Photocatalytic Degradation Of Rhodamine Research Articles

Preparation and Photocatalytic Performance for Degradation of Rhodamine B of AgPt/Bi4Ti3O12 Composites.

Loading a noble metal on Bi4Ti3O12 could enable the formation of the Schottky barrier at the interface between the former and the latter, which causes electrons to be trapped and inhibits the recombination of photoelectrons and photoholes. In this paper, AgPt/Bi4Ti3O12 composite photocatalysts were prepared using the photoreduction method, and the effects of the type and content of noble metal on the photocatalytic performance of the catalysts were investigated. The photocatalytic degradation of rhodamine B (RhB) showed that the loading of AgPt bimetallic nanoparticles significantly improved the catalytic performance of Bi4Ti3O12. When 0.10 wt% noble metal was loaded, the degradation rate for RhB of Ag0.7Pt0.3/Bi4Ti3O12 was 0.027 min−1, which was respectively about 2, 1.7 and 3.7 times as that of Ag/Bi4Ti3O12, Pt/Bi3Ti4O12 and Bi4Ti3O12. The reasons may be attributed as follows: (i) the utilization of visible light was enhanced due to the surface plasmon resonance effect of Ag and Pt in the visible region; (ii) Ag nanoparticles mainly acted as electron acceptors to restrain the recombination of photogenerated electron-hole pairs under visible light irradiation; and (iii) Pt nanoparticles acted as electron cocatalysts to further suppress the recombination of photogenerated electron-hole pairs. The photocatalytic performance of Ag0.7Pt0.3/Bi4Ti3O12 was superior to that of Ag/Bi4Ti3O12 and Pt/Bi3Ti4O12 owing to the synergistic effect between Ag and Pt nanoparticles.

Enhanced UV and visible light photocatalytic properties of synthesized AgBr/SnO2 composites

Composites (AgBr/SnO2) comprised of AgBr and SnO2 with different molar % of bare SnO2, have been synthesized by simple precipitation methods; the bare SnO2 used, was synthesized by hydrothermal procedure. Samples have been characterized by X-ray diffraction (XRD), N2-adsorption, UV–vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photocatalysts was evaluated through photocatalytic degradation of rhodamine B (RhB) and caffeic acid (CAFA) under UV and Visible illumination. In photocatalytic degradation studies, for both substrates, conversion rates of around 95% were found in 45 min of both UV-illumination and 85% under visible lighting. These conversion rates were superior than the conversion rates of pure parental components, AgBr and SnO2 under the same experimental conditions. At least, for RhB no loss of photocatalytic activity has been observed after five recycles although the mineralization degree progressively diminished along the recycles. The enhanced photocatalytic degradation of AgBr/SnO2 compounds was attributed, in part, to a synergistic increase in adsorption viability, as well as to the effective separation of photoinduced load carriers that resulted from the formation of a heterojunction according to the type II junction. Radical scavengers’ experiments indicated that active oxidant species as O2.−, ·OH and h+ all are involved in this photocatalytic system, although it seems that O2.− played the major role in the photocatalytic degrading of RhB by AgBr/SnO2 composites. In summary, coupling AgBr with SnO2 remarkably improves the photocatalytic activity under both UV and visible-illumination with respect to the parental components. These features open the route to future applications of this material in the field of environmental remediation.

Fabrication of novel magnetic ZnO hollow spheres/pumice nanocomposites for photodegradation of Rhodamine B under visible light irradiation

The present study deals with the synthesis of ZnO hollow spheres-pumice nanocomposite via a hydrothermal method by employing pumice as the magnetic support. The physicochemical properties of prepared nanocomposites were characterized by XRD, XRF, FT-IR, FE-SEM, TEM, DRS, VSM, PL, BET, and ICP-OES. The photocatalytic activity of samples was evaluated by photocatalytic degradation of Rhodamine B (RhB) as a model pollutant. The influence of operating parameters such as solution pH, initial concentration of pollutant, ZnO loading, photocatalyst dosage, light source, and pumice effect was investigated. The sample with 15 wt% ZnO gave the highest photocatalytic activity at initial concentration of 5 mg/L, pH = 9, and 10 g/L of nanocomposite under visible light irradiation. According to obtained results, the major active species in the photodegradation process were the holes. Also, the obtained results from the COD technique indicated that about 86% of RhB was mineralized at the optimized conditions.

Fabrication of superhydrophobic Ag@ZnO@Bi2WO6 membrane disc as flexible and photocatalytic active reusable SERS substrate

Nowadays, there is a great influence of the innovated semiconductor heterojunction on the improvement of photocatalysis in organic pollutants elimination and the Raman signals multiplexing towards quantitative determination. Here, it was an attempt to develop a heterostructure membrane-based platform employing a filtration system to degrade and detect various target molecules at trace level in liquid samples. Herein, the ZnO nanorods/Bi2WO6 nanocomposites (ZBW) were prepared by a moderate temperature hydrothermal method; thereafter ZBW was encrusted with in-situ photoreduced silver nanoparticles (AgNPs) to form AgNPs@ZBW (Ag@ZnO@Bi2WO6) platform. The superhydrophobic AgNPs@ZBW platform encompasses both photocatalytic degradation of rhodamine B (RhB) under UV-irradiation and label-free surface-enhanced Raman scattering (SERS) evaluated for rhodamine 6G (R6G) and RhB. The AgNPs@ZBW exhibited superior photocatalytic and SERS activities for organic dyes degradation. As a result, the photocatalytic efficiency for dyes was 97.95% in 140 min. From the recycling experiment, it was manifested that AgNPs@ZBW maintained superb photocatalytic activity and stability after five cycles of use for SERS analysis. As-prepared platform displayed a scalable SERS response from 100 µM to 1 nM and enhancement factor of 3.2 × 105 and 1.2 × 105 for R6G and RhB, respectively, using an excitation wavelength of 532 nm, laser power of 3.2 mW and time of exposure of 10 s. Displayed trending of superhydrophobic membrane-based SERS substrates is assumed to lead abounds of change in the field of photocatalytic materials, SERS assay, and organic chemical analysis.

Preparation of Nested g-C₃N₄ Fiber Surrounding Graphene Oxide and Its Photocatalytic Degradation of Rhodamine B.

g-C₃N₄ and graphene oxide (GO) are simultaneously introduced into electrospun polyacrylonitrile (PAN) nanofibers to form a nested structure. By Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), g-C₃N₄ has been perfectly introduced into the PAN@GO nanofiber membrane and affects the porosity of the fiber itself. Comparison of nested electrospinning PAN/PAN@GO and different proportions of PAN@g-C₃N₄/PAN@GO nanofibers has a different effect on reducing the concentration and absorption of rhodamine B (RhB) dye in the visible region. Combined with the advantages of g-C₃N₄ and GO and the performance of fibers in the photocatalytic process, the optimal nested PAN@g-C₃N₄/PAN@GO nanofibers were selected. These results indicate that the nested PAN@g-C₃N₄/PAN@GO nanofibers with high photocatalytic activity have great potential in the treatment of printing and dyeing wastewater.

Photocatalytic degradation of Rhodamine B dye with TiO2 immobilized on SiC foam using full factorial design

Textile effluents treatment is one of the important environmental challenges nowadays. Photocatalysis has proven its effectiveness for the removal of recalcitrant compounds, and it is considered as a green technology for the treatment of effluents. However, good photocatalytic yield is strongly related to the operating parameters. In this study, a supported TiO2 on a β-SiC foam was tested for the removal of Rhodamine B (RhB). The photocatalytic discoloration of RhB synthetic solution in our condition was about 90%. The effects of each parameter were assessed through a full factorial design. Sixteen tests were carried out and the response was RhB removal. The most influent parameters were TiO2/β-SiC foam quantity, the concentration of RhB, the volume of H2O2 and pH. Their contributions on RhB removal were, respectively, 53.01, 30.49, 2.7, and 2.48% according to Pareto diagram. Analysis of the coefficients shows that initial concentration of RhB and volume of H2O2 had a negative effect on the response. However, the quantity of TiO2/β-SiC foam and pH had a positive effect on the response. The influence of the flow rate on the process was assessed. The results showed a slight increase in RhB removal. Furthermore, the aging test of TiO2/β-SiC foam on the photocatalytic efficiency was carried out after ten successive photocatalysis tests. Only 6.7% loss of yield was observed. These results are very encouraging for an application at the industrial scale.

Characterization of zinc oxide nanocrystals with different morphology for application in ultraviolet‐light photocatalytic performances on rhodamine B

ZnO nanostructures of different morphology (nanorods, nano-leaf, nanotubes) were favourably grown using a chemical precipitation process. The prepared ZnO nanostructures were characterized systematically using absorption spectroscopy, emission spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared studies. XRD results showed the hexagonal wurtzite phase of the synthesized ZnO nanostructures. Structural properties such as average crystallite size, lattice constants, volume of the unit cell, atomic fraction, and structural bonds were also studied. The optical band gap of the synthesized ZnO nanocrystals varied from 3.52 eV to 3.69 eV with high quantum yield of the blue emission (~420 nm). Urbach energy for ZnO nanocrystals was calculated to be 0.702 eV, 0.901 eV, and 0.993 eV for nanorods, nano-leaf, and tube like ZnO crystals, respectively. Morphology of the fabricated nanostructures was investigated using SEM. Photocatalytic degradation of rhodamine B (Rh B) in solution under UV irradiation was explored with different ZnO morphology. Photocatalytic experiments showed that ZnO nano-leaf had a higher degradation rate of photocatalytic activity of photodegrading Rh B compared with the other tube shape and rods shape nanostructures. The Rh B dye degraded considerably by ∼79.05%, 74.41%, and 69.8% within 120 min in the presence of the as-fabricated fern nano-leaf, nanotubes, and nanorods of the ZnO nanocrystals at room temperature.

Fabrication and characterization of B/Sn-doped ZnO nanoparticles via mechanochemical method for photocatalytic degradation of rhodamine B

Undoped and B/Sn-doped ZnO nanoparticles are successfully produced by a simple mechanochemical method, and are characterized by XRD, FTIR, EDX, SEM, XPS and BET techniques. The XRD studies reveal that the prepared nanoparticles possess the hexagonal wurtzite structure of ZnO. The presence of various functional groups (–OH, –CH, Zn–O) are observed by FTIR. It is clear from EDX analysis that B, Sn, Zn and O elements are present in the nanoparticles. SEM images confirm the relatively smooth surface of B/Sn-doped ZnO nanoparticles. XPS results indicate that B and Sn are successfully doped into ZnO matrix. The photocatalytic performances of undoped and B/Sn-doped ZnO nanoparticles are investigated for the degradation of aqueous solution of Rhodamine B (RhB) dye in natural sunlight irradiation. The photocatalytic degradation of RhB dye in 1 h with B/Sn-doped ZnO nanoparticle is about 70.2%, which is significantly enhanced compared with the undoped ZnO (51.8%).

Straightforward Synthesis of SnO2/Bi2S3/BiOCl-Bi24O31Cl10 Composites for Drastically Enhancing Rhodamine B Photocatalytic Degradation under Visible Light.

The pursuit of robust photocatalysts that can completely degrade organic contaminants with high performance as well as high energy efficiency, simplicity in preparation, and low cost is an appealing topic that potentially promotes photocatalysts for being used widely. Herein, we introduce a new and efficient SnO2/Bi2S3/BiOCl–Bi24O31Cl10 (SnO2/Bi2S3-Bi25) composite photocatalyst by taking advantage of the robust, simple, and potentially scalable one-pot synthesis, including the hydrothermal process followed by thermal decomposition. Interestingly, we observed the formation of BiOCl–Bi24O31Cl10 (abbreviated as Bi25) heterojunctions derived from reactions between Bi2S3 and SnCl4·5H2O precursor solutions under the hydrothermal condition and thermal decomposition of BiOCl. This Bi25 heterojunction acts as an interface to reduce the recombination of photogenerated electron–hole (e––h+) pairs as well as to massively enhance the visible light harvesting, thereby significantly enhancing the photocatalytic degradation performance of the as-prepared composite photocatalyst. In detail, the photocatalytic degradation of Rhodamine B (RhB) activated by visible light using 15% SnO2/Bi2S3-Bi25 shows the efficiency of 80.8%, which is superior compared to that of pure Bi2S3 (29.4%) and SnO2 (0.1%). The SnO2/Bi2S3-Bi25 composite photocatalyst also presents an excellent photostability and easy recovery from dye for recycling. The trapping test revealed that the photogenerated holes play a crucial factor during the photocatalytic process, whereas superoxide radicals are also formed but not involved in the photocatalytic process. Successful fabrication of SnO2/Bi2S3-Bi25 composite photocatalysts via a straightforward method with drastically enhanced photocatalytic performance under visible light activation would be useful for practical applications.

1D-2D Ag nanowire/g-C3N4 hybrid obtained via a post-mechanical-mixing route for photocatalytic Rhodamine B degradation

The photocatalytic degradation of Rhodamine B (Rh B) wastewater using Ag/g-C3N4 composites has aroused great interests. To date, the composite is dominated by Ag nanoparticles (AgNPs) on the g-C3N4 surface. Only a few studies have concentrated on 1D Ag nanowires (AgNWs) wrapped with g-C3N4 which could bring some new aspects. The wrapped structures can provide large interface, which promotes the exciton dissociation. Moreover, AgNWs with high conductivity can facilitate a fast charge transfer from g-C3N4 and therefore suppress the charge recombination. Herein, a facile approach via a post-mechanical-mixing route has been used to fabricate 1D-2D AgNWs/g-C3N4 composites with enhanced photocatalytic activity for Rh B degradation. AgNWs staggered arrangement can form a conductive network for fast charge transfer. The light absorption of the hybrid in the visible-light region is increased due to the light-scattering from 1D AgNWs. Moreover, conformal contact between AgNWs and g-C3N4 promotes the separation of photo-induced electron-hole pairs. The AgNWs/g-C3N4 hybrid for 2 wt% achieves the best photocatalytic activity for Rh B dye degradation. This work reports an idea using 1D–2D metal-organic hybrid materials as photocatalysts and proposes a facile post-mechanical-mixing method for fabricating hybrids toward various applications.

Photocatalytic Degradation of Rhodamine B by Highly Effective Heterostructure Pd/Bi2MoO6 Nanocomposites Synthesized by Photoreduction Deposition Method

A photoreduction deposition method was developed to produce Pd nanoparticles supported on Bi2MoO6 nanoplates used for photodegradation of rhodamine B (RhB) under visible light irradiation. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and photoluminescence spectroscopy. In this research, orthorhombic Bi2MoO6 nanoplates remain unchanged although metallic cubic Pd nanoparticles were loaded on top of Bi2MoO6 nanoplates. Heterostructure 10% Pd/Bi2MoO6 nanocomposites have the highest efficiency of 98.30% within 90 min because the loaded Pd nanoparticles played the role in separating of photo-induced electron–hole pairs containing in Bi2MoO6. A mechanism for photocatalysis of heterostructure Pd/Bi2MoO6 nanocomposites was also proposed and discussed.

Photocatalytic Degradation of Rhodamine B by C and N Codoped TiO2 Nanoparticles under Visible-Light Irradiation

C and N codoped TiO2 nanoparticles were synthesized via a solvothermal method. The degradation of Rhodamine B by the photocatalyst C, N-TiO2 was investigated under visible-light irradiation generated by using a 36 W compact fluorescent lamp which is characterized by wavelengths from 400 to 650 nm. The structure and properties of the obtained photocatalyst have been systematically investigated using X-ray diffraction, TEM, UV-Vis, FT-IR, and BET techniques. The experimental results revealed that C, N codoped TiO2 nanoparticles were successfully synthesized, with an average diameter of 9.1 nm. C, N-TiO2 nanoparticles exhibited an energy band gap of 2.90 eV, which were lower than pristine TiO2 (3.34 eV), C-TiO2 (3.2 eV), and N-TiO2 (3.03 eV). The degradation of Rhodamine B by C, N-TiO2 indicated that, under visible-light irradiation, the optimal dose of the photocatalyst was 1.8 g/L, and the removal of Rhodamine B was almost complete after 3 hours of reaction. The photocatalytic degradation of Rhodamine B in the range of 5–100 mg/L showed that the process followed the first-order kinetics according to the Langmuir–Hinshelwood model. The highest apparent rate constant (0.0427 min−1) was obtained when the initial concentration of Rhodamine B was 5 mg/L, whereas the former decreased with the increase in the initial concentration of Rhodamine B. Moreover, C and N codoped TiO2 nanoparticles presented a high potential for recycling, which was characterized by a removal efficiency of more than 86% after three cycles.

Exploring the Effect of Morphologies of Fe(III) Metal‐Organic Framework MIL‐88A(Fe) on the Photocatalytic Degradation of Rhodamine B

AbstractMetal‐organic frameworks built from [Fe3(μ3‐O)(COO)6] clusters and fumaric acid ligand, the so‐called MIL‐88 A(Fe) is a well‐known environment‐friendly promising material for many applications. In this paper, three different morphologies of MIL‐88 A(Fe) such as rod, diamond and spindle have been synthesized separately by reacting FeCl3•6H2O and fumaric acid in 1 : 1 metal‐ligand stoichiometric ratio using two different solvents such as water and DMF via hydrothermal method. The morphology of the products and their particle sizes were obtained using SEM and three distinct morphologies viz., rod, diamond and spindle were clearly distinguished by TEM. All the three samples were characterized by FT‐IR, PXRD, UVDRS, PL, XPS and BET, and the effect of the morphologies of MIL‐88 A(Fe) on the photocatalytic degradation of Rhodamine B (RhB) was studied under sunlight. The addition of an H2O2 electron acceptor can markedly enhance the photocatalytic Rhodamine B degradation of MIL‐88 A(Fe). Among these three, rod‐shaped morphology of MIL‐88 A(Fe) shows the higher photocatalytic effect for the degradation of Rhodamine B under sunlight due to its lower band gap, high surface area, and lower electron‐hole recombination rate which enable them the transfer of electrons for the photocatalytic degradation. We found that 98% degradation of RhB in 50 min has taken place by using r‐MIL‐88 A(Fe) as the catalyst under sunlight.

Polyvinylidene Fluoride Electrospun Fibers Loaded TiO2 for Photocatalytic Degradation and Oil/Water Separation

In this study, electrospun polyvinylidene fluoride (PVDF)-based nanofibrous membranes embedding TiO2 were prepared and used for photocatalytic degradation and oil/water separation. The nanofibrous membranes were characterized by scanning electron microscopy (SEM), transmission electronic microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) spectroscopy, thermal performance analysis, and oil/water separation analysis. And the degradation of rhodamine B dye was also investigated. Results showed that the fiber diameter and thermal stability of the membranes decreased with the increasing of TiO2. Meanwhile, the fiber surface roughness and specific surface area increased. The analysis of TEM, XRD and FTIR indicated that TiO2 existed in the PVDF membranes. When the TiO2 content was 12 %, the fiber diameter of the membranes was about 110 nm, and the photocatalytic degradation of rhodamine B dye efficiency was up to 97 %. The reaction rate constant was 0.02057 min−1. At 0.01 MPa vacuum, oil separated from water effectively, which proves that separation can be easily conducted with a low energy cost. Thus, the prepared membranes have a very high application prospect in the purification of reclaimed water and separation of oil and water.

Niobium Pentoxide Samples with Addition of Manganese at Different Concentrations and Calcination Temperatures Applied in the Photocatalytic Degradation of Rhodamine B

In order to improve the photocatalytic effect of Nb2O5, manganese from 1% to 10% was added by the polymeric precursor’s method. The samples obtained were subjected to different calcination temperatures from 400 to 700 °C. Characterization of the synthesized materials was performed by XRD, IR, Raman and Diffuse Reflectance Spectroscopy (DRS) spectroscopy, FE-SEM, Brunauer–Emmett–Teller (BET) method, Photoluminescence (PL) and Dynamic Light Scattering (DLS). Photocatalytic performance for degradation of Rhodamine B was also evaluated. The Rietveld refined X-Ray Diffraction (XRD) pattern of Nb2O5:Mn 1.0 wt.% (700 °C) sample was similar to that of the un-doped oxide, therefore indicating that Nb was replaced by Mn and, consequently, there are not significant variations in the oxide structure. The Nb2O5:Mn 10.0 wt.% (700 °C) sample has the lowest band gap energy. The specific surface area (SBET) PL value increased as manganese concentration increased. The Nb2O5:Mn 5.0 wt.% (700 °C) sample has an Eg of 3.15 eV and morphological and surface characteristics that made it an appropriate photocatalyst in the Rhodamine B degradation. The novelty of this work relies on the use of a small quantity of Mn ions as dopants leading to Nb2O5:Mn nanostructured particles without using any surfactant or other additives.

Synthesis and properties of nanostructured Cr-doped hematite fibres

Cr-doped α-Fe2O3 fibres were synthesized by combining electrospinning and the thermal treatment of electrospun composite fibres at 500 °C. XRD analysis showed the formation of solid solutions with a corresponding small decrease in the unit-cell volume due to a difference between the ionic radii of Fe3+ and Cr3+ cations. Mossbauer spectroscopy showed that the incorporation of Cr3+ into the α-Fe2O3 crystal structure induced a decrease in the hyperfine magnetic field. Doping of α-Fe2O3 with Cr3+ also influenced the shape and position of IR bands in relation to reference α-Fe2O3 fibres in the corresponding FT-IR spectra. The FE-SEM images of Cr-doped α-Fe2O3 fibres showed that they consisted of interconnected nanoparticles and possessed a hollow substructure. The photocatalytic degradation of rhodamine B using electrospun fibres was also investigated.

Fabrication of mesoporous titanium dioxide using azadirachta indica leaves extract towards visible-light-driven photocatalytic dye degradation

An environmental benign, straightforward and financially savvy technique has been developed to fabricate mesoporous titanium dioxide (TiO2) nanostructure utilizing Azadirachta indica leaves extract. The aqueous extract of Azadirachta indica leaves act as a template which upon calcination at high temperature generated mesoporous TiO2. The structure of the mesoporous TiO2 was confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and isothermal gas adsorption-desorption (BET). It has been found that the crystallinity and pore diameter of mesoporous titanium dioxide (TiO2) depends on the amount of Azadirachta indica leaves extract, resulting in enhanced crystallinity with an increasing amount of Azadirachta indica leaves extract. The pore diameter was found somewhere in the range from 16.67 to 46.19 nm, and the BET surface area varies from 8.55–157.35 m2/g. Finally, we have explored as-synthesized mesoporous TiO2 for visible-light-driven photocatalytic degradation of rhodamine 6 G (R6 G) dye. It is noteworthy that the photocatalytic degradation rate of R6 G in presence of as-synthesized mesoporous TiO2 depends only on the amount of plant extract used and not on temperature and other factors. This is presumably due to the increased optical band gap of TiO2.

Synthesis of Bi4Ti3O12-BaTiO3 nanocomposite, manifesting high dielectric and unique magnetic nature applicable in heterogeneous photocatalytic activity for degradation of Rhodamine B dye

ABSTRACT Bi4Ti3O12-BaTiO3 (BTO-BT) nanocomposite, a Aurivillius oxide, which is synthesised by modified solid-state route, and characterised by various techniques like FTIR, XRD, TEM, UV-DRS, Zetasizer Nano-ZS, AFM, BET, SEM-EDX and XPS for the phase identification, microstructural analysis, bandgap determination, elemental analysis and oxidation state of the material. Formation of BTO-BT nanocomposite (orthorhombic and cubic) confirmed by Le-Bail fitting analysis with the help of XRD data. The electrical measurement of the material showed the existence of semiconducting grains and insulating grain boundaries responsible for Maxwell relaxation and a high dielectric constant of value 4.75 × 103 at 368 K was observed. The Magnetic behaviour studied by SQUID indicates it to be magnetically frustrated materials. The material was found to be applicable in photocatalytic degradation of Rhodamine B under UV light through major reactive species, i.e. OH . radicals and O2 .- generated during the photocatalytic reaction proved to be following the first-order kinetics.

Synthesis of ferroelectric 0.9KNbO3-0.1Ba(Nb1/2Ni1/2)O3-δ through one step hydrothermal reaction: Characterization and photocatalytic properties

0.9KNbO3-0.1Ba(Nb1/2Ni1/2)O3-δ (KBNNO) powder was synthesized through one step hydrothermal method at 200 ​°C. The effect of KOH concentration (1 M-18 M) and the effect of reaction time (30 min-12 ​h) on phase evolution and powder morphology were investigated. To get maximum perovskite phase atleast 10 ​M KOH concentration and 12 ​h soaking time were required. Characterization by X-ray diffraction, Raman spectroscopy, FESEM, TEM and XPS confirms the phase, structure, morphology and composition. The Powder morphology varies from spherical to irregular shape, to rod like nature, to cube shape when KOH concentration of the starting solution in the range of 4-6 ​M, 8-12 ​M and 14-18 ​M, respectively. UV–vis absorption spectroscopy indicates that KBNNO has significant absorption in the visible range compared to that of KNbO3. The photocatalytic degradation of Rhodamine B (RhB) shows an enhanced photocatalytic activity of KBNNO in comparison with KNbO3 synthesized under similar conditions. Finally, a mechanism for the enhanced charge separation and photodegradation is proposed.

Production of carbon-doped titanium dioxide (C–TiO2) from polytitanium-coagulated sludge as an adsorbent or photocatalyst for pollutant removals

Chemically enhanced primary sedimentation (CEPS) using titanium coagulants could produce the Ti-loaded sludge with promising material recycle and utilization options. This study investigated two approaches for the recovery and utilization of Ti-based CEPS sludge: (1) a current technology of sludge calcination in the absence of N2 atmosphere to transform Ti to carbon-doped TiO2 (C–TiO2, with a low C content) as a photocatalyst, and (2) a prospective technology of carbonization of the sludge in the presence of N2 atmosphere to produce C–TiO2 (high C content) as an adsorbent. Both approaches can be applied for the recycle and utilization of the materials of the Ti-based CEPS sludge. Calcination at 400–800 °C led to the predominant anatase-TiO2 formation (spherical granules with particle size of around 20–25 nm), while rutile crystal phase appeared at 900 °C. The as-obtained C–TiO2 performed effectively for the adsorption or photocatalytic degradation of rhodamine B (RB) and methyl orange (MO), as the model pollutants, in wastewater treatment. The C–TiO2 with rich activated carbon content (20.0–38.3%, functioned as adsorbents) achieved high-efficient RB and MO adsorption by up to 98% in 20 min, while the C–TiO2 with low activated carbon content (1.5–12.6%, functioned as photocatalysts) degraded 99.6% of RB and 97.0% of MO from initial 20 mg/L in 210 min by photocatalytic degradation under UV illumination.