Degradation Of Methylene Blue Solution Research Articles

Green synthesis of zinc oxide nanoparticles using Terminalia arjuna bark extract: structural, optical and photocatalytic study

Abstract Zinc oxide (ZnO) nanoparticles have been successfully synthesized by using Terminalia arjuna bark extract via a green route. Structural analysis using X-ray diffraction confirmed the prepared samples are crystalline having hexagonal wurtzite structure with space group P63 mc and average crystallite size is found to be 8.93 nm. Rietveld refinement of the data was carried out using Material Analysis Using Diffraction (MAUD) software and reliability parameters of the refinement have been obtained. Optical properties of the sample investigated by ultraviolet – visible diffuse reflectance spectroscopy reveal an absorption peak to lie at 348 nm and the direct optical band gap energy using Kubelka–Munk function is found to be 3.20 eV. Morphological investigation using scanning electron microscopy revealed that ZnO nanoparticles are nearly spherical and agglomerated. Energy-dispersive X-ray spectrometry analysis showed the presence of Zn and O only. Transmission electron microscopy imaging confirmed the predominant hexagonal structure of the prepared nanoparticles having average particles size of 9.66 nm, which is in agreement with the X-ray diffraction result. Fourier transform infrared spectroscopy was used to identify the functional groups and different vibrational modes present in the sample. The photocatalytic activity of the prepared ZnO nanoparticles was studied using methylene blue (MB) dye under a single wavelength UV light source (λ = 254 nm). The degree of degradation of MB solution was about 56 % within 120 min of illumination to UV light and the degradation reaction follows first order kinetics with rate constant 0.00434 min−1.

Study on the preparation and performance of PVDF/SMA/CdS Fenton-like membrane with both separation and dye degradation functions

Nowadays, the discharge of wastewater causes serious environmental pollution, affecting the living environment and the health of human beings. So the problem of wastewater treatment is imminent. In this context, the PVDF/SMA/CdS membranes had oil-water separation and dye degradation effects were prepared by using non-solvent phase transition and in-situ deposition methods. Its separation efficiency reached more than 98%, and the oil-water removal rate was at more than 90% after 5 times of recycling. Under visible light irradiation, it could completely degrade methylene blue solution (MB, 10 mg·L-1, pH=3) within 20 min, cochineal solution (Ponceau 4R) within 12 min, and chromium blue-black R (EBR) solution within 6 min, and the degradation rate was at more than 95% after 5 cycles. Therefore, the PVDF/SMA/CdS membrane can effectively treat wastewater. This study opens up a promising avenue for wastewater treatment technology with high potential for application.

Effect of Fe doping on crystalline phase, structure and photocatalytic properties of TiO2 thin films

Undoped and Fe-doped TiO2 thin films were fabricated on Si substrates using sol-gel method. XRD and Rietveld refinement results show the anatase to rutile transition in the system. SEM and AFM spectra demonstrate that the generation of agglomeration phenomena after Fe doping provides the nucleation point for the phase transition, and the difference in the Gibbs free energies of the two phases provides the driving force for the phase transition. XPS measurements verify that the formation of oxides after Fe doping contributes to the surface thermodynamic equilibrium and the possibility of the surface atomic rearrangements during the anatase to rutile phase transition. The energy band diagram illustrates at the level of electronic structure that the phase transition raises the position of the conduction band minimum of the film and the oxide of Fe that is formed becomes the charge complex center. Finally, the results of degradation of methylene blue solution under simulated visible light irradiation show that Fe doping reduces the photocatalytic ability of TiO2 films. The corresponding mechanism is proposed to explain the photocatalytic activity by which Fe3+ of larger radius replaces Ti4+ to promote the transition of the film from anatase to rutile and to act as a charge complex center.

Low-temperature synthesis, characterization and photocatalytic properties of lanthanum vanadate LaVO4

In this study, we have successfully prepared tetragonal lanthanum vanadate LaVO4 nanoparticles by a facile co-precipitation method at room temperature. The obtained materials were characterized using different structural and micro-structural techniques such as the characterization by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectrum (DRS), transmission electron microscopy (TEM), and Raman spectrometry. The obtained structure is crystallized in single tetragonal phase with pin-like nanostructure. A main optical transition with bandgap energy of 3.26 eV is evidenced, and the average lifetime of charges carriers was found to be 1 ns Furthermore, the photoluminescence occurs in the visible light range. The photocatalytic activity was evaluated by the photocatalytic degradation of methylene blue (MB) with initial concentration of 10 mg L−1. The result indicates that LaVO4 particles showed a best photocatalytic activity of 98.2% degradation for methylene blue solution after irradiation of 90 min under visible light. Furthermore, the photocatalytic mechanism and reusability were studied.

Mechanically Robust Hybrid Coatings for Antifogging, Antireflection, and Self‐Cleaning Applications

AbstractIn this work, a novel multifunctional film with durable antifogging performance and remarkable optical property is designed. By doping and hybridization to build an organic–inorganic siloxane network, the surface achieves long‐lasting wettability and superhydrophilicity with a water contact angle of 0°, which is maintained within 10° for over 130 days. The low refractive index endows the hybrid film with excellent optical property, which the average transmittance (380–1100 nm) of the film is 97.60% with the peak transmittance of 99.48%. By this design, the film performs well in the felt abrasion test, water impact test, X‐cut tape test, tape‐peeling test, chemical stability test, and anti‐dust test. Due to the abundant hydroxyl radicals on the surface, the film also exhibits excellent performance, achieving 92.73% degradation of methylene blue solution (10 ppm) and 39.53% degradation of rhodamine B (10 ppm) with good reproducibility in cyclic measurements.

Copper-and-Nitrogen-Codoped Zirconium Titanate (Cu-N-ZrTiO<sub>4</sub>) as a Photocatalyst for Photo-Degradation of Methylene Blue under Visible-Light Irradiation

Synthesis and characterization of copper-and-nitrogen-codoped zirconium titanate (Cu-N-ZrTiO4) as a photocatalyst for the degradation of methylene blue (MB) have been conducted. The main purpose of this research was to investigate the co-doping effect of copper and nitrogen dopants in ZrTiO4 as a photocatalyst for the photodegradation of MB. Titanium-(IV) tetraisopropoxide (TTIP) was dissolved into ethanol and mixed with aqueous zirconia (ZrO2) suspension containing 10% nitrogen (N) (w/w to Ti) from urea and various amount of copper as dopants. The calcination was performed at temperatures of 500, 700, and 900 °C. The composites were characterized using Fourier transform infrared spectrophotometer (FTIR), X-ray diffractometer (XRD), scanning electron microscopy with energy dispersive X-ray (SEM-EDX) mapping, and specular reflectance UV-Visible spectrophotometer (SRUV-Vis). The degradation of 4 mg L−1 MB solution was conducted for various irradiation times. Characterization shows a significant decrease of the ZrTiO4 band gap from 3.09 to 2.65 eV, which was given by the composite with the addition of 4% Cu and calcination of 900 °C. Cu-N-ZrTiO4 composite can degrade MB solution up to 83% after 120 min under the irradiation of visible light.

Near-Infrared (NIR) Silver Sulfide (Ag2S) Semiconductor Photocatalyst Film for Degradation of Methylene Blue Solution.

A silver sulfide (Ag2S) semiconductor photocatalyst film has been successfully synthesized using a solution casting method. To produce the photocatalyst films, two types of Ag2S powder were used: a commercialized and synthesized powder. For the commercialized powder (CF/comAg2S), the Ag2S underwent a rarefaction process to reduce its crystallite size from 52 nm to 10 nm, followed by incorporation into microcrystalline cellulose using a solution casting method under the presence of an alkaline/urea solution. A similar process was applied to the synthesized Ag2S powder (CF/syntAg2S), resulting from the co-precipitation process of silver nitrate (AgNO3) and thiourea. The prepared photocatalyst films and their photocatalytic efficiency were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV-visible spectroscopy (UV-Vis). The results showed that the incorporation of the Ag2S powder into the cellulose films could reduce the peak intensity of the oxygen-containing functional group, which indicated the formation of a composite film. The study of the crystal structure confirmed that all of the as-prepared samples featured a monoclinic acanthite Ag2S structure with space group P21/C. It was found that the degradation rate of the methylene blue dye reached 100% within 2 h under sunlight exposure when using CF/comAg2S and 98.6% for the CF/syntAg2S photocatalyst film, and only 48.1% for the bare Ag2S powder. For the non-exposure sunlight samples, the degradation rate of only 33-35% indicated the importance of the semiconductor near-infrared (NIR) Ag2S photocatalyst used.

Preparation, characterization and photocatalytic properties of Er-doped ZnO nanoparticles synthesized by combustion method

Abstract Erbium-doped zinc oxide (Er-doped ZnO) as a visible-light-driven photocatalyst was prepared by combustion method and followed by calcination at 600 °C for 2 h. The samples were characterized by means of X-ray diffraction, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. X-ray diffraction patterns of ZnO samples with and without Er dopant confirm the formation of pure hexagonal wurtzite ZnO phase. The X-ray diffraction peaks of ZnO were shifted to the lower 2θ angle when Er was doped to ZnO matrix. Their transmission electron microscopy images show that the addition of Er can play a role in significantly changing their particle size. Average particle sizes of the as-prepared samples were 69.15 ± 14.47 nm, 68.33 ± 17.06 nm, 16.38 ± 4.02 nm and 27.00 ± 5.27 nm for 0 %, 1 %, 3 % and 5 % Er-doped ZnO samples, respectively. Raman spectra of the Er-doped ZnO samples were able to be used to identify the presence of defect and structural disorder in the ZnO lattice. The ZnO samples with and without Er dopant were tested for the degradation of methylene blue under visible light irradiation. Upon increasing the doped Er content, the degradation of methylene blue solution under visible light irradiation was enhanced. In this research, the 3 % Er-doped ZnO nanoparticles have the highest efficiency of 98.26 % under visible light irradiation within 100 min.

Visible-light photocatalytic degradation of dyes by TiO[formula omitted]–Au inverse opal films synthesized by Atomic Layer Deposition

TiO2–Au composite planar films and inverse opals were synthesized by Atomic Layer Deposition (ALD) using Direct Liquid Injection for TiO2 deposition and for the injection of preformed Au nanoparticles (NPs). A few nanometers thick layer of TiO2 was deposited after the Au NPs. Thermal annealing at 380 °C allowed to remove the polystyrene beads template and to form anatase TiO2.The obtained inverse opals have a layered structure of hollow TiO2 spheres interconnected by channels formed at the template beads contacts. Au NPs are homogeneously distributed on the surface. Their localized surface plasmon resonance (SPR) at 587 nm confirm that they are embedded in TiO2. These photocatalysts were tested for the degradation of methylene blue solutions under visible-light illumination. A significant photocatalytic effect is reported with a 95% degradation after 7 h of exposure only for the composite inverse opal. This results from the transfer of hot electrons from the NPs excited at their SPR to the conduction band of TiO2. They generate reactive oxygen species at the surface of TiO2 which are involved in the initial stage of MB degradation. These results highlight the potential of ALD for the fabrication of complex composite structures for application in photocatalysis.

Fabrication of omnidirectional broadband dual-functional coating with high optical and self-cleaning properties for photovoltaic application

Escalating the transmitted irradiation, which diminishes due to the undesirable reflection at the interfaces and the surface dirt, requires a simultaneous functioning of antireflection and self-cleaning coating for photovoltaic modules. In this regard, an unprecedented, facile, economical, reproducible, and eco-friendly fabrication of dual-functional coatings (Anti-reflective and Self-cleaning) with high optical and photocatalytic properties is demonstrated. Highly crystalline MgF2 and TiO2 nanoparticles are successfully synthesized by the solvothermal method, and these nanoparticles are utilized to develop a dual-functional coating. HR-TEM and XRD are used to analyze the synthesized nanoparticles, and FE-SEM measures the coating morphology and thickness. The established dual-functional coating exhibits a 5 % enhancement in transmittance compared to uncoated glass in the 380–1100 nm wavelength range. The developed coating also shows high omnidirectional broadband antireflective property with 5–33 % net enhancement in the transmittance in the angle of incidence from 10 to 80°. The coating also exhibited good photocatalytic self-cleaning activity by degrading Methylene blue solution in 3 h with minimal loss in transmission. The bilayer dual-functional coating exhibited a net enhancement of 3.5 % in the power conversion efficiency for coated glass placed over a mini-module compared to uncoated glass positioned over a mini-module. This bilayer dual-functional coating offers enormous potential benefits and is highly conceivable for many applications.

Hydrothermal Synthesis of Co-Exposed-Faceted WO3 Nanocrystals with Enhanced Photocatalytic Performance.

In this paper, rod-shaped, cuboid-shaped, and irregular WO3 nanocrystals with different co-exposed crystal facets were prepared for the first time by a simple hydrothermal treatment of tungstic acid colloidal suspension with desired pH values. The crystal structure, morphology, specific surface area, pore size distribution, chemical composition, electronic states of the elements, optical properties, and charge migration behavior of as-obtained WO3 products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), fully automatic specific surface area and porosity analyzer, UV–vis absorption spectra, photoluminescence (PL) spectra, and electrochemical impedance spectroscopy (EIS). The photocatalytic performances of the synthesized pHx-WO3 nanocrystals (x = 0.0, 1.5, 3.0, 5.0, and 7.0) were evaluated and compared with the commercial WO3 (CM-WO3) nanocrystals. The pH7.0-WO3 nanocrystals with co-exposed {202} and {020} facets exhibited highest photocatalytic activity for the degradation of methylene blue solution, which can be attributed to the synergistic effects of the largest specific surface area, the weakest luminescence peak intensity and the smallest arc radius diameter.

Synergistic degradation of methylene blue by laser cavitation and activated carbon fiber

Methylene blue is widely used, but highly toxic and difficult to be degraded. In this paper, a new method of synergistic degradation of methylene blue by laser cavitation and activated carbon fiber is proposed. This paper theoretically studies the synergistic degradation effect, including radical oxidation effect, shock wave breakdown effect and activated carbon fiber surface adsorption effect. The deep degradation of methylene blue was studied experimentally, and the key influencing factors were analyzed. The results show that: the reason why methylene blue can be degraded is because of the oxidation effect of hydroxyl radicals, thermal decomposition and adsorption of molecules on the surface of carbon fibers. The main factors affecting the degradation rate of methylene blue solution are laser energy and initial concentration of solution. The degradation rate increased by 37.4% with the increase of laser energy (12–48 mJ) and decreased by 2.6% with the increase of initial concentration (0.01–0.05 mg/ml). The maximum degradation rate (93%) of methylene blue solution was reached at 48 mJ and 0.01 mg/ml for 30 min. Compared with the traditional adsorption degradation of carbon fibers, the degradation rate of the synergistic degradation of methylene blue solution by laser cavitation and activated carbon fibers can be increased by about 80% in a short time (30 min).

Effects of substrate temperature and sputtering gas composition on physical properties and photocatalytic activities of WOx thin films deposited via radiofrequency sputtering

Tungsten oxide (WOx) is expected to act as a photocatalytic material under visible light. We have deposited WOx thin films using radiofrequency sputtering and evaluated the photocatalytic activities of the films via degradation of methylene blue solution. The optical absorbance, crystallization, and surface morphology of the WOx thin films were also investigated. The absorption edge of the WOx thin films was shifted to the long-wavelength region when the substrate temperature was high and the O2 gas flow rate was low. Crystallization proceeded when the substrate temperature was high and additional WOx diffraction peaks were appearing with low O2 gas flow during growth. Furthermore, the grain size of the WOx thin films was smaller when the O2 gas flow was high. The photocatalytic activity was higher when the substrate temperature and O2 gas flow rate were low.

Microflowery, Microspherical, and Fan-Shaped TiO2 Crystals via Hierarchical Self-Assembly of Nanorods with Exposed Specific Crystal Facets and Enhanced Photocatalytic Performance

In this paper, khaki titanium dioxide (TiO2) crystals via hierarchical self-assembly of nanorods with different morphologies and specific exposed crystal facets were prepared for the first time by using a TiCl3 treatment process in the presence and absence of morphology-controlling agents. The crystal structure, morphology, microstructure, specific surface area, and separation efficiency of photogenerated electron-hole pairs of the synthesized TiO2 crystals were characterized. The photocatalytic and recycled performances of the synthesized TiO2 crystals in the presence of shape-controlling agents, such as ammonium sulfate (AS), ammonium carbonate (AC), and urea, and the absence of shape-controlling agents (the obtained TiO2 crystals were expressed as AS-TiO2, AC-TiO2, urea-TiO2, and No-TiO2, respectively) were evaluated and compared with the commercial TiO2 (CM-TiO2) crystals. The AS-TiO2 microspheres with exposed uncertain facets exhibited enhanced photocatalytic activity for the degradation of methylene blue solution, which can be attributed to the combined effect of the anatase phase structure, relatively larger specific surface area, and the effective separation of the photogenerated electron-holes.

Investigation of the effect of ytterbium doping on photoluminescence and photocatalytic activity of Li4Ti5O12

AbstractThis work reports the combined effect of the morphology and crystallization to investigate the role of Yb3+ as an additive in Li4Ti5O12 crystals on its photocatalytic and photoluminescence (PL) properties. With the pure phase, the synthesized samples have a spherical morphology and spherical structure with good crystallinity and uniform particle size distribution. Li4Ti5O12 doped with ytterbium (Yb3+), were obtained by a new optimized hydrothermal approach. The crystal properties and surface morphology of the synthesized compounds were examined by X‐ray diffraction method and field emission scanning electron microscopy. Bond structures and surface areas were investigated by Fourier transform infrared spectroscopy and Brunauer‐Emmett‐Teller analyses. Finally, the excitation and emission spectra were obtained by a PL spectrophotometer. The PL results show that room‐temperature PL of Yb3+ doped Li4Ti5O12 phosphor has an emission peak at 710 nm which can be attributed to Li4Ti5O12 crystal defect emission. Moreover, it has been found that Yb doping resulted in enhancement of photocatalytic activity, evaluated by monitoring the degradation of methylene blue solution. Note that, 0.01% Yb doped lithium titania phosphor exhibited excellent photocatalytic activity.

Photocatalytic degradation of methylene blue (MB) with Cu1–ZnO single atom catalysts on graphene-coated flexible substrates

Single-atom catalyst of Cu1@ZnO/GPET synthesized via hydrothermal method is shown to exhibit excellent photocatalytic activity towards the degradation of methylene blue solution due to high electron–hole separation efficiency.

Photocatalytic performance of TiO2/Eggshell composite for wastewater treatment

The utilization of eggshells as a primary source for developing value-added materials has received significant attention recently due to its ability as an excellent adsorbent and support. This study used the solid-state dispersion method to prepare composite photocatalyst TiO2/eggshells of different ratios. TiO2 and eggshell photocatalysts were also used as control samples. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) analyses were used to characterize the samples. Finally, the efficiency of the composite photocatalyst was evaluated in the suspension system using methylene blue (MB) solution as the target pollutant. Among three different ratios, TiO2/eggshell (1:9) is the optimum ratio that achieved the highest adsorption and 56.41% photocatalytic degradation of MB solution. Besides, pure eggshells exhibited relatively high adsorption but did not show any significance in photocatalytic degradation. It proves that the ability of eggshell as an adsorbent is very high even though it only acted as support to the TiO2 in the TiO2/eggshell composite photocatalyst. The increased surface area of the TiO2/eggshell composite photocatalyst could enhance MB solution adsorption and photocatalytic degradation, thereby increasing its effectiveness. Overall, it can be concluded that eggshell has excellent potential as support for photocatalyst and as an environmentally friendly catalyst.

The Effect of Sodium Hydroxide Concentration on the Structure of Iron Oxides@Bacterial Cellulose and their Catalytic Activity for Methylene Blue Degradation in Solution

Heterogeneous fenton , although offering promises for large scale wastewater treatment, is still hindered in its practicality due to its modest catalytic activity. The usage of catalyst supportas been demonstrated previously toecrease the overall particle size to improve its catalytic performance. In this demonstration, fenton catalysts were prepared using the sol-gel method and bacterial cellulose (BC) as catalyst support, with varying sodium hydroxide (NaOH) concentrations (0.01; 0.1 and 1 M). NaCl impurities' presence was successfully eliminated by reducing NaOH concentration relative to the previous 4 M concentration. Lower NaOH concentration leads to a more favorable condition for the formation of smaller non-agglomerated particles and magnetite (Fe3O4) as its main crystalline phase. It was found that the best performing catalyst was produced using 1 M NaOH and was able to degrade Methylene blue solution up to 53.8% remaining dye concentration within two hours.

Investigation of shape effect of silver nanostructures and governing physical mechanisms on photo-activity: Zinc oxide/silver plasmonic photocatalyst

Plasmonic composites consisting of silver nanostructures and zinc oxide semiconductor have better photocatalytic performance than pure zinc oxide. To prepare the composites, nanostructures of zinc oxide particles, gold spheres, and three different silver morphology including cubes, spheres, and wires were synthesized. A detailed study of the main mechanisms governing the activity of plasmonic photocatalysts showed that the improvement of photocatalytic performance is attributed to localized surface plasmon resonance-mediated energy transfer from silver to zinc oxide. This mechanism, which is performed using non-radiative (near-field) and radiation (far-field) processes, led to an increase in the concentration of e−/h+ pairs near the semiconductor. We also showed that the increase of the photocatalytic activity depends on the shape of the silver nanostructures in the composites. Our theoretical and experimental studies have shown that composites containing silver cubes have the highest increase of photocatalytic activity compared to other morphologies. The percentage of photocatalytic degradation of methylene blue solution in presence of silver cubes was about 15% higher than that of other morphologies. Therefore, by controlling the shape of noble metal nanostructures, the photocatalytic activity of a semiconductor can be maximized and adjusted.

Synergy mechanism for TiO2/activated carbon composite material: Photocatalytic degradation of methylene blue solution

AbstractTo improve the photocatalytic effect of TiO2 and the possibility of recycling, three different types of commercial activated carbon (AC) are used to prepare the TiO2/AC composite photocatalyst using the sol–gel method. The properties and catalytic activity of TiO2/AC composite are evaluated in comparison with bare TiO2, based on several characterization techniques and methylene blue (MB) photodegradation studies. The results show that the addition of AC improves the degradation effect of MB. The TiO2/AC‐(L) composite material has the best photocatalytic effect. The efficiency of removing the MB solution in 60 min reaches 99.43% at the initial concentration of MB 20 mg/L and material dosage 400 mg/L. The synergy between the adsorption characteristics of the AC surface and the photocatalytic activity of TiO2 is the main reason for increasing the MB degradation rate. Hydroxyl radicals play a major role in the process of photocatalysis. The addition of AC enhances the formation of hydroxyl radicals and superoxide radicals, thereby improving the photocatalytic performance of the material. Compared with bare TiO2, the three TiO2/AC composite photocatalysts can maintain excellent photocatalytic effect after four cycles of experiments and are easier to recycle and reuse.