Dye Degradation Test Research Articles

Critical role of the heterojunction interface of silver decorated ZnO nanocomposite with sulfurized graphitic carbon nitride heterostructure materials for photocatalytic applications

The heterojunctions formed at the interfaces between the metal oxide and graphitic carbon nitride (g-C3N4) play a critical role in photocatalytic reactions. Herein, we synthesized a series of heterostructures by the integration of 7% Ag-decorated ZnO nanocomposite (NC) with different contents (3.5–75 wt%) of sulphur-doped graphitic carbon nitride (S-g-C3N4). A unique heterostructure formed between Ag/ZnO and S-g-C3N4 generates a vast number of heterojunctions and abundant catalytic active sites for photocatalytic degradation. The material characterization was performed by XRD, SEM, TEM, XPS, FTIR, UV-Vis spectroscopy, BET surface area, and transient photocurrent response. The as-synthesized 7% Ag/ZnO NC showed maximum methylene blue (MB) degradation among the series (0–9%) under visible irradiation. Interestingly, the 25% Ag/ZnO/S-g-C3N4 heterostructure exhibited a significant increase in photodegradation of MB and 98% dye degraded in only 60 min, which was degraded up to 59% by 7% Ag/ZnO NC. Moreover, the photo-corrosion of ZnO NPs was inhibited by simultaneous doping with Ag and coupling with S-g-C3N4, which was verified through cyclic photo-degradation with six consecutive dye degradation tests. The synergistic effects of the Ag/ZnO/S-g-C3N4 heterojunction, enhanced photocatalytic activity, and photo-corrosion resistance were demonstrated successfully.

Designing highly potential photocatalytic comprising silver deposited ZnO NPs with sulfurized graphitic carbon nitride (Ag/ZnO/S-g-C3N4) ternary composite

A series of ternary-composite were synthesized by the integration of 7% silver-mixed ZnO NPs with different contents (3.5–75 wt%) of sulfur-doped graphitic carbon nitride (S-g-C3N4). A unique ternary-composite formed between Ag/ZnO and S-g-C3N4 generates a vast number of catalytic active sites for photocatalytic degradation. The as-synthesized 7% Ag/ZnO nanocomposite showed maximum methylene blue (MB) degradation rate among the series (0–9%) under visible light. The synergistic effects of the Ag/ZnO/S-g-C3N4 ternary-composite enhanced photocatalytic activity, and photo-corrosion resistance was demonstrated successfully. The photo-corrosion of ZnO NPs was inhibited by simultaneous mixing Ag and coupling with S-g-C3N4, which was verified through cyclic photo-degradation with six consecutive dye degradation tests. Interestingly, the 25% Ag/ZnO/S-g-C3N4 ternary-composite exhibited a significant increase in photodegradation of MB.

Diatomite/silver phosphate composite for efficient degradation of organic dyes under solar radiation

In this study, an effort has been made to synthesize diatomite/silver phosphate (DT/AgP) composites and dye degradation test was carried out to evaluate the photocatalytic activity under solar light irradiation. Diatomite–silver phosphate composites with different DT/AgP ratios were prepared by precipitation of Ag3PO4 on diatomite that led to the formation of small Ag3PO4 particles on the diatomite surfaces. UV–visible diffuse reflectance analysis shows that DT/AgP composites can absorb visible wavelength, whereas TiO2 catalyst only work under UV irradiance. Compared to pure AgP, the composite samples show higher specific surface area measured by Brunauer–Emmett–Teller analysis. Dye degradation test under solar light irradiation reveals that the photocatalytic reaction follows a pseudo-first-order rate law and the composite catalyst with DT/AgP ratio 1:0.8 shows better catalytic activity towards both rhodamine B and methyl orange degradation. As reference, a well-known commercial TiO2 (Evonik-P25) was used in dye degradation test. It could be presumed that deposition of silver phosphate clusters (Ag3PO4, AgP) on diatom frustules (diatomite) provided an efficient photocatalyst activated by solar light irradiation.

Surface modification of brick by zinc oxide and silver nanoparticles to improve performance properties

Due to its versatility, durability, and mechanical stability, brick is an important construction material. In the current study, the brick surface was coated by ZnO nanoparticles based on chemical deposition and modified by silver nanoparticles to create a hydrophobic property on the brick surface as well as photocatalytic and antibacterial properties. The modified brick nanocomposite was characterized by FESEM, XRD, and UV–Visible and then, hydrophobicity, photocatalytic, and antibacterial properties were investigated. Suitable values of bandgap energy of 3.25 eV and 3.22 eV were obtained for the brick modified by ZnO and ZnO/Ag, respectively. By using the dye degradation test under UV irradiation, the brick modification significantly increased the photocatalytic property. The antibacterial property of the nanocomposite was investigated by the disk diffusion method based on staphylococcus aureus and bacillus cereus as gram-positive bacteria and Escherichia coli and pseudomonas aeruginosa as gram-negative bacteria and the experiments showed acceptable results. The results of flexural strength and efflorescence test showed that flexural strength of the brick modified by ZnO/Ag is almost 1.8 times more than non-coated brick and the modified brick represented less efflorescence on the surface. The results showed the improvement of the applicable properties of the brick.

Phase, optical property, and photocatalytic performance behaviors of non-stoichiometric bismuth oxyiodide

Due to the unique layered structures and narrow bandgap, bismuth oxyiodide has become a new photocatalyst with high efficacy. Herein, a series of bismuth oxyiodide with different atomic ratio of Bi:I have been successfully synthesized via hydrothermal methods through simply changing the ratio of Bi and I raw materials, and the composition, optical property, and photocatalytic performance behaviors were investigated. X-ray diffraction patterns, scanning electron microscope images, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy spectra, and ultraviolet–visible spectra analysis confirmed the as-prepared bismuth oxyiodides were Bi7O9I3, Bi3O5I2, and BiOI microspheres with different sizes and bandgaps, which decreased with increased ratios of Bi:I. Due to the larger specific surface areas and the narrower bandgap, Bi7O9I3 can produce more superoxide under simulated sunlight irradiation than Bi3O5I2 and BiOI microspheres. Photocatalytic dye degradation test showed that Bi7O9I3 presented the best photocatalytic performance, followed by Bi3O5I2 and BiOI.

Synthesis of titanium oxide thin films by spray pyrolysis method and its photocatalytic activity for degradation of dyes and ciprofloxacin

Titanium oxide (TiO2) thin film was obtained using the spray pyrolysis method. The structural properties of the thin film obtained were examined by X-ray diffraction (XRD) and it was found that it also had a tetragonal structure. The morphological feature was examined with scanning electron microscopy (SEM). In addition, the optical properties of the film were examined and the forbidden energy range was calculated. Photocatalytic properties of TiO2 thin film on dyestuff and antibiotic were investigated. Methyl blue and malachite green were used in the dye degradation test of the thin film. In particular, it was found to have a high degradation of 86% after 100 minutes on malachite green. Moreover, the degradation on ciprofloxacin after 90 minutes was found as 93%. The reusability ciprofloxacin antibiotic was investigated and it was found that synthesized TiO2 thin film has excellent stability

Pyridinic N–reduced graphene oxide and ZnO composite synergistically enhance photocatalytic performance

This paper reports the synthesis of nitrogen-doped reduced graphene oxide (N-rGO)/zinc oxide (ZnO) composite photocatalysts by one-step hydrothermal method. Taking urea as the nitrogen source, ammonia is released at high temperature, and reduced graphene oxide (rGO) has a strong adsorption effect on ammonia, which is more conducive to improving the nitrogen doping efficiency in the nitrogen doping process. The results of the dye degradation test showed that when the nitrogen content was 4 wt%, the photocatalytic degradation ability of the catalyst was the best, which was 88% higher than that of pure zinc oxide. The X-ray photoelectron spectroscopy (XPS) test showed that the catalytic effect of the sample dominated by pyridinic nitrogen was significantly improved. Besides, fluorescence tests have confirmed that highly conductive rGO can simultaneously capture or transfer photoelectrons within the system, thereby enhancing the photoelectron migration and reducing the private carrier recombination efficiency. N-rGO could act as an active electron accelerator, induce and enhance synergistic coupling, promote photocatalytic redox reactions, and dramatically improve the photocatalytic ability of modified graphene-based composite.

Demonstration of Visible Light-Activated Photocatalytic Self-Cleaning by Thin Films of Perovskite Tantalum and Niobium Oxynitrides.

Metal oxynitrides adopting the perovskite structure have been shown to be visible light-activated photocatalysts, and therefore, they have potential as self-cleaning materials where surface organic pollutants can be removed by photomineralization. In this work, we establish a route for the deposition of thin films for seven perovskite oxynitrides, CaTaO2N, SrTaO2N, BaTaO2N, LaTaON2, EuTaO2N, SrNbO2N, and LaNbON2, on quartz and alumina substrates using dip-coating of a polymer gel to form an amorphous oxide precursor film, followed by ammonolysis. The initially deposited oxide films were annealed at 800 °C, followed by ammonolysis at temperatures from 850 to 1000 °C. The perovskite oxynitride thin films were characterized using XRD and EDX, with band gaps determined using Tauc plots derived from UV-vis spectroscopic data. A cobalt oxide co-catalyst was deposited onto each film by drop casting, and the photocatalytic activity assessed under visible light using dichloroindophenol dye degradation in the presence of a sacrificial oxidant. The light source used was a solar simulator equipped with a 400 nm cut-off filter. The dye degradation test demonstrated photocatalytic activity in all samples except EuTaO2N and BaTaO2N. The three most active samples were SrNbO2N, CaTaO2N, and SrTaO2N. The cobalt oxide loading was optimized for these three films and found to be 0.3 μg cm-2. Further, catalytic tests were conducted using stearic acid degradation, and this found the film of SrNbO2N with the cobalt oxide co-catalyst to be the most active for complete mineralization of this model pollutant.

Batik Home Industry Wastewater Treatment Using UVC/Ozon Oxidation Method: Case Study in Cibelok Village, Pemalang, Indonesia

Batik is one of Indonesia’s cultural heritages that spread across various regions with their unique characteristics. One of the regions that have batik industries is Pemalang Regency. However, batik industries also contribute to liquid waste. Wastewater containing pollutants such as waxes, resins, dyes, and binders such as silicates produce high concentrations of Biochemical Oxygen Demand (BOD) and vibrant colors. There are still many batik enterprises that discard wastewater directly to the environment without being processed first. This study aims to degrade Remazol Black B and Biochemical Oxygen Demand (BOD) dyes in batik liquid waste to contact time variations 0, 15, 30, 45, 60 minutes with UVC-Ozone oxidation methods. The Ozone-UVC method is an alternative method for decolorization and degradation of BOD. The dye degradation test was carried out using Spectroquant UV/VIS Spectrophotometer, and the BOD degradation test was carried out using Dissolved Oxygen - DO Meter AZ-8403. The result shows that the BOD degradation at batik wastewater was from 190.17 – 96.83 mg/L. Visually, the increase in treatment time makes the sample look clearer (decolorization), evidenced by the sample image and decreased absorbance results.

Effect of photocatalytic activity on cobalt titanate (CoTiO3) nanostructures

Cobalt titanate (CoTiO3) nanostructures were synthesized in the form of nanoparticles and nanofibers by sol–gel and electrospinning techniques respectively. The effective photocatalytic activities of CoTiO3 nanofibers have been experimentally demonstrated in comparison with CoTiO3 nanoparticles. Their structural analysis was confirmed using X-Ray Diffraction (XRD) technique which revealed that the synthesized CoTiO3 nanostructures possessed rhombohedral crystal structure. The morphological and optical properties of the synthesized nanostructured materials were characterized by Scanning Electron Microscopy (SEM) and UV–Visible Diffused Reflectance Spectroscopy (UV-DRS). The photocatalytic dye degradation test performed using Methylene Blue (MB) under visible light ambience showcased an enhanced degradation rate for CoTiO3 nanofibers when compared with CoTiO3 nanoparticles.

Visible light driven recyclable micromotors for “on-the-fly” water remediation

Abstract Organic pollutant, originating from both industry and domestic waste, has been greatly threatening the waters all over the world. Micromotors, integrated with photocatalysis, provide a promising solution to this critical challenge. In this work, by taking advantage of the positive motion of the micromotors and visible light response of photocatalysis, we fabricated BiOI microspheres based micromotors and applied them into organic pollutant removal in water. The motion characterization and dye degradation tests demonstrate that “on-the-fly” water remediation is realized under visible light irradiation. What’s more, with the iron oxide nanoparticles embedded, the micromotors are recycled using magnet and reused in organic pollutant degradation.

Use of Au/N-TiO2/SiO2 photocatalysts in building materials with NO depolluting activity

Abstract Two factors are key in the design of a TiO2 photocatalyst for building materials that meets the requirements for environmental applications: the TiO2 light absorption restricted to UV and its poor adhesion to the substrates. In this work, two strategies of TiO2 modification, nitrogen doping and AuNPs deposition, were combined in order to promote the TiO2 photoactivity under solar radiation. By the other hand, the Au/N–TiO2 photocatalysts were incorporated in a silica sol allowing their application by spray on three different building material substrates (limestone, granite and concrete), where the sol spontaneously produced Au/N–TiO2/SiO2 well-adhered coatings. The samples photoactivity was evaluated by dye degradation tests and NO abatement measurements. The obtained results demonstrated that the AuNPs considerably enhanced the photoactivity of N–TiO2, doubling the amount of NOx removed under UV–visible light. In addition, the role of the substrate and the TiO2/SiO2 ratio of the coating were also investigated. The coatings practically triplicated their depolluting effectiveness on concrete in comparison with their application on limestone. A direct correlation between the TiO2 loading and the photoactivity was observed, increasing NOx abatement by a factor of 1.3 when the Au/N–TiO2 loading of the coating was raised from 10 to 25%. However, the Au presence can induce evident colour modifications of the treated substrates that can limit the product application on certain substrates.

Visible light-driven g-C3N4@ZnO heterojunction photocatalyst synthesized via atomic layer deposition with a specially designed rotary reactor

A g-C3N4@ZnO heterojunction is demonstrated using atomic layer deposition (ALD) of ZnO. A specially designed rotary reactor was used to maintain mechanical dispersion of g-C3N4 powder during the ALD process. Stable, uniform, and intimate heterojunctions between g-C3N4 and ZnO were produced, which induced effective charge separation; thus, the photocatalytic activity of the composites was enhanced. The photocatalytic performance was evaluated by the degradation of methylene blue dye. The photocatalytic reaction rate constant of the optimal g-C3N4@ZnO with five ALD cycles was five times and two times higher than those of pristine g-C3N4 and g-C3N4@TiO2 composite, respectively. Furthermore, the photocorrosion of ZnO was inhibited by coupling with g-C3N4, which was confirmed through cyclic photo-degradation with three consecutive dye degradation tests. The synergistic effects of the g-C3N4@ZnO heterojunction, enhanced photocatalytic activity and photocorrosion resistance were proven.

Transparent ZnO crystallized glass ceramics for photocatalytic and antibacterial applications

The synthesis of the transparent ZnO crystallized 9.35K2O-9.35CaO-42.05ZnO-23.36B2O3-9.35SiO2-6.54Al2O3 glass was done using a melt-quenching and heat-treatment route. Three different heat treatments were provided to get different amounts of ZnO crystals in the glass matrix. The X-ray diffraction technique confirmed the ZnO crystallization in the glass matrix. Further characterization was performed using Raman and photoluminescence techniques. The bandgap decreased (3.75–3.14 eV) with an increase in ZnO crystallization. The flower-type morphology of ZnO crystallites was observed using a scanning electron microscope. Contact angle measurements showed an increase in hydrophilicity with the increase in ZnO crystallization. During the photocatalytic ink test using smart Resazurin (Rz) ink, ZnO crystallized glass samples cleaned all ink within 5 h. 78% degradation was observed in Rhodamine B dye (pollutant) using one of the ZnO crystallized samples during the photocatalytic dye degradation test, showing its promising photocatalytic properties. ZnO crystallized glasses portrayed good antibacterial property against Escherichia coli (Gram-negative bacteria). Complete depletion of bacteria within 60 min exposure under ultraviolet irradiation was recorded with one of the ZnO crystallized glasses without any external intervention.

Characterization of TiO2/WO3 composite produced with recycled WO3 nanoparticles from W Ni Fe alloy

Abstract In this study, tungsten was recovered in the form of WO3 nanoparticle from tungsten heavy alloys (W Ni Fe) through a chemical method. In this process nanoparticles of WO3 with crystallite sizes of 21.2 nm were obtained, which were then used to produce TiO2/WO3 composites. The nanoparticles were evaluated using XRD, FESEM, BET, and DRS analyses. The results of TiO2/WO3 composites evidenced that as WO3 rises in amount, the specific surface area and band gap lower, so that the 50%WO3 compound in the composite resulted in the specific surface area of 62.1 m2/g and band gap of 2.77 eV. In order to compare the photocatalytic performance of the composites, methyl orange dye degradation test was carried out under the radiation of UV-Vis light. The results indicated that the composite of TiO2 20%WO3 with the specific surface area of 58.2 m2/g, and band gap energy of 2.94 eV had the highest efficiency in removing the dye. This enhancement in the photocatalytic performance might be due to an improvement in light absorption properties, and a reduction in recombination rate of the electron-holes produced by light.

Highly efficient photocatalytic bismuth oxide coatings and their antimicrobial properties under visible light irradiation

The aim of the present paper is to assess the antimicrobial activity of novel narrow band gap semiconductor photocatalysts under visible light irradiation, compared to titanium dioxide, which is the conventionally used photocatalytic material. Bismuth oxide, bismuth tungstate and titanium dioxide coatings were prepared using pulsed DC reactive magnetron sputter deposition onto batches of 2 mm spherical glass beads that were agitated during the deposition process to ensure uniform coverage. Additional coatings were deposited onto flat glass substrates for specific analytical techniques. Following deposition, the coatings were annealed in air at 673 K for 30 min to enable crystal structure development. Annealed coatings were analysed with SEM, EDX, XRD, XPS, AFM, UV–vis spectroscopy and water contact angle measurements. The photocatalytic properties of the coatings were initially assessed via a Rhodamine B dye degradation test under visible light irradiation. Antimicrobial efficiency of the coatings was tested via inactivation of E. coli; additionally, bacterial adhesion experiments were performed for all types of the studied coatings. It was found that the performance of bismuth oxide for both dye degradation and bacterial inactivation experiments under visible light was superior to that observed for either bismuth tungstate or titanium dioxide. Moreover, bismuth oxide coatings (and to a lesser extent – bismuth tungstate), due to its hydrophobic nature was able to inhibit bacterial adhesion to the surface.

Remazol Brilliant Blue Degradation Using Contact Glow Discharge Electrolysis Reactor with Air Injection and NaCl Solution

Remazol Brilliant Blue dye waste is one of the liquid waste produced from the textile industry and harmful to the environment. Contact Glow Discharge Electrolysis (CGDE) method is an effective method to degrade dye waste by producing OH radicals which will be used in liquid waste degradation process. This study aims to determine the effect of anode depth, temperature, and flow rate of air injection on the production of hydroxyl radicals and dye degradation of Remazol Brilliant Blue. This research was conducted in batch reactor with electrolyte NaCl 0,03 M. Variation which done is anode depth which is 0,5 cm; 2 cm; 4 cm, temperature of 40°C; 50°C; 60°C, and air injection flow rate of 0 lpm and 2.5 lpm. The research was conducted by voltage - current characteristic test, hydroxyl radical production test, and dye degradation test. Remazol Brilliant Blue degradation reached 96.15% within 30 minutes where the tension was 750 V, 0.03 M NaCl solution concentration, Fe2+ 40 ppm, 2 cm anode depth, 50°C temperature, and 2.5 lpm air injection flow rate.

Synthesis and Characterization of TiO2 Nanoparticles for the Reduction of Water Pollutants

The aim of this manuscript was the optimization of the synthesis of TiO2 nanoparticles (TiO2 NPs) with conditions that could be easily reproducible at the industrial level. Several procedures were tested and those with C12H28O4Ti and CO(NH2)2 as precursors seemed the most promising and, consequently, were improved with different molar ratios, lower temperatures and the addition of NH4Cl as a secondary dopant of nitrogen. The obtained samples were studied with analytical techniques such as X-ray powder diffraction (XRPD) and field emission scanning electron microscopy (FESEM). To complete the study, dye degradation and bacteriological tests were also performed. The results indicate that it is possible to obtain TiO2 NPs at lower temperatures with respect to those used in the literature; the best candidate that could satisfy all the requirements was a sample with a molar ratio of C12H28O4Ti:CO(NH2)2 at 2:1 and obtained at 50 °C.

Photocatalytic activity of V-doped TiO2 thin films for the degradation of methylene blue and rhodamine B dye solutions

Highly-transparent V-doped TiO2 thin films were prepared by sol-gel processing, spin coated on fused silica glass substrates, and annealed in air at 450 °C for 2 h. All of the films were comprised of anatase as the sole crystalline phase. The XPS data suggested that V formed an interstitial solid solution with anatase. The formation of an unsaturated solid solution at the lowest doping level of 0.05 mol% resulted in the formation of lattice defect sites, which enhanced anatase recrystallisation, grain growth, and crystallinity. In contrast, the formation of supersaturated/oversaturated solid solutions at the higher doping levels of 0.10–1.00 mol% resulted in lattice deformation, partial amorphisation, precipitation, and liquid formation. The coexistence of multiple valence states, viz., Ti4+/3+, V4+/3+, and possibly V5+ in the doped TiO2 films was attributed to intervalence charge transfer. Dye degradation tests revealed that the 0.05 mol% V-doped films showed the best photocatalyic performance and this was attributed to the combined effects of greater anatase crystallinity and reduced band gap. In contrast, increasing V-doping levels resulted in gradual decreases in the photocatalytic performance, which are attributed principally to the decrease in areal density of the surface-active sites owing to liquid-phase densification. The greater degradation of MB solution relative to that of RhB solution is attributed principally to the cationic nature of MB, which allows greater adsorption on the photocatalyst surface in comparison to the anionic RhB.

Experimental and theoretical investigations of photocatalytic activity of Cu doped ZnO nanoparticles

Undoped and Cu doped ZnO nanopowders were synthesized by very simple and cost-effective soft chemical method by varying copper concentration as 10at%, 20 at% and 30 at% for dye degradation test. Dense nanosheets of wurtzite structure with preferential growth of (101) were formed. The crystallite size decreases from 66.810nm to 20.360nm when the Cu content is increased. The photoluminescence results confirm the shift of near band edge emission (NBE) towards the lower wavelength with increasing doping concentration. Energy dispersive X-ray analysis (EDX) studies confirms the presence of Zn, O and Cu elements in the prepared nano powders. Photocatalytic activity test was conducted for the prepared nanopowders against Methylyne Blue (MB) dye under visible light. The observed results show that the photocatalytic efficiency of the prepared nanopowders increase with the increase of Cu content. Theoretical study based on electrode potentials was performed by employing density functional theory (DFT) in order to validate the experimental results.