Photocatalytic Degradation Of Various Dyes Research Articles

In-Depth Photocatalytic Degradation Mechanism of the Extensively Used Dyes Malachite Green, Methylene Blue, Congo Red, and Rhodamine B via Covalent Organic Framework-Based Photocatalysts

Photocatalytic degradation technology has received much attention from researchers in the last few decades, due to its easy and cost-effective nature. A lot of review articles have been published on dyes via photocatalytic degradation, but most of the review articles lack a detailed and in-depth photocatalytic degradation mechanism of dyes. Numerous review articles are available on photocatalysis. Here, in this review article, we are mainly focused on the complete and in-depth photocatalytic degradation mechanism of four commonly used dyes such as Malachite Green, Methylene Blue, Congo Red and Rhodamine B, which will be highly useful for the new researchers that work on dyes’ photocatalytic degradation. Initially, various aspects of dyes have been included in this review article, comprehensively. The main focus was on the covalent organic framework-based photocatalysts for dyes’ photocatalytic degradation, due to their porous nature and various unique properties. Various synthesis routes and the photocatalytic performance of covalent organic frameworks and composite of covalent organic frameworks have been highlighted in this review article. In the last section of this review article, the main stimulus was the four mentioned dyes’ properties, uses, and toxicity, and the photocatalytic degradation mechanism through various paths into environmentally friendly and less-harmful compounds in the presence of photocatalysts. Factors effecting the photocatalytic degradation, economic cost, challenges and future aspects of photocatalytic technology were also included in this review article. This review article will be highly useful for those researchers that work on the photocatalytic degradation of various dyes and search for the complete degradation of complex dye molecules.

A Nanocomposite of ZnO and N,P‐Co‐Doped Carbon Dots for the Photocatalytic Degradation of Various Dyes and their Kinetic Study

AbstractEnvironmental pollution is becoming more severe by the day, and it is critical to discover an effective method to overcome and reduce pollution. Because nanomaterials are important in all fields, we employed a ZnO‐based N and P doped carbon quantum dots (NPCdots) nanocomposite to degrade multiple dyes including Methylene blue (MB), Methyl orange (MO), and Rhodamine B (RhB). ZnO‐based NPCdots nanocomposite (ZnO‐NPCdots) was synthesized using a single step solvothermal technique, and the resulting nanocomposite was analysed using XRD, HRTEM, and XPS. These analyses unequivocally demonstrate that the ZnO‐NPCdots nanocomposite was successfully formed. The prepared nanocomposite was then used for the photocatalytic degradation of the different dyes under UV light, and it shows an effective catalytic property. In addition, four different kinetic models viz., zero order, pseudo first order, parabolic diffusion model, and modified Freundlich models were used to analyse the reaction‘s kinetics and actual catalytic phenomenon behind the reaction. The modified Freundlich model was found to be effective, indicating the surface phenomenon of the catalyst.

Impact of titania phase structure and surface reactivity on the photocatalytic degradation of various dyes and textile wastewater

Titania (TiO2) powders have been prepared by precipitation method in different precipitation media which contain sulfate, nitrate or organic species. Photocatalytic degradation of different dyes and a real textile wastewater have been conducted with these powders along with commercial powder Degussa P25 for comparison. Ethyl alcohol (organic medium), sulfuric acid (sulfate medium) and nitric acid (nitrate medium) have been used to dissolve titanium precursor for the precipitation of TiO2 in ammonia solution. UV-Vis DRS and XPS results indicate that S doping in sulfate medium precipitated powder and N doping in nitrate medium precipitated powder has been occurred and the presence of S or N containing impurities on the grain boundaries have been improved light absorption of TiO2 significantly. However, these powders have exhibited low surface reactivities. The highest surface reactivity has been obtained with the powder precipitated in organic medium which also has the highest crystallite sizes (76 nm rutile and 34 nm anatase crystallites) with relatively low rutile weight percentage (10.0%). The surface-normalized rate constants of this powder are 0.02038 min-1.m-2 in real textile wastewater degradation and 0.0161 min-1.m-2 in methyl orange degradation, which are 0.01563 and 0.0091 min-1.m-2, respectively, for Degussa P25. Results have shown that this powder show 30-70% higher surface reactivities compared to Degussa P25. The main structural difference of organic medium precipitated powder and Degussa P25 has been found to be the anatase-rutile weight ratio and crystallite size of rutile phase whereas band gap energy of Degussa P25 is lower and other properties are not significantly different.

Photocatalytic study of metal oxide enhanced ZnO synthesized by a one-step cyclic-microwave method: The role of the p-n heterostructure

In this work, the role of the p-n junction in the photocatalytic degradation of various dyes in contaminated wastewater was studied. The n-type ZnO was synthesized by the cyclic-microwave method and was enhanced by various metal oxides, e.g., CuO, NiO, and Fe2O3. The materials were characterized by various methods. The degradation of Methylene blue (MB), Methyl orange (MO), and Rhodamine B (RhB) under the photocatalysts and UV light irradiation was examined. From the results, the performance of the dye degradation by the p-n CuO/ZnO and NiO/ZnO materials was better than that of the pure ZnO. On the other hand, the n-n heterostructure Fe2O3/ZnO showed a decrease in photocatalytic performance. The photocatalyst with the highest performance was Ni(5)-ZnO, which can degrade dyes contaminating water by greater than 99.71%. The physical principle behind the increase in the photocatalytic performance is due to the formation of the p-n junction by CuO and NiO to the n-type ZnO, resulting in the efficient generation of electron-hole pairs.

Sargassum myriocystum-mediated TiO2-nanoparticles and their antimicrobial, larvicidal activities and enhanced photocatalytic degradation of various dyes

Recently, the phyco-synthesis of nanoparticles has been applied as a reliable approach to modern research field, and it has yielded a wide spectrum of diverse uses in fields such as biological science and environmental science. This study used marine natural resource seaweed Sargassum myriocystum due to their unique phytochemicals and their significant attributes in giving effective response on various biomedical applications. The response is created by their stress-tolerant environmental adaptations. This inspired us to make an attempt using the above-mentioned charactersitics. Therfore, the current study performed phycosynthesis of titanium dioxide nanoparticles (TiO2-NPs) utilising aqueous extracts of S. myriocystum. The TiO2-NPs formation was confirmed in earlier UV–visible spectroscopy analysis. The crystalline structure, functional groups (phycomolecules), particle morphology (cubic, square, and spherical), size (∼50–90 nm), and surface charge (negative) of the TiO2-NPs were analysed and confirmed by various characterisation analyses. In addition, the seaweed-mediated TiO2-NPs was investigated, which showed potential impacts on antibacterial activity and anti-biofilm actions against pathogens (Staphylococcus aureus, S. epidermidis, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, and Klebsiella pneumoniae). Additionally, some evaluations were performed on larvicidal activities of TiO2-NPs in oppose to Aedes aegypti and Culex quinquefasciatus mosquitos and the environmental effects of photocatalytic activities against methylene blue and crystal violet under sunlight irradiation. The highest percent of methylene blue degradation was observed at 92.92% within 45 min. Overall, our findings suggested that S. myriocystum mediates TiO2-NPs to be a potent disruptive material for bacterial pathogens and mosquito larvae and also to enhance the photocatalytic dye degradation.

Sunlight-induced photocatalytic degradation of various dyes and bacterial inactivation using CuO-MgO-ZnO nanocomposite.

Novel tri-phase CuO-MgO-ZnO nanocomposite was prepared using the co-precipitation technique and investigated its physical properties using characterization techniques including XRD, FTIR, Raman, IV, UV-vis, PL, and SEM. The application of grown CuO-MgO-ZnO nanocomposite for the degradation of various dyes under sunlight and antibacterial activity against different bacteria were studied. The XRD confirmed the existence of diffraction peaks related to CuO (monoclinic), MgO (cubic), and ZnO (hexagonal) with CuO phase 40%, MgO 24%, and ZnO 36%. The optical energy gap of nanocomposite was 2.9 eV, which made it an efficient catalyst under sunlight. Raman and FTIR spectra have further confirmed the formation of the nanocomposite. SEM images revealed agglomerated rod-shaped morphology. EDX results showed the atomic percentage of a constituent element in this order Cu>Zn>Mg. PL results demonstrate the presence of intrinsic defects. The photocatalytic activity against methylene blue (MB), methyl orange (MO), rhodamine-B (RhB), cresol red (CR), and P-nitroaniline (P-Nitro) dyes has shown the excellent degradation efficiencies 88.5%, 93.5%, 75.9%, 98.8%, and 98.6% at 5 ppm dye concentration and 82.6%, 83.6%, 64.3%, 93.1%, and 94.3% at 10 ppm dye concentration in 100 min, respectively, under sunlight illumination. The higher degradation is due to the generation of superoxide and hydroxyl radicals. The recyclability test showed the reusability of catalyst up to the 5th cycle. The antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Proteus Vulgaris, Staphylococcus aureus, and Pseudomonas aeruginosa bacteria with the zone of inhibition 30, 31, 30, 30, and 30 mm, respectively, was achieved.

(In1-xFex)2O3 nanostructures for photocatalytic degradation of various dyes

In this work, Fe-doped In2O3 nanostructures have been prepared using a simple chemical route. Various physio-chemical properties have been investigated. XRD results show that Fe dopant induces no impurity phase in cubic In2O3. For optical properties, Fe dopant induced blue-shift appears in absorption spectrum of In2O3. A comparison of photocatalytic activity of neat In2O3 and Fe-doped In2O3 nanoparticles has been obtained. An enhancement of UV light triggered photocatalytic activity to photodegrade methylene blue, RhB and methyl orange upto 83%, 95.36% and 93.77% respectively has been achieved. The existence of oxygen vacancies in Fe doped In2O3 and optimized bandgap makes Fe doped In2O3 a potential photocatalyst.

Synthesis, Photoluminescence and Photocatalytic Activity of Tetragonal SnO2 Prepared by Hydrothermal Sol-Gel Method

Luminescent SnO2 material was synthesized by a hydrothermal assisted sol-gel method. X-ray powder diffraction analysis indicates that the as-synthesized SnO2 is a tetragonal phase and the calculated lattice parameters a and c are 0.474 and 0.318 nm, respectively. Scanning electron microscopy shows that the prepared tetragonal SnO2 particles have regular rhombic shape and are polydisperse without any agglomeration. Ultraviolet-visible absorption spectroscopy was used to study the light-absorbing properties and bandgap of tetragonal SnO2, and the value of bandgap is obtained to be 2.894 eV. The emission spectrum detected at λex = 230 nm showed two peaks located at 375 and 415 nm, the first having the strongest luminescence intensity. The fluorescence emission spectra also show that an emission peak at 510 nm is observed when the λex is 400 nm. Photocatalytic experiments indicate that the tetragonal SnO2 exhibits a strongly enhanced photocatalytic activity than commercial nano-SnO2 in photocatalytic degradation of various dyes under visible light irradiation. The photocatalytic mechanism is discussed on the basis of X-ray photoelectron spectroscopy (XPS) data, Fourier transform infrared (FTIR) spectra, electrochemical measurements and photocatalytic experiments results.

Photocatalytic decolorization of methylene blue using zinc oxide supported on mesoporous silica nanoparticles

Various dyes that are used in textile, paper, cosmetics and plastics industries may produce harmful effects on the health of living organisms and the environment if not treated properly before being discharged into water bodies. Among many techniques, photocatalytic process is one of the promising treatment for these dyes. Zinc oxide (ZnO) is well-known comparable with TiO2 due to its unique properties and numerous advantages. While, mesoporous silica nanoparticles (MSN) is an excellent solid support for heterogeneous catalysts due to its high surface area, thermal and mechanical stability, highly uniform pore distribution, tunable pore size, and unique hosting properties. Therefore, in this study, ZnO/MSN (ZM) catalysts were prepared and its physicochemical properties was characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The catalyst was tested on the photodecolorization of methylene blue (MB) dye. The results showed that the interaction between ZnO and MSN support could enhanced the photocatalytic activity. The 0.5 g L-1 of 5ZM was found to give the highest degradation (80 %) of 10 mg L-1 of MB solution at pH 7 after 3 h under UV light irradiation. The photodecolorization followed the pseudo first-order Langmuir-Hinshelwood kinetic model. This study demonstrated that the prepared 5ZM has a potential to be used in photocatalytic degradation of various dyes as well as organic pollutants.

Photocatalytic Degradation of Various Dyes by Strontium Titanate Nanoparticles

A simple polyacrylamide gel method was used to prepare strontium titanate (SrTiO3) nanoparticles. X-ray diffraction (XRD) analysis reveals that single-phase SrTiO3 can be synthesized at a calcination temperature of 550 °C. Scanning electron microscope (SEM) observation shows that the as-prepared SrTiO3 particles are regularly shaped like spheres and highly uniform in size with an average diameter of ~55 nm. Ultraviolet (UV)-visible diffuse reflectance spectrum analysis indicates that the bandgap of the sample is 3.23 eV. The Brunauer-Emmett-Teller (BET) specific surface area of the sample is measured, by the N2 adsorption-desorption technique, to be 26.4 m2•g−1. The photocatalytic experiments reveal that the SrTiO3 nanoparticles can effectively degrade various dyes including congo red (CR), rhodamine B (RhB), methyl orange (MO), and methylene blue (MB) under UV irradiation.

Investigation on solar photocatalytic degradation of various dyes in the presence of Er 3+:YAlO 3/ZnO–TiO 2 composite

In this work, Er 3+:YAlO 3/ZnO–TiO 2 and ZnO–TiO 2 composites were prepared by the ultrasonic dispersion and liquid boiling method. In succession, they were then characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Acid red B as a model dye compound was degraded under solar light irradiation to evaluate the photocatalytic activities of the Er 3+:YAlO 3/ZnO–TiO 2 and ZnO–TiO 2 composites. We found that the photocatalytic activity of ZnO–TiO 2 composite can be enhanced by adding an appropriate amount of Er 3+:YAlO 3. We reviewed influencing factors, such as Er 3+:YAlO 3 content, heat-treated temperature and heat-treated time on the photocatalytic activity of the Er 3+:YAlO 3/ZnO–TiO 2 composites. In addition, the effects of solar light irradiation time, dye initial concentration, Er 3+:YAlO 3/ZnO–TiO 2 amount and solution acidity on the photocatalytic degradation of acid red B dye in aqueous solution were investigated in detail. Simultaneously, the degradation and comparison of other dyes such as methyl orange (MO), rhodamine B (RM-B), azo fuchsine (AF), congo red (CG-R) and methyl blue (MB) were also reviewed. In addition, we attempted to explore both the principle of possible excitation of Er 3+:YAlO 3/ZnO–TiO 2 under solar light irradiation and the mechanism of photocatalytic degradation.

Synthesis, Structure, and Photocatalytic Activity in Orthorhombic Perovskites LnVO3 and Ln1−xTixVO3 (Ln = Ce, Pr, and Nd)

Orthorhombic perovskite type LnVO3 and Ln1−xTixVO3 (Ln = Ce, Pr, and Nd) have been synthesized by the solid state method. The structures of these compounds have been unequivocally established based on high resolution powder X-ray diffraction data using Rietveld refinement methodology followed by difference Fourier analysis. It is shown that substitution of Ti occurs at the vanadium site and not at the cerium site. The compounds have been tested for photocatalytic degradation of various dyes and substituted phenols. It is observed that doping of Ti remarkably improves the photodegradation efficiency of these orthorhombic perovskites.

Synthesis, characterization, redox and photocatalytic properties of Ce1−xPdxVO4 (0 ≤ x ≤ 0.1)

Zircon-type CeVO4 and Ce1−xPdxVO4 (0.02≤x≤0.1) were synthesized by a single step solution combustion method. The materials were characterized by powder X-ray diffraction, magnetic measurement and temperature-programmed reduction (TPR) with H2. The redox properties of CeVO4 and Ce0.98Pd0.02VO4 have been investigated by temperature-programmed reduction. The gas-phase and liquid-phase catalytic properties of CeVO4 and Ce0.98Pd0.02VO4 were investigated. Ce0.98Pd0.02VO4 shows better catalytic activity than CeVO4 towards CO oxidation by O2, NO reduction by CO and the photocatalytic degradation of various dyes. This higher catalytic activity of Ce0.98Pd0.02VO4 can be attributed to the lattice labile oxygen and high surface area compared to that of CeVO4.

Photocatalytic degradation of various dyes by combustion synthesized nano anatase TiO2

The 8–10nm pure anatase phase titania with 156m2/g BET surface area was prepared by solution combustion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and BET surface area. This catalyst was used for the photocatalytic degradation of various dyes such as heteropolyaromatic dye (Methylene blue), anthraquinonic dye (Alizarin S), and azoic dyes (Methyl red, Congo red, and Orange G). The effect of catalyst loading, initial concentrations of the dyes, pH, and transition metal doping on TiO2 was investigated. Substitution of TiO2 with transition metal had a detrimental effect on the photocatalytic activity. However, this inhibition effect was not observed with Pt impregnated TiO2. This was attributed to the metals being in ionic state in metal substituted TiO2 synthesized by combustion method, and zero state of metal in impregnated catalysts as evidenced by XPS study. The degradation of dyes was also investigated in solar exposure. The photoactivity of the combustion synthesized titania was higher than commercial TiO2 (Degussa P-25) for both UV and solar exposure. The experimental data followed Langmuir–Hinshelwood (L–H) rate form and the kinetic parameters were obtained.

Decolourization of textile industry wastewater by the photocatalytic degradation process

The photocatalytic degradation of various dyes (Orange II, Orange G, Congo Red, Indigo Carmine, Crystal Violet, Malachite Green, Remazol Blue and Methyl Yellow) has been studied, using P25 Degussa as catalyst. All dye solutions underwent a decolourization. The kinetics of reaction have been studied and were found to be zero or first order with respect to the dyes. This was compared with the adsorption properties. The effect of the addition of hydrogen peroxide has been studied. An enhancement of the rate has been observed in all cases and the order with respect to the additive was found to be almost zero. It is difficult to give a general picture of the kinetics using these very different dyes but the process was found to be effective for the decolourization of textile wastewater.