Methylene Blue Aqueous Solution Research Articles

Evidence of cathodic peroxydisulfate activation via electrochemical reduction at Fe(II) sites of magnetite-decorated porous carbon: Application to dye degradation in water

Peroxydisulfate (PDS, S2O82−)-based advanced oxidation processes have been developed as an alternative to those based on OH, as PDS activation yields a much more stable radical like SO4− that can maintain the oxidation ability of water treatment systems for longer time. Here, the electrochemical PDS activation has been investigated using reticulated vitreous carbon (RVC) substrate modified with Fe3O4 nanoparticles (NPs) as cathode. The NPs were exhaustively characterized by different surface analysis techniques (TEM, SEM) and Mössbauer spectroscopy. Cyclic voltammetry and linear sweep voltammetry with a rotating disk electrode allowed concluding that the main electrocatalytic role in the cathodic PDS activation to SO4− corresponded to the Fe(II) active sites continuously promoted upon cathodic polarization. These sites were less catalytic for O2 reduction reaction, although it was still feasible with n = 2.7 electrons as determined from Koutecky-Levich analysis. Both cathodic reactions followed an inner-sphere reaction mechanism. The Fe3O4-modified RVC cathodes were employed to electrolyze Methylene Blue aqueous solutions at pH 3.5, employing different current values and PDS concentrations. Dissolved O2 was purged to impede the competitive cathodic H2O2 production and Fenton’s reaction. The occurrence of dye adsorption/electrosorption on the cathode reduced the mass transport limitations, enhancing the reaction between SO4− and organic molecules. The best operation conditions to reach total and fast color removal at 18 min were 2 mM PDS and 10 mA, yielding > 80% TOC abatement at 45 min. Reproducible degradation profiles were found after 5 runs, thereby ensuring the stability of the Fe3O4-modified RVC, with no iron sludge production.

Cyanophycean (Cyanobacterial) diversity from the Lakhimpur-Khiri District of Northern Uttar Pradesh, India

In the present study, the cyanophycean diversity of the Lakhimpur-Khiri district, northern Uttar Pradesh, India, has been investigated for the first time. Algae samples were collected in plastic bottles and preserved in 3-4% formalin from Lakhimpur-Khiri district of northern Uttar Pradesh in different seasons from 2015 to 2016. The field photographs of the selected localities were also taken and the location of each site noted down. For the Microscopic study of Cyanophycean algae, the samples were stained with 1 % aqueous methylene blue solution according to the standard method. The observations and photomicrography were done with help of Nikon Labophot-11 microscope. A total of 31 cyanophycean algal taxa have been recorded from different water bodies of Lakhimpur-Khiri. These algal taxa belong to 14 genera and 9 families of the division Cyanophyata. Of these, Oscillatoria (7), Phormidium (4) and Lyngbya (3) are abundant.

Usability, durability and regeneration of Ag/ZnO coated microreactor for photocatalytic degradation of methylene blue

The microreactor, which was manufactured for the treatment of aqueous methylene blue (MB) solution, was coated with ZnO photocatalyst with different silver content using the spray pyrolysis method. Dye removal from water as a result of photocatalytic reaction at various residence times under UV-A irradiation was investigated. Here, the effect of morphological structures of ZnO-coated surfaces with and without silver on water treatment was observed. In addition, the effects of hydrogen peroxide at different rates on degradation and catalyst strength were investigated. As a result of experiments, 91% methylene blue degradation was obtained with 1% Ag doped ZnO coated microreactor for a residence time of 2.5 minutes. With the addition of 10% hydrogen peroxide, 96% of methylene blue removal was achieved. It was observed that if the photocatalyst coated reactors were operated for more than 40 hours, the removal efficiency decreased to approximately 62% and remained almost constant and again, returned to their previous performance when regenerated by hydrogen peroxide. In this study, for the first time, Ag/ZnO catalyst was coated on aluminum microreactor by spray pyrolysis method and the usability, durability and regeneration of this reactors were evaluated for the photocatalytic degradation of methylene blue under UV-A irradiation. The individual effects of UV radiation, H2O2 content and the catalyst on degradation were also investigated.

A supramolecular gel made from an azobenzene-based phenylalanine derivative: synthesis, self-assembly, and dye adsorption

In the present work, a new supramolecular gel of azobenzene-based phenylalanine derivative (AZO-Phe) and its application in methylene blue (MB) adsorption have been developed. The gelator has shown great ability to form stable gels with a critical gelation concentration as low as 1.0 mg/mL in EtOH/H 2 O. The studies also showed that the gel has a good adsorptive performance to MB in aqueous solution. The adsorption process and mechanism of MB on AZO-Phe gel was systematic investigated. Batch experiments were performed to study the effects of initial dye concentration, contact time and pH on the adsorption performance of AZO-Phe gel. The adsorption process and data was fitted well with Langmuir isotherm model and pseudo-second-order kinetic model. Moreover, AZO-Phe gelator could be recovered after MB adsorption, and rate of recovery was achieved 95%. These results provide a mixed solvent gel method for the purification of dye-polluted water systems, while also paving the way for future design of functionalized supramolecular self-assemble systems.

Photocatalytic degradation of methylene blue dye using poly(3‐hydroxybutyrate)/poly(ethylene glycol)/titanite films and membranes

AbstractIn this work, novel poly(3‐hydroxybutyrate) (PHB)/poly(ethylene glycol) (PEG)/titanite (CaTiSiO5) composites in the form of films and membranes are used for the photocatalytic degradation of methylene blue (MB) in aqueous solution. Films and membranes are prepared from PHB and PEG with either 80 or 93 mol% of titanite. For comparison purposes, titanite powder, films, and membranes of PHB and PEG with no titanite added, are also analyzed. To study the behavior of the materials, X‐ray diffraction, luminescence, field emission scanning electron microscopy, and Raman spectroscopy, are used. Additionally, contact angle was measured by the sessile drop technique. Materials are placed in a beaker containing the MB aqueous solution under constant stirring and exposed to UV light for 12 h. With respect to the initial concentration (C0), the relative MB concentration (C/C0) is measured every hour employing UV–visible spectroscopy. The obtained results showed that by using 0.010 g of titanite powder, approximately 30% of the MB is degraded after 12 h of UV irradiation. The highest MB degradation is obtained with 0.320 g of the polymer/ceramic membrane (0.310 g of polymers and 0.010 g of titanite), where approximately 90% of MB is degraded.

Synthesis, Characterization and Photocatalytic Behavior of SiO2 @nitrized-TiO2 Nanocomposites Obtained by a Straightforward Novel Approach.

We report on the facile synthesis of SiO2@nitrized‐TiO2 nanocomposite (NST) by calcination of TiO2 xerogel with OctaAmmonium POSS® (N‐POSS; POSS=polyhedral oligomeric silsesquioxanes). The as‐obtained nanoporous mixed oxide is constituted by uniformly distributed SiO2 and nitrized‐TiO2, where the silica component is present in an amorphous state and TiO2 in an anatase/rutile mixed phase (92.1 % vs. 7.9 %, respectively) with very small anatase crystallites (3.7 nm). The TiO2 lattice is nitrized both at interstitial and substitutional positions. NST features a negatively charged surface with a remarkable surface area (406 m2 g−1), endowed with special adsorption capabilities towards cationic dyes. Its photocatalytic behavior was tested by following the degradation of standard aqueous methylene blue and methyl orange solutions under UV and visible light irradiation, according to ISO 10678:2010. For comparison, analogous investigations were carried out on a silica‐free N−TiO2, obtained by using NH4Cl as nitrogen source.

Effect of Annealing Temperature on Structural and Optical Properties of ZnTiO3 Perovskite Layers Deposited on Silicon for Photocatalytic Applications

AbstractIn this paper, we investigate the effect of annealing temperature on structural, optical, and photocatalytic properties of nanostructured ZnTiO3 thin films deposited on Si substrates. ZnTiO3 coatings were prepared by consecutive sol‐gel method and further deposited on Si substrates by spin‐coating. The obtained films were annealed at three various temperatures namely 700 °C, 800 °C, and 900 °C. X‐ray diffraction analysis shows that the crystallite size of the films grows from 100 to 125 nm as the annealing temperature increases from 700 to 900 °C. At the same time, the roughness increases from 232 to 289 nm and the band gap dwindles from 3.73 to 3.05 eV. ZnTiO3 coatings annealed at 700 °C exhibits the highest photodegradation rate about 74 % to catalyze the degradation of the Methylene Blue aqueous solution. We demonstrate that this high photocatalytic activity is attributed to the structural and optical properties of prepared samples.

Fabrication of a novel Co/Ni-MOFs@BiOI composite with boosting photocatalytic degradation of methylene blue under visible light

In this work, cobalt/nickel-based metal-organic frameworks (Co/Ni-MOFs) modified bismuth oxyiodine (BiOI) composite (Co/Ni-MOFs@BiOI) was successfully prepared via a hydrothermal method and used as a novel light-driven photocatalyst for the degradation of cationic methylene blue (MB) in aqueous solutions under visible-light irradiation. It was found that Co/Ni-MOFs in combination with BiOI greatly improved the capability of absorbing visible light, resulting in boosting photocatalytic degradation of MB in aqueous solutions without any chemical additives. The photocatalytic activity of Co/Ni-MOFs@BiOI composites toward MB was enhanced significantly, almost 4 times higher than that of Co/Ni-MOFs, which could be attributed to the reduction of electron-hole pair recombination as well as synergetic effect. Moreover, the results of parallel experiments showed that Co/Ni-MOFs@BiOI composites could be used as a highly efficient photocatalyst to decompose other dyes including crystal violet (CV), rhodamine 6G (R6G), malachite green (MG), congo red (CR) and methyl orange (MO) under the visible light illumination. The trapping experimental results showed that superoxide radicals (·O2−) was the primary reactive species in the photodegradation reaction of MB, and a possible photodegradation mechanism of MB in the presence of Co/Ni-MOFs@BiOI was proposed.

Layer by layer self-assembly MoS2/ZIF-8 composites on carboxyl cotton fabric for enhanced visible light photocatalysis and recyclability

A novel strategy for preparing Zeolitic Imidazolate Frameworks-8 (ZIF-8) based photocatalytic material with high efficiency, durability and recyclability is proposed. ZIF-8 is prepared by self-assembly layer-by-layer on carboxyl cotton fabric. The coordination bond formed by metal ions and carboxyl groups of carboxyl cotton fabric greatly enhances the interaction between particles and fabric. Semiconductor MoS2 is grown in situ on the surface of ZIF-8 to improve photocatalytic activity of ZIF-8. The morphology and structure of prepared MoS2/ZIF-8/Carboxyl cotton are characterized. The influence of layer-by-layer self-assembled ZIF-8 on the charge separation efficiency and optical properties of functional materials are investigated by electrochemical impedance spectroscopy and photocurrent. Under visible light irradiation, this functionalized fabric has good degradability to methylene blue. About 99.8% of methylene blue aqueous solution is degraded after exposure to visible-light for 21 min. Furthermore, about 94.8% photocatalytic activity is still maintained even after six times of recycling. Possible mechanisms accounting for the enhanced photocatalytic properties are proposed. This fabrication method used in this study shows great potential in the development of textile-based multifunctional photocatalytic materials with high degradation efficiency and high recovery rate.

Regulation of the Volume Flow Rate of Aqueous Methyl Blue Solution and the Wettability of CuO/ZnO Nanorods to Improve the Photodegradation Performance of Related Microfluidic Reactors.

Six CuO/ZnO nanorod (CuO/ZnONR)-based microfluidic reactors were constructed for different UV irradiation durations, with which an aqueous methylene blue (MB) solution was photodegraded at varied volume flow rate Q. Via numerical and experimental routes, the effects of the Q on the kinetic adsorption rate constant Ka and the initial rate constant KA of the CuO/ZnONR-based microfluidic reactors were discussed. Moreover, a reverse contacting angle (CA) trend of CuO/ZnONRs to the reaction constant K curve of corresponding CuO/ZnONR-based microfluidic reactor suggested that the CA of CuO/ZnONRs was another key influencing factor that affected greatly the photodegradation performance of the microfluidic reactors. The Q of the aqueous MB solution and the UV irradiation duration for the photodeposition of CuO/ZnONRs were optimized to be 125 μL/min and 1.0 h, the K of the CuO/ZnONR-based microfluidic reactors reached 4.84 min-1, and the related ΔKA/K was less than 6%. Similarly, these methods and results can be employed not only to enhance the mass transport and adsorption of specific species within other nanostructured matrix material-coated microchannels but also to enlarge the actual contacting surface areas between these microchannels and the related solution, which further improve the performance of other nanostructured catalyst-based microfluidic reactors, rGO microfluidic voltage generation, and a GOx/AuNW enzymatic glucose microfluidic sensor.

Degradation of Methylene Blue Using Microplasma Discharge – A Relative Study with Photodegradation

Large-scale production and application of synthetic dyes have become a matter of concern as it is a major factor responsible for environmental pollution. Most dyeing effluents are discharged into water bodies and lands without being treated, which ultimately pollutes the groundwater making it unfit for consumption. The present study explains the degradation of one of such synthetic dyes Methylene blue (MB), using non-thermal Microplasma treatment. The aqueous solution of MB was treated with an array of air microplasma discharge at atmospheric pressure. Different concentrations (10 ppm, 20 ppm) of MB solution were treated for various treatment time and chemical parameters like pH, electrical conductivity, total dissolved solids and salinity was measured. The degradation percentage reached 100% in 15 min of treatment for 10 ppm MB solution, and 20 min of treatment for 20 ppm MB solution indicated by the color change from blue to a clear solution. The reactive oxygen species (ROS) and reactive nitrogen species (RNS) formed during the microplasma treatment are responsible for MB degradation. Same volume of MB solution was irradiated by direct sunlight for photodegradation and was found to degrade the solution of 10 ppm by 96% and 20 ppm by 93% in 10 hours of treatment. Experimental results indicated that microplasma treatment was effective for dye degradation, without the need for pretreatment process or chemicals.

Iron Species-Supporting Hydrophobic and Nonswellable Polytetrafluoroethylene/Poly(acrylic acid-co-hydroxyethyl methacrylate) Composite Fiber and Its Stable Catalytic Activity for Methylene Blue Oxidative Decolorization.

Polytetrafluoroethylene emulsion was ultrasonically mixed with an extremely spinnable poly(acrylic acid-co-hydroxyethyl methacrylate) solution to get a dispersion with good spinnability, and the obtained dispersion was then wet-spun into water-swellable fiber. Crosslinking agents and iron species were simultaneously introduced into the water-swellable fiber through simple impregnation and water swelling. A composite fiber with Fenton reaction-catalyzing function was then fabricated by sequentially conducting crosslinking and sintering treatment. Due to crosslinking-induced good resistance to water swelling and PTFE component-induced hydrophobicity, the composite fiber showed a highly stable activity to catalyze H2O2 to oxidatively decolorize methylene blue (MB). Within nine cycles, the composite fiber could decolorize more than 90% of MB within one minute in the presence of H2O2 and did not show any attenuation in MB decolorization efficiency. The composite fiber still could reduce the total organic carbon of MB aqueous solution from 18.3 to 10.3 mg/L when used for the ninth time. Therefore, it is believable that the prepared fiber has good and broad application prospects in the field of dye wastewater treatment.

TiO2–SiO2 nanocomposites from technological wastes for self-cleaning cement composition

Nanocomposites TiO2–SiO2 that can produce self-cleaning concretes with increased strength were studied in this work. We synthesized TiO2–SiO2 nanocomposites from industrial raw materials and waste products. We studied TiO2–SiO2 properties by Fourier transform infrared spectra, X-ray diffraction, and thermogravimetric/derivative thermogravimetric analyses. We established that obtained TiO2–SiO2 nanocomposites to comprise rutile and amorphous silica (TS-1), a mineral-like weakly-crystallized ivanyukite (TS-2), anatase and amorphous silica (TS-3, TS-4). The specific surface area of the studied powders changed in the range 50–534 m2 g−1. We evaluated the photocatalytic performances of the TiO2–SiO2 nanocomposites in methylene blue aqueous solution under UV. TS-2 and TS-3 samples performed a higher photocatalytic activity than a commercial P25 photocatalyst. We added 1.0 wt % TiO2–SiO2 to cement paste and studied its properties and structure by compressive strength test, TG/DTA analysis and scanning electron microscopy. The resulting cement paste determined to have increased compressive strength, reduced pore size, decreased structure defects and increased density of cement stone. The cement paste determined to possess self-cleaning properties both in the UV and visible light.

Synthesis and Characterization of Fly Ash-based Geopolymer Membrane for Methylene Blue Dye Removal

Utilization of fly ash-based geopolymer membranes for the removal of environmentally hazardous materials has become an attractive route due to its cheaper processing cost and prolonged use. This paper reports the preparation of geopolymer composite membranes and the filtration performance of the prepared geopolymer membranes for the removal of methylene blue (MB) contaminant. The geopolymer membrane was prepared by the dissolution of raw material, i.e., fly ash in alkaline activator i.e., sodium hydroxide solution. Various proportions of foaming agents as a mixture of hydrogen peroxide and egg white were added to investigate their impacts on the prepared membrane pore structures and morphology. The morphology, pore structure and functional groups of geopolymeric composite membranes were characterized using field-emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis and Fourier Transform Infrared spectroscopy (FTIR) respectively. The performance of the membranes was evaluated for the removal of MB in aqueous solution using a lab-scale membrane filtration setup. The performance tests revealed a promising result with all the rejection was above R>90% for membranes GE0, GE1, GE2.5 and GE5, meanwhile the best permeation obtained was 15 L/m 2.h when GE5 was used. The results were correlated to BET and FESEM results which showed that the pore structures of GE5 were homogeneous and uniform while having the highest pore size which is 19.60 nm.

Simple Fabrication of PEG Modified W<sub>18</sub>O<sub>49</sub> for Enhanced Adsorption Performance towards Methylene Blue

The W18O49 nanoparticles were synthesized by solvothermal method with tungsten chloride as raw material and n-propanol as solvent. Polyethylene glycol 400 (PEG-400) was modified for W18O49 nanoparticles (W18O49@PEG). The structure and morphology of W18O49 and W18O49@PEG were characterized by XRD and SEM. Methylene blue aqueous solution was used as wastewater adsorption model. And the comparative experiments with other absorbent materials, such as artificial zeolite and activated carbon were also conducted. The results revealed that after modifying by PEG-400, W18O49 has a better adsorption performance than other materials due to its large specific surface area and high surface energy. Finally adsorption circulation experiment was performed，the results indicate that the W18O49@PEG nanoparticles show great potential in the treatment of colored wastewater.

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Zinc Metal-Organic Framework Growing on the Surface of Fruit Peels and Its Photocatalytic Activity.

The development of water treatment materials using environmentally friendly natural biomasses as substitutes plays an increasingly important role in environmental protection. Zeolitic imidazolate framework-8 (ZIF-8) is often used for the catalytic degradation of dye wastewater, but due to its small particle size, its disadvantage of easy agglomeration prevents it from being fully functional. Herein, we report an efficient method for synthesizing biomasses/ZIF-8 using four different fruit peels as carriers. ZIF-8 nanoparticles are in-situ grown uniformly on their surface. The Brunauer–Emmett–Teller surface area of shaddock peel/ZIF-8 was found to be 752.15 m2g–1. After catalytic activity comparison, the loose shaddock peel/ZIF-8 showed the fastest and most significant degradation efficiency of 94% in methylene blue aqueous solution and could be used multiple times through a simple washing process.

S-doped NiFe-based catalyst for fast degradation of methylene blue by heterogeneous photo-Fenton reaction.

S-doped NiFe-based particles were prepared by a solvothermal method and used to degrade methylene blue (MB) aqueous solutions with visible light in a heterogeneous Fenton reaction. The obtained solid samples were characterized by XRD, SEM, TEM, and XPS. It was found that 0.2 gL-1 NiFe2S4 can degrade 99.8% MB solution within 6 min in the presence of 5 mM H2O2 and natural pH. The recycle experiments results indicate that the NiFe2S4 catalyst possessed better stability than NiFe2O4. Furthermore, NiFe2S4 particles can be easily separated from contaminant solution by using a magnet due to their excellent ferromagnetism. COD analysis experiments indicated that the COD removal rate of NiFe2S4 is 73.1% in 30 min. A possible mechanism was proposed, and the degradation products were measured by LC-MS.

Synthesis and characterization of SiO2-TiO2 nanoparticles and their effect on the strength of self-cleaning cement composites

SiO2-TiO2 mixed oxides have been used in this research to improve compressive strength and self-cleaning characteristics of cement. SiO2-TiO2 samples have been synthetized by the heterocoagulation method and characterized by a series of techniques, such as infrared spectra with Fourier transform, X-ray diffraction and thermogravimetric/derivative thermo-gravimetric analyses. Photocatalytic characteristics of the prepared specimens have been evaluated in methylene blue aqueous solution under ultraviolet ray irradiation. It has been found that the structural-adsorption, surface properties, and the photocatalytic activity of the SiO2-TiO2 depend on the final stage calcination temperature. The experimental results have shown that the material which was heated to 800 °C exhibited a high-specific surface area (307.1 m2·g−1) and highest photocatalytic activity. The physico-mechanical characteristics of the specimens were tested using a compressive strength study, thermogravimetric/differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM) to investigate characteristics of cement pastes containing SiO2-TiO2 and without them. It has been determined that the use of SiO2-TiO2 having a specific surface area of more than 300 m2·g−1 allows reducing the amount of additive in the production of cement paste with improved technical characteristics. Results achieved have shown the optimum amount of SiO2-TiO2 in the cement paste composition to be 0.1–0.5%. Besides, the discoloration test has been used to estimate the photocatalytic activity on the treated cement surface.

Study of adsorption of methylene blue in aqueous solution onto activated carbon prepared using low cost domestic oven based heating system

In this work activated carbon was prepared from teak wood charcoal using very low-cost oven based heating system. Firstly, charcoals were grinded with a domestic grinder and then activated with 25% CaCl2 solution and then heated with 250C for different times. And then experiment was carried out through 2.5 × 10-5 methylene blue aqueous solution by taking activated Charcoal into it and kept one hour for adsorption. Adsorption capacity was estimated by taking the different amount of activated carbon. The result indicates that prepared activated carbon be effectively used for water purification application through adsorption of the dye.