Performance For Methylene Blue Degradation Research Articles

Facile synthesis of Ag2ZrO3 nanocrystals with highly enhanced visible-light photocatalytic activity

Abstract This paper describes the synthesis of Ag2ZrO3 nanocrystals using coprecipitation and microwave-assisted hydrothermal methods. These nanocrystals were characterized by means of X-ray diffraction, micro-Raman spectroscopy, Fourier transform infrared absorption spectroscopy, field emission scanning electron microscopy, and UV–Visible spectroscopy, and their photocatalytic performance for methylene blue degradation under visible-light irradiation has been tested. The X-ray diffraction, micro-Raman spectroscopy, Fourier transform infrared absorption spectroscopy analyses indicate that the Ag2ZrO3 nanocrystals have good crystallinity and no secondary phases. The UV–Visible spectroscopy results showed a variation in the optical band gap values (2.71–2.97 eV) with increasing temperature, which indicates the possible presence of defects in the crystal lattice at a medium range. Field emission scanning electron microscopy images revealed that the nanocrystals have uneven spherical shapes and average particle size around 50–70 nm. The good photocatalytic efficiency can be attributed to defects in the silver zirconate structure capable of forming the active adsorption sites. Finally, we discuss a photocatalytic mechanism to understand the photocatalytic process in cationic dye (methylene blue) degradation in aqueous solution.

Flash combustion synthesis using two different fuels and characterization of LiF-doped TiO2 for the photocatalytic applications

The flash combustion method was used to prepare LiF-doped TiO2 photocatalysts materials using glycine or urea as a fuel with different weight percentage of LiF. The synthesized powders have been characterized by thermogravimetric analysis (TG), scanning electron microscope (SEM) with energy dispersive spectrometer (EDX) analyzer, the specific surface area measurement was performed by BET. The crystallization and the phase transformation anatase-rutile for the powders have been verified by XRD. SEM micrographs for these powders shows the presence of nanoparticles. To investigate the optical band gap of the synthesized samples, UV–Vis spectroscopy was conducted using the diffuse reflectance mode (DRS). The O2−/F− substitution and the presence of Ti3+ centers was confirmed by electron paramagnetic resonance (EPR) analysis. The photocatalytic activity of the TiO2-xLiF powders were evaluated through the photocatalytic degradation of Methylene blue (MB) in water under UV–visible light exposure. The results indicated that during the flash combustion synthesis, the nature of the fuel and the percentage of the doping element led to the presence of different polymorphs of TiO2 which influences the photocatalytic efficiency attributed to the synergistic effect between the two phases (anatase and rutile). The LiF-doped TiO2 powders synthesized by flash combustion in both cases (by using glycine or urea) showed high performance in MB degradation compared to commercial TiO2 and undoped synthesized TiO2 powders, with an optimal degradation of 99 % achieved with 2 wt % LiF-doped TiO2 using glycine as a fuel and after 6 h of UV–Vis irradiation.

Dielectric Barrier Discharge Plasma Coupled with Cobalt Oxyhydroxide for Methylene Blue Degradation.

In this study, the coupled use of a double dielectric barrier discharge (DDBD) and CoOOH catalyst was investigated for the degradation of methylene blue (MB). The results indicated that the addition of CoOOH significantly promoted MB degradation performance compared to the DDBD system alone. In addition, both the removal rate and energy efficiency increased with an increase in CoOOH dosage and discharge voltage. After 30 min of discharge treatment in the coupled system (with CoOOH of 150 mg), the removal rate reached 97.10% when the discharge voltage was 12 kV, which was 1.92 times that in the single DDBD system. And when the discharge time was 10 min, the energy efficiency could reach 0.10 g (k·Wh)-1, which was 3.19 times better than the one in the single DDBD system. Furthermore, the addition of CoOOH could also significantly enhance the TOC and COD removal rates of MB. In the DDBD-coupled-with-CoOOH system, TOC and COD were 1.97 times and 1.99 times those of the single DDBD system after 20 min of discharge treatment with a discharge voltage of 12 kV and 100 mg of CoOOH. The main active substances detected in the coupled system indicated the conversion of the active species H2O2 and O3 into a more oxidizing ·OH was enhanced through the addition of a CoOOH catalyst, resulting in the more effective decomposition of MB and intermediate molecules.

Enhanced Visible Light Photocatalytic Activity of g-C3N4/SiO2@TiO2 Heterojunction Fabricated by Hydrothermal Synthesis

Photocatalysts that can utilize sunlight energy have attracted attention. In this study, g-C3N4 and mesoporous SiO2@TiO2 particles were mixed by hydrothermal synthesis. g-C3N4 was made by a simple method of directly heating melamine. Mesoporous SiO2@TiO2 was prepared using the stover method. These two types of particles were then mixed by hydrothermal synthesis. Hydrothermal synthesis reduced the size of the g-C3N4 particles, and they bound more closely with the TiO2 particles. The degradation of methylene blue dye by visible light was performed to evaluate the organic degradation of the mixed particles. In addition, the mixed particles were formed into a thin film by the spin-coating method. The film's methylene blue degradation performance and the film's power generation performance in a battery were evaluated. The film showed high convenience in the practical application of photocatalytic degradation of organic pollutants because it can be easily separated from the treated liquid after organic matter degradation.

Co nanoparticles anchored N, B, F codoped carbon as an efficient peroxymonosulfate activator for rapid catalytic degradation of organic pollutants

Rational design and exploration of low-cost and robust carbocatalysts with multiple active sites for peroxymonosulfate (PMS) activation towards wastewater purification is challenging. Herein, Co nanoparticles anchored N, B, F-codoped porous carbon (Co@NBFOC) was synthesized and characterized thoroughly, which displayed superior PMS activation ability due to the synergy of multiple active sites. The Co@NBFOC-3/PMS system possessed excellent methylene blue (MB) oxidation capacity over a wide initial pH applicability (4-10) and showed high tolerance for Cl−, NO3−, SO42− and humic acid, while CO32−, HCO3− and HPO42− displayed a considerable inhibiting effect on it. Moreover, the Co@NBFOC-3/PMS system could afford acceptable MB degradation performance in different water matrix and universal applicability in eliminating a variety of organic pollutants. Both free radical pathway and nonradical pathway collectively contributed to MB degradation based on scavenging experiments, EPR measurements and electrochemical analyses. Particularly, ·O2−, 1O2, surface-bonded radicals (·SO4−ads and ·OHads) and catalyst mediated electron transfer were the major contributors, followed by ·SO4−free. Metallic Co, pyridinic-N moieties, graphitic-N moieties, BCO2 moieties, CO groups, the carbon atoms adjacent to graphitic-N, defects and ionic CF moieties on Co@NBFOC-3 surfaces corporately contributed to PMS activation. The main degradation intermediates were analyzed by HPLC-MS and the possible MB degradation pathways were proposed. This work not only improves the fundamental understanding of active sites in multi-heteroatom doped carbocatalysts, but also provides some guidance for future development of high-efficient carbon-based catalysts in PMS-based advanced oxidation processes.

Facial synthesis of the trimetallic Au-Pt-Pd nanofluids and performance for methylene blue degradation

The rapid expansion of the chemical industry leads to more environmental pollutants that are difficult to break down through traditional treatment methods. Therefore, it is crucial to introduce a new class of catalysts. The current study examines the simple production and catalytic abilities of Au-Pt-Pd nanofluids (NFs), promising agents for nano catalysts. We have used a one-pot microwave-assisted reduction approach to synthesize the trimetallic NFs. The UV–Vis spectroscopy results indicate that a clear single plasmon resonance peak of NFs has been identified within the 519–545 nm range. Furthermore, the morphological feature of the as-synthesized NFs has been analysed using a transmission electron microscope. The NFs have an average size of 9–12 nm and are spherical in shape. The analysis of the synthesized NFs by energy-dispersive X-ray spectroscopy indicates that they formed in the ratio of 1.3:1:4.3.

Pyrrolic N and persistent free radical synergistically promote catalytic degradation of dyes via Fe2O3/activated biochar derived from Taihu blue algae

Fe-based activated biochar composites are promising catalysts for environmental remediation. However, the limited efficiency of Fe(III)/Fe(II) cycling reaction of commercial Fe2O3 at neutral conditions still impeded the catalytic performance of the heterogeneous Fenton-like catalysts. In this work, high-performance Fe2O3/activated biochar Fenton-like catalysts with Taihu blue algae (hazardous algae to aquatic ecosystems) as carbon precursors were synthesized and used for the degradation of methylene blue (MB). The physicochemical properties of Fe2O3/activated biochar composites including pore structure, the generated N species, and persistent free radicals (PFRs) were effectively tailored by activation temperatures. ACK-7-Fe (prepared under the activation temperature, 700 °C) showed a stronger adsorption ability while ACK-8-Fe (800 °C) exhibited superior MB degradation performance (∼99.97% in 30 min at neutral pH). The former was ascribed to the formation of more mesopores with suitable size which was beneficial for MB adsorption. The latter is due to the promoting effect of pyrrolic N and PFRs on the Fe(III)/Fe(II) cycle, responsible for the high catalytic efficiency of ACK-8-Fe. The hydroxyl radicals were the dominant active radicals evidenced by scavenging experiments and electron spin resonance. Moreover, the. The ACK-8-Fe exhibited superior reusability, which was crucial for its practical applications.

Electrochemical studies of halide perovskite and its correlation for photocatalytic applications

Lead based hybrid organic-inorganic halide perovskite (LHP) possess extraordinary optical, electronic and structural properties. A simple perovskite formed by the cation (MA+) with anion (I− and Br−) enhance efficacy of catalytic reaction towards organic pollutant or more specifically dye degradation. This study focuses on a comparative photo-electrochemical study of MAPbX3 (; X = I, Br) whose physical and chemical properties are examined by XRD, FTIR, FESEM, EDX, UV–Vis and Raman spectroscopy. The results obtained from the photocatalytic studies depicted that the I and Br based MAPbX3 perovskite which are synthesised in monitored ambient conditions, evinced appreciable photocatalytic performance for methylene blue degradation. The experiments performed in visible light resulted in a removal percentage of 77% for MAPbBr3 and 88% for MAPbI3 in 140 mins under Xenon lamp based solar stimulator. The cyclic voltammetry plots revealed the quasi-reversible nature of both the samples as well as the qualitative information about the oxidation and reduction processes giving us estimates of mechanism corresponding to calculated HOMO and LUMO positions.

Enhanced sunlight photo-catalytic performances of ZnO/ZnNb2O6/Nb2O5 composites for organic pollutant degradation

The current study is focused on the development of zinc oxide-based ternary photo-catalysts that exhibit a good photocatalytic activity in methylene blue (MB) dye degradation, under sunlight irradiation. Indeed, the composites are prepared according to this proportion:(1-x) ZnO/xNb2O5, (x = 0; 0.01; 0.05; 0.1; 0.15; 0.2). In fact, X-ray diffraction patterns demonstrate that, for x = 0.01, a binary composite ZnO/ZnNb2O6 is formed. While ternary composite ZnO/ZnNb2O6/Nb2O5 is formed from x = 0.05. The linear and nonlinear optical properties are studied. So, compared to the ZnO (3.24 eV), the prepared composites exhibit a gap energy red-shift (3.18–3.22 eV), probably due to the interactions between oxide phases. Furthermore, the composites exhibit a high optical conductivity, which proves their high photo-responses. On the other hand, the increase of Nb2O5 amount led to an enhancement of nonlinear properties. Moreover, the photocatalytic tests demonstrate an excellent photocatalytic performance in MB degradation that reaches 100% after 120 min sun-light irradiation. Especially for 5% sample which exhibit also the best kinetic rate. These results allowed us to consider the ZnO/ZnNb2O6/Nb2O5 composites as promising materials for environmental applications.

Photocatalytic activity of ZnO nanoparticles synthesized from zinc nitrate and botanical extracts of neem, chrysanthemum, Mexican marigold and shiitake mushroom

AbstractBackgroundGreen synthesis emerges as a need to obtain functional materials, but this also involves following certain principles that imply methods and inputs that are friendlier to health and the environment. A wide variety of materials can be synthesized under these principles, one of them being ZnO, which can be used for environmental, electronic and biomedical applications to mention a few. In this work, ZnO nanoparticles (NPs) were synthesized using aqueous extracts of neem, chrysanthemum, Mexican marigold and shiitake mushroom and subsequently used to degrade methylene blue (MB) under solar light irradiation. The NPs were characterized by UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis to investigate the structural, optical and electronic properties of the NPs.ResultsThe results indicate the formation of hemispherical NPs with aggregates in a size range of 5.38–28.37 nm. All the samples presented a hexagonal wurtzite crystalline structure. The best photocatalytic performance for MB degradation was shown by ZnO NPs obtained using Mexican marigold (0.0873 ± 0.008 min−1) followed by those obtained using shiitake mushroom (0.0602 ± 0.002 min−1), neem (0.0365 ± 0.02 min−1) and chrysanthemum (0.0357 ± 0.01 min−1).ConclusionsBotanical aqueous extracts have the potential to be used in the synthesis of semiconductor materials, as they allow the modification of the size and band gap. Many of the phytochemicals present in the extracts help to improve the interaction between catalyst and pollutants, in this case MB, and therefore have a positive impact on the degradation of textile pollutants. © 2022 Society of Chemical Industry (SCI).

Synergistic copper-modified covalent triazine framework for visible-light-driven photocatalytic degradation of organic pollutant

The current investigation studies the covalent triazine framework (CTF) with copper modification. The analyses comprised several characterizations including, i.e. FTIR (Fourier Transform Infrared Spectroscopy), XPS (X-ray Photoelectron Spectrometer), SEM/EDX (Field Emission Scanning Electron Microscopy/Energy-dispersive X-ray), XRD (X-ray Diffractometer), BET (Brunauer–Emmett–Teller) isotherm and surface area, and UV–vis DRS (Diffuse Reflection Spectroscopy). Additionally, the effect of additional oxidants and scavengers is studied. The copper-modified CTF (CTF-Cu) was found to have favorable properties for photocatalysis purposes compared to pristine CTF-1. The copper modification extends visible light absorption, reduces estimated band gap energy, and modifies the microstructure and chemical composition of the pristine CTF-1 facet. Conclusively, the CTF-Cu exhibited higher performance for methylene blue degradation.

Synthesis of Ag2CrO4/Ag/Fe3O4/RGO nanocomposite as a suitable photocatalyst for degradation of methylene blue in aqueous media: RSM modeling, kinetic and energy consumption studies

In this research, an Ag2CrO4/Ag/Fe3O4/RGO nanocomposite (AAFR-NCPs) with unique properties was synthesized. The structural and morphological properties of the AAFR-NCPs were characterized by the FT-IR, XRD, FE-SEM, EDS, DLS, BET, and VSM techniques. The XRD analysis showed an average crystallite size of 7 nm. The FE-SEM images showed that the synthesized AAFR-NCPs possessed a spherical shape and average particle size of 48.5 nm. The DLS results and pHzpc measurement analysis indicated that the surface charge and zero-point charge pH of AAFR-NCPs were at −29.8 mV, and 7.35, respectively. According to the BET results, the average surface area and pore diameter size distribution of the synthesized composite were 73.64 m2/g and 5.86 nm respectively. The corresponding total pore volume of the nanocomposite was 0.2574 cm3/g, which is in good agreement with the estimated results from the BJH method (0.2682 cm3/g). In addition, the VSM results showed that AAFR-NCPs had significant magnetization properties, equal to 41.6 emu/g, which is comparable with the magnetization level of pure Fe3O4 (50.05 emu/g). Moreover, the band gap energy (Eg) of the prepared AAFR-NCPs is estimated to be 1.62 eV. The photocatalytic activity and optimization of the methylene blue (MB) photodegradation process using the synthesized AAFR-NCPs were investigated by the Box Behnken design and by Design Expert software. In this regard, a limited number of influential variables were studied, including the concentration of MB, amount of AAFR-NCPs as the photocatalysts (Cat), pH, and irradiation time (t). A polynomial equation was obtained corresponding to the degradation efficiency (DE) for the experimental data. The calculated R2, Adj-R2, and Pred-R2 values in the model were 0.991, 0.981, and 0.952, respectively indicating a reasonable proportion between the model fitting and experimental data. DE of 97.6 was achieved under optimum conditions of [MB]o = 12 mg/L, [Cat] = 10 mg/L, pH = 2 and ∼103 min time of treatments. The kinetic model under optimum conditions, obeying the pseudo-first-order kinetic model, was studied, with a rate constant (k) of 0.0213 1/min. As the concentrations of MB increased from 5 to 30, the kinetic rate constant decreased 5 times lower as 0.0363 to 0.0073 1/min. Under the obtained optimum conditions, DE irradiation was about 52 % in visible light, which showed the synthesized AAFR-NCPs have good performance for MB degradation in visible light. Finally, under optimal conditions of the process, the electrical energy consumption (EEC) was evaluated and achieved at 450.7 KWh/m3. In addition the criteria for a consistent assessment of the process were proposed and its value of 2.15 × 10−2 was calculated and the results were compared with the other relevant reported processes.

Integrated MnO2 nanosheet ultrafiltration ceramic membrane with micro-nano bubbles for catalytic treatment of dye wastewater

Membrane filtration integrated with micro-nano bubbles (MNBs) is an attractive technology for treating dye wastewater given its efficiency and environmental compatibility. However, the amount of ·OH generated during the disintegration of MNBs is insufficient in practical applications. This work presents the characterisation of a modified Al2O3 ceramic membrane (CM) with the MnO2 nanosheet (MnO2/Al2O3 CM), which provides dual functions of membrane filtration and MNB catalysis. Here, a novel MNB catalytic membrane reactor (MNB-CMR) was constructed by applying the modified MnO2/Al2O3 CM for treating the simulated dye wastewater, i.e., methylene blue (MB). The MB degradation showed that the MNB-CMR improved 17% decolorization rate and 20% total organic carbon removal rate compared to the integrated MNB process with the non-modified CM. The MNB-CMR exhibited excellent catalytic performance and fouling resistance. Besides, the effects of MNB-CMR operational parameters such as the initial methylene blue (MB) concentration, reaction temperature, solution flux, and solution pH on the MB degradation performance were investigated. Based on the scavenging experiments of reactive oxygen species (ROS), the reaction of singlet oxygen (1O2) or hydroxyl radicals (·OH) was elucidated as the primary ROS responsible for the oxidation of MB in the MNB-CMR. In addition, the XPS results showed that the redox couple of Mn(IV)/Mn(III) on the surface of the MnO2/Al2O3 CM was responsible for MNB catalysis. Finally, we proposed a possible degradation pathway of MB. This work shows an attractive alternative wastewater treatment process to relieve membrane fouling and enhance MNB catalysis concurrently.

Synthesis of Heterostructure of ZnO@MOF-46(Zn) to Improve the Photocatalytic Performance in Methylene Blue Degradation

The heterostructure of ZnO and MOF-46(Zn) was synthesized to improve the photocatalytic performance of ZnO and prove the synergistic theory that presented the coexistence of ZnO and MOF-46(Zn), providing better efficiency than pure ZnO. The heterostructure material was synthesized by using prepared ZnO as a Zn2+ source, which was reacted with 2-aminoterephthalic acid (2-ATP) as a ligand to cover the surface of ZnO with MOF-46(Zn). The ZnO reactant materials were modified by pyrolysis of various morphologies of IRMOF-3 (Zn-MOF) prepared by using CTAB as a morphology controller. The octahedral ZnO obtained at 150 mg of CTAB shows better efficiency for photodegradation, with 85.79% within 3 h and a band gap energy of 3.11 eV. It acts as a starting material for synthesis of ZnO@MOF-46(Zn). The ZnO/MOF-46(Zn) composite was further used as a photocatalyst material in the dye (methylene blue: MB) degradation process, and the performance was compared with that of pure prepared ZnO. The results show that the photocatalytic efficiency with 61.20% in the MB degradation of the heterostructure is higher than that of pure ZnO within 60 min (90.09% within 180 min). The reason for this result may be that the coexistence of ZnO and MOF-46(Zn) can absorb a larger range of energy and reduce the possibility of the electron–hole recombination process.

Peroxymonosulfate activation by algal carbocatalyst for organic dye oxidation: Insights into experimental and theoretical

Preparation of nitrogen-doped algal carbocatalyst (NC) for peroxymonosulfate (PMS) activation to oxidative degrade methylene blue (MB), and the mechanism of radical and nonradical pathway in N-C/PMS system are investigated. Firstly, a series of N-doped carbonaceous materials (NC) were prepared using nitrogen-rich Taihu blue algae biomass as precursor at different annealing temperatures. It was found that the NC prepared by annealing at 800 °C (N-C-8) showed an optimal MB degradation performance of over 99% after 60 min. Confirmed by electron paramagnetic resonance (EPR) analyses and radical quenching experiments, radical and nonradical pathway (1O2 oxidation and electron-transfer) are both involved in MB degraded process. Moreover, both graphitic N derived from the intrinsic Taihu blue algae, and nitrogen vacancy evolved from nitrogen dopants decomposition exhibited high correlation with the MB removal rate in the N-C/PMS system. Finally, three possible degradation pathways of MB were proposed based on the Density Functional Theory (DFT) calculation and identified intermediates. Overall, this work provides a new insight into the intrinsic roles of nitrogen-dopants and nitrogen vacancies on the as-prepared carbocatalyst for PMS activation, and advances the understanding of the resource utilization of algal biomass.

Enhanced photocatalytic performance for methylene blue degradation of TiO2 by transition metal oxides hybrid MxOy (M = Fe, V, W)

Water contamination along with the environmental issues resulted by industrial wastewaters have caused a trend in applying semiconducting photocatalysts, among which TiO2 composites have been particularly focused on to overcome the drawbacks of titanium(IV) oxide. The experimental results indicated that TiO2 is combined transition metal oxides MxOy (M = Fe, V, W) for higher photocatalytic activity than pure TiO2 for the degradation of methylene blue 20mg/l (MB) under visible light irradiation. The improvement of photocatalytic activity can be attributed to the reduction of the electron-hole recombination rate due to the formation of MxOy/TiO2. Electron can tranfer easily in the composite with bangap energy  is smaller than pure TiO2. The result is the light absorption of the modified TiO2 showed an apparent extension to visible light region with TiO2-MxOy. The photocatalysis efficiency under visible light irradiation of TiO2-WO3 is higher than TiO2-V2O5, TiO2-Fe2O3 due to the valence potential energy of WO3 is very large, can oxidize water to create OH• to help decompose strongly organic substances.

Nitrogen and bismuth-doped rice husk-derived carbon quantum dots for dye degradation and heavy metal removal

In this study, heteroatoms doped carbon quantum dots were synthesized using rice husk as a biowaste precursor. The effects of nitrogen and bismuth doping are investigated by adjusting the amount of ethylenediamine (EDA) as the nitrogen source, and bismuth nitrate pentahydrate as the bismuth source. HRTEM analysis depicted the formation of spherical carbon quantum dots, with a size of less than 10 nm. FTIR and XPS analysis confirmed the presence of essential functional groups and chemical composition in both of the doped carbon quantum dots. UV–Vis spectra showed peaks which are associated to the electronic transition of the C = C bonding. The addition of EDA and bismuth nitrate pentahydrate tuned the fluorescence intensity and shifted the emission wavelength from the blue region to green one. The performance of the doped rice husk derived carbon quantum dots (RHCQDs) was evaluated via photodegradation of the methylene blue (MB), under a 300 W Xenon lamp. as well as via copper (II) removal. N-RHCQDs (10 vol%) and Bi-RHCQDs (5 wt%) demonstrated the highest MB degradation performance, at 72.16% and 68.91%, respectively. The degradation of MB of the two doped RHCQDs fitted with the pseudo-second kinetic model. The doped RHCQDs were then tested for copper (II) removal, obtaining removal performance of 56.23% and 33.13%, respectively. The results suggest that the Cu (II) adsorption onto the N-RHCQDs and Bi-RHCQDs agrees with the pseudo-second kinetic model and the Langmuir isotherm, with maximum adsorption capacity of 5.73 and 4.08 mg/g, respectively.

Two facile synthesis routes for magnetic recoverable MnFe2O4/g-C3N4 nanocomposites to enhance visible light photo-Fenton activity for methylene blue degradation

High-efficiency photocatalyst MnFe2O4/g-C3N4 nanocomposites were successfully synthesized to degrade methylene blue (MB). Two types of magnetic recoverable nanocomposite (MG1 and MG2), which were fabricated using co-precipitation and calcination methods, were characterized using various analytical techniques and applied as heterogeneous catalysts for H2O2 activation under simulated sunlight irradiation. The results revealed that composing g-C3N4 in the composites improved the MnFe2O4 crystallinity and increased the material magnetism which facilitated them for efficient recovery using an external magnet. The MG2 synthesis strategy effectively suppressed particle aggregation and immensely increased the active surface area more than for MG1. The quenching experiments revealed that photogenerated electrons played an important role in the catalytic reaction and singlet oxygen (1O2) was a dominant reactive species for MB degradation. The XPS analysis before and after treatment confirmed that the generated 1O2 was derived from the interaction of metal ions and oxygen vacancy in the H2O2 activation. While both nanocomposites exhibited excellent catalytic ability at near-neutral pH levels and for different real water matrices, MG2 had better MB degradation performance but greater difficulty with gravity settling due to its much smaller particle sizes. Therefore, MG2 large-scale production may require more cumbersome steps. However, both nanocomposites showed high crystallinity and very low metal leaching after several uses and still maintained their magnetism. These observations support the use of our MG nanocomposites as potential photocatalysts to activate H2O2 for the degradation of an organic contaminant in water.

Molecularly imprinted polymer-based photocatalyst for highly selective degradation of methylene blue

ZnO quantum dots were synthesized by chemical precipitation, CuFe2O4 nanoparticles were prepared by in situ synthesis of cellulose, and then ZnO/CuFe2O4 (ZCF) composites were fabricated. A photocatalyst (ZCF@MB-MIP) with specific molecule recognition and photocatalytic degradation characteristics was then produced by a surface imprinting method using methylene blue (MB) as the template molecule. The structure of ZCF@MB-MIP was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and X-ray diffraction. The photocatalytic efficiency of ZCF@MB-MIP and its specific recognition performance in MB degradation was analyzed. The adsorption kinetics of MB by ZCF@MB-MIP conformed to the quasi-secondary adsorption kinetics model. ZCF@MB-MIP displayed effective photocatalytic degradation of MB under natural light. The degradation rate reached 95.8%, which was much higher than those of ZCF, CuFe2O4 nanoparticles, and a non-imprinted reference sample under the same conditions. This work is a useful reference for the construction of photocatalysts that show highly selective recognition of dye molecules.

Preparation of manganese oxide-porous carbon nanocomposites by self-activation and their enhanced performance for methylene blue degradation

Manganese oxides and their composites are promising catalysts for the Fenton-like reaction, which generates hydroxyl radical to eliminate the ever-growing organic pollutants in water. Here, a new solution synthesis approach combined with the self-activation carbonization process has been developed to prepare the MnOx-porous carbon nanocomposites (MnOx-C(SiO2)). First, Mn ions are easily incorporated into resorcinol-formaldehyde (RF) resin with the help of polyacrylic acid (PAA) and then transformed into MnOx particles during carbonization. When the Mn-RF sphere is coated in a silica shell in advance, the pyrolysis process can endow the product with a high BET surface area of 962.8 m2 g−1, much larger than that of the counterpart prepared without SiO2 coating (MnOx-C). In the meantime, the SiO2 shell also prevents the in situ formed MnOx particles from getting larger, making them well dispersed in the porous carbon. The size of MnOx particles in MnOx-C(SiO2) is only 5 nm, which shows superior catalytic performance toward methylene blue (MB) degradation via the Fenton process. The MB degradation rate is close to 100% and remains 98.9% after five cycles.