Photodegradation Efficiency Of Methylene Blue Research Articles

Ca-doped g-C3N4 was prepared by two-step calcination for efficient photodegradation of methylene blue

Ca-doped g-C3N4 was prepared by two-step calcination for efficient photodegradation of methylene blue

Synthesis of Novel Nanocomposite CaO/AC/ZnO from Biogenic Wastes of Date Palm Seeds from The Najran Region (Saudi Arabia) and Eggshells for Degradation of Methylene Blue

Metal nanoparticles and activated carbon-based nanocomposite materials are gaining popularity due to their numerous potential applications in a wide range of materials science areas. The current study aims to create novel photocatalyst frameworks for nanocomposites that were synthesized from biogenic waste and used to photodegrade methylene blue (MB) in wastewater under visible light. The activated carbon from date seeds was calcinated at a temperature of 700°C for two hours, and its surface was improved using zinc oxide nanoparticles and calcium oxide nanoparticles manufactured from eggshells at 900oC. XRD, FT-IR, SEM, BET, and TEM analyses were used to characterize the produced nanocomposites. The synthesized nanocomposite photocatalytic activity was evaluated by degrading MB dyes, its model of water pollution. The results showed that the nanocomposite CaO/AC/ZnO has a mesoporous structure with great sorption capability. Also, the photodegradation efficiency of MB using AC, CaO, AC/ZnO, and CaO/AC/ZnO nanocomposite was 33.23, 37.58, 54.61, and 88.92%, respectively, after100 min of sunlight irradiation indicating that photodegradation efficiency increases by improving the surface properties of AC. The CaO/AC/ZnO nanocomposite exhibited a 96.7% removal efficiency of MB following 120 min of visible light radiation exposure. Therefore, the CaO/AC/ZnO nanocomposite has a promising opportunity to function as a versatile and effective photocatalyst for photodegradation of organic dyes in wastewater.

Preparation and Characterization of Carbon Doped ZnO and Its Effectiveness as Photocatalyst under Visible Light

Carbon-doped ZnO (C-ZnO) was prepared and characterized by XRD, SEM, EDX and FT-IR spectroscopy. The substitution of oxygen in the lattice of ZnO by carbon greatly extends its optical sensitivity in the visible light due to the band gap’s shrinkage, which promotes the effectiveness of electron-hole separation. SEM images showed that the surface of C-ZnO catalyst is different from that of undoped ZnO. Analysis of the elements present in the sample was done by EDX which affirms that the prepared sample contains Zn, O and C atoms. The existence of ZnO as wurtzite is confirmed by XRD analysis exhibiting little deviation of the peak position due to the presence of carbon in substitutional sites. FT-IR analysis also supports these results. Under visible light irradiation, the prepared C-ZnO shows better photocatalytic efficiency on methylene blue (MB) than un-doped ZnO. The optimum photodegradation efficiency of MB has been observed when 2 percent C-doped ZnO obtained at 300˚C calcination temperature.
 Dhaka Univ. J. Sci. 71(2): 127-133, 2023 (July)

A green approach for the degradation of toxic textile dyes by nickel oxide (NiO-SD) NPs: Photocatalytic and kinetic approach

By utilizing the combustion process, nanoparticles can be produced quickly, easily, and in an environmentally friendly manner. In this study, sheep dung is employed as fuel for the synthesis of nickel oxide nanoparticles (NiO-SD), and characterization techniques such as XRD, FTIR, UV, FESEM, and EDX, are used to confirm the as-desired nanoparticles. Malachite green (MG) and methylene blue (MB), respectively, are used as benchmark dyes to measure the photocatalytic effectiveness of the material and systematically investigated the effects of the light source, dye concentration, dose of photocatalyst, and pH value on the effectiveness of photocatalyst and photodegradation kinetics. It is found that the NiO-SD, when exposed to UV light, shows good removal effectiveness of the MB and MG dyes, according to the photodegradation data of 99.9% and 96.8%, respectively. The remarkable photodegradation efficiency of MB and MG dyes over the developed photocatalyst is also explained by a plausible photo-catalytic process. The green-manufactured photocatalyst can be a promising for ecological applications such as waste-water remediation.

Visible light-assisted photocatalytic degradation of methylene blue by 1D/2D CdxOy clusters based on metal-organic frameworks without H2O2

Metal-organic frameworks (MOFs) photocatalysts, which contain metal oxo-clusters and organic chromophore linkers, have high visible light absorption utilization, large porosity, specific surface area, effective photogenerated electron and hole separation capabilities. Herein, two types of CdxOy cluster complexes, namely 1D CdxOy cluster Cd-mBDC (mBDC: 1,3-benzenedicarboxylic acid) and 2D CdxOy cluster Cd-2-NH2-mBDC (2-NH2-mBDC: 2-aminoisophthalic acid) were successfully synthesized, and their photocatalytic activity were evaluated by photocatalytic degradation of methylene blue (MB) under visible light without H2O2. The 2D CdxOy cluster of Cd-2-NH2-mBDC can be simplified as a two-dimensional mesh (3.82)(32.82) topology by considering the Cd ions as connected nodes. In addition, conditional experiments showed that the clusters photocatalyst could achieve the best catalytic efficiency under initial dye concentration of 10 mg/L and pH value of 7. Compared with Cd-mBDC, the introduction of amino auxochrome in Cd-2-NH2-mBDC broadened the absorption range and improved the visible light utilization, and the rigid 2D cluster structure facilitated the transfer of photogenerated electrons and enhanced stability. For Cd-2-NH2-mBDC, the photodegradation efficiency of MB could reach 88.44% within 180 min (0.121 min−1) and basically unchanged during five-cycles degradation process. Therefore, Cd-2-NH2-mBDC displays excellent photocatalytic activity and stability for degradation of MB under visible light. Furthermore, the possible mechanism of photocatalytic degradation properties has been also deduced.

Construction of ternary heterostructured Ag/Ag2O@ZnO@g-C3N4 nanocomposite as an widened visible light photocatalyst for the organic oxidation

Two dimension g-C3N4 was synthesized by thermal polymerization using mixture urea and melamine. The metal oxide Ag2O and ZnO were loaded to nanolayer of g-C3N4. The composites Ag/Ag2O@ZnO@g-C3N4 were constructed by Ag2O and ZnO which were defined for p-type and n-type semiconductor to form heterojunctions. The samples were characterized by X ray diffraction(XRD), transmission electron microscopy(TEM), X ray photoelectron spectroscopy (XPS) and UV/Vis diffuse reflectance spectroscopy (UV–vis DRS). The experiment results indicate that Ag2O and ZnO were uniformly loaded to nanolayer of g-C3N4 and heterojunction of Ag/Ag2O@ZnO@g-C3N4 was constructed. The photocatalytic activity of Ag/Ag2O@ZnO@g-C3N4 was characterized by degradation of methylene blue (MB) under the widened visible light-driven. The photodegradation efficiency of MB was 64.486%, 87.724%, 91.611%, 96.700% and 99.999% over g-C3N4, ZnO@g-C3N4, Ag/Ag2O@g-C3N4, Ag/Ag2O@ZnO@g-C3N4-1 and Ag/Ag2O@ZnO@g-C3N4-2, respectively. The results show that the photocatalytic activity of Ag/Ag2O@ZnO@g-C3N4 was enhanced based on the p-n structure which decreased the recombination rates of photoinduced electron hole between metal oxide and g-C3N4. Finally, photocatalytic mechanism of Ag/Ag2O@ZnO@g-C3N4 was discussed for ternary heterostructured catalysts.

One-step preparation of RGO/Fe3O4\u2013FeVO4 nanocomposites as highly effective photocatalysts under natural sunlight illumination

The study used a one-step hydrothermal method to prepare Fe3O4–FeVO4 and xRGO/Fe3O4–FeVO4 nanocomposites. XRD, TEM, EDS, XPS, DRS, and PL techniques were used to examine the structurally and morphologically properties of the prepared samples. The XRD results appeared that the Fe3O4–FeVO4 has a triclinic crystal structure. Under hydrothermal treatment, (GO) was effectively reduced to (RGO) as illustrated by XRD and XPS results. UV–Vis analysis revealed that the addition of RGO enhanced the absorption in the visible region and narrowed the band gap energy. The photoactivities of the prepared samples were evaluated by degrading methylene blue (MB), phenol and brilliant green under sunlight illumination. As indicated by all the nanocomposites, photocatalytic activity was higher than the pure Fe3O4–FeVO4 photocatalyst, and the highest photodegradation efficiency of MB and phenol was shown by the 10%RGO/Fe3O4–FeVO4. In addition, the study examined the mineralization (TOC), photodegradation process, and photocatalytic reaction kinetics of MB and phenol.

Boron Doped ZnO Nanostructures for Photo Degradation of Methylene Blue, Methyl Orange and Rhodamine B.

The design of sensitive and efficient photo catalyst for the energy and environmental applications with minimum charge recombination rate and excellent photo conversion efficiency is a challenging task. Herein we have developed a nonmetal doping methodology into ZnO crystal using simple solvothermal approach. The boron (B) is induced into ZnO. The doping of B did not make any significant change on the morphology of ZnO nano rods as confirmed by scanning electron microscopy (SEM) without considerable change on periodic arrangement of nanostructures. The existence of B, Zn, and O is shown by energy dispersive spectroscopy (EDS). The X-ray diffraction (XRD) patterns are well matched to the hexagonal phase for both pristine ZnO and B-doped ZnO. The XRD has shown slight dislocation of 2theta degree. The UV-visible spectroscopy was used to measure the optical bandgap and photo catalytic activity for the degradation of organic dyes. The nonmetal doped ZnO has shown potential and outstanding photo catalytic activity for the photo degradation of methylene blue (MB), methyl orange (MO) and rhodamine B in aqueous solution. The photo degradation efficiency of MB, MO and rhodamine B is found to be 96%, 86% and 80% respectively. The enhanced photo catalytic activity of B-doped ZnO is indexed to the inhibited charge recombination rate due to the reduction in the optical bandgap. Based on the obtained results, it can be said that nonmetal doping is excellent provision for the design of active materials for the extended range of applications.

Vapor deposition of g-C3N4 on TiO2 nanosquares for efficient photodegradation of MB and Cr6+ under visible light

Herein, a novel composite photocatalyst was prepared by the vapor deposition of g-C3N4 on TiO2 nanosquare, dominated with {001} facets. The deposition method is robust, convenient, and effective. The surface topography and structure of the composites were analyzed by XRD, XPS, SEM, and TEM. The mechanism for enhanced photocatalysis was studied using PL, PC, UV–vis-NIR-DRS, TRPL, EIS and EPR. The photocatalytic activities of the fabricated composites were evaluated by the degradation of methylene blue (MB) and hexavalent chromium ions (Cr6+) under visible light irradiation. The photodegradation of MB and Cr6+ was completed in 50 and 40 min, respectively. Based on a pseudo-first-order kinetic model (ln(C0/C) = kt), the measured the degradation rate constant for MB using gCN/TO5 was 4.6 and 35.9 times higher than that of pure g-C3N4 and TiO2, respectively. Similar results were found for the Cr6+ degradation. The outstanding photocatalytic performance of the g-C3N4 on TiO2 composite was ascribed to the presence of the TiO2/g-C3N4 heterojunctions, which effectively improved the separation of the photoexcited electrons and holes hence the enhancement of visible-light photoactivity. Overall, this work showed a convenient and efficient method for fabricating the visible light photocatalysts with established possible mechanisms for the photoactivity of the hybrid photocatalytic composite material.

Large-scale synthesis of porous Bi2O3 with oxygen vacancies for efficient photodegradation of methylene blue

Photocatalytic degradation of organic pollutants has become a hot research topic because of its low energy consumption and environmental-friendly characteristics. Bismuth oxide (Bi2O3) nanocrystals with a bandgap ranging from 2.0 eV to 2.8 eV have attracted increasing attention due to high activity of photodegradation of organic pollutants by utilizing visible light. Though several methods have been developed to prepare Bi2O3-based semiconductor materials over recent years, it is still difficult to prepare highly active Bi2O3 catalysts in large scale with a simple method. Therefore, developing simple and feasible methods for the preparation of Bi2O3 nanocrystals in large scale is important for the potential applications in industrial wastewater treatment. In this work, we successfully prepared porous Bi2O3 in large scale via etching commercial BiSn powders, followed by thermal treatment with air. The acquired porous Bi2O3 exhibited excellent activity and stability in photocatalytic degradation of methylene blue. Further investigation of the mechanism witnessed that the suitable band structure of porous Bi2O3 allowed the generation of reactive oxygen species, such as O2−· and ·OH, which effectively degraded MB.

Layer-by-layer assembly of Ag2S quantum dots-sensitized ZnO/SnO2 core-shell nanowire arrays for enhanced photocatalytic activity

Ag2S quantum dots-sensitized ZnO/SnO2 core-shell nanowire arrays were successfully synthesized layer by layer through hydrothermal growth, atomic layer deposition, and successive ionic layer adsorption and reaction process. By introducing the two-layer semiconductors, the bandgap of ZnO component in the arrays was slightly modulated, while the light absorption was obviously improved with an absorptivity higher than 95% in visible and ultraviolet range. In contrast to the ZnO NW arrays, the photocurrent response of the ZnO/SnO2/Ag2S NW arrays for the visible light was improved from 0.42 μA to 22.5 μA, and the photodegradation efficiency of methylene blue was increased from 45.24% to 71.61%, and 42.61% to 57.58%, respectively in visible light and ultraviolet light. Band structure analysis indicated that the coating layer brought different staggered gaps and suitable band alignment for efficient photocatalytic performance, which could be extended to design heterogeneous semiconductor nanomaterials for their potential applications.

Construction of β-FeOOH@tunicate cellulose nanocomposite hydrogels and their highly efficient photocatalytic properties.

The environmentally friendly materials fabricated from renewable marine resources have aroused worldwide concerns. Here, for the first time, tunicate cellulose was dissolved in LiOH/urea aqueous solution at -12 °C after ball-milling, and its molecular weight was determined with laser light scattering. Hydrogels were fabricated from the cellulose solution by regenerating in ethanol, and β-FeOOH nanoparticles (NPs) were in-situ synthesized to obtain β-FeOOH/cellulose composite hydrogels (TCH-Fe). The tunicate cellulose hydrogels (TCH) not only disperse uniformly and immobilize firmly the β-FeOOH NPs, but also acted as structural materials for continuous flow photocatalytic system. The photocatalytic degradation of methylene blue (MB) over TCH-Fe achieved up to 99.89% in 30 min under visible-light irradiation, and maintained as high as ∼98% after treatment for 8 h, indicating a highly efficient photodegradation of MB. We provided a low-cost and facile method to construct new sustainable materials derived from marine biomass with highly efficient photocatalytic properties.

Efficient Photocatalytic Removal of Methylene Blue Using a Metalloporphyrin-Poly(vinylidene fluoride) Hybrid Membrane in a Flow-Through Reactor.

A novel combination of a poly(vinylidene fluoride) (PVDF) membrane with pore size 0.2 μm and a photosensitizer 5,10,15,20-tetrakis (pentafluorophenyl)-21H,23H-porphine palladium(II) (PdTFPP) makes a promising hybrid material for the generation of singlet oxygen (1O2) and, thus, water treatment applications. The fabricated photocatalytic membrane exhibits permeability of 4280 ± 250 L·m-2·h-1·bar-1 and stable photocatalytic degradation performance over a 90 h period, when illuminated with green light (528 ± 20 nm) and operated in a dead-end, single-pass configuration. Methylene blue (MB) degradation of 83% was achieved for MB concentration of 1 mg·L-1 under the flow rate of 0.1 × 10-3 L·min-1 (flux of 30 L·m-2·h-1), light intensity of 21 mW·cm-2, and PdTFPP loading of 25 μmol·g-1. Due to an enhanced mass transfer, the reaction rate of MB removal (with apparent rate constant of kapp = 6.52 min-1) results in an efficient photodegradation of MB inside the PdTFPP-PVDF membrane. The influence of experimental parameters such as catalyst loading, flow rate, light intensity, and solute concentration on MB removal was investigated. This research enables the application of photocatalytic PdTFPP-PVDF membranes as a potential technology for water decontamination under visible-light illumination.

Hydrothermal and sol-gel low-temperature synthesis of tin, silver co-doped TiO2 nanoparticles with enhanced photocatalytic efficiency: artificial neural network modelling

Pure anatase TiO2 nanoparticles with various Ag and Sn contents were synthesized by hydrothermal and sol-gel low-temperature methods. Structural and morphological characterizations of synthesized nanoparticles were performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and N2 adsorption/desorption isotherm and brunauer-emmett-teller (BET) techniques. The effect of synthesis procedure on the crystalline structure, crystal size, surface area, pore size distribution and photocatalytic activity of synthesized samples were studied. The photocatalytic activity was tested vs. degradation of methylene blue (MB) under black light radiation. Ag/Sn-TiO2 nanoparticles synthesized by hydrothermal method showed higher photoactivity during the degradation of MB under black light irradiation because of being enhanced in the specific surface area, total pore volume, and its reduction in the crystallite size. An artificial neural network (ANN) comprising four input variables (mol% of dopant ions, photocatalyst dosage, initial dye concentration, and pH of the solution), eight neurons and an output variable (degradation efficiency %) was optimized, tested and validated for MB degradation by Ag/Sn-TiO2 nanoparticles synthesized via hydrothermal method. The results showed that the predicted data from the designed ANN model are in good agreement with the experimental data with a correlation coefficient (R2) of 0.979. A 98.9% photodegradation efficiency of MB was achieved by utilizing 0.07 mol% Ag and 0.03 mol% Sn co-doped TiO2 at pH = 12.

Amorphous Fe2O3 nanoparticles embedded into hypercrosslinked porous polymeric matrix for designing an easily separable and recyclable photocatalytic system

The use of polymer sorbents in wastewater treatment can generate large-scale secondary waste due to the oxidation of the polymer matrix, stemming from the ionogenic functional groups or impurities. In this work, amorphous Fe2O3 nanoparticles were embedded into a porous non-ionogenic polymer matrix (Porolas) using two different Fe(III) salts (iron nitrate and iron oxalate) for designing an easily separable and recyclable photocatalytic system. The Fe2O3-Porolas composites were prepared by a simple method: an impregnation of the Porolas by Fe(III) salts and calcination at 250 °C for 1 h. The sorption capacity and photocatalytic activity of the Fe2O3-Porolas composites were evaluated by the removal of methylene blue (MB) from model-contaminated water under UV light irradiation in the presence of oxalic acid. The characterization results, particularly from X-ray photoelectron spectroscopy and Mössbauer spectroscopy, confirmed the formation of highly dispersed amorphous Fe2O3 nanoparticles that are embedded in the Porolas matrix. An increase in the content of the embedded Fe2O3 nanoparticles decreased specific surface area (SBET), MB sorption capacity, and apparent photodegradation rate constant (kapp) but increased the photodegradation efficiency of MB. The enhancement in MB removal can be attributed to the photocatalytic activities of the Porolas and Fe2O3 nanoparticles (heterogeneous photocatalysis), sorption effect, and leaching of Fe ions in aqueous solution (homogeneous photocatalysis). The scaffold network of the Porolas and highly dispersed Fe2O3 nanoparticles additionally contributed to the enhancement of photocatalytic activity of the Fe2O3-Porolas composite. Almost complete decolorization of MB (96–98%) and more than 97% TOC were achieved in this study, confirming simultaneous mineralization of both MB and OA in aqueous solution. The Fe2O3-Porolas composite can be easily prepared and inexpensive to design an easily separable and recyclable photocatalytic system for wastewater treatment.

Expression of concern: One-pot sol-gel synthesis of reduced graphene oxide uniformly decorated zinc oxide nanoparticles in starch environment for highly efficient photodegradation of methylene blue.

Expression of concern for ‘One-pot sol–gel synthesis of reduced graphene oxide uniformly decorated zinc oxide nanoparticles in starch environment for highly efficient photodegradation of methylene blue’ by Majid Azarang et al., RSC Adv., 2015, 5, 21888–21896.

Synthesis, structure, luminescence and photocatalytic properties of an uranyl-2,5-pyridinedicarboxylate coordination polymer

An uranium coordination polymer, namely [(UO2(pydc)(H2O)]·H2O (1) (H2pydc=2,5-pyridinedicarboxylic acid), has been obtained by hydrothermal method and characterized by X-ray single crystal structure determination. Structural analysis reveals that complex 1 exhibits 1D chain coordination polymer, in which UO22+ ions are bridged by 2,5-pyridinedicarboxylate ligands and the chains are connected into a 3D supramolecular network by O–H···O hydrogen bond interactions and π–π stacking interactions. The photocatalytic properties of 1 for degradation of methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) under Hg-lamp irradiation have been performed, and the amount of the catalyst as well as Hg-lamp irradiation with different power on the photodegradation efficiency of MB have been investigated. Elemental analyses, infrared spectroscopy, TG-DTA analyses and luminescence properties were also discussed.

Hydrothermal synthesis of cobalt-doped ZnS for efficient photodegradation of methylene blue

Abstract A series of coral-like Co-doped ZnS were synthesized by hydrothermal method and used for efficient photodegradation of methylene blue. The chemical composition and microstructure of the Co-doped ZnS were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, scanning electron microscope, and transmission electron microscopy. The results showed that the Co atoms were incorporated into the Zn-S lattice, forming solid solution-type phase. As the Co dopant concentration increases from 0 to 22.49 at.%, the calculated band gap energy of the doped ZnS decreases from 3.32 to 2.65 eV, which enables stronger absorption of visible light. Furthermore, the Co dopant could act as electron trapping center, which inhibits the recombination of the photoinduced electrons and holes. As such, the Co-doped ZnS micro-corals showed higher photodegradation efficiency for methylene blue compared with pristine ZnS. The optimized photocatalytic activity was achieved on 5.49 at.% Co-doped ZnS.

N-doped carbon quantum dots/TiO2 hybrid composites with enhanced visible light driven photocatalytic activity toward dye wastewater degradation and mechanism insight

N-doped carbon quantum dots/TiO2 (NCQDs/TiO2) hybrid composites were prepared via a simple and efficient low-temperature process. The resulted composites were characterized by various techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy and high-resolution TEM, and UV–vis diffuse reflectance spectra. The results indicated that the NCQDs were successfully introduced onto the TiO2 surface. The photocatalytic activity of the NCQDs/TiO2 hybrid composites were investigated by using Methylene blue (MB) as the target pollutant. The photodegradation efficiency of MB over 1NCQDs/TiO2 was 86.9% within 420 min, which was much higher than those of pristine TiO2 (53.8%) and the hybrid composites with other NCQDs contents (lower than 80.1%). This suggested that the NCQDs played important roles for MB degradation under visible light irradiation. The functions of NCQDs were discussed and a new synergistic mechanism was proposed for the degradation of MB on the surface of NCQDs/TiO2 hybrid composites. The enhanced activities were attributed to the interfacial transfer of photogenerated charges from the conductive band (CB) of TiO2 to NCQDs, leading to effective charge separation of TiO2.

Construction of carbon nanodots/tungsten trioxide and their visible-light sensitive photocatalytic activity

Herein we designed a simple and effective method for synthesizing carbon nanodots/tungsten trioxide nanocomposite with high photocatalytic activity. The as-prepared carbon nanodots/ tungsten trioxide has strong photoabsorption under visible light irradiation. Then, carbon nanodots/tungsten trioxide was successfully applied to the degradation of methylene blue. The photodegradation efficiency of methylene blue can be reached as high as 100% after 0.5h visible light illumination. In addition, carbon nanodots/tungsten trioxide could also be used to degrade rhodamine B and methyl orange. Most importantly, the photocatalytic activity of carbon nanodots/tungsten trioxide did not exhibit obvious changes after five cycles. The results indicate that carbon nanodots/tungsten trioxide has potential applications in the degradation of organic pollutants in industrial waste water.