Complete Photodegradation Research Articles

Perovskite derived oxygen vacancies-rich BiOBr nanosheets for highly efficient photocatalysis

BiOBr has garnered significant attention for photocatalysis owing to its distinctive layered structure. Nevertheless, it is full of challenges to synthesize high-quality BiOBr nanosheets by a simple room-temperature strategy due to the rapid chemical reaction between (Bi2O2)2+ cations and Br- anions. Herein, a Cs3Bi2Br9 conversion strategy is proposed to fabricate BiOBr nanosheets with highly exposed (001) facets. BiOBr nanoclusters can grow on the surface of Cs3Bi2Br9 during the hydrolysis process, which can prevent further corrosion of Cs3Bi2Br9, resulting in a sluggish BiOBr formation rate. During the conversion process, atom rearrangement occurs, leading to the creation of abundant oxygen vacancies. Furthermore, through precise adjustment of the amount of Cs, we can finely modulate the width and thickness of BiOBr nanosheets. As a result, the optimal sample achieves complete photodegradation of rhodamine B under 12.5 min of light irradiation. Utilizing this facile and convenient preparation method, an ohmic heterojunction comprising MXene and BiOBr has been synthesized, effectively promoting the separation of photogenerated carriers. Excitingly, the fabricated BiOBr/MXene exhibits higher photocatalytic efficiency than the single BiOBr, which can degrade rhodamine B within 7.5 min.

Complete photodegradation of tetracycline induced by surface microenvironment of graphitic carbon nitride/silver phosphate

Silver phosphate (Ag3PO4) is a promising photocatalyst, but the photo-corrosion issue limits an effective and comprehensive photocatalysis degradation of tetracycline (TC). In this work, a unique graphitic carbon nitride-Ag3PO4 (KCN-AP(40 %)) core-shell structure was prepared via a simple chemical sedimentation method. The unique graphitic carbon nitride sheet encloses Ag3PO4 to trap excited electrons from the conduction band position of Ag3PO4, suppressing the reduction of Ag+ and Ag metal deposition on the surface of Ag3PO4. Under visible light irradiation, the optimized KCN-AP(40 %) can photodegrade nearby 100 % of TC within 20 min with a first-order kinetic constant of 0.127 min−1, which is 3.34 and 3.97-folds higher than those of Ag3PO4 and graphitic carbon nitride, respectively. A series of factors that may affect photoactivity of KCN-AP (40 %) including pH, inorganic ions, and organic matter are investigated. In final, the photodegradation mechanisms and intermediates were proposed based on ex-situ HPLC-MS. This work explains the deep decomposition of TC and presents a facile approach for designing and manufacturing Ag3PO4 based nanohybrids.

Full carbon upcycling of organophosphorus wastewater enabled by interface photolysis

The key of wastewater treatment is to reduce the toxicity of organic pollutants and ideally undergo mineralization, typically accompanying the formation of greenhouse gas CO2 in large amounts. Here, a full carbon upcycling strategy for efficient valorization of organic phosphorus (OPs) contaminants enabled by interface photolysis was developed, in which the van der Waals interface effect based on the interfacial heterojunction interaction could efficiently regulate the electron density of the UCN/CdS NPs photocatalyst interface to benefit the construction of the interface-orienteering electron pump and edge active sites. The synergistic catalysis of ·OH on the C sites and holes on the Cd sites at the photocatalyst interface edge could realize the complete photodegradation of glyphosate wastewater in 2 h to exclusively afford gas fuel CO (4124 μmol g−1) and glycine (86 %), which was likewise applicable to an extensive scope of OPs for nigh quantitative carbon upcycling. Quantum calculations elaborated that the Cd edge sites with the ability to enrich holes induced by the van der Waals interface effect could reduce the activation energy of CP bond cleavage of glyphosate activated by ·OH, resulting in CP bond scission selectivity of ca. 91.5 %, which is vital to full carbon upcycling. The oriented interface engineering offers a more eco-friendly photocatalytic protocol to facilitate both wastewater treatment and carbon resource recovery.

Surface plasmon resonance effect of silver decorated on BiOCl and its enhanced sunlight-active photodegradation of rhodamine B (RhB) dye and ofloxacin (OFL) antibiotic

Fast electron-hole recombination rate is the major problem concerning low photocatalytic performance of the UV-active BiOCl photocatalyst. To overcome this drawback, decoration of noble metals on the surface of semiconducting photocatalysts can be regarded as one of the promising strategies to improve the photoactivity due to a synergy of heterojunction formation and surface plasmon resonance effect. However, the huge dosage (larger than 10 wt%) of the noble metal incorporated on photocatalyst surface causes high cost in production of the final product. In this work, solvothermally grown BiOCl photocatalyst was decorated with low silver metal loading of 2.5–10 wt%. The tetragonal 2.5 wt%Ag/BiOCl photocatalyst exhibited complete photodegradation of Rhodamin B (RhB) dye and ofloxacin (OFL) antibiotic under natural solar light. The enhancement of the resultant photocatalytic efficiency is possibly due to increasing of charge carrier separation efficiency at the interface together with the formation of the Schottky barrier at the Ag/BiOCl interface so that an improvement in quantum efficiency and an increase in the photocatalytic activity are expected. In addition, well dispersion of silver on BiOCl also leads to red shift in the absorption of light toward visible regime. This is due to the local surface plasmon resonance (LSPR) effect of Ag on BiOCl surface. The synthesized Ag/BiOCl photocatalyst displays enhanced photocatalytic activity with great structural stability after five times of use indicating its excellent cycling ability. The present finding offers a new pathway to create a silver decorated BiOCl for complete removal of harmful dye and antibiotic in aqueous solution. The treatment of toxic organic pollutants in the natural water can be done very easily by utilization of the green technology based on photocatalytic method with the beneficial of abundant solar energy.

Ferroelectric‐Photocatalysts for Degradation of Phthalate: Doped BiFeO3‐Graphene Oxide Nanocomposites

AbstractA complete photocatalytic degradation of dibutyl phthalate (DBP) using ferroelectric doped‐bismuth ferrite‐ (BiFeO3; BFO) graphene oxide (GO) nanocomposites is achieved. The local ferroelectric properties of doped BFO photocatalysts supported onto GO is well‐utilized for photodegradation of pollutant. A complete photodegradation of DBP under ultraviolet light irradiation is achieved within 2.5 h, traced by gas chromatography. The best photocatalytic activity of Bi0.95Ag0.05Fe0.95Mn0.05O3‐GO (ABMGO) nanocomposite is attributed to its large intrinsic local ferroelectric polarization, which suppresses the recombination of photoinduced charge carriers and the presence of Ag+ and Mn4+ as new active sites on the large surface of ABMGO speeds up the photodegradation of DBP. The possible mechanism of photodegradation of DBP is presented using mass spectrometry includes several intermediate products; phthalic acid, benzoic acid, benzaldehyde, and hydroquinone and 3‐methyl butyric acid which are harmless for the environment compared to DBP.

Photocatalytic wastewater treatment and disinfection using green ZnO-NP synthesized via cera alba extract

This is the first report to describe the green fabrication of zinc oxide nanoparticles starting with cera alba (beeswax) extract as an eco-friendly reducing and capping agent. The reaction of zinc nitrate with an aqueous extract of Cera Alba resulted in the formation of zinc oxide nanoparticles (ZnO-W). Treatment of ZnO-W at 550 °C gave pure zinc oxide nanoparticles (ZnO-G). Various techniques, including FT-IR, XRD, TGA, SEM, and HR-TEM, were used to analyze the structures of synthesized nanoparticles. A methylene blue dye solution was used to evaluate the photocatalytic activity. The impact of catalyst dose, reaction time, and pH on photocatalytic degradation under sunlight was studied. At optimal conditions, complete photodegradation of 10 ppm methylene blue occurs in 40 min. The antimicrobial activity of ZnO-G was evaluated against three microbial strains: Bacillus cereus, Escherichia coli, and Candida albicans. The impact of exposing the ZnO-G to various light wavelengths (265 nm, 346 nm, visible light, and sunlight) to inhibit microbial growth was investigated. The best result was obtained when ZnO-G was exposed to 265 nm light. This study's findings support using ZnO-G prepared via cera alba as a powerful photocatalytic and antimicrobial agent.

One-pot synthesis of Ag-modified SrTiO3: synergistic effect of decoration and doping for highly efficient photocatalytic NOx degradation under LED

Strontium titanate is an ideal cubic-structure perovskite oxide that finds application in hydrogen production and water pollutants degradation field. However, its photocatalytic activity is limited under UV irradiation due to its wide energy band bap (∼ 3.2 eV). To overcome this limitation, different strategies, such as metal-doping or metal-decoration, have emerged. Here, Ag-modified-SrTiO3 photocatalysts were prepared for the first time by a cheap, simple and sustainable approach based on the use of Ag-enriched wastewaters. The Ag-decorated SrTiO3 synthesized by a two steps method photodegraded by nearly 77% of NOx within 3 h. The Ag-modified SrTiO3 prepared by aone-pot synthesis led to a doubly modification of the oxide: Ag+ doping and Ag nanoparticles-decoration. In this case the use of Ag-enriched wastewaters led to poor photocatactivity of the photocatalyst, probably related to the presence of other metals in the waste. However, the use of a pure Ag precursor permitted the fabrication of a highly efficient material achieving complete photodegradation of NOx, exhibiting a photoactivity 4 times higher than bare SrTiO3 and 1.3 times more active than Ag-decorated material. The photocatalytic enhancement was attributed to the combined effect of Ag-doping and Ag-decoration on SrTiO3, which contributed to a narrow band gap (2.80 eV), as well as the formation of heterojunctions that promotes the separation of photogenerated charges, respectively. This material showed good stability during recycling tests, maintaining high performances after five cycles. Eventually, active species were identified using various scavengers by trapping holes and radicals generated during the photocatalytic degradation process.

One-pot synthesis of porous TiO2/BiOI adsorbent with high removal efficiency and excellent recyclability towards tetracyclines

Considerable efforts have focused on pursuing the efficient removal of antibiotic contaminants by combining adsorbents with photocatalysts. However, the reported adsorbents/photocatalysts still suffer from critical drawbacks including low adsorption rate, low mineralization rate, and complicated preparation procedures, greatly restricting their practical application. In this work, we report a facile method to develop porous TiO2/BiOI adsorbent through a one-pot hydrothermal process and subsequently low-temperature calcination (280 °C). Adsorption experiment shows that porous TiO2/BiOI realizes almost complete removal (99.4%) of tetracyclines, far beyond the values of BiOI (20.2%) and TiO2 (71.1%). Notably, one-pot synthesis promotes the mass production of TiO2/BiOI without obvious loss in adsorption capacity. More importantly, TiO2/BiOI adsorbent can be simply regenerated by complete photodegradation of the adsorbed tetracyclines on TiO2/BiOI, and regains above 98% of its adsorption capacity for 10 cycles, successfully overcoming the limitations of environment-unfriendly regeneration conditions, low adsorption capacity, and poor recyclability for most of the reported adsorbents/photocatalysts. Additionally, adsorption mechanism is deduced to be mainly electrostatic attraction, hydrogen bonding, and pore filling according to adsorption performance. Therefore, the design concept we present here provides a new perspective for the development of reactive adsorbents with excellent removal efficiency and recyclability through a facile one-pot synthesis.

Photoactive conjugated polymer-based strategy to effectively inactivate RNA viruses

To efficiently combat viral infectious diseases, it is important to develop broadly applicable countermeasures, and efficient antiviral systems can be developed by elaborating the relationship of antiviral efficiency with the interactions between antiviral agents and viruses. In the present study, conjugated polymer (CP)-based photodynamic therapy was used to inhibit RNA virus infections. A severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudotyped virus composed of an SARS-CoV-2 envelope coated with the S protein and luciferase RNA genome was employed to assess antiviral efficiency. Three cationic CPs with different backbone structures, fluorene-co-phenylene (PFP), thiophene (PMNT), and phenylene vinylene (PPV), exhibit different photoinactivation effects. The highly efficient photoinactivation of PPV and PMNT is derived from the complete photodegradation of spike proteins, nucleocapsid proteins and nucleic acids of SARS-CoV-2 after binding to the viral spike proteins. Although PFP showed the highest efficiency in the photodegradation of spike proteins due to its strong binding affinity, ineffective viral inhibition was observed, which occurred because the viral gene was partially damaged under light irradiation and the process of delivering the viral gene to cells received assistance. This work preliminarily reveals the effect of CP-virus interactions on their photoinactivation activity and should be beneficial for further research on the development of highly efficient antiviral PDT agents.

Photodegradation study of the fenvalerate insecticide by 1H NMR, 13C NMR, and GC-MS and structural elucidation of its transformation products

The photolysis of fenvalerate, a pyrethroid insecticide, was studied in acetonitrile by 1H nuclear magnetic resonance (NMR) and 13C NMR to identify the site of bond cleavage and gas chromatography-mass spectrometry (GC-MS) to establish the chemical structure of fenvalerate photoproducts. Ultraviolet (UV) irradiation of fenvalerate solutions was performed for 18 h with a solar light simulator, and the photolysis reaction obeyed first-order kinetics. Photolysis half-life time (t1/2) values ranged between 15.25 and 21.63 h (mean photodegradation percentage = 51.7 %) for 1H NMR and between 4.55 and 8.06 h (mean photodegradation percentage > 80 %) for 13C NMR. We observed five sites of bond cleavage, namely carbonyl-tertiary carbon, tertiary carbon-tertiary carbon, carbonyl-oxygen, carboxyl-tertiary carbon, and aromatic carbon-tertiary carbon, yielding photoproducts formation. GC-MS was associated with 1H NMR and 13C NMR to obtain a complete photodegradation mechanism. Before UV irradiation, two chromatogram peaks were obtained, due to the two fenvalerate isomers. Under irradiation, both peaks decreased, and new peaks appeared, corresponding to photoproduct formation. After a 12- to 13-h irradiation, 99.39 % of fenvalerate was degraded with a mean rate constant of 0.305 h–1. The chemical structure of the formed photoproducts was identified, either by using the National Institute of Standards and Technology (NIST) mass spectral database or by interpreting the mass spectra. Finally, a detailed mechanism was proposed for fenvalerate photodegradation.

Perovskite LaNiO3/Ag3PO4 heterojunction photocatalyst for the degradation of dyes.

Pristine lanthanum nickelate (LaNiO3), silver phosphate (Ag3PO4) and perovskite lanthanum nickelate silver phosphate composites (LaNiO3/Ag3PO4) were prepared using the facile hydrothermal method. Three composites were synthesized by varying the percentage of LaNiO3 in Ag3PO4. The physical properties of as-prepared samples were studied by powder X-ray diffraction (pXRD), Fourier-transform infrared (FT-IR), Scanning electron microscopy (SEM) and Energy-dispersive X-ray (EDX). Among all synthesized photocatalysts, 5%LaNiO3/Ag3PO4 composite has been proved to be an excellent visible light photocatalyst for the degradation of dyes i.e., rhodamine B (RhB) and methyl orange (MO). The photocatalytic activity and stability of Ag3PO4 were also enhanced by introducing LaNiO3 in Ag3PO4 heterojunction formation. Complete photodegradation of 50mg/L of RhB and MO solutions using 25mg of 5%LaNiO3/Ag3PO4 photocatalyst was observed in just 20min. Photodegradation of RhB and MO using 5%LaNiO3/Ag3PO4 catalyst follows first-order kinetics with rate constants of 0.213 and 0.1804min-1, respectively. Perovskite LaNiO3/Ag3PO4 photocatalyst showed the highest stability up to five cycles. The photodegradation mechanism suggests that the holes ( h +) and superoxide anion radicals plays a main role in the dye degradation of RhB and MO.

Modification of a Z-scheme ZnO-CuO nanocomposite by Ag loading as a highly efficient visible light photocatalyst

This paper has conducted a comparative study between ZnO-CuO and ZnO-CuO-Ag nanocomposites from a characterization and photodegradation mechanism point of view. The photocatalysts with different CuO contents and Ag loadings were synthesized through a quick and convenient co-precipitation method. The microstructural analysis showed the ZnO nanorods and CuO quasi-spherical formation with uniform distribution and proper contact, while Ag induced morphological changes to aggregation of spherical nanoparticles. X-ray photoelectron spectroscopy (XPS) proved the presence of metallic Ag (Ag0) in the Ag-loaded samples. 5 mol.% Ag loading in the ZnO-7.5 mol.%CuO nanocomposite increased band gap energy from 2.85 to 2.94 eV. Significant PL (photoluminescence) intensity reduction was observed by compositing 7.5 mol.% CuO, whereas Ag loading did not cause notable change. Among various prepared nanocomposites, the ZnO-7.5 mol.%CuO with 5 mol.% Ag loading was found to be the most influential with almost complete photodegradation efficiency toward methylene blue (MB) after 90 min under visible light irradiation. Both ZnO-CuO and ZnO-CuO-Ag nanocomposites exhibited a Z-scheme mechanism for charge transfer proposed based on the radical scavenging experiments. Superoxide radicals were the main active species participating in photocatalytic reactions. The loaded Ag acted as an electron mediator and improved the charge separation efficiency in the ZnO-CuO-Ag nanocomposite. The recycling of the nanocomposite was evaluated and the results showed a reusable photocatalyst with high stability for environmental wastewater purification.

Green Assembly of Covalently Linked BiOBr/Graphene Composites for Efficient Visible Light Degradation of Dyes.

A novel high-performance BiOBr@graphene (BiOBr@G) photocatalyst with a new assembly structure had been demonstrated using a facile hydrothermal method through chemical bonding of reduced graphene oxide and structure-defined BiOBr flakes for improving charge separation and transfer performance, which were first synthesized at room temperature in immiscible solvents without corrosive acids. The prepared samples were characterized, and the BiOBr@G composite realized an efficient assembly portfolio of graphene and BiOBr flakes with defined structures, verified by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman and X-ray photoelectron spectroscopy (XPS), in which BiOBr flakes were covalently linked with the assembled graphene sheets through the Bi–C bond. This composite exhibited remarkable visible light absorbance and efficient photoinduced charge splitting characteristics in comparison with those of pure BiOBr, as established by DRS absorption, photoluminescence radiation, and photocurrent study. Hence, a very small amount (5 mg) of the BiOBr@G composite displayed a complete photodegradation effect on the rhodamine B dye under only 15 min of visible light excitation, which was three times faster than that of pure BiOBr and extremely superior to that of commercial P25. This was probably ascribed to the well-defined BiOBr structure itself, elevated light absorbance, and Bi–C chemical bond inducing quick charge separation and transfer in the BiOBr@G composite. Additionally, investigations on the photocatalytic mechanism displayed that the photogenerated holes in the BiOBr valence band and derivative superoxide radicals played vital roles in the photodegradation of RhB dyes, as reinforced by the electron spin resonance method, where the covalent linking of BiOBr and graphene served as an effective pathway for charge transportation.

Bandgap Variations and Photodegradation Efficiency on Inclusion of SiO2 in TiO2-rGO Nanocomposite for High Performance Photocatalysis

SiO2 is an excellent support material due to its flexible pore size and can be used as an adsorbent for the removal of toxic materials from water. Nanocrystalline TiO2-rGO is previously reported to show complete photodegradation for azo dyes. In pursuit of enhancing the adsorption capability of the system, we have incorporated SiO2 in TiO2-rGO nanocomposite which has drastically reduced the crystallinity of the matrix. Analysis of the bandgap variations is pursued here, which is crucial for enhanced light absorption and high performance photocatalysis.

Double Z-Scheme ZnCo2O4/MnO2/FeS2 photocatalyst with enhanced photodegradation of organic compound: Insights into mechanisms, kinetics, pathway and toxicity studies

The present work highlights the preparation of double Z-scheme ZnCo2O4/MnO2/FeS2 nanocomposite (NCs) and investigated its photocatalytic activity against methyl orange (MO) dye degradation under visible light. An array of techniques was carried out to characterize the nanoparticles (NPs) in order to evaluate their morphological, structural, optical, and photocatalytic properties using FE-SEM, TEM, XRD, N2 adsorption and desorption studies, PL, UV–visible spectrophotometer, XPS, Raman, and UV–vis DRS analysis. The degradation efficiency of NCs was tested along with different parameter studies such as different pH, NCs concentration, dye concentration, reusability and structural stability. The NCs exhibited complete photodegradation of MO dye under visible light within 80 min at pH 4. The structural and compositional stability of the prepared NCs over 6 consecutive cycles was tested via XRD and XPS analysis. The results of active species trapping experiments showed that O2−• and OH• are responsible for the degradation of MO dye. The TOC analysis showed 95% of mineralization by the prepared NCs. The MO dye degradation pathway was determined using GC-MS/MS analysis and drafted all the intermediates involved. End product toxicity via seed germination and intermediate toxicity study using ECOSAR software results in less toxicity of end product compared to parent compound. Finally, the genotoxicity of the prepared NCs was evaluated using Allium cepa and showed its no causes of cytotoxicity & genotoxicity by the prepared NCs. ZnCo2O4/MnO2/FeS2 NCs exhibited its high photocatalytic activity and the toxicity studies confirms that there is no cause of any environmental impact.

Filling Polyoxoanions into MIL-101(Fe) for Adsorption of Organic Pollutants with Facile and Complete Visible Light Photocatalytic Decomposition.

Transition metal-substituted polyoxometalates (POMs) were filled into a metal–organic framework (MOF) to construct a series of POM@MOF composites (PMo12O40@MIL-101, PMo11VO40@MIL-101, PMo10V2O40@MIL-101). The composite materials possess ultra-high adsorption ability, especially for PMo10V2O40@MIL-101, with an adsorption capacity of 912.5 mg·g−1 for cationic antibiotic tetracycline in wastewater, much higher than that of isolated MIL-101(Fe) and the commonly used adsorption materials, such as activated carbon and graphene oxide. In particular, they can be used as efficient photocatalysts for the photodegradation of antibiotics under visible light irradiation. The complete photodegradation of the adsorbed species can induce the facile reusability of these composites for multiple cycles. This work opens an avenue to introduce POMs into an MOF matrix for the simultaneous adsorption and photodegradation of antibiotics.

Encapsulation-Led Adsorption of Neutral Dyes and Complete Photodegradation of Cationic Dyes and Antipsychotic Drugs by Lanthanide-Based Macrocycles.

Molecular architectures offering large cavities can accommodate guest molecules, while their compositional engineering allows tunability of the band gap to support photocatalysis using visible light. In this work, two lanthanide (Ln)-based macrocycles, synthesized using a cobalt-based metalloligand and offering large rectangular cavities, exhibited selective adsorption of neutral dyes over both anionic and cationic dyes. Both Ln macrocycles illustrated complete photodegradation of cationic dyes using visible light without the use of any oxidant. Both Ln macrocycles exhibited complete photodegradation of not only cationic dyes but also a few phenothiazine-based antipsychotic drugs. Photocatalysis involved the generation of reactive oxygen species (ROS), which was corroborated with the band gap of two Ln macrocycles. These results were supported by radical scavenger studies and the quantitative estimation of superoxide and hydroxyl radicals. Complete photodegradation of both dyes and drugs was confirmed by spectral studies, while the generation of CO2 and N2 gases was established by gas chromatography. Importantly, Ln macrocycles were able to distinguish between the neutral dyes that were quantitatively adsorbed and the cationic dyes/drugs that were completely photodegraded.

TiO2–rGO nanocomposites with high rGO content and luminescence quenching through green redox synthesis

We developed TiO2–rGO nanocomposites with high exfoliated rGO content upto 47.1% (TG4) by weight hitherto not reported, through green redox synthesis. Progressive reduction of TiO2 nanocrystal size and their in situ intercalation occurred on increasing rGO via one pot synthesis, not reported previously and forming highly stable Ti–O–C bonds. With increase in rGO content, the exfoliation in the nanocomposite was also limited to single-few layered graphene oxide sheets through use of ascorbic acid avoiding restacking, and thereby the recombination of photogenerated carriers. TG4 showed 50% photoluminescence (PL) quenching indicating long-lived electron transfer state with rGO and apparent rate of nonradiative excited state decay of 1.15 × 108 s−1. Details of lattice orientation, Raman spectra, electronic states and PL lifetime decay are discussed to elucidate effective charge carrier separation in the nanocomposite. Near complete photodegradation of Alizarin Yellow GG azo dye, an industrial pollutant, could be obtained under direct sunlight using TG4 as catalyst.

A study on how to control the supramolecular amphiphilic assembly of anionic bola surfactant with calixpyridinium

The fabrication of supramolecular amphiphiles by the host–guest interactions between macrocycles and surfactants is an effective method to improve the physical and chemical properties of amphiphiles. However, as far as we know, lowering the critical micelle concentration of anionic surfactant by the complexation of macrocyclic host is scarcely studied. In this work, we systematically studied the host–guest interactions between calixpyridinium and four select anionic bola surfactants. Only congo red that has a conjugated linker could assemble into supramolecular amphiphile with calixpyridinium accompanied by a decreased critical micelle concentration. As a result, the pKa value of congo red shifted significantly. Moreover, the calixpyridinium–congo red supramolecular amphiphilic assembly exhibited a valuable visible-light response for the complete photodegradation of congo red.

Hydrothermal synthesis of ZnO photocatalyst for detoxification of anionic azo dyes and antibiotic

The ZnO photocatalysts were prepared by a hydrothermal method by using the Zn2+/OH− mole ratio of 1:5, 1:12, and 1:18 denoted as ZnO-1, ZnO-2, and ZnO-3, respectively. All prepared photocatalysts showed the hexagonal phase with the band gap energy of around 3.19 eV and the specific surface area of about 10.6 m2g-1. These photocatalysts remained stable even heating up to 1000 °C. Interestingly, the synthesized ZnO-1photocatalyst provided the lowest PL intensity among all prepared photocatalysts. This indicated the lowest electron-hole recombination rate at the interface. Therefore, this sample exhibited the highest photoactivity. The complete photodegradation of RR141, CR, and OFL pollutants after 20, 60 and 180 min of solar light irradiation, respectively, was obtained. The photodegradation of the pollutants correlated well with the first-order kinetics model. The corresponding rate constants of 0.1432, 0.0494 and 0.0304 min−1 toward degradation of RR141, CR and OFL, respectively, were reported. The stability of the ZnO-1 photocatalyst after three times of use was confirmed. The ZnO-1 photocatalyst still provided high performance even after the third cycle indicating its promising reusability. The photogenerated electron played a vital role in removal of the pollutants. The present research demonstrates a promising route for fabrication of ZnO photocatalyst with high efficiency for detoxification of organic pollutants in wastewater.