Electron scavenger-assisted photocatalytic degradation of amido black 10B dye with Mn 3 O 4 nanotubes: A response surface methodology study with central composite design

Electro-, photo-, and photoelectrochemical degradation of chloramphenicol on self-doping Ti nanotubes

In this work, the photo-, electro-, and photo-electro-oxidation of chloramphenicol was investigated. The photo-experiments were carried out with different irradiation sources (an ultraviolet and a simulated solar source) using self-doped titanium nanotubes (SDTNT), a very promising and innovative material that deserves further investigations in the degradation of different pollutants. The photo-electrooxidation (j = 15 mA cm-2) under simulated solar irradiation presented the best efficiency, with ca. 100% degradation and kinetic constant of k = 0.04427 min-1. The FTIR analysis demonstrated a structural modification of the standard molecule occurred for all conditions used, suggesting a modification in functional groups responsible for the biological activity. Furthermore, the TOC analysis showed a significant mineralization of the pollutant (66% from the initial concentration). In addition, both photo-electrooxidation approaches have demonstrated a positive value of S, where the simulated solar irradiation reached the highest value S = 0.6960. The experimental results pointed out evidence that the methodology employed herein for chloramphenicol degradation is greatly interesting and the photo-electrooxidation under simulated solar irradiation is a promising approach for this purpose.

Exploring the Potential of Nickel Oxide Nanoparticles Synthesized from Dictyota bartayresiana and its Biological Applications

The present study validates the impact of nickel oxide nanoparticles (NiONPs) biosynthesized from the brown seaweed Dictyota bartayresiana (DB) and its biological applications. The phytochemicals analyzed in the seaweed extract served as a reducing, capping or stabilizing agent in the formation of nanoparticles. UV visible spectrum of nickel oxide nanoparticles synthesized from DB (DB-NiONPs) represented a prominent peak at 392 nm which validates its formation. Fourier Transmission Infrared Spectroscopy (FT-IR) showcased the presence of functional groups in the biomolecules which aids in the stabilization of DB-NiONPs. The X-ray diffractometry (XRD) revealed the crystalline nature of DB-NiONPs and the particle size was calculated as 18.26 nm. The Scanning electron microscope (SEM) illustrates the irregularly shaped DB-NiONPs and the desired elements were depicted in energy dispersive X-ray (EDX) spectrum which confirms the purity of DB-NiONPs. The DB-NiONPs efficiently decolorised the Black B133 (BB133) dye to 86% in 25 min. The data of adsorption studies well fitted into Langmuir isotherm and pseudo-second order kinetic model. The thermodynamic study substantiated the spontaneous, feasible and endothermic process of adsorption. DB-NiONPs revealed enhanced antimicrobial, larvicidal and nematicidal activities against the selected microbes, larva of Culex pipens and juveniles of Meloidogyne incognita respectively. The phytotoxicity studies revealed the DB-NiONPs had a positive impact on the germination and growth of green gram seedlings.

Photocatalytic boron nitride-based nanomaterials for the removal of selected organic and inorganic contaminants in aqueous solution: A review

Boron nitride (BN) coupled with various conventional and advanced photocatalysts has been demonstrated to exhibit extraordinary activity for photocatalytic degradation because of its unique properties, including a high surface area, constant wide-bandgap semiconducting property, high thermal-oxidation resistance, good hydrogen-adsorption performance, and high chemical/mechanical stability. However, only limited reviews have discussed the application of BN or BN-based nanomaterials as innovative photocatalysts, and it does not cover the recent results and the developments on the application of BN-based nanomaterials for water purification. Herein, we present a complete review of the present findings on the photocatalytic degradation of different contaminants by various BN-based nanomaterials. This review includes the following: (i) the degradation behavior of different BN-based photocatalysts for various contaminants, such as selected dye compounds, pharmaceuticals, personal care products, pesticides, and inorganics; (ii) the stability/reusability of BN-based photocatalysts; and (iii) brief discussion for research areas/future studies on BN-based photocatalysts.

Bifunctional quaternary magnetic composite as efficient heterojunctions photocatalyst for simultaneous photocatalytic visible light degradation of dye and herbicide pollutants from water and bacterial disinfection

In the present study, the magnetic Fe3O4/Ag2C2O4/Ag3PO4/Ag nanocomposite were prepared through a simple co-precipitation method by using calendula officinalis seed extract as a stabilizer. The fabricated quaternary photocatalyst was applied for to degrade food dye Brilliant Blue FCF (BB) and herbicide Paraquat (PQ) as contaminants at binary mixture in a batch and continuous flow-loop photoreactor under visible light irradiation and also the antibacterial properties was investigated. The fabricated nanocomposite was determined by XRD, FESEM, EDX, BET&BJH, UV-DRS, FT-IR and VSM methods to gain insight about structure, morphology, purity, surface area, optical, functional group and magnetic properties. The photoelectrochemical experiments, PL and DRS indicate the successful coupling of the active semiconductors. The degradation efficiency of BB and PQ was announced to be 88.9% and 92.72% under optimal conditions with a high reaction rate constant value (0.03 and 0.0326 min-1), respectively. The quaternary photocatalyst exhibited superior photocatalytic performance compared with Ag3PO4/Ag2C2O4 and Ag2C2O4. Various scavengers were used to explore the mechanism of photocatalytic performance and supports that [Formula: see text] and OH. is main active species in the degradation process of BB and PQ, respectively. Furthermore, the Fe3O4/Ag2C2O4/Ag3PO4/Ag also demonstrated bactericidal activity against Staphylococcus aureus (S. aureus) as gram-positive bacteria and Escherichia coli (E. coli) as gram-negative bacteria.

Assessment on the photocatalytic and phytotoxic activities using ecobenevolently synthesized iron oxide nanoparticles from the root extracts of Glycyrrhiza glabra

The present study is the first attempt to utilize the root extracts of Glycyrrhiza glabra as a novel biological route for the synthesis of iron oxide nanoparticles (Fe2O3NPs) under optimized conditions. The process variables namely concentration of ferric chloride, root extract of G. glabra and temperature were optimized using Response Surface Methodology (RSM) to obtain high yield. Phytochemicals mediated the reduction process and served as capping and stabilizing agent. The biosynthesized Fe2O3NPs characterized using UV-Vis spectroscopy exhibited a prominent peak at 350 nm. The crystallinity and valence state of Fe2O3NPs was confirmed by XRD and XPS. The surface functionalization of the nanoparticles was confirmed from the presence of functional groups in the FT-IR spectrum. The FESEM analysis revealed the biosynthesized Fe2O3NPs are irregular and the EDX spectrum recorded the presence of iron and oxygen in the synthesized nanoparticles. The biosynthesized Fe2O3NPs exhibited an appreciable photocatalytic activity against methylene blue under sunlight with a maximum decolorisation efficiency of 92% within 180 min of reaction time. The experimental data of adsorption studies well fitted with Langmuir isotherm and pseudo-second order kinetic model. The thermodynamic study proved to be spontaneous, feasible and endothermic in nature. The phytotoxicity study revealed 92% germination and increased seedling growth in the green gram seeds exposed to Fe2O3NPs. Hence the study established the efficiency of biosynthesized of Fe2O3NPs in photocatalytic and phytotoxic activities.

3D N-doped carbon derived from zeolitic imidazole framework as heterogeneous catalysts for decomposition of pulp and paper mill effluent: Optimization and kinetics study

Three specific catalysts, namely ZIF-67 (zeolitic imidazolate framework-67), Co@NCF (Co@Nitrogen-Doped Carbon Framework), and 3D NCF (Three-Dimensional Nitrogen-Doped Carbon Framework), were prepared and studied for pulp and paper mill effluent degradation using heterogeneous activation of peroxymonosulfate (PMS). Numerous characterizations, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and N2 adsorption, were used to characterize the properties of three different catalysts. 3D NCF is remarkably effective at heterogeneous activation of PMS to generate sulfate radicals to degrade pulp and paper mill effluent (PPME) compared to the other as-prepared catalysts. The catalytic activity reveals a sequence of 3D NCF > Co@NCF > ZIF-67.3D NCF could degrade organic pollutants in 30 min at an initial COD concentration of 1146 mg/L of PPME, 0.2 g/L catalysts, 2 g/L PMS, and 50 °C. Consequently, it was observed that the degradation of PPME using 3D NCF followed first-order kinetics, with an activation energy of 40.54 kJ mol-1. Overall, 3D NCF/PMS system reveals promising performance for PPME removal.

Optical and Photocatalytic Properties of Cobalt-Doped LuFeO3 Powders Prepared by Oxalic Acid Assistance

B-site cobalt (Co)-doped rare-earth orthoferrites ReFeO3 have shown considerable enhancement in physical properties compared to their parent counterparts, and Co-doped LuFeO3 has rarely been reported. In this work, LuFe1-xCoxO3 (x = 0, 0.05, 0.1, 0.15) powders have been successfully prepared by a mechanochemical activation-assisted solid-state reaction (MAS) method at 1100 °C for 2 h. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies demonstrated that a shrinkage in lattice parameters emerges when B-site Fe ions are substituted by Co ions. The morphology and elemental distribution were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The UV-visible absorbance spectra show that LuFe0.85Co0.15O3 powders have a narrower bandgap (1.75 eV) and higher absorbance than those of LuFeO3 (2.06 eV), obviously improving the light utilization efficiency. Additionally, LuFe0.85Co0.15O3 powders represent a higher photocatalytic capacity than LuFeO3 powders and can almost completely degrade MO in 5.5 h with the assistance of oxalic acid under visible irradiation. We believe that the present study will promote the application of orthorhombic LuFeO3 in photocatalysis.

Removing unreacted amino groups in graphitic carbon nitride through residual heating to improve the photocatalytic performance

In most of the research about graphitic carbon nitride (g-C₃N₄), g-C₃N₄ is prepared through the calcination of nitrogen-rich precursors. However, such a preparation method is time-consuming, and the photocatalytic performance of pristine g-C₃N₄ is lackluster due to the unreacted amino groups on the surface of g-C₃N₄. Therefore, a modified preparation method, calcination through residual heating, was developed to achieve rapid preparation and thermal exfoliation of g-C₃N₄ simultaneously. Compared with pristine g-C₃N₄, the samples prepared by residual heating had fewer residual amino groups, a thinner 2D structure, and higher crystallinity, which led to a better photocatalytic performance. The photocatalytic degradation rate of the optimal sample for rhodamine B could reach 7.8 times higher than that of pristine g-C₃N₄.

Investigating the effect of hydrogen peroxide as an electron acceptor in increasing the capability of slurry photocatalytic process in dye removal

The hydrogen peroxide role in photocatalytic degradation of an anionic azo dye, Acid Orange 7 (AO7), was investigated in a slurry reactor. Commercial ZnO nanoparticles with an average size between 10 to 30 nm were used as catalysts. Optimum conditions for different parameters, including dye concentration (10-100 mg/L), catalyst concentration (0.1-0.5 g/L), and pH (5-10), were determined first in the absence of H₂O₂. Changes in the COD were measured for the optimum condition. The impact of adding hydrogen peroxide at different concentrations to the system operating at optimum conditions was investigated. It was observed that 0.416 mM hydrogen peroxide increased the system's efficiency and decreased reaction time by 40 min. The reaction followed first-order kinetic. Hydrogen peroxide alone did not contribute to oxidizing the contaminant, and its positive impact was attributed to decreasing electron-hole recombination in the photocatalytic process. Not only can the hydrogen peroxide-assisted photocatalytic process decrease retention time in treatment units, but it can also result in more contaminant degradation. Therefore, it can reduce the treatment cost.

Electronic transitions of SWCNTs in comparison to GO on Mn3O4/TiO2 nanocomposites for hydrogen energy generation and solar photocatalysis

The conductivity of metal/metal oxide-doped TiO₂ nanomaterials is enhanced by the incorporation of carbonaceous materials, e.g. single-walled carbon nanotubes (SWCNTs) and graphene oxide (GO).

Reduction of hexavalent chromium and degradation of tetracycline using a novel indium-doped Mn2O3 nanorod photocatalyst

This study investigates the photocatalytic reduction of hexavalent chromium (Cr(VI)) and degradation of tetracycline (TC) via visible-light-active In-doped Mn₂O₃ photocatalysis. Mn₂O₃ photocatalysts loaded with different In doses are prepared using a simple hydrothermal method, and the results indicate the formation of Mn₂O₃ nanorod-like structures with good crystallinity. The most significant photocatalytic parameters, namely the catalyst and substrate concentrations, pH, and co-existing ions for the Cr(VI) reduction and TC degradation reactions are systematically examined. Result demonstrates that the Cr(VI) reduction and TC mineralization efficiencies of 52% and 40%, respectively are achieved at the optimum pH of 7, undoped Mn₂O₃ (10 mg/L), and Cr(VI) or TC concentration of 50 mg/L. However, these efficiencies are remarkably increased to 95% and 93%, respectively, when 10 mg/L of 5% In-doped Mn₂O₃ is used as the photocatalyst under the same reaction conditions. Moreover, the co-existing HCO₃^- anions and Ca²⁺ and Mg²⁺ divalent cations considerably deteriorate the performance of the In-doped photocatalysts compared with the SO₄^2- and Cl^- anions and Na⁺ and K⁺ monovalent cations. Liquid chromatography-mass spectrometry analysis reveals that the photodegradation of TC is mainly driven by the elimination of the -CH₃ group followed by the subsequent cleavage of the primary -NHCH₃ group.

New insights into MnOOH/peroxymonosulfate system for catalytic oxidation of 2,4-dichlorophenol: Morphology dependence and mechanisms

Sulfate radical-based advanced oxidation processes (SR-AOPs) have received increasing attention as viable technology for recalcitrant organics removal from polluted waters. As for heterogeneous catalyst, it is crucial to reveal the effect of morphology on its catalytic activity and mechanism, providing guidelines for rational design of morphology-dependent catalysts. Hence, in this study, we selected manganese oxyhydroxide (MnOOH) as the peroxymonosulfate (PMS) activator and synthesized different morphological MnOOH with the same crystal structure. The catalytic activity of MnOOH follows: nanowires > multi-branches > nanorods. Different morphological MnOOH had different physical and chemical characterization such as specific surface area, Lewis sites, ζ-potential and redox potential, which played positive roles in catalytic activity of MnOOH as PMS activator. Unexpectedly, it was found that ζ-potential was more crucial than specific surface area, redox potential and Lewis sites. Notably, nanowires exhibited higher positive zeta potential, which was favor of promoting interfacial reactivity between HSO₅^- and surface of MnOOH. Furthermore, •OH, SO₄•^-, O₂•^- and ¹O₂, were involved in the MnOOH/PMS system. Moreover, the cycle of Mn (III)/Mn (II) accelerated MnOH⁺ formation. This study provided a new understanding of manganese-catalyzed peroxymonosulfate activation and elucidated the relationships between morphology of catalyst and its catalytic activity.

The investigation of Amido black 10B adsorption-photocatalytic degradation using the synergistic effect of Cr-doped ZnO/CDs nanocomposite under solar light

In this work, the modification of ZnO nanoparticles with green synthesized carbon dots and Cr yielded a nanocomposite named Cr-doped ZnO/CDs. Further, 0.48 g/L of this nanocomposite was able to remove (95 ± 1) % of 25 mg/L Amido black 10B (AB10B) from a solution, by adsorption process less than 5 min. The photocatalytic property of Cr-doped ZnO/CDs was able to improve the removal efficiency of AB10B to 99% during irradiation of sunlight within 15 min. The maximum adsorbent capacity of Cr-doped ZnO/CDs nanocomposite was 152.4 mg/g. Unmodified ZnO nanoparticles (0.48 g/L) were able to remove only 30% of the dye within 60 min of irradiation. Its modification showed coupling the absorption and photocatalytic process dramatically increased the dye removal efficiency. Adsorption isotherm investigation indicated that the experimental data were fitted satisfactorily by the Langmuir model. This method is an economical method because the Cr-doped ZnO/CDs synthesis was easy and inexpensive, the dye removal time was very short, and infinite sunlight is required to remove the dye with high efficiency. Graphical abstract.

Facile synthesis of laccase mimic Cu/H3BTC MOF for efficient dye degradation and detection of phenolic pollutants

Herein, we report an effectual method for designing a novel form of nanozyme laccase mimic namely Cu/H3BTC, using copper ions and 1,3,5-benzene tricarboxylic acid (1,3,5-H3BTC). This Cu-based metal-organic framework (MOF) was synthesized through a simple procedure of mixing of two usual reagents at room temperature. Amido Black 10B (AB-10B) was chosen as a model dye for degradation consequences. Results showed that Cu/H3BTC MOF revealed significantly higher catalytic efficacy under certain conditions like high pH, extreme temperature and high salt conditions and it has long-term storage stability, which can lead to a significant decline in catalytic activity of laccase. In addition, the degradation of AB-10B was up to 60% after ten cycles, showing good recyclability of Cu/H3BTC MOF. The UV-visible spectral changes clearly showed that Cu/H3BTC MOF is an effective laccase mimic for the degradation of azo dye AB-10B, which was degraded more easily within the time duration of 60 min. The Cu/H3BTC MOF also possessed fundamental activities like laccase with regard to oxidation of the phenolic compounds. Moreover, a technique for the quantitative detection of epinephrine by Cu/H3BTC MOF was established. These findings help to understand the laccase-like reactivity and provide a basis for the future design and application of metal-based catalysts.

Effect of peroxomonosulfate, peroxodisulfate and hydrogen peroxide on graphene oxide photocatalytic performances in methyl orange dye degradation

Carbocatalyst GO photocatalytic mechanism and performances in the presence of an electron scavenger (ES) has been consciously discussed herein. Single layer GO photocatalyst has been synthesized by Hummer's method and photocatalyst characteristics are gathered by different analytical methods. Studies ensured the formation of a good crystalline GO that contains number of oxygenated functional groups, with average crystalline size of the sp² domain in 18.24 nm. Optical studies suggest that optical band gap of the GO nanosheet photocatalyst is found in the range of 3.19-4.4 eV. TEM analysis confirms the formation of a single layer GO nanosheet. Photocatalytic study justifies that in the absence of ES, 24% mineralization efficiency is achieved with GO as a photocatalyst, whereas in the presence of ES such as PMS, PDS and HP the mineralization efficiency is considerably enhanced up to 91%, 77% and 65% respectively. Moreover, photocatalytic degradation intermediate byproducts were also examined through LC-MS analysis. The study substantiates methyl orange dye degradation undergoes via the multiple degradation pathway such as (i) azo bond cleavage and hydroxylation, (ii), asymmetric cleavage followed by reduction of sulfonate group and aromatic ring removal and (iii) consecutive demethylation reactions and sulfonate group removal. Rationalized the contributing effects of process parameters towards the photocatalytic degradation of methyl orange using a RSM based on CCD validation. The validation reveals that most significant process parameter affects degradation process are the irradiation time, catalyst loading and choice of ES.

Controllable vapor phase fabrication of F:Mn3O4thin films functionalized with Ag and TiO2

The first example of vapor phase fabrication of Mn₃O₄(hausmannite) thin films chemically modified with fluorine and functionalized with Ag and TiO₂, resulting in high purity composites with an intimate constituent contact.