Efficient photocatalytic degradation of doxycycline by coupling α-Bi2O3/g-C3N4 composite and H2O2 under visible light

Defect-engineered dual Z-scheme core-shell MoS2/WO3-x/AgBiS2 for antibiotic and dyes degradation in photo and night catalysis: Mechanism and pathways

Water pollution caused by antibiotics and synthetic dyes and imminent energy crises due to limited fossil fuel resources are issues of contemporary decades. Herein, we address them by enabling the multifunctionality in dual Z-scheme MoS2/WO3-x/AgBiS2 across photolysis, photo Fenton-like, and night catalysis. Defect, basal, and facet-engineered WO3-x is modified with MoS2 and AgBiS2, which extended its photoresponse from the UV-NIR region, inhibited carrier recombination, and reduced carrier transfer resistance. The electric field rearrangement leads to a flow of electrons from MoS2 and AgBiS2 to WO3-x and intensifies the electron population, which is crucial for night catalysis. When MoS2/WO3-x/AgBiS2 was employed against doxycycline hydrochloride (DOXH), it removed 95.65, 81.11, and 77.92 % of DOXH in 100 minutes during photo-Fenton (PFR), night-Fenton (NFR), and photocatalytic (PCR) reactions, respectively. It also effectively removed 91.91, 98.17, 99.01, and 98.99 % of rhodamine B (RhB), Congo red (CR), methylene blue (MB), and methylene orange (MO) in Fenton reactions, respectively. ESR analysis consolidates the ROS generation feature of MoS2/WO3-x/AgBiS2 using H2O2 with and without irradiation. This work provides a strategy to eliminate the deficiencies of WO3-x and is conducive to the evolution of applications seeking to combat environmental and energy crises.

Construction of p-n-p nano heterojunction through coupling La2O3, (BiO)2CO3 and Ag3PO4 for effective photocatalytic degradation of doxycycline: Insights into mechanism, pathway and intermediate toxicity evaluation

The present work is centred around the development of La2O3/(BiO)2CO3/Ag3PO4 (LBA), a p-n-p nano-heterojunction to photodegrade doxycycline under visible light irradiation. Here, ultrasonication assisted co-precipitation method was employed to synthesize the photocatalyst. The photocatalyst was characterized using different analysis such as SEM, TEM, elemental mapping, XRD, XPS, FTIR, Raman, BET, DRS, PL and EIS which confirmed the successful fabrication of LBA and their excellent ability to refrain the e-/h+ recombination owing to the construction of the heterojunction. LBA was found to degrade DOX by 91.75 % with the high mineralization of 87.23%. The impact of the reaction parameters influencing the photodegradation process including the concentration of the NCs and DOX, pH and the influence of the commonly present anions were studied. The stability and reusability of the LBA was assessed through subjecting it to four cycles of photodegradation of DOX. In addition, the recovered LBA was characterized through XPS and XRD analysis to confirm the particles stability and reusability. The active participation of the photogenerated charges and the reactive oxygen species were identified through the scavenging assay and ESR analysis. Further, GC-MS/MS analysis was performed to put forward a plausible photodegradation pathway. The toxicity of the end products as well as the intermediates was predicted through ECOSAR software.

Preparation of TiO2/Fe-MOF n‒n heterojunction photocatalysts for visible-light degradation of tetracycline hydrochloride

Visible-light-assisted photocatalysis has been recognized as an effective solution to the degradation of various pollutants including antibiotics, pesticides, herbicides, microplastics, and organic dyes. Herein, an n-n heterojunction TiO₂/Fe-MOF photocatalyst is reported, designed via hydrothermal synthesis route. TiO₂/Fe-MOF photocatalyst was characterized by XPS, BET, EIS, EDS, DRS, PL, FTIR, XRD, TEM, SEM and HRTEM techniques. Inspired by XRD, FTIR, XPS, EDS, TEM, SEM, and HRTEM analyses, the successful synthesis of n-n heterojunction TiO₂/Fe-MOF photocatalysts was proved. The migration efficiency of the light-induced electron-hole pairs was confirmed by the PL and EIS tests. TiO₂/Fe-MOF exhibited a significant performance for tetracycline hydrochloride (TC) removal under visible light irradiation. TC removal efficiency for TiO₂/Fe-MOF (15%) nanocomposite reached 97% within 240 min, ca. 11 times higher than pure TiO₂. The photocatalytic enhancement of TiO₂/Fe-MOF could be attributed to the broadening the light response range, forming an n-n junction between Fe-MOF and TiO₂ components, suppressing charge recombination. Based on recycling experiments, TiO₂/Fe-MOF had a good potential to be used in consecutive TC degradation tests.

Enhanced photocatalytic degradation performance of In2O3/g-C3N4 composites by coupling with H2O2

Environmental pollution by organic pollutants poses a great threat to the ecosystem and human development. Solar-powered catalytic oxidation technology can solve the existing energy and pollution crisis. Hence, in this work, cubic nano-In₂O₃ modified g-C₃N₄ composite was synthesized by in situ calcination, then it was coupled with hydrogen peroxide for the degradation of antibiotic under visible light. The results of SEM and XPS showed that In₂O₃ and g-C₃N₄ were closely combined. The catalytic oxidation efficiency of the antibiotic doxycycline was greatly improved when the as-prepared compound was coupled with hydrogen peroxide, and 88.2% of doxycycline was degraded within 80 min. By designing the active species inhibition test, it was found that a large number of hydroxyl radicals were generated in the system after adding hydrogen peroxide, which accelerated the degradation of the target. Hydrogen peroxide not only acts as a source of hydroxyl radical, but also as an active electron acceptor, which promotes the separation of photogenerated electron-hole pairs in the composite photocatalyst. Therefore, the double oxidation system formed by In₂O₃/g-C₃N₄ coupled with hydrogen peroxide can degrade the target at a higher rate. This work provided a research basis for the synthesis of In₂O₃ with regular morphology and simplified synthesis of In₂O₃/g-C₃N₄, and explored the practicability of the coupling method of double advanced oxidation for pollutant degradation.

Efficient degradation of tetracycline under the conditions of high-salt and coexisting substances by magnetic CuFe2O4/g-C3N4 photo-Fenton process

For the effective degradation of tetracycline (TC), a facilely prepared magnetic CuFe₂O₄/g-C₃N₄ (CFO/g) photocatalyst was successfully constructed. The structure, morphology, composition, optical, and magnetic properties of CFO/g were characterized. CFO/g demonstrated excellent photo-Fenton performance of TC in the presence of high-Cl^-, NO₃^-, HCO₃^-, HPO₄^2-, SO₄^2- and humic acid. Ten cycles of experiments with the removal rate of TC only decreasing by 2.8% confirmed the stability and high activity of CFO/g. The dissolved concentrations of Fe and Cu ions were 0.013 and 0.009 mg L^-1, respectively. Its excellent magnetic properties made CFO/g easier to be recycled than traditional catalysts. ·OH and O₂·^- were proposed to be the main active species in the photo-Fenton system. The CFO/g heterojunction enhanced the separation of photogenerated electron-hole pairs and visible light absorption range. Furthermore, the identification of intermediates suggested that TC degradation was classified into two pathways, and the most critical and rapid degradation was achieved within the first 30 min. The TC and its intermediates did not significantly inhibit the growth activity of Escherichia coli. This research provided a promising application of magnetic photocatalysts in wastewater treatment of pharmaceuticals and personal care products.

Study on visible light photocatalytic performance of BiVO4 modified by graphene analogue boron nitride

In this study, a variety of boron nitride (BN) modified BiVO₄ (BN-BiVO₄) composites with visible-light response were prepared and used to degrade tetracyclines (TCs), including tetracycline (TC) and oxytetracycline (OTC). When treating the TCs solution under visible light irradiation, 4BN-BiVO₄ displayed high photocatalytic performance (87.1% for TC and 86.2% for OTC), which were 3.6 and 2.3 times than that of BiVO₄, respectively. Photoluminescence spectroscopy (PL) and transient photocurrent proved that the combination of BN and BiVO₄ effectively promotes the efficient separation of photogenerated electrons and holes in the material, resulting in enhanced photocatalytic activity. Further, radical trapping experiments in combination with electron spin resonance (ESR) revealed that ·OH radicals and holes were the predominant reactive species. Ultimately, the possible photocatalytic mechanism for TCs degradation was proposed on the basis of the experiments and characterization analysis. This study offers a new promising approach for the design of photocatalysts with visible-light response for efficient TCs elimination.

Green synthesis of two-electron centre based ZnO/NiCo2S4 QDs-OVs using Punica granatum fruit peel extract for an exceptional visible light photocatalytic degradation of doxycycline and ciprofloxacin

Biosynthesis of nanomaterials using plant extract makes them attractive in the field of photocatalysis as they are environmental friendly. The current study focused on the biosynthesis of ZnO/NiCo₂S₄ QDs (NCs) using Punica granatum fruit peel extract as the reducing agent. The nanomaterials were characterized with XRD, FTIR, Raman, SEM, TEM, UV-vis DRS, BET, PL, EIS, and ESR analysis and were used for photocatalytic degradation of doxycycline (DOX) and ciprofloxacin (CIP). The bandgap of ZnO is 3.2 eV, and the decoration of NiCo₂S₄ QDs aids in narrowing the bandgap (2.8 eV), making the NCs visible light active. The fabricated NCs achieved 99 and 89% degradation of DOX and CIP respectively. The photocatalytic efficiency of ZnO/NiCo₂S₄ QDs was much higher compared to individual ZnO and NiCo₂S₄ QDs. The half-life period of DOX and CIP were evaluated to be 58 and 152 min respectively. The percentage of TOC removal in the photodegraded product of DOX and CIP was estimated to be 99 and 89% respectively, indicating the mineralization of the compounds. The enhanced photocatalytic efficiency of the NCs was attributed to the narrowed visible light active bandgap, synergistic charge transfer across the interface, and lower charge recombination. The intermediates formed during the photocatalytic degradation of DOX and CIP were analyzed using GC-MS/MS analysis, and the photodegradation pathway was elucidated. Also, the toxicity of the intermediates was computationally analyzed using ECOSAR software. The fabricated ZnO/NiCo₂S₄ QDs have excellent stability and reusability, confirmed by XRD and XPS analysis. The reusable efficiency of the NCs for the photocatalytic degradation of DOX and CIP were 98.93, and 99.4% respectively. Thus, the biologically fabricated NCs are shown to be an excellent photocatalyst and have wide applications in environmental remediation.

Enhancement in Photocatalytic Efficiency of Commercial TiO2 Nanoparticles by Calcination: A Case of Doxycycline Removal

In this study, the pure and calcined forms of Degussa TiO2 were applied for photocatalytic removal of doxycycline - a broad-spectrum tetracycline antibiotic. The calcination of TiO2 at 500 °C enhanced the photocatalytic efficiency of the TiO2 under optimal operational conditions of 5 ppm of doxycycline, 0.25 g/L of TiO2, pH 6.5, 120 min, and room temperature. In addition, the changes in morphology, crystal structure, and optical properties of the materials before and after calcination were observed by scanning electron microscopy, X-ray diffraction, and UV-Visible spectroscopy. The reaction kinetics of the doxycycline removal was also investigated based on the Langmuir-Hinshelwood model with a correlation coefficient R2 of >80%. Results showed that the photocatalytic ability of TiO2 is stable and enhanced after being calcined at a suitable temperature of 500 °C. This opens up the potential application of TiO2 in the treatment of emerging organic pollutants in water. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Phytofabrication of bimetallic silver-copper/biochar nanocomposite for environmental and medical applications

In the current study, a novel, green, low-cost, and sustainable path for the phyto-fabrication of Ag-Cu biochar nanocomposite (Ag-Cu/biochar) by Atriplex halimus biomass and aqueous extract is described. Surface plasmon resonance peaks were detected at 450 nm and 580 nm signifying the formation of both silver and copper nanoparticles, respectively on the biochar surface. XRD analysis confirmed the crystal structure of the phytosynthesized Ag-Cu/biochar whereas FT-IR, SEM, EDX, and XPS analyses confirmed the successful phytofabrication of the composite. Ag and Cu nanoparticles loaded on the biochar surface were almost spherically-shaped with a particle size ranging from 25 nm to 45 nm. Zeta potential of -25.5 mV showed the stability of Ag-Cu/biochar. The potential of this novel nanocomposite in the removal of doxycycline (DOX) was evident under different conditions as it reached nearly 100% under the optimum reaction conditions (DOX concentration; 50 ppm, pH; 9, a dose of Ag-Cu/biochar; 0.01 g, temperature; 25 °C, and H₂O₂ concentration; 100 mM). The promising regeneration of Ag-Cu/biochar was evident as the removal efficiency was 81% after 6 consecutive cycles. Ag-Cu/biochar was also shown an excellent antimicrobial activity against gram-negative bacteria as well a promising antioxidant activity.

Study on visible light photocatalytic performance of MIL-100(Fe) modified by carbon nanodots

The emerging porous material metal organic framework (MOFs) has caught researchers' attention in the field of photocatalysis. In this study, a visible light-driven carbon nanodots/MIL-100(Fe) photocatalytic material was prepared by in situ synthesis method. The study found that the composite material loaded with 2.5 mg C-dots (2.5-carbon nanodots/MIL-100(Fe)) showed the best tetracycline degradation efficiency with 4.2 times higher than that of MIL-100(Fe) materials in a neutral environment. The superiority of 2.5-carbon nanodots/MIL-100(Fe) in degrading tetracycline is attributed to the fact that C-dots have the ability to act as acceptors and donors of electrons, thus promoting electron transfer and inhibiting electron-hole recombination. Moreover, the 2.5-carbon nanodots/MIL-100(Fe) also showed high stability after five cycles of the photodegradation reaction. The quenching experiment proved that the main active substances that degrade tetracycline were O₂^- and h⁺. The study of carbon nanodots /MIL-100(Fe) composite materials provides new thoughts and methods for the removal of organic pollutants.

An intriguing Z-scheme titania loaded on fibrous silica ceria for accelerated visible-light-driven photocatalytic degradation of ciprofloxacin

A novel Z-scheme titania loaded on fibrous silica ceria (Ti-FSC) was triumphantly fabricated via hydrothermal followed by electrolysis method and evaluated for the visible-light degradation of ciprofloxacin (CIP). Noticeably, Ti-FSC exhibits as an efficient photocatalyst for CIP photodegradation with 95% as followed by titania loaded on fibrous silica (Ti-FS) (68%), Ti-CeO₂ (35%), FSC (47%), FS (22%), and CeO₂ (17%). The combination of the inherent merits of Ti loaded on FSC is able to realize the crucial role of Ce in harnessing the high dispersion of Ti, which could beneficial for improving the performance proven by XRD, FESEM, TEM and FTIR. Consequently, high dispersion of Ti on FSC has worthwhile towards the interaction of the Si-O-Ti, Ce-O-Ti, and Si-O-Ti, which could enhance the CIP photodegradation by providing more surface defects, narrowing the band gap, improving electron-hole separation and suppressing electron-hole recombination that revealed by XPS, UV-vis/DRS, Nyquist plots and PL studies, respectively. The scavenger study revealed that the controlling species in the system was hydroxyl radical and holes. A potential Z-scheme heterojunction mechanism for Ti-FSC was deduced from the band structure analysis. The possible photodegradation pathway was proposed based on GCMS analysis. Besides, the acceptable reusability, which exceeded 90% of degradation indicated the great application potential of Z-scheme Ti-FSC in wastewater treatment and others application.

Improved performance of Zn-doped SnO2 modified g-C3N4 for visible light-driven photocatalysis

The low-cost composite of g-C₃N₄ modified by Zn-doped SnO₂ nanoparticles was prepared for the first time in this work. The characterization results of XRD and SEM demonstrated that Zn was successfully doped into SnO₂. The formed Sn-O-Zn bonds and interaction between the Zn-doped SnO₂ sample and g-C₃N₄ in the composite were explored by FT-IR and XPS technologies. Photocatalytic degradation experiments showed that the as-prepared optimal composite photocatalyst displayed enhanced photocatalytic reactivity towards both dyes and antibiotics, which could degrade 85.6% of RhB and 86.8% of tetracycline within 30 and 90 min, respectively. The oxygen vacancies formed in SnO₂ after Zn doping could capture the photogenerated electrons of g-C₃N₄, thereby promoting the separation of photogenerated electron-hole pairs, then more ·O₂^- and holes can be generated during the visible light-driven photocatalytic reaction, so that the composite of Zn-doped SnO₂/g-C₃N₄ acquired higher photocatalytic activity and accelerated the degradation of target organics. Active species capturing experiments and ESR detection results also confirmed that ·O₂^- and holes were the main active species in the reaction process. This work developed a novel g-C₃N₄-based photocatalyst with no noble metal, low price, and high photocatalytic activity, which could provide a cost-effective and high-efficiency strategy for wastewater treatment.

Green synthesis of bimetallic Ag/ZnO@Biohar nanocomposite for photocatalytic degradation of tetracycline, antibacterial and antioxidant activities

In this work, a simple and green synthesis procedure for phytofabrication Zinc oxide-silver supported biochar nanocomposite (Ag/ZnO@BC) via Persicaria salicifolia biomass is investigated for the first time to uphold numerous green chemistry such as less hazardous chemical syntheses. XRD technique showed the crystal structure of the phytosynthesized Ag/ZnO@BC, whereas UV-visible spectroscopy, FT-IR, SEM, EDX, TEM, and XPS analyses indicated the successful biosynthesis of the nanocomposite. Testing the photocatalytic potential of this novel nanocomposite in the removal of TC under different conditions unraveled its powerful photodegradation efficiency that reached 70.3% under the optimum reaction conditions: TC concentration; 50 ppm, pH; 6, a dose of Ag/ZnO@BC; 0.01 g, temperature; 25 °C, and H₂O₂ concentration; 100 mM. The reusability of Ag/ZnO@BC was evident as it reached 53% after six cycles of regeneration. Ag/ZnO@BC was also shown to be a potent antimicrobial agent against Klebsiella pneumonia as well as a promising antioxidant material. Therefore, the current work presented a novel nanocomposite that could be efficiently employed in various environmental and medical applications.

Green synthesis of manganese-cobalt-tungsten composite oxides for degradation of doxycycline via efficient activation of peroxymonosulfate

The advanced oxidation process of peroxymonosulfate activated by solid catalyst is one of the main technologies to solve the pollution of antibiotics in water environment.In this work, a series of composites (MCW) containing Mn, Co, and W were synthesized using green ball milling, which does not produce the three wastes (waste gas, waste water and industrial residue). It shows a unique and high catalytic activity for peroxymonosulfate-based degradation of doxycycline (DC) under the pH condition between 4 and 9, and it can be reused five times. MCW composites remove DC using singlet oxygen and superoxide free radicals, as well as a large number of oxygen vacancies for electron storage. The formation rate of free radicals is determined by the conversion rates of Mn³⁺/Mn²⁺ and Co³⁺/Co²⁺. In addition, there are three ways to degrade DC to form 18 kinds of intermediates, and the toxicity of all the intermediates were predicted by ECOSAR program. The highly active catalysts obtained using a green synthetic route for the activation of peroxymonosulfate show a great potential for decontamination of antibiotics wastewater.

Facile Synthesis of Gold Nanoparticles for Anticancer, Antioxidant Applications, and Photocatalytic Degradation of Toxic Organic Pollutants

In the current study, a facile, rapid, and ecologically safe photosynthesis of gold nanoparticles (AuNPs) that remained stable for 3 months is reported to advocate the main aspects of green chemistry, such as safer solvents and auxiliaries, and the use of renewable feedstock. Zi-AuNPs were phytosynthesized by the aqueous extract of Ziziphus spina-christi leaves, and numerous techniques were employed for their characterization. The results demonstrated the successful phytofabrication of crystalline AuNPs with brownish-black color, spherical nanoparticles with a size between 0 and 10 nm, a plasmon peak at 540 nm, and a surface charge of -25.7 mV. Zi-AuNPs showed an effective photodegradation efficiency (81.14%) against malachite green and a good recycling capacity of 69.2% after five cycles of regeneration. The cytotoxicity test by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay signified a high anticancer efficiency for both Zi-AuNPs and Z. spina-christi extract against human breast cancer cells (MCF7 cell line) with IC₅₀'s of 48 and 40.25 μg/mL, respectively. Highly efficient antioxidant capabilities were proven with 2,2-diphenyl-1-picrylhydrazyl (DPPH) removal percentages of 67.5% for Zi-AuNPs and 92.34% for Z. spina-christi extract.

Enhanced photodegradation of doxycycline (DOX) in the sustainable NiFe2O4/MWCNTs/BiOI system under UV light irradiation

In this study, a magnetic NiFe₂O₄/MWCNTs/BiOI composite were fabricated and applied for enhanced and sustainable photocatalytic degradation of doxycycline (DOX) under UV light irradiation. The as-synthesized material was characterized by a series of techniques and its photocatalytic property was assessed via a couple of batch tests. With the pH at 3.0 and NiFe₂O₄/MWCNTs/BiOI loading of 1.5 g L^-1, the DOX degradation (at 45 mg L^-1) efficiency could achieve 92.18% with the reaction rate constant k of 0.0072 min^-1. The high mineralization of DOX suggests the strong oxidation of both the parent pollutant and the intermediary products in the ternary catalyst system. DRS spectra indicated that compared with BiOI, the introduction of NiFe₂O₄ and MWCNTs reduces the band gap energy of the NiFe₂O₄/MWCNTs/BiOI. The quenching test illustrates that h⁺, OH and O₂^- all functioned in the developed photocatalytic system, where O₂^- and h⁺ play the dominant roles in DOX degradation. The more efficient electron-h⁺ separation and more oxidizing species induced by UV light resulted in the significant improvement of DOX abatement in the developed coupling system compared with that on either BiOI or NiFe₂O₄/MWCNTs. The magnetic property of NiFe₂O₄/MWCNTs/BiOI enables its easy separation of the solid catalyst from the reaction solution and the sustainable application in the photocatalysis. Based on the intermediates of DOX decomposition identified by UPLC-MS, the possible degradation routes were proposed accordingly.

Simple fabrication and unprecedented visible light response of NiNb2O6/RGO heterojunctions for the degradation of emerging pollutants in water

Utilization of environmentally friendly and effective synthesis methods to fabricate visible light responsive photocatalysts with impressive catalytic performance is desirable in photocatalytic water treatment.