Degradation Of Methylene Blue Solution Research Articles

Direct Sunlight Active Sm<sup>3+</sup> Doped TiO<sub>2</sub> Photocatalyst

TiO2 and Sm3+ doped TiO2 nanocrystalline has been successfully synthesized by a modified sol-gel method. As synthesized samples of TiO2 and Sm3+ doped TiO2 were calcined at 300, 500, 700 and 800OC and characterized by various techniques such as XRD, UV/Vis Reflectance spectroscopy, FTIR, SEM-EDS and TEM. The crystallite size of Sm3+ doped TiO2 at all calcination temperature is lower than that of TiO2 due the doping Sm3+ ion and thereby induced more nanobehavior. FTIR spectroscopy confirmed the presence of Ti-O and Ti-O-Ti bond in TiO2, in Sm3+ doped TiO2 along with Ti-O and Ti-O-Ti, the presence Sm-O and Ti-O-Sm bonds are confirmed. Diffuse reflectance spectra showed that the Sm3+ doped TiO2 have a significant shift to longer wavelengths and an extension of the absorption in the visible region compared to the TiO2. SEM images confirmed that the particles are agglomerated and the particle size was decreased in the Sm3+ doped TiO2 in comparison with the TiO2. EDS analysis showed the presence of Sm3+ ion present in the lattice of TiO2 in doped sample. Finally the photocatalytic activity of TiO2 and Sm3+ doped TiO2 at various calcinations temperatures was investigated by the degradation of methylene blue solution under UV light and visible light. Doping with the samarium ions significantly enhanced the overall photocatalytic activity for MB degradation under both UV and visible light irradiation. The results showed that the Sm3+ doped TiO2 sample calcined at 700 OC shows the highest photocatalytic activity under UV light and visible light irradiation.

Influence of acid chain length on the properties of TiO2 prepared by sol-gel method and LC-MS studies of methylene blue photodegradation

Nano-sized titanium dioxide photocatalysts were synthesized by hybrid hydrolytic nonhydrolytic sol-gel method using aliphatic organic acid templates to study the effect of chain length on their properties. X-ray diffraction pattern indicated crystalline anatase phase. The Barrett-Joyner-Halenda surface area measurement gave surface area ranging from 98.4 to 205.5m2/g and was found to be dependent on the chain length of the aliphatic acid. The longer chain acids rendered the material with high surface area. The organic acids acted as bidentate ligand and a surfactant in controlling the size and the mesoporosity. The size of the TiO2 nanoparticulate was found to be in the range of 10–18nm. The catalyst prepared by employing long chain acids octanoic acid and palmitic acid had smaller size, narrow pore radius, higher surface area and showed better photocatalytic activity than the commercially available Degussa P25 catalyst for the degradation of methylene blue dye. A new intermediate was identified by tandem liquid chromatography mass spectrometry studies during the degradation of methylene blue solution.

Carbon Nanodots from Frying Oil as Catalyst for Photocatalytic Degradation of Methylene Blue Assisted Solar Light Irradiation

Carbon nanodots (C-Dots) of frying oil could be a photocatalyst for the degradation of methylene blue solution with assisted solar light irradiation. C-Dots of frying oil were resulted from the heating process at T = 300?C for 2 h. C-Dots of frying oil were used as a catalyst in methylene blue solution with variations the number of C-Dots and the time of solar light irradiation. The results of photocatalytic process show the degradation of concentration from methylene blue solution. It was observed from the color change of the solution and the absorbance intensity decreases with increasing time of photocatalytic process. FTIR spectra showed that the hydroxyl functional group -OH changes and more widened at wavenumber 3468 cm-1 because the result of photocatytic process of methylene blue solution is water (H2O) and carbon dioxide (CO2). Meanwhile, the intensity of the alkene functional group C = N at wavenumber 1650 cm-1 decreased during the photocatalytic process. These results indicate that C-Dots of frying oil have an excellent potential to be developed as a photocatalyst materials.

Construction of carbon quantum dots/proton-functionalized graphitic carbon nitride nanocomposite via electrostatic self-assembly strategy and its application

Carbon quantum dots (CQDs) and graphitic carbon nitride (g-C3N4), as advanced metal-free material catalysts have been the focus of considerable attention because of their superior photocatalytic activities. In this study, we developed a novel approach to obtain CQDs/g-C3N4 nanocomposite with effective interfacial contact by incorporating negatively charged CQDs and tailor-made proton-functionalized g-C3N4via the electrostatic self-assembly strategy. Then, the morphology and microstructure of the new nanocomposite were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The CQDs and proton-functionalized g-C3N4 nanocomposite exhibited excellent electron transfer properties though electrochemical impedance spectroscopy (EIS), significantly enhanced photoactivity in the photoelectrochemical i–t curve test and degradation of methylene blue solution under visible light irradiation. These results demonstrated that the electrostatic self-assembly strategy process is a promising method of fabricating uniform metal-free material catalysts for an extensive range of applications.

Band gap narrowing and photocatalytic studies of Nd3+ ion-doped SnO2 nanoparticles using solar energy

Pure and Nd3+-doped tin oxide (SnO2) nanoparticles have been prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive spectroscopy and UV–visible spectroscopy. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO2 phase which is further confirmed by TEM analysis. Neodymium doping introduces band gap narrowing in the prepared samples and enhances their absorption towards the visible-light region. The photocatalytic activity of all the samples was evaluated by monitoring the degradation of methylene blue solution under day light illumination and it was found that the photocatalytic activity significantly increases for the samples calcined at 600 than 400°C, which is due to the effective charge separation of photogenerated electron–hole pairs. The efficiency of photocatalysts was found to be related to neodymium doping percentage and calcination temperature.

The role of multi-level structure for the improved photocatalytic performance of TiO2 fiber nanomaterial

A TiO2 multi-structured fiber nanomaterial was prepared via a template-assisted two-step method, and the effect of the pH value of the precursor solution on the structure of TiO2 nanofibers was mainly investigated. The samples were characterized by X-ray diffraction and scanning electron microscopy. The photocatalytic degradation of methylene blue solution was used as the model reaction to evaluate the photocatalytic property of the as-prepared TiO2 nanomaterials. Results indicated that the pH value of the precursor solution obviously influenced the formation and microstructure and photocatalytic activity of the TiO2 fiber nanomaterials. The multi-structured fiber nanomaterial showed better photocatalytic property. It was considered that high efficiencies of reactant molecules adsorption, light absorption, and separation of photogenerated e −–h + pairs played crucial roles for enhancing its photocatalytic property. In particular, the need of better understanding the relation of the light absorption and charge transport to the nanostructure has to be pointed out in this paper.

Influence of Dy dopant on photocatalytic properties of Dy-doped ZnWO4 nanorods

0–3mol% Dy-doped ZnWO4 nanorods as UV-light-responsive photocatalyst were synthesized by a hydrothermal method. The effect of Dy dopant on phase, morphologies and photocatalytic activities of ZnWO4 was investigated. Their phase and morphologies were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. In this research, the products are of monoclinic ZnWO4 nanorods with [021] growth direction. The photocatalysis was evaluated through degradation of methylene blue solution under UV radiation, with 3mol% Dy-doped ZnWO4 at the highest activity.

Development of visible light activated TiO2 thin films on stainless steel via sol spraying with emphasis on microstructural evolution and photocatalytic activity

Visible light activated nitrogen doped TiO2 thin films were developed on 304 stainless steel by sol spraying method using a common painting airbrush. Thin films with different thickness were prepared and calcined at various temperatures from 400 to 600°C. The samples were studied using ellipsometry, XRD, GIXRD, XPS, DRS, SEM and FESEM. Photocatalytic activities of the films were investigated by measuring their ability to degrade methylene blue solution under visible light irradiation. Results revealed that uniform nanostructured films with a thickness range of 29–150nm were successfully prepared on stainless steel by sol spraying. Doping nitrogen into TiO2 structure restricted the crystallite growth of anatase phase and reduced the band gap energy to 2.85eV and therefore, activated TiO2 in visible light region. Increasing calcination temperature not only promoted crack formation in thin films, but also encouraged Fe diffusion from substrate into thin films structure. However, the N doped TiO2 film calcined at 500°C with a thickness of 150nm indicated a significant photocatalytic activity in visible light with 22% higher efficiency in comparison with undoped TiO2 film. Development of TiO2 based photocatalytic thin films by a simple method of airbrushing, builds up the hope for industrial scale applications in future.

Incorporation of N-doped TiO2 nanorods in regenerated cellulose thin films fabricated from recycled newspaper as a green portable photocatalyst

In this work, an environmental friendly RC/N-TiO2 nanocomposite thin film was designed as a green portable photocatalyst by utilizing recycled newspaper as sustainable cellulose resource. Investigations on the influence of N-doped TiO2 nanorods incorporation on the structural and morphological properties of RC/N-TiO2 nanocomposite thin film are presented. The resulting nanocomposite thin film was characterized by FESEM, AFM, FTIR, UV–vis–NIR spectroscopy, and XPS analysis. The results suggested that there was a remarkable compatibility between cellulose and N-doped TiO2 nanorods anchored onto the surface of the RC/N-TiO2 nanocomposite thin film. Under UV and visible irradiation, the RC/N-TiO2 nanocomposite thin film showed remarkable photocatalytic activity for the degradation of methylene blue solution with degradation percentage of 96% and 78.8%, respectively. It is crucial to note that the resulting portable photocatalyst produced via an environmental and green technique in its fabrication process has good potential in the field of water and wastewater treatment application.

Structural, optical, photocatalytic, and antimicrobial activities of cobalt-doped tin oxide nanoparticles

In this study, pure and Co-doped tin oxide (SnO2) nanoparticles were synthesized by sol–gel method, and the effect of Co-doping on the structural, optical, photocatalytic, and antimicrobial activities was studied. The prepared samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV–visible diffuse reflectance spectroscopy, and N2 adsorption/desorption analysis. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO2 phase which is further confirmed by TEM analysis. The optical spectra showed redshift in the absorption edge of doped samples, which enhances their absorption toward the visible light region. The photocatalytic activity of all the samples was assessed by monitoring the degradation of methylene blue solution under daylight illumination, and it was found that the photocatalytic activity significantly increases with the increase in dopant concentration, which is due to the effective charge separation of photogenerated electron–hole pairs. The antimicrobial studies investigated against standard bacterial and fungal strains showed enhanced antimicrobial activity in doped samples, which can be attributed to the production of reactive oxygen species and large surface area of the nanoparticles.

Photocatalytic Activity Inhibition by ZnO-SiO<sub>2</sub> Nanocomposites Synthesized by Sonochemical Method

Here, ZnO particles and ZnO-SiO2 nanocomposites synthesized by sonochemical method under continuous ultrasound irradiation were reported. For an hour ultrasound irradiated by ultrasonic horn at atmospheric condition, nanorods and spherical structures with crystalline sizes 33 and 17 nm were obtained for ZnO and ZnO-SiO2, respectively, revealed that silica inhibited the particles and crystal growth. FTIR analysis also indicated that silica covered the ZnO particles. In addition, photocatalytic activity was also inhibited by silica in which ZnO without and with silica had degradation rate 69% and 48%, respectively, to degrade methylene blue solution under direct sunlight irradiation for an hour. The addition of SiO2 to ZnO gives an advantage in some application to avoid excessive degradation by controlling their photocatalytic activity.

Niobium substituted magnetite as a strong heterogeneous Fenton catalyst for wastewater treatment

In this study, a series of Nb substituted magnetites; Fe3−xNbxO4 (x=0.0, 0.022, 0.049, 0.099, and 0.19) were prepared and characterized by XRD, BET surface area, TEM, VSM, XPS, and chemical experiments. The magnetite inverse spinel structure and magnetic property were maintained in all the synthetized samples. A significant decrease in crystal size (≈two times) and increase in specific surface area (≈three times) were observed with increased Nb content, resulting in higher adsorption capacity of the samples. In addition, the reactivity of the synthetized samples was examined through degradation of methylene blue solution using Fenton-like reaction. It was found that the incorporation of niobium significantly improved the degradation of methylene blue of which total MB removal was achieved within 180min at higher molar ratios of Nb (x=0.19). This could be attributed to the generated oxygen vacancies on the surface of catalysts, the contribution of the introduced Nb cations in Fenton oxidation cycle for regeneration of Fe2+ cations, and increase in adsorption capacity of the samples due to larger surface area. The MB degradation through Fe2.79Nb0.19O4/H2O2 system was well described by the pseudo-first-order equation in kinetics. All samples showed good stability under the studied pH conditions. The amount of niobium leached was not detectable in neutral and basic solutions and the samples could be reused in oxidation process for several times without a significant decrease in their catalytic efficiency. The results proved that incorporation of niobium into magnetite significantly improved the characteristics and effectiveness of the heterogeneous catalyst for Fenton treatment of recalcitrant effluents.

Detection of Oxygen Species Generated in the Presence of CNT by Loading ZnS

ZnS-CNT nanocomposites were synthesized using simple cheap and less toxic ZnCl2 as the zinc (II) precursor. The prepared nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectra. XRD and TEM results indicate that the prepared product is ZnS nanoparticles and has a grain size of 30 nm in diameter. DRS show that ZnS-CNT possesses the absorption profile across the whole visible-light region. The generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide to 1,5-diphenyl carbazone. It is found that the photocurrent density and the photocatalytic effect increase in the case with the modified ZnS. Excellent catalytic degradation of methylene blue solution was observed using the ZnS-CNT composites under visible light irradiation. It is proposed that both the strong visible-light absorption and the multiple exciton excitations contribute to the high visible-light photocatalytic activity.

Photoluminescent and photocatalytic properties of bismuth doped strontium aluminates blended with titanium dioxide

Bismuth co-doped long persistent phosphor (LPP) powders were obtained by a combustion synthesis technique followed by a post-annealing under carbon atmosphere. Bismuth content was varied from 1.0 to 15.0mol%. X-ray diffraction analysis revealed that the powders show mainly a mixture of three phases: the SrAl2O4, the SrAl14O25 and the Sr2Al6O11 crystalline phases. Photocatalyst composites were obtained by wet mixing of TiO2 anatase and LPP powders followed by annealing in air at 450°C. Photoluminescence measured spectra under 380nm excitation show a tunable emission from green (510nm) to greenish-blue (463nm) in which peak wavelength localization is related to the Bi content. Photoluminescence intensity decreases as Bi content increases. Degradation of methylene blue solutions, irradiated by UV light (254nm), was monitored by the decrease of its 650nm absorption peak in regular periods. The best photocatalytic activity is observed when in the composite blend a 2.0mol% of Bi content was used, and complete methylene degradation is reached after 210min. These photocatalyst composite powders are potential candidates to clean-up wastewater applications, and might be potential candidates for photocatalytic hydrogen generation in aqueous solutions.

Synthesis and Characterization of High Efficiency and Stable Spherical Ag3PO4 Visible Light Photocatalyst for the Degradation of Methylene Blue Solutions

A facile method for the synthesis of Ag3PO4 visible light photocatalyst has been developed to improve the photocatalytic activity and stability. The as‐prepared samples are investigated by X‐ray powder diffraction, scanning electron microscopy, infrared spectroscopy, photoluminescence (PL) spectroscopy, and UV‐Vis diffuse reflectance spectroscopy techniques. The results reveal that the prepared Ag3PO4 has cube structure with a band gap of 2.26 eV. The as‐prepared samples show higher photocatalytic activity for methylene blue (MB) degradation than that of N‐TiO2 under visible light irradiation.

Sol–gel synthesis of mesoporous anatase–brookite and anatase–brookite–rutile TiO2 nanoparticles and their photocatalytic properties

TiO2 photocatalysts with a mixture of different TiO2 crystal polymorphs have customarily been synthesized hydrothermally at high temperatures using complicated and expensive equipment. In this study TiO2 nanoparticles with a mixture of TiO2 crystals were synthesized using a modified sol–gel method at low temperature. In order to form nanoparticles with different polymorphs a series of samples were obtained at pH 2, 4, 7 and 9. Raw samples were calcined at different temperatures ranging from 200 to 800°C to evaluate the effect of the calcination temperature on the physico-chemical properties of the samples. XRD results revealed that a mixture of anatase and brookite can be obtained in the as-synthesized samples and in those calcined up to 800°C depending on the pH used to obtain the final product. Indeed, a mixture of anatase brookite and rutile; or a sample with only rutile phase can be yielded through further calcination of the as-prepared samples at temperatures ⩾600°C due to phase transformation. The photocatalytic performance of the samples with a mixture of anatase–brookite; anatase–brookite–rutile; and anatase–rutile (Degussa P25 TiO2) was exquisitely investigated in the degradation of methylene blue solutions. The samples obtained at pH 2 and calcined at 200°C possessed the highest activity of all due to its superior properties. This study elucidates a facile method suitable for the synthesis of TiO2 with different mixtures of TiO2 polymorphs with desirable properties for various applications.

Three-dimensional flower-like hybrid BiOI–zeolite composites with highly efficient adsorption and visible light photocatalytic activity

Three-dimensional flower-like hybrid BiOI–zeolite composites were synthesized via a simple, facile and environmentally-benign hydrothermal method. And the synthetic mechanism of the flower-like BiOI–zeolite hierarchical structures was discussed. The as-obtained BiOI–zeolite samples exhibited excellent performance in the degradation of methylene blue solution under visible light irradiation. The influence of different Bi/I molar ratios and surfactants was studied. The degradation rate of MB by BiOI–zeolite composite photocatalysts can reach 94.8% under visible light irradiation for 10 min, when the Bi/I molar ratio is 1:1 and is surfactant free. This implies its huge application potential as photocatalysts in degradation of pollutants under visible light.

Fabrication of Antibacterial Titanium Implant Using Anodic Oxidation Technique

In the present study, we demonstrated that antibacterial titanium can be simply fabricated by anodic oxidation technique, which involves connecting the Ti to the anode and then applying a direct current through the electrolyte. The substrate was soaked in 100−mM NH4NO3, 100−mM (NH4)2SO4, and (NH4)3PO4aqueous solutions, after which a constant current of 50 mA cm-2 was galvanostatically applied for 30 min. The substrate was thereafter annealed at 723 K in air for 5 h, in order to improve the crystallinity. The XRD pattern showed the layer comprised TiO2 with anatase and/or rutile type structures. All the anodized substrate could degrade methylene blue solution under ultraviolet (UV) and visible light illuminations. Antibacterial activities of the treated substrates were estimated using Escherichia coli (E.coli). The anodized Ti substrate showed sufficient antibacterial activity under weak UV light illumination with the intensity of 100 μW cm-2. In conclusion, anodic oxidation is expected as one of the promising surface treatments, in order to improve the safety of Ti devices in human use.

Enhancing the photocatalytic activity of nanocrystalline TiO2 by co-doping with fluorine and yttrium

Fluorine and yttrium codoped TiO2 nanoparticles were prepared using a simple sol–gel method. The products were characterized with various spectroscopic and analytical techniques to determine their structural, morphological, optical absorption and photocatalytic properties. The results reveal that neither F nor Y doping causes obvious absorption edge shift in TiO2. Photoluminescence (PL) emission spectra present that the PL signal is enhanced, suggesting a decrease of photo-generated charge carrier separation efficiency, after the F or Y doping. The synergistic action by the F and Y doping leads to the highest photocatalytic activity for the degradation of methylene blue solution in the 0.05% (F, Y)-codoped sample (15 times of that over the pure TiO2). With the increase of Y doping level, the photocatalytic performance in the codoped samples increases firstly and then decreases. The photocatalytic activity variations after the F and Y doping were interpreted by the formation of photocatalytic reactive oxygen species induced by the dopings.

Photocatalytic Performance of ZnO Nanoparticles Synthesized by Microwave-Assisted Process Using Zinc-Dust Waste as a Starting Material

This study aimed to use the zinc dust which is a waste from hot-dip galvanizing plant for the synthesis of ZnO nanoparticles using microwave-assisted process. The precursor solution was prepared by dissolved as received zinc-dust powder in nitric acid. Then it was precipitated by NaOH at required pH and microwave irradiated in a household microwave oven at power of 100W for 10-20 min. The effects of preparation conditions and an addition amount of poly ethylene glycol (PEG; MW2000) for synthesis of ZnO on its properties were investigated. The synthesized nanoparticles were characterized for their phase structure, morphology and surface area by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET), respectively. The photocatalytic activity was determined by the degradation of methylene blue solution under UV irradiation. It was found that microwave heat treatment and addition of optimum amount of PEG could enhance the photocatalytic activity of precipitated ZnO particles. The resultant ZnO particles prepared by an addition of 0.25wt% PEG and microwave irradiation for 20 min exhibited the highest photodegradation rate among other products.