Characterization of the hydrothermally synthesized nano-TiO2 crystallite and the photocatalytic degradation of Rhodamine B

Enhanced Photocatalytic Degradation by the Preparation of a Stable La-Doped FeTiO3 Photocatalyst: Experimental and DFT Study

The rapid photocarrier recombination limits the photocatalytic activity of iron titanate (FeTiO3) to be further improved. Developing novel approaches to inhibit the rapid recombination rate of the FeTiO3 photocatalysts is crucial for efficiently degrading pollutants in wastewater. Rare earth ions, with unique electron dispositions and large ion radii, could effectively inhibit photocarrier recombination. Herein, novel lanthanum (La)-doped FeTiO3 photocatalysts were designed and successfully synthesized. The photocatalytic performance of the 12 mol % La/FeTiO3 photocatalyst was superior in degrading tetracycline hydrochloride (TCH), methylene blue (MB), and brilliant blue (BB). These degradation rate constants (k) were 0.12358, 0.01357, and 0.03064 L mg-1 min-1, respectively, which were 12.83, 1.61, and 7.78 times that of pure FeTiO3. The photoelectronic tests and density functional theory (DFT) calculations revealed that the La 4f orbital forms an impurity energy level in the conduction band of FeTiO3. This level narrows the bandgap and acts as an electron acceptor, capturing photoexcited electrons and inhibiting the rapid recombination of photoexcited electron-hole pairs in FeTiO3. This work enhances the potential of FeTiO3 in the photocatalysis field and provides important insights into the efficient degradation of organic pollutants in wastewater.

Impact on the Photocatalytic Dye Degradation of Morphology and Annealing-Induced Defects in Zinc Oxide Nanostructures

In this study, three different morphologies, nanoflower (NF), nano sponge (NS), and nano urchin (NU), of zinc oxide (ZnO) nanostructures were synthesized successfully via a mild hydrothermal method. After synthesis, the samples were annealed in the atmosphere at 300, 600, and 800 °C. Although annealing provides different degradation kinetics for different morphologies, ZnO NS performed significantly better than other morphologies for all annealing temperatures we used in the study. When the photoluminescence, electron paramagnetic resonance spectroscopy, BET surface, and X-ray diffraction analysis results are examined, it is revealed that the defect structure, pore diameter, and crystallinity cumulatively affect the photocatalytic activity of ZnO nanocatalysts. As a result, to obtain high photocatalytic activity in rhodamine B (RhB) degradation, it is necessary to develop a ZnO catalyst with fewer core defects, more oxygen vacancies, near band emission, large crystallite size, and large pore diameter. The ZnO NS-800 °C nanocatalyst studied here had a 35.6 × 10^-3 min^-1 rate constant and excellent stability after a 5-cycle photocatalytic degradation of RhB.

Robust visible light active CoNiO2-BiFeO3-NiS ternary nanocomposite for photo-fenton degradation of rhodamine B and methyl orange: Kinetics, degradation pathway and toxicity assessment

Sustainable wastewater treatment is crucial to remediate the water pollutants through the development of highly efficient, low-cost and separation free photocatalyst. The aim of this study is to construct a novel CoNiO₂-BiFeO₃-NiS ternary nanocomposite (NCs) for the efficient degradation of organic pollutants by utilising visible light. The NCs was characterized by various physiochemical techniques, including HR-TEM, SEM, XPS, FT-IR, ESR, EIS, PL, UV-visible DRS, and N₂ adsorption and desorption analysis. The photocatalyst exhibits extraordinary degradation efficiency towards MO (99.8%) and RhB (97.8%). The intermediates were determined using GC-MS analysis and the degradation pathway was elucidated. The complete mineralization was further confirmed by TOC analysis. The CoNiO₂-BiFeO₃-NiS ternary NCs have shown excellent photostability, structural stability and reusability even after six cycles and it is confirmed by XRD and XPS analysis. The kinetic study reveals that the photodegradation of the dyes follows first order reaction. The influence of different pH, dye concentrations and NCs dosages were investigated. The intermediate toxicity was predicted by computational stimulation using ECOSAR software. The NCs shows promising potential for ecological safety which demonstrates its practical application in the treatment of waste water pollutants in large scale.

In-situ, Ex-situ, and nano-remediation strategies to treat polluted soil, water, and air - A review

Nanotechnology, as an emerging science, has taken over all fields of life including industries, health and medicine, environmental issues, agriculture, biotechnology etc. The use of nanostructure molecules has revolutionized all sectors. Environmental pollution is a great concern now a days, in all industrial and developing as well as some developed countries. A number of remedies are in practice to overcome this problem. The application of nanotechnology in the bioremediation of environmental pollutants is a step towards revolution. The use of various types of nanoparticles (TiO₂ based NPs, dendrimers, Fe based NPs, Silica and carbon nanomaterials, Graphene based NPs, nanotubes, polymers, micelles, nanomembranes etc.) is in practice to diminish environmental hazards. For this many In-situ (bioventing, bioslurping, biosparging, phytoremediation, permeable reactive barrier etc.) and Ex-situ (biopile, windrows, bioreactors, land farming etc.) methodologies are employed. Improved properties like nanoscale size, less time utilization, high adaptability for In-situ and Ex-situ use, undeniable degree of surface-region to-volume proportion for possible reactivity, and protection from ecological elements make nanoparticles ideal for natural applications. There are distinctive nanomaterials and nanotools accessible to treat the pollutants. Each of these methods and nanotools depends on the properties of foreign substances and the pollution site. The current designed review highlights the techniques used for bioremediation of environmental pollutants as well as use of various nanoparticles along with proposed In-situ and Ex-situ bioremediation techniques.

Photocatalytic properties, mechanical strength and durability of TiO2/cement composites prepared by a spraying method for removal of organic pollutants

TiO₂/cement composites were prepared by a spraying method to degrade organic pollutants. After coated with waterproof liquid, pure cement pastes/mortars were sprayed with TiO₂ suspensions with different TiO₂ contents and spraying times. Photocatalytic properties, mechanical strength and durability were studied. Maximum photocatalytic activity and uniform TiO₂ distribution were achieved at the optimal conditions of 10 wt% TiO₂ content in suspension and 3 spraying times. The TiO₂/cement pastes had better degradation performance over Rhodamine B (RhB) and methylene blue (MB) than that over methyl orange (MO). After 20 times of cycling degradation, the photocatalytic efficiencies had no significant reduction. The TiO₂/cement mortars had good mechanical strengths, meeting the mechanical demands of wastewater treatment tanks. In durability, the TiO₂/cement mortars had better water penetration resistance, chloride penetration resistance and anti-carbonation than pure cement mortars.

Transforming micelles into mixed micelles: a promising approach to tune the catalytic performance of imidazolium-based surface active ionic liquids toward degradation of rhodamine B

Herein, we demonstrate that the catalytic performance of imidazolium-based surface-active ionic liquid (SAIL) micelles can be significantly enhanced through the addition of an appropriate type and amount of intelligently conceived amphiphile to form mixed micelles. Specifically, we show that the catalytic performance of 1-dodecyl-3-methyl imidazolium chloride (DDMIMCl) micelles toward the reductive degradation of rhodamine B (RhB), a carcinogenic dye extensively used in multiple industrial applications, can be appreciably boosted through addition of Brij56, a nonionic surfactant. Detailed kinetic investigations on the catalytic performance of pre- and post-micellar concentrations of DDMIMCl and its mixed micelles with Brij56 over various mole fractions, toward the reductive degradation of RhB, are presented. The data analyzed in light of Berezin's kinetic model suggest that the addition of Brij56 to DDMIMCl micelles significantly enhances their catalytic performance. The catalytic activity exhibited by the DDMIMCl-Brij56 (X_Brij56 = 0.2) mixed micellar system is better than that reported for many state-of-the-art nanoparticle/homogenous catalysts. The results explained in light of Berezin's kinetic model are well supported by physico-chemical studies like conductometry, fluorimetry and dynamic light scattering. The presented results anticipate stimulation of extensive research activity for exploiting the mixed micellization approach as a novel avenue for modulating the catalytic performance of SAILs.

Microwave-Assisted Synthesis of Cobalt Oxide/Reduced Graphene Oxide (Co3O4–rGo) Composite and its Sulfite Enhanced Photocatalytic Degradation of Organic Dyes

One-pot synthesis of Co3O4 nanocrystals on reduced graphene oxide (rGO) was carried out by reacting cobalt nitrate, L-arginine, extract of Laportae aestuans as oxidant, fuel and reducing agent, respectively, in a domestic microwave. Morphologies of Co3O4–rGo (RGCO) composite was elucidated using UV-Vis, FT-IR, TEM, SEM, EDX, XRD and photoluminescence spectroscopies. The synthesized RGCO composite was applied as heterogeneous photocatalyst in the activation of Na2SO3 (sulfite) as sacrificial agent to degrade cationic dyes: rhodamine B (RhB) and methylene blue (MB), under visible light, at neutral pH 7.0. Photocatalytic performance of as-prepared RGCO was significantly enhanced in the presence of Na2SO3. Enhanced photocatalytic activity of RGCO was attributed to the synergistic effects between sulfite radicals generated in situ, and reduced graphene oxide, in which rGO served as electron sink to suppress recombination of photogenerated charge carriers. Plausible mechanistic pathways responsible for the activation of sulfite anions in situ are presented in this paper.

Photocatalytic performance and dispersion stability of nanodispersed TiO2 hydrosol in electrolyte solutions with different cations

The existence of electrolytes in aquatic environment on the photocatalytic performance and coagulation of nanodispersed TiO₂ hydrosol and the corresponding photocatalytic alteration were investigated by studying cations (Na⁺, K⁺, Ca ²⁺, Mg²⁺, and Al³⁺). The photocatalysis reactions of nano TiO₂ with different dosages of electrolytes were measured by monitoring the degradation of Rhodamine B (RhB) under ultraviolet A (UV-A) irradiation over time. The results showed that the photocatalytic performance of TiO₂ was improved by the presence of Al³⁺, while the performance was impaired by the other tested cations. The negative influences of divalent ions on the photocatalytic performance of TiO₂ were more significant than monovalent ions. The TiO₂ sol dispersed stable at nano scale at low concentration of electrolyte (<0.01 mol/L) with slight change of pH, and coagulated into micro sizes at high concentration of electrolytes (>0.1 mol/L) with larger increase or decrease of pH. The positive effects of Al³⁺ on the photodegradation rate of RhB might relate to the strong hydrolytic action of Al³⁺ in aquatic solutions. The photocatalytic processes of TiO₂ in the presence of all ions followed the Langmuir-Hinshelwood model, and the reaction kinetic constant was increased with the decrease of pH caused by different cations. These work suggested a new perspective about the relationship between coagulation and photocatalytic performance of TiO₂ hydrosols in electrolyte with hydrolysable cations, which demonstrated that TiO₂ hydrosols may be suitable as photocatalysts in aquatic environments.

ZnO–TiO2: Synthesis, Characterization and Evaluation of Photo Catalytic Activity towards Degradation of Methyl Orange

Here in, we report the synthesis and characterization of ZnO–TiO2 composite as a potential photo catalyst for photo degradation of methyl orange under UV irradiation. ZnO–TiO2 with 1:1 ratio was synthesized via wet incipient impregnation method using TiO2 and Zn(NO3)2 ⋅ 6H2O as precursor material and the prepared composite was characterized by XRD, EDX and SEM. The synthesized composite was employed as photo catalyst for photo degradation of methyl orange. The photo degradation results showed that ZnO–TiO2 exhibited better catalytic performance than ZnO and TiO2 alone. The methyl orange photo degradation efficiency was determined to be 98, 75 and 60% over ZnO–TiO2, ZnO and TiO2 respectively using 50 mL solution of 100 mg/L at 40 °C for 120 min. The ZnO–TiO2 catalyzed photo degradation of methyl orange followed pseudo-first-order kinetic in terms of Langmuir–Hinshelwood mechanism.

Efficacious separation of electron-hole pairs in CeO2-Al2O3 nanoparticles embedded GO heterojunction for robust visible-light driven dye degradation

Herein, we have developed a facile and one pot synthesis of ternary CeO₂-Al₂O₃@GO nanocomposite via wet chemical method. The structural and morphological characteristics of the synthesized nanocomposite was investigated using UV-DRS, FT-IR, XRD, FE-SEM, HR-TEM, EDX and TGA analysis. The CeO₂-Al₂O₃@GO composite was tested for its ability to photocatalytically degrade Rhodamine B (RhB) under visible light illumination. The influence of various operational parameters such as pH, catalyst dosage and initial dye concentration on the photo degradation was investigated in detail. The synthesized CeO₂-Al₂O₃@GO composite shows greater photocatalytic degradation of RhB (99.0%) under visible light irradiation than the raw CeO₂, Al₂O₃, and GO catalysts and any other reported nanocomposite materials. The recyclability results also demonstrate the excellent stability and reusability of the CeO₂-Al₂O₃@GO nanocomposite. This work will be beneficial in the field of industrial and engineering applications in the degradation of organic pollutants. Also, a study of this kind will definitely stimulate many researches in the recently emerging field of solar-driven water splitting.

Integration of membrane filtration and photoelectrocatalysis using a TiO2/carbon/Al2O3 membrane for enhanced water treatment

Coupling membrane filtration with photocatalysis provides multifunction involving filtration and photocatalytic degradation for removing pollutants from water, but the performance of photocatalytic membrane is limited due to the quick recombination of photogenerated electron-holes in photocatalytic layer. Herein, a TiO2/carbon/Al2O3 membrane was designed and constructed through sequentially depositing graphitic carbon layer with good electro-conductivity and TiO2 nanoparticles layer with photocatalytic activity on Al2O3 membrane support. When light irradiated on the membrane with a voltage supply, the photogenerated electrons could be drained from photocatalytic layer and separated with holes efficiently, thus endowing the membrane with photoelectrocatalytic function. Membrane performance tests indicated that the photoelectrocatalytic membrane filtration (PECM) showed improved removal of natural organic matters (NOMs) and permeate flux with increasing voltage supply. For PECM process at 1.0 V, its NOMs removal was 1.2 or 1.7 times higher than that of filtration with UV irradiation or filtration alone, and its stable permeate flux was 1.3 or 3 times higher than that of filtration with UV irradiation or filtration alone. Moreover, the PECM process exhibited special advantage in removing organic chemicals (e.g., Rhodamine B), which displayed 1.3 or 3 times higher removal than that of filtration with UV irradiation or filtration alone.

Effects of coating with different ceromers on the impact strength, transverse strength and elastic modulus of polymethyl methacrylate

The aim of this study was to evaluate the mechanical properties of polymethyl methacrylate (PMMA) after coating with different ceromers. For transverse strength and modulus of elasticity tests, specimens of 65×10×2.5 mm dimensions were prepared (5 groups, n=10). For impact strength test, specimens of 60×7.5×4 mm dimensions were prepared (5 groups, n=10). Test group specimens were coated with one of four different types of ceromers, and specimens in the control group were not coated. After specimens were tested for transverse and impact strengths, the data were analyzed with Kruskal-Wallis and Conover post hoc tests (p<0.05). GLYMOTEOS-TiO2 and A174-TEOS significantly increased the transverse strength of PMMA. All ceromers caused a statistically significant increase in the elastic modulus of PMMA. While GLYMO-TEOS-ZrO2 significantly decreased the impact strength, the other ceromers did not cause any statistically significant difference in impact strength. Coating with ceromers substantially improved the mechanical properties of PMMA.

An inhibitory effect of self-assembled soft systems on Fenton driven degradation of xanthene dye Rhodamine B

Rhodamine B (RhB) is known to be a common organic pollutant despite having various technical applications. Treatment of effluents containing such compounds is important so as to minimize their effect on environment. Advanced Oxidation Processes (Fenton and Fenton like reactions) are such methods that can oxidize the contaminants powerfully and non-selectively. This work investigates the oxidation kinetics of dye RhB by hydroxyl radical (OH) generated via Fenton reaction in presence of surfactant assemblies of varying architectures using spectrophotometric, spectrofluorometic and tensiometric methods. The presence of surfactants viz. cationics, non-ionics and some binary mixtures in the pre-micellar and post micellar concentration ranges were found to inhibit the degradation of RhB to a varying degree. However, the reaction was totally inhibited in anionic surfactant. The experimental data was fitted to a pseudo first order kinetic model and the kinetic parameters obtained thereof were explained on the basis of the nature and type of interaction between the cationic form of RhB and the surfactants of varying architectures. The work has a critical significance in view of the fact that degradation studied in presence of surfactant assemblies is more representative than studied in aqueous solution because such conditions compare well with the conditions prevailing in the environment.

Magnetic Nanoscaled Fe3O4 as an Efficient and Reusable Heterogeneous Catalyst for Degradation of Methyl Orange in Microwave-Enhanced Fenton-Like System

In this study, the Fe3O4magnetic nanoparticles (MNPs) were synthesized as heterogeneous catalysts to effectively degrade methyl orange. The coulping method of microwave irradiation and Fenton-like reaction was used for degradation of methyl orange waste water. The effects of Fe3O4dosage, initial H2O2concentration, catalyst cycles, reaction temperature and so on were assessed systematically. The experimental results showed that the microwave-assisted Fenton-like process using H2O2/Fe3O4was the most effective treatment process compared with other traditional methods. According to degradation of methyl orange, it has been found that the oxidation by Fenton-likes reagent is dependent on Fe3O4dosage, H2O2dosage, reaction temperature. The results indicate that under the optimal conditions, the removal rate of methyl orange could reach nearly 100%. Moreover, six cyclic tests for methyl orange degradation showed that the magnetic catalyst was very stable, recoverable, highly active, and easy to separate using an external magnet. Hence, the coulping method of microwave irradiation and Fenton-like reaction with magnetic nanomaterials of Fe3O4as the catalyst has potential use in organic pollutant removal.

One-Step Synthesis and High-Efficiency Decoloration of Multifunctional Porous-C/Fe3 O4 Nanospheres by Using a Sandwich-Structured Precursor with Three Roles

A new strategy for the one-step synthesis of multifunctional porous-C/Fe₃ O₄ nanospheres has been successfully developed by using ferrocenyl formic acid as a precursor. Based on its special structure, this sandwich structural precursor of ferrocenyl formic acid plays three roles in the synthesis process: it simultaneously serves as the carbon and iron source, templating agent, and pore-forming agent. The proposed synthesis is corroborated by characterization through SEM, TEM, XRD, FTIR spectroscopy, Raman spectroscopy, BET surface area measurements, BJH distributions, and vibrating sample magnetometry. The average diameter of as-synthesized porous-C/Fe₃ O₄ nanospheres is about 400 nm. Because of the porous structure of carbon nanospheres and its surface plasmon resonance with attached Fe₃ O₄ nanoparticles, the as-synthesized porous-C/Fe₃ O₄ nanospheres exhibit high activity toward the decoloration of rhodamine B. In addition, the resultant composites present ferromagnetic behavior with a magnetization saturation of 13.76 emu g^-1 , can be easily separated and recycled by an external magnet field for use in a variety of applications.

The effects of externally applied pressure on the ultrasonic degradation of Rhodamine B

The present manuscript compares the ultrasonic degradation of Rhodamine B dye under atmospheric (1 bar) and elevated pressures (1.6 and 2 bar). The degradation was studied as a function of the bulk liquid temperature and initial dye concentration at two different values of mechanical amplitudes (ultrasonic intensities). Results indicate that at the low amplitude an increase in the applied pressure increases the dye removal rate, whereas at the high amplitude, the same increase in the pressure has a minimal effect on the degradation of the dye. Furthermore, at low amplitudes an increase in the bulk liquid temperature from 5 to 35 °C increases the dye degradation by 10%. At higher intensities, the same increase in temperature has negative or no effect on the dye removal. An increase in the initial dye concentration by one order of magnitude significantly lowers the dye degradation rate regardless of the applied amplitude. Though these results are caused by numerous physical and chemical processes taking place during ultrasonic cavitation, the number of cavitation sites, bubble temperature and consequently, the amount of oxidative species inside the bubble seem to be the most important ones in determining the extent of the degradation of molecules in the bulk liquid.

Ultrasound assisted synthesis of doped TiO2 nano-particles: characterization and comparison of effectiveness for photocatalytic oxidation of dyestuff effluent

The present work deals with the synthesis of titanium dioxide nanoparticles doped with Fe and Ce using sonochemical approach and its comparison with the conventional doping method. The prepared samples have been characterized using X-ray diffraction (XRD), FTIR, transmission electron microscopy (TEM) and UV-visible spectra (UV-vis). The effectiveness of the synthesized catalyst for the photocatalytic degradation of crystal violet dye has also been investigated considering crystal violet degradation as the model reaction. It has been observed that the catalysts prepared by sonochemical method exhibit higher photocatalytic activity as compared to the catalysts prepared by the conventional methods. Also the Ce-doped TiO(2) exhibits maximum photocatalytic activity followed by Fe-doped TiO(2) and the least activity was observed for only TiO(2). The presence of Fe and Ce in the TiO(2) structure results in a significant absorption shift towards the visible region. Detailed investigations on the degradation indicated that an optimal dosage with 0.8 mol% doping of Ce and 1.2 mol% doping of Fe in TiO(2) results in higher extents of degradation. Kinetic studies also established that the photocatalytic degradation followed the pseudo first-order reaction kinetics. Overall it has been established that ultrasound assisted synthesis of doped photocatalyst significantly enhances the photocatalytic activity.

Effect of low Fe3+ doping on characteristics, sonocatalytic activity and reusability of TiO2 nanotubes catalysts for removal of Rhodamine B from water

Fe-doped titanium dioxide (TiO(2)) nanotubes were prepared using sol-gel followed by hydrothermal methods and characterized using various methods. The sonocatalytic activity was evaluated based on oxidation of Rhodamine B under ultrasonic irradiation. Iron ions (Fe(3+)) might incorporate into the lattice and intercalated in the interlayer spaces of TiO(2) nanotubes. The catalysts showed narrower band gap energies, higher specific surface areas, more active surface oxygen vacancies and significantly improved sonocatalytic activity. The optimum Fe doping at Fe:Ti=0.005 showed the highest sonocatalytic activity and exceeded that of un-doped TiO(2) nanotubes by a factor of 2.3 times. It was believed that Fe(3+) doping induced the formation of new states close to the valence band and conduction bands and accelerated the separation of charge carriers. Leached Fe(3+) could catalyze Fenton-like reaction and led to an increase in the hydroxyl radical (OH) generation. Fe-doped TiO(2) nanotubes could retain high degradation efficiency even after being reused for 4 cycles with minimal loss of Fe from the surface of the catalyst.

Retracted Article: Polycaprolactone composites with TiO2 for potential nanobiomaterials: tunable properties using different phases

TiO₂ nanoparticles of different phases play a key role in property alteration of nanocomposite fibers.

Higher visible photocatalytic activities of nitrogen doped In2TiO5 sensitized by carbon nitride

N-doped In(2)TiO(5) modified by carbon nitride (CN) composite (NICN) has been prepared by the pyrogenation of the mixture of urea and In(2)TiO(5) through a polymerizable complex (PC) method. The powder samples were characterized by XRD, FESEM, TEM, UV-vis, and XPS. It is shown by XRD that the precursor sintered at 1000°C is pure and nitrogen dopant does not change the crystal structure of In(2)TiO(5). FESEM and TEM reveal a hole-like morphology of the prepared NICN. With the increase of nitrogen content, the light absorption onset of In(2)TiO(5) shifts from 410 nm to 450 nm, revealing significant narrowing of the band gap. XPS results suggest that only 2.2% of the nitrogen atoms were doped into In(2)TiO(5) through the urea pyrogenation method. Furthermore, the decomposition of Rhodamine B (Rh-B) under visible light reveals that Rh-B can be degraded completely within 20 min and recycling experiments indicate NICN has stable structure and durable photocatalytic activity, suggesting a promising utilization of such photocatalyst under visible light. Finally, an innovative mechanism of N-doped In(2)TiO(5) sensitized by carbon nitride polymer is proposed.

Preparation and characterization of photoactive composite kaolinite/TiO(2)

Preparation of nanocomposite kaolinite/TiO(2), using hydrolysis of titanyl sulfate in the presence of kaolin was addressed. A variable (kaolin)/(titanyl sulfate) ratio has been used in order to achieve the desired TiO(2) content in prepared nanocomposites. Calcination of the composites at 600 °C led to the transformation of the kaolinite to metakaolinite and to origination of metakaolinite/TiO(2) composites. The prepared samples were investigated using X-ray fluorescence spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry and diffuse reflectance spectroscopy in the UV-VIS region. Structural ordering of TiO(2) on the kaolinite particle surface was modeled using empirical force field atomistic simulations in the Material Studio modeling environment. Photodegradation activity of the composites prepared was evaluated by the discoloration of Acid Orange 7 aqueous solution.

Degradation of a xanthene dye by Fe(II)-mediated activation of Oxone process

A powerful oxidation process using sulfate radicals activated by transition metal mediated Oxone process has been evaluated in depth by monitoring the degradation of a xanthene dye Rhodamine B (RhB) in aqueous solution. Ferrous ion was chosen as the transition metal due to its potential catalytic effect and wide availability in dyeing industrial effluent. The effects of parameters including reactant dosing sequence, Fe(II)/Oxone molar ratio and concentration, solution pH, and inorganic salts on the process performance have been investigated. Total RhB removal was obtained within 90 min under an optimal Fe(II)/Oxone molar ratio of 1:1. The RhB degradation was found to be a two-stage kinetics, consisting of a rapid initial decay and followed by a retarded stage. Additionally, experimental results indicated that the presence of certain anions had either a positive or negative effect on the process. The inhibitory effect in the presence of SO(4)(2-) was elucidated by a proposed formula using Nernst equation. Furthermore, dye mineralization in terms of TOC removal indicates that stepwise addition of Fe(II) and Oxone can significantly improve the process performance by about 20%, and the retention time required can be greatly reduced comparing with the conventional one-off dosing method.

MOF-derived ZnO and ZnO@C composites with high photocatalytic activity and adsorption capacity

Nanostructured ZnO materials have unique and highly attractive properties and have inspired interest in their research and development. This paper presents a facile method for the preparation of novel ZnO-based nanostructured architectures using a metal organic framework (MOF) as a precursor. In this approach, ZnO nanoparticles and ZnO@C hybrid composites were produced under several heating and atmospheric (air or nitrogen) conditions. The resultant ZnO nanoparticles formed hierarchical aggregates with a three-dimensional cubic morphology, whereas ZnO@C hybrid composites consisted of faceted ZnO crystals embedded within a highly porous carbonaceous species, as determined by several characterization methods. The newly synthesized nanomaterials showed relatively high photocatalytic decomposition activity and significantly enhanced adsorption capacities for organic pollutants.

Synthesis of nanocrystalline anatase TiO2 by one-pot two-phase separated hydrolysis-solvothermal processes and its high activity for photocatalytic degradation of rhodamine B

Si-doped and un-doped nanocrystalline TiO(2) samples have been synthesized by simple one-pot water-organic two-phase separated hydrolysis-solvothermal (HST) processes, and characterized by XRD, BET, TEM, FT-IR, DRS and surface photovoltage techniques. The effects of the solvothermal temperature and Si doping on the anatase thermal stability, and on the photocatalytic activity for degrading rhodamine B were investigated in detail. The results show that, as the solvothermal temperature rises, the crystallinity and thermal stability of the resulting nano-sized anatase TiO(2) gradually increase. Noticeably, the as-prepared TiO(2) obtained at appropriate solvothermal temperature (160 degrees C) exhibits high photocatalytic activity. Moreover, although Si doping does not improve the photocatalytic activity of the as-prepared anatase TiO(2), it greatly enhances the anatase thermal stability and inhibits crystallite growth during the process of post-thermal treatment. Interestingly, the Si-doped TiO(2) post-treated at high temperature displays much higher photocatalytic activity than commercial P25 TiO(2). It is clearly demonstrated that the joint effects of high anatase crystallinity and large surface area lead to high photocatalytic activity. This work provides a simple and effective strategy for the synthesis of high-performance TiO(2)-based functional nanomaterials.

Ultrasonic degradation of Rhodamine B in the presence of hydrogen peroxide and some metal oxide

In this research, degradation of Rodamine B in the presence of (hydrogen peroxide), (hydrogen peroxide+ultrasound), (hydrogen peroxide+aluminum oxide), (hydrogen peroxide+aluminum oxide+ultrasound with different ultrasound power), (hydrogen peroxide+iron oxide) and (hydrogen peroxide+iron oxide+ultrasound with different ultrasound power) were investigated at 25 degrees C. The apparent rate constants for the examined systems were calculated by pseudo-first-order kinetics. The results indicate that the rate of degradation was accelerated by ultrasound. The rate of degradation was increased by increasing power ultrasound. The efficiency of the (hydrogen peroxide+iron oxide+ultrasound) system for degradation of Rodamine B was higher than the others examined.

Nanosized BiVO4 with high visible-light-induced photocatalytic activity: ultrasonic-assisted synthesis and protective effect of surfactant

Nanosized BiVO4 with high visible-light-induced photocatalytic activity was successfully synthesized via ultrasonic-assisted method with polyethylene glycol (PEG). The BiVO4 sample prepared under ultrasonic irradiation with 1g PEG for 30 min was consisted of small nanoparticles with the size of ca. 60 nm. The effects of ultrasonic irradiation and surfactant were investigated. The nanosized BiVO4 exhibited excellent visible-light-driven photocatalytic efficiency for degrading organic dye, which was increased to nearly 12 times than that of the products prepared by traditional solid-state reaction. Besides decoloring, the reduction of chemical oxygen demand (COD) concentration was also observed in the degradation of organic dye, further demonstrating the photocatalytic performance of BiVO4. After five recycles, the catalyst did not exhibit any significant loss of photocatalytic activity, confirming the photocatalyst is essentially stable. Close investigation revealed that the crystal size, BET surface area, and appropriate band gap of the as-prepared BiVO4 could improve the photocatalytic activities.

Photo-reductive decolorization of an azo dye by natural sphalerite: case study of a new type of visible light-sensitized photocatalyst

Natural sphalerite, which represents a new class of mineral-based catalyst, was characterized and investigated for photo-reduction of an azo dye methyl orange (MO) under visible light. After 2h of visible light irradiation, a complete decolorization of the MO solution was achieved. The degradation rate was related to the pH conditions. Spectra from FT-IR analysis indicate an initial adsorption of MO to sphalerite via its sulfonate group. Further reduction of the adsorbed MO by sphalerite under light irradiation led to the destruction of the azo structure, as indicated by the results from UV-vis, FT-IR and ESI-MS analyses. The visible light-induced photocatalytic reductive activity of natural sphalerite was mainly attributed to the distribution of foreign metal atoms in its crystal lattice, which reduces the intrinsic bandgap of sphalerite and also broadens its spectra responding range. In addition, the high conduction band potential of natural sphalerite may also enhance the photo-reduction of MO.

Photocatalytic antibacterial performance of Sn(4+)-doped TiO(2) thin films on glass substrate

Pure anatase, nanosized and Sn(4+) ion doped titanium dioxide (TiO(2)) particulates (TiO(2)-Sn(4+)) were synthesized by hydrothermal process. TiO(2)-Sn(4+) was used to coat glass surfaces to investigate the photocatalytic antibacterial effect of Sn(4+) doping to TiO(2) against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). Relationship between solid ratio of TiO(2)-Sn(4+) in coatings and antibacterial activity was reported. The particulates and the films were characterized using particle size analyzer, zeta potential analyzer, Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), SEM, AAS and UV/VIS/NIR techniques. The results showed that TiO(2)-Sn(4+) is fully anatase crystalline form and easily dispersed in water. Increasing the solid ratio of TiO(2)-Sn(4+) from 10 to 50% in the coating solution increased antibacterial effect.