Photodegradation Of Methyl Orange Research Articles

Clay Minerals/TiO2 Composites—Characterization and Application in Photocatalytic Degradation of Water Pollutants

TiO2 used for photocatalytic water purification is most active in the form of nanoparticles (NP), but their use is fraught with difficulties in separation from solution or/and a tendency to agglomerate. The novel materials designed in this work circumvent these problems by immobilizing TiO2 NPs on the surface of exfoliated clay minerals. A series of TiO2/clay mineral composites were obtained using five different clay components: the Na-, CTA-, or H-form of montmorillonite (Mt) and Na- or CTA-form of laponite (Lap). The TiO2 component was prepared using the inverse microemulsion method. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopy/energy dispersive X-ray spectroscopy, FTIR spectroscopy, thermal analysis, and N2 adsorption–desorption isotherms. It was shown that upon composite synthesis, the Mt interlayer became filled by a mixture of CTA+ and hydronium ions, regardless of the nature of the parent clay, while the structure of Lap underwent partial destruction. The composites displayed high specific surface area and uniform mesoporosity determined by the size of the TiO2 nanoparticles. The best textural parameters were shown by composites containing clay components whose structure was partially destroyed; for instance, Ti/CTA-Lap had a specific surface area of 420 m2g−1 and a pore volume of 0.653 cm3g−1. The materials were tested in the photodegradation of methyl orange and humic acid upon UV irradiation. The photocatalytic activity could be correlated with the development of textural properties. In both reactions, the performance of the most photoactive composites surpassed that of the reference commercial P25 titania.

Photocatalytic activity of selenium decorated graphitic carbon nitride nanocomposites for dye Industries wastewater remediation

In situ selenium-doped graphitic carbon nitride, also known as Se-g-C3N4(SCN), were created in the current study by employing inexpensive urea and selenium metal powder as precursor materials. SEM (scanning electron microscopy), XRD (X-ray diffraction), FTIR (Fourier-transform infrared spectroscopy), as well as TEM (transmission electron microscopy) techniques were utilized to describe the morphological characteristics, optical characteristics, and structural characteristics of the treated photocatalyst. Because of its potential use in photocatalytic environmental pollution remediation, graphitic carbon nitride (g-C3N4), a metal-free photocatalyst, has received a lot of interest. This work not only offers a straightforward method to improve the photocatalytic performance for g-C3N4 but also creates a new path for the logical preparation of efficient polymeric photocatalysts. The results demonstrate that does not alter the crystalline structure of the sample but instead increases the surface area of g-C3N4 by dispersing it widely. Three different photocatalytic composites of g-C3N4 and SeNPs in the mass ratios of 1:1, 2:1, and 3:1, denoted SCN1, SCN2, and SCN3, were created for the methylene blue (MB) and methyl orange (MO) photodegradation. The combined photocatalytic degradation rate of MB after 150 min in visible light (500–800 nm) was 52.4% for g-C3N4, 75.4% for SCN1, 87.8% for SCN2, and 81.3% for SCN3. For methyl orange, the photocatalytic activity of produced materials was also investigated. The analysis's outcome reveals astonishing deterioration values were 45.6% for g-C3N4, SCN1 (62.5%), SCN2 (74.1%), and SCN3(68.5%), respectively. The synthesized photocatalyst offers great potential for the effective removal of dye industeries wastewater remediation.

Enhanced photocatalytic efficiency of BaTiO3 augmented by ZnS nanospheres via Type-II heterojunction for methyl orange degradation

The degradation of organic pollutants is significantly influenced by the recombination of photogenerated electron–hole pair, electron transfer and surface area of a photocatalyst. Barium titanate (BaTiO3) exhibits low photocatalytic activity due to the rapid recombination of photoinduced charge carriers. Hence, the photocatalytic performance of BaTiO3 (BTO) nanoparticles was improved by the construction of heterostructure with the addition of ZnS. BaTiO3 and ZnS were prepared using solid-state metathesis (SSM) and hydrothermal methods, respectively. Subsequently, a series of [(1-x)BaTiO3/(x)ZnS, x = 10, 30, 50 and 70 wt%] heterostructures were successfully constructed through a simple calcination method using pre-prepared BaTiO3 and ZnS. The XRD, FTIR, Raman, XPS and HRTEM analyses revealed the formation of heterostructure between the BTO and ZnS. The positron annihilation lifetime spectroscopy (PALS) results suggest the existence of defects within the materials. To explore the photocatalytic activity, the photodegradation of methyl orange (MO) dye was carried out under UV light illumination for 3 h. Among all the compositions, the heterostructure 70 BaTiO3/30 ZnS (BTZS(70-30)) demonstrated remarkable photocatalytic activity (91.38 %) which is 5.3 times higher than the pristine BTO (17.16 %). The improved photocatalytic activity of heterostructures may result from the effective charge carrier separation facilitated by the type –II band alignment structure between BTO and ZnS, as well as surface defects like oxygen (Vo), and sulphur (Vs) vacancies. The lowest photoluminescence of BTZS (70-30) clearly substantiated the observed high photocatalytic activity. The scavenger outcomes validated that superoxide radicals (•O2−) and holes (h+) played predominant role in the degradation of MO and a detailed explanation was provided for the plausible mechanism.

Development of δ-Bi2O3/Bi2SiO5 heterostructures based on biogenic silica for photocatalytic treatment from organic pollutants

ABSTRACT δ-Bi2O3/Bi2SiO5 heterostructural photocatalysts with different contents of bismuth in samples (X-Bi-Si, where X = 10–60% Bi2O3) were prepared by the facile sol–gel method using bismuth nitrate and biogenic silica from rice husk biomass as precursors. FT-IR, scanning electron microscope, XRD, energy-dispersive X-ray fluorescence, and UV–Vis methods were systematically used to characterize the as-obtained materials. The photodegradation of methyl orange (MO) in neutral aqueous solutions (pH (6.8)) under UV irradiation was studied to evaluate their photocatalytic activities. The phase composition, morphology, and photocatalytic activity of the samples depended on the content of bismuth oxide in the samples. The maximum degree of MO degradation was 45% for 50-Bi-Si samples containing photoactive δ-Bi2O3 and Bi2SiO5 phases.

Bi2O3/MoO3 composites: A synergistic approach towards photocatalytic degradation and enhanced antimicrobial activity

The escalating concerns over the water containments and public health pose the great threat to sustainable environment. In this quest there is strong need of advance materials with sustainable solutions that provides the innovative methods for wastewater treatment. This article explores an in-depth study of synergistic effect of composites for photo degradation of methyl orange (MO) and tetracycline (TC) along with the antimicrobial activity. The composites were synthesized through facile hydrothermal method with the weight concentration of 1%, 3%, 5%, 7% of MoO3 represented by BOMO-1, BOMO-3, BOMO-5 and BOMO-7 respectively. Enhanced photocatalytic reported attributed to efficient charge separation and active sites formation of composites. Moreover significantly improved antibacterial activity of nanostructures occurs because of hetrojunction formation. The synergistic potential of Bi2O3/MoO3 composites resulted the generation of Reactive oxygen species (ROS) which performs the redox reaction to improved their activities. Additionally the fabricated nanomaterials evaluated by different characterization to check their optical, structural, morphological and electronic properties. The dual functionality of Bi2O3/MoO3 makes it a promising material for wastewater treatment as well as environmental remediation. These results predict its widely use for advance catalysis and hydrogen evolution procedure in near future.

Oxygen-deficient AgIO3 for efficiently photodegrading organic contaminants under natural sunlight

Defect engineering is regarded as an effective strategy to boost the photo-activity of photocatalysts for organic contaminants removal. In this work, abundant surface oxygen vacancies (Ov) are created on AgIO3 microsheets (AgIO3-OV) by a facile and controllable hydrogen chemical reduction approach. The introduction of surface Ov on AgIO3 broadens the photo-absorption region from ultraviolet to visible light, accelerates the photoinduced charges separation and migration, and also activates the formation of superoxide radicals (•O2−). The AgIO3-OV possesses an outstanding degradation rate constant of 0.035 min−1, for photocatalytic degrading methyl orange (MO) under illumination of natural sunlight with a light intensity is 50 mW/cm2, which is 7 and 3.5 times that of the pristine AgIO3 and C–AgIO3 (AgIO3 is calcined in air without generating Ov). In addition, the AgIO3-OV also exhibit considerable photoactivity for degrading other diverse organic contaminants, including azo dye (rhodamine B (RhB)), antibiotics (sulflsoxazole (SOX), norfloxacin (NOR), chlortetracycline hydrochloride (CTC), tetracycline hydrochloride (TC) and ofloxacin (OFX)), and even the mixture of organic contaminants (MO-RhB and CTC-OFX). After natural sunlight illumination for 50 min, 41.4% of total organic carbon (TOC) for MO-RhB mixed solution can be decreased over AgIO3-OV. In a broad range of solution pH from 3 to 11 or diverse water bodies of MO solution, AgIO3-OV exhibits attractive activity for decomposing MO. The MO photo-degradation process and mechanism over AgIO3-OV under natural sunlight irradiation has been systemically investigated and proposed. The toxicities of MO and its degradation intermediates over AgIO3-OV are compared using Toxicity Estimation Software (T.E.S.T.). Moreover, the non-toxicity of both AgIO3-OV catalyst and treated antibiotic solution (CTC-OFX mixture) are confirmed by E. coli DH5a cultivation test, supporting the feasibility of AgIO3-OV catalyst to treat organic contaminants in real water under natural sunlight illumination.

Photocatalytic bioheteronanostructures by integrating multicomponent Cu2O–Au nanoparticles into ZnO-coated butterfly wings colored by photonic nanoarchitectures

Complex biological photocatalytic heteronanostructures were produced by the integration of different multicomponent Au–Cu2O nanoparticles (NPs) into the blue-colored photonic nanoarchitectures occurring in the wings of male Polyommatus icarus butterflies. Both bare wings and wings conformally coated by 15-nm ZnO by atomic layer deposition were used as substrates. The NPs were characterized by UV–visible spectroscopy, focus stacking optical microscopy, and electron microscopy. After the deposition of the different NPs, the photocatalytic performance of the samples under visible light illumination was tested by the photodegradation of methyl orange in aqueous solution monitored continuously by an immersion probe. It was found that the components of the biological hetero-nanoarchitecture: ZnO-coated wings and wings without ZnO with deposited NPs exhibited poor catalytic performance. But the combined system: ZnO-coated wings with NPs deposited onto them exhibited sixfold to eightfold increase in their catalytic performance. This increase is attributed to the extension of the ZnO absorption into the visible range and to the formation of the heterojunction between the n-type ZnO and the p-type Cu2O NPs which resulted in the charge transfer of the photogenerated carriers. As the samples exhibited good stability under the continuous magnetic stirring, they can be used in flow-through systems suitable for wastewater remediation. The biological templates for the hetero-nanoarchitectures were produced by the controlled breeding of herbivorous insects, which does not raise any environmental concerns.

Effect of vanadium doping on magnetic properties and photocatalytic activity of magnesium ferrite: Role of surface charge and dyes adsorption

Spinel magnesium ferrite nanoparticles play an important role in a variety of disciplines, particularly in environmental applications as magnetically separable photocatalysts. MgFe2-1.67xVxO4 with x = 0.0, 0.05, 0.10, and 0.20 were synthesized using the combustion method. X-ray diffraction (XRD) indicated that only the cubic spinel ferrite phase with the Fd3m space group was formed in all doped Mg-ferrite. The cell parameter increased at (x = 0.05) and thereafter dropped with increasing vanadium ion concentration. The saturation magnetization (Ms) increased from 26.181 to 28.953 with x = 0.05, then decreased with further doping. Additionally, the band gap energy (Eg) decreased with increasing v-doping; Eg for MgFe2O4 was 1.79 eV and decreased to 1.71 eV at x = 0.20. All the V-doped MgFe2O4 shows an increase in the efficiency of methyl orange photodegradation relative to undoped MgFe2O4. The boosting in photocatalytic activity of V-doped MgFe2O4 due to electron-hole separation, caused by oxygen vacancies. V-doping changes the point of zero charge of ferrite and increase the MO adsorption, consequently, enhances the photocatalytic degradation. V-doped MgFe2O4 has proved to be an effective magnetically separable and easily reusable photocatalyst withstand seven cycles of recyclability using MgFe2-1.67xVxO4 with x = 0.10, and only 4 % loss of its photocatalytic performance.

Elimination of synthetic dyes by clamshell derived photo-active hydroxyapatite

Herein, a novel designed hydroxyapatite (HAp) derived from freshly calcined clamshell waste through the wet precipitation method was synthesized. HAp has been developed as a heterogeneous photocatalyst for the anionic dye methyl orange (MO) degradation. The pH on synthesizing HAp was varied in basic conditions. The results show HAp formed at pH more than 10. The MO photodegradation was done under UV-light irradiation for 120 min. HAp catalyst showed the optimum MO degradation efficiency using rod-like structure HAp synthesized at pH 12. HAp with optimum photodegradation efficiency was optimized for the catalyst loading and the pH of the MO solution. MO at pH 6 with 0.05 g catalyst loading showed the highest degradation efficiency around 97 % using HAp prepared at pH 12 with band gap at 4.990 eV. This finding brings a new insight on natural sources materials as photo-active in sustainable of persistent water pollutants.

Utilizing waste corn straw to photodegrade methyl orange and methylene blue: Photothermal effect of biochar enhances photodegradation efficiency

The burning of corn straw will cause serious air pollution, and the utilization of corn straw can avoid the burning of corn straw and reduce environmental pollution. The pyrolysis of corn straw into biochar (BC) is a promising approach to apply corn straw in environmentally sustainable development. Dye wastewater such as methyl orange (MO) and methylene blue (MB) is a pollution that poses a threat to human health and the environment. Herein, biochar/TiO2 (BC/TiO2) and biochar/ZnO (BC/ZnO) were prepared by pyrolysis of corn straw for the photodegradation of MO and MB in water. The MO removal rates of BC/TiO2 and BC/ZnO are up to 83.3 % and 76.2 %, respectively, and the MB removal rates of BC/TiO2 and BC/ZnO are 78.6 % and 71.4 %, respectively. The photothermal effect of BC improves the surface temperature of photocatalysts and promotes the separation and transfer of photogenerated electron-hole pairs, enhancing the photodegradation of MO and MB efficiencies. Three-dimensional (3D) FDTD simulations were performed to investigate the mechanism of photothermal effect in BC/TiO2 and BC/ZnO. This work provides a promising approach to the utilization of corn straw.

Efficient Catalytic Degradation of Methyl Orange by Various ZnO-Doped Lignin-Based Carbons.

Herein, a series of ZnO-doped lignin-based carbons (LC/ZnO) were successfully prepared from different types of lignin and used for methyl orange (MO) photocatalytic degradation. The apparent morphology, internal structure, and photoelectric properties of prepared LC/ZnO composites and their effects on subsequent MO photocatalytic degradation were investigated by various characterization techniques. The results showed that the LC/ZnO composites that were prepared in this work mainly consisted of highly dispersed ZnO nanoparticles and lignin-based carbon nano-sheets, which were beneficial for subsequent photogenerated electrons and holes formation, dispersion, and migration. The MO could be significantly degraded with various ZnO-doped lignin-based carbons, especially over the LCSL/ZnO, and the maximum degradation rate was 96.9% within 30 min under the simulated 300w sunlight exposure. The experiments of free radical elimination showed that the photocatalytic degradation of MO over LC/ZnO were a result of the co-action of multiple free radicals, and h+ might play the predominant roles in MO degradation. In addition, the pH of the solution had little effect on MO degradation, and the MO could be effectively degraded even in an alkaline solution of pH = 12.0. The cycling experiments showed that the prepared LC/ZnO had a good stability for MO photodegradation, especially for LCSL/ZnO, even after 5 times recycling, and the degradation rate of MO only dropped from 97.0% to 93.0%. The research not only provided a fundamental theory for the efficient photocatalytic degradation of MO by LC/ZnO composites, but also offered a new insight into lignin valorization.

Refinement of Nanoporous Cu by Polyvinylpyrrolidone and Photodegradation of Methyl Orange by Cu2O Nanowires and Nanoporous Cu Photocatalysts

Refinement of nanoporous Cu (NP Cu) by the addition of Polyvinylpyrrolidone (PVP) in HF solution during dealloying of Ti40.6Zr9.4Cu40.6Ni6.3Sn3.1 amorphous ribbons and effect of the surface coverage of Cu2O nanowires obtained by immersing NP Cu in dehydrated ethanol on the photodegradation of methyl orange (MO) pollutants were investigated. The sizes of pores and ligaments of NP Cu decrease significantly with the increase of PVP concentration in the dealloying solutions, accompanied by a drastic decrease in the surface diffusivity and the dislocation defect densities. The surface coverage of Cu2O nanowires becomes higher with an increase of the PVP reagents. The Cu2O nanowires@nanoporous Cu (Cu2O@NP Cu) catalysts show excellent photocatalytic activity towards the degradation of MO under the sunlight due to the existence of large amounts of heterojunctions between Cu2O nanowires and Cu ligaments in nanoscale.

MgAl Oxide Coatings Modified with CeO2 Particles Formed by Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy: Photoluminescent and Photocatalytic Properties

MgAl oxide coatings composed of MgO and MgAl2O4 phases were doped with CeO2 particles via plasma electrolytic oxidation (PEO) of AZ31 magnesium alloy in a 5 g/L NaAlO2 water solution. Subsequently, particles of CeO2 up to 8 g/L were added. Extensive investigations were conducted to examine the morphology, the chemical and phase compositions, and, most importantly, the photoluminescent (PL) properties and photocatalytic activity (PA) during the photodegradation of methyl orange. The number of CeO2 particles incorporated into MgAl oxide coatings depends on the concentration of CeO2 particles in the aluminate electrolyte. However, the CeO2 particles do not significantly affect the thickness, phase structure, or surface morphology of the coatings. The PL emission spectrum of MgAl oxide coatings is divided into two bands: one in the 350–600 nm range related to structural defects in MgO, and another much more intense band in the 600–775 nm range attributed to the F+ centres in MgAl2O4. The incorporated CeO2 particles do not have a significant effect on the PL intensity of the band in the red spectral region, but the PL intensity of the first band increases with the concentration of CeO2 particles. The PA of MgAl/CeO2 oxide coatings is higher than that of pure MgAl oxide coatings. The MgAl/CeO2 oxide coating developed in aluminate electrolyte with a concentration of 2 g/L CeO2 particles exhibited the highest PA. The MgAl/CeO2 oxide coatings remained chemically and physically stable across multiple cycles, indicating their potential for applications.

Increasing photocatalytic activity of magnetite NPs with the inclusion of methyl orange and Evans blue functional groups in the photoactivation of acid sites

In this paper, The photocatalytic reactions of methyl orange (MO) and Evans Blue (EB) are conducted on four distinct magnetite nanoparticles (NPs) samples. This study investigates, for the first time in literature, the impact of the inclusion of chromophores and auxochromes in the photoactivation of Brönsted and Lewis’s acid sites on the photocatalytic activity. In so doing, free functional groups of MO and EB that are not photodegraded have been analyzed using FTIR spectroscopy. This analysis leads to infer photoactivated acid site densities. FTIR analysis of initial residual solutions of MO and EB revealed lower contents of free functional groups of EB compared to MO. Based on this finding, it would be expected that EB would demonstrate better photodegradation due to the lower contents of its functional groups. However, the obtained results contradicted this assumption, indicating an opposite behavior. Moreover, FTIR analysis of final residual solutions revealed that functional groups of MO were highly photodegraded compared to EB. Also, calculated MO photodegradation capacities, yields, and kinetics constants were found to be higher than those of EB. This suggests that parameters other than band gap energy may control the photoactivation of Brönsted and Lewis’s acid sites and thus photocatalytic activity. Indeed, functional groups are involved in increasing the photocatalytic activity. The higher contents of MO functional groups lead to better increasing the photocatalytic activity of magnetite NPs.

Surface plasmon resonance and heterojunction formation in Ag/AgI/Ag3VO4 photocatalyst for efficient photodegradation of methyl orange

A novel Ag/AgI/Ag3VO4 plasmonic photocatalyst was synthesized through ion exchange technique, followed by photoreduction. Various techniques including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible diffuse reflection (UV-DRS) were undertaken to characterize the phase structure, morphology, chemical composition, and optical properties of Ag/AgI/Ag3VO4. The catalytic activity measurements were conducted using decomposing methyl orange (MO) irradiated with visible light. Compared with Ag/AgI and pure Ag3VO4, the Ag/AgI/Ag3VO4 composite significantly enhanced catalytic activity, resulting in 94.4% degradation of MO within 15 min of visible light. Ag/AgI/Ag3VO4 exhibited remarkable catalytic activity, which was because of the intimate heterojunction formation, and the surface plasmon resonance (SPR) effect of Ag nanoparticles (NPs), thereby boosting carrier separation. Furthermore, quenching tests confirmed that the majority of active species were •O2− and h+ during the catalytic reaction. This study discussed a plausible catalytic system mechanism that effectively separates photocreated carriers in the Ag/AgI/Ag3VO4 composite to enhance MO degradation activity.

Advanced Photodegradation of Azo Dye Methyl Orange Using H2O2-Activated Fe3O4@SiO2@ZnO Composite under UV Treatment.

The Fe3O4@SiO2@ZnO composite was synthesized via the simultaneous deposition of SiO2 and ZnO onto pre-prepared Fe3O4 nanoparticles. Physicochemical methods (TEM, EDXS, XRD, SEM, FTIR, PL, zeta potential measurements, and low-temperature nitrogen adsorption/desorption) revealed that the simultaneous deposition onto magnetite surfaces, up to 18 nm in size, results in the formation of an amorphous shell composed of a mixture of zinc and silicon oxides. This composite underwent modification to form Fe3O4@SiO2@ZnO*, achieved by activation with H2O2. The modified composite retained its structural integrity, but its surface groups underwent significant changes, exhibiting pronounced catalytic activity in the photodegradation of methyl orange under UV irradiation. It was capable of degrading 96% of this azo dye in 240 min, compared to the initial Fe3O4@SiO2@ZnO composite, which could remove only 11% under identical conditions. Fe3O4@SiO2@ZnO* demonstrated robust stability after three cycles of use in dye photodegradation. Furthermore, Fe3O4@SiO2@ZnO* exhibited decreased PL intensity, indicating an enhanced efficiency in electron-hole pair separation and a reduced recombination rate in the modified composite. The activation process diminishes the electron-hole (e-)/(h+) recombination and generates the potent oxidizing species, hydroxyl radicals (OH˙), on the photocatalyst surface, thereby playing a crucial role in the enhanced photodegradation efficiency of methyl orange with Fe3O4@SiO2@ZnO*.

Merits of photocatalytic activity of synthesized (ZnxCu(1−x)Fe2O4); x = (0–1) magnetic nanoparticles for wastewater treatment

Synthesis of crystalline zinc copper ferrite nanoparticles was achieved via a simple co-precipitation method. Scanning electron microscope (SEM) is utilized to give the morphological characterization of the prepared samples. A transmission electron microscope (TEM) was employed for further identification and confirmation of the particle size and morphology. Moreover, X-ray diffraction (XRD) and Fourier transformation infrared (FTIR) spectroscopy were utilized to examine crystalline structure and chemical structure, respectively. The photocatalytic performance of Zn0.5Cu0.5Fe2O4 nanoparticles under UV light was assessed by decolorization of methyl orange (MO) azo dye. The efficiency of photocatalytic degradation of 20 ppm of MO by Zn0.5Cu0.5Fe2O4 nanoparticles 15 mg was 96% after 135 min at an ambient temperature of 25 °C and pH value of 3. Further interpretation was carried out and a proposed mechanism for the MO photodegradation over Zn0.5Cu0.5Fe2O4 nanoparticles was suggested.

Novel ternary PPy–ZnFe2O4/fly ash-cenosphere photocatalysts for photodegradation of methyl orange under UV light

In this study, fly ash cenospheres (FACs), characterized by their floating properties and inherent photocatalytic activity, were used as a carrier to support ZnFe2O4 material and doped with conductive polymer polypyrrole (PPy) to prepare a novel ternary PPy–ZnFe2O4/FACs (PPy–ZF) composite catalyst. X-ray diffraction, Fourier transform infrared spectroscopy, TEM, and scanning electron microscopy were used to characterize the structure, morphology, and optical properties of the samples prepared. In particular, a 20 mg/L methyl orange (MO) solution at pH 4 was given 0.075 g of PPy–ZF catalyst to add, and after 30 min of dark adsorption, followed by irradiation for 180 min, 98.54% of the MO was removed. The material was also shown to have good stability and reusability through three cycles of use. Additionally, the material exhibited good photocatalytic activity for other dyes. The results of photocatalytic experiments showed their significantly enhanced photocatalytic activity toward MO, which was mainly attributed to the synergistic effect of PPy and ZnFe2O4 on the surface of FACs, leading to a high separation efficiency and a low rate of photogenerated charge complexation. In addition, cyclic tests demonstrated the stability and reusability of the composite. The leading role in the photocatalytic degradation of MO was demonstrated by the radical trapping experiment, which showed ·O2 − and h+. The present study can significantly improve the photocatalytic performance of the floating materials of ZnFe2O4/FACs, which is beneficial to solve the current energy crisis and environmental pollution problems. It has certain reference significance to solve the problems of environmental pollution, waste recycling, and catalyst recycling in the future.

Hydrophobic and Photocatalytic Treatment for the Conservation of Painted Lecce stone in Outdoor Conditions: A New Cleaning Approach

Self-cleaning and hydrophobic treatments based on TiO2 and SiO2 nanoparticles are widely applied for the preservation of cultural heritage materials, to improve their resilience in polluted environments. Excellent results have been obtained on stone materials, but experiments on painted stone surfaces, such as wall paintings and polychrome plasters used in historic buildings, are still limited. In this work, we present a study on the use of water dispersions of TiO2 nanoparticles obtained via sol-gel and organically modified silica (OrMoSil) for cleaning and protective purposes on Lecce stone, a carbonate stone, widely used for its excellent workability but easily attacked by atmospheric agents and pollutants. First, we evaluated the harmlessness of the treatment on Lecce stone through colorimetric tests, water absorption by capillarity and permeability to water vapor. The photocatalytic activity of the TiO2 nanoparticles was assessed by photo-degradation of methyl orange and methylene blue dyes. The dispersion was then applied on painted samples prepared according to ancient recipes to confirm the effectiveness of the cleaning. The proposed TiO2/OrMoSil-based coating can act as a self-cleaning and protective treatment on lithic surfaces to prevent degradation phenomena and preserve the original appearance of the monument.

Synthesis and application of ZSM-5/Graphene composite for photocatalytic degradation of industrial dyes

Various materials and technologies are being employed to address the concern of increased wastewater generation. In this work, the synthesis of ZSM-5 (Zeolite Socony Mobil-5) and graphene (GR) composite, their characterisation, and application for the removal of dyes are presented. Two composites of ZSM-5 and GR composites were prepared via the hydrothermal method by varying the loading amount of GR, i.e. 1% and 5%, and labelled as GZ1 and GZ5. The parent and composite materials were characterised using field emission scanning electron microscope (FE-SEM), x-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), x-ray photoelectrons spectroscopy (XPS), Raman, and Fourier transform infrared (FTIR). The materials were then employed for the photodegradation of methyl orange (MO) dye. The adsorption efficiencies for ZSM-5, GR, GZ1, and GZ5 were found as 0%, 17.8%, 0%, and 16% respectively. According to photodegradation results, the GZ1 composite exhibits the maximum degradation efficiency of 75.3% for 20 ppm of MO, within 180 min of light exposure. The scavenger studies were performed to evaluate the role of active oxygen species (AOS) in the photocatalysis mechanism. All studies were performed with the catalyst dosage of 0.5 mg ml−1. The degradation efficiencies for GR, GZ5, and Z5 were reported as 34.2%, 20.8%, and 17.5%, respectively. On increasing the irradiation time to 240 min, the degradation efficiency of GZ1 reached 92%. The removal efficiencies for MO (7 ppm) and methyl blue (5 ppm) in a 12-ppm dye mixture were observed to be 98% and 97.2% respectively within 180 min of light exposure with GZ1 composite.