show higher photocatalytic activity than that of TiO2nanobelts or Fe-doped product with high Fe-content.

Facile Preparation of Ag-Coated TiO<SUB>2</SUB> Nanobelts and Their Photocatalytic Activities

This article describes facile preparation of Ag nanoparticles coated on TiO2 nanobelts and their visible-light photocatalysis activity toward the degradation of Rhodamine B. An Ag complex was adsorbed onto the TiO2 nanobelts by impregnation of the nanobelts into an [Ag(NH3)2]NO3 aqueous solution, and subsequently the Ag precursor was reduced at room temperature by a glucose solution to form Ag nanoparticle-coated TiO2 nanobelts. The visible-light photodegradation of Rhodamine B on such nanocomposite was studied and showed much higher photocatalytic activity than commercial P-25 TiO2 nanoparticles and pure TiO2 nanobelts. Using a seeding preparation procedure through dropwise addition of fresh aqueous solution of NH2NH2 and AgNO3 alternately, larger Ag particles on TiO2 nanobelts were obtained.

Hierarchical mesoporous phosphorus and nitrogen doped titania materials: Synthesis, characterization and visible-light photocatalytic activity

Hierarchical mesoporous P- and N-doped titanias were synthesized by the direct phosphation from phosphoric acid and the following nitridation with urea solution. The resulting materials were characterized by XRD, nitrogen adsorption, SEM, TEM, UV–vis, FT-IR and XPS analysis, and their photocatalytic activities were tested by the visible-light photodegradation of Rhodamine B solution. A bimodal mesopore size distribution with a macroporous structure was observed, rendering high surface area with thermal stability. N-doping of the hierarchical mesoporous titania resulted in the band-gap narrowing with improved photocatalytic activity. However, the phosphated titania exhibited higher photocatalytic activity than the N-doped one, but with larger band-gap energy. Further nitridation of phosphated titania resulted in narrower band-gap of the N,P-codoped titania than either N- or P-doped one, exhibiting the further enhanced photocatalytic activity.

Visible-Light Photodegradation of Rhodamine B on Carbon Doped Titanium Oxide Thin Film Prepared by Atmospheric MOCVD

Carbon doped TiO2 and pure TiO2 thin films were prepared by atmospheric metal organic chemical vapor deposition (MOCVD) method. Both pure TiO2 and carbon doped TiO2 films are in anatase structure. X-ray photoelectron spectra (XPS) of the carbon doped TiO2 film indicate carbon atoms occupy oxygen sites and form Ti-C bonds in TiO2 lattice. In UV-VIS absorption spectra, it can be found that the carbon doped TiO2 film has a red-shifted absorption edge compared with the pure TiO2 film. In the photocatalytic decomposition experiment of Rh.B, carbon doped TiO2 exhibited remarkably visible light activity.