Photocatalytic degradation of levofloxacin by ternary Ag2CO3/CeO2/AgBr photocatalyst under visible-light irradiation: Degradation pathways, mineralization ability, and an accelerated interfacial charge transfer process study

Unveiling the photocatalytic marvels: Recent advances in solar heterojunctions for environmental remediation and energy harvesting

In the quest for effective solutions to address Environ. Pollut. and meet the escalating energy demands, heterojunction photocatalysts have emerged as a captivating and versatile technology. These photocatalysts have garnered significant interest due to their wide-ranging applications, including wastewater treatment, air purification, CO2 capture, and hydrogen generation via water splitting. This technique harnesses the power of semiconductors, which are activated under light illumination, providing the necessary energy for catalytic reactions. With visible light constituting a substantial portion (46%) of the solar spectrum, the development of visible-light-driven semiconductors has become imperative. Heterojunction photocatalysts offer a promising strategy to overcome the limitations associated with activating semiconductors under visible light. In this comprehensive review, we present the recent advancements in the field of photocatalytic degradation of contaminants across diverse media, as well as the remarkable progress made in renewable energy production. Moreover, we delve into the crucial role played by various operating parameters in influencing the photocatalytic performance of heterojunction systems. Finally, we address emerging challenges and propose novel perspectives to provide valuable insights for future advancements in this dynamic research domain. By unraveling the potential of heterojunction photocatalysts, this review contributes to the broader understanding of their applications and paves the way for exciting avenues of exploration and innovation.

Insight into Fe-O-Bi electron migration channel in MIL-53(Fe)/Bi4O5I2 Z-scheme heterojunction for efficient photocatalytic decontamination

Building a heterojunction is a fascinating option to guarantee sufficient carrier separation and transfer efficiency, but the mechanism of charge migration at the heterojunction interface has not been thoroughly studied. Herein, MIL-53(Fe)/Bi4O5I2 photocatalyst with a Z-scheme heterojunction structure is constructed, which achieves efficient photocatalytic decontamination under solar light. Driven by the newly-built internal electric field (IEF), the formation of Fe-O-Bi electron migration channel allows for rapid separation and transfer of charge carriers at the heterojunction interface, confirmed by the material characterization and density functional theory (DFT) calculation. The narrower band gap and improved visible light response also contribute to the enhanced photocatalytic activity of composite materials. With levofloxacin as the target pollutant, the optimal MIL-53(Fe)/Bi4O5I2 achieves complete removal of pollutant within 150 min, the photocatalysis rate of which is ca. 4.4 and 26.0 times that of pure Bi4O5I2 and MIL-53(Fe), respectively. Simultaneously, the optimal composite material exhibits satisfactory photodegradation of seven fluoroquinolones, and the photocatalysis rates are as follows: lomefloxacin > ciprofloxacin > enrofloxacin > norfloxacin > pefloxacin > levofloxacin > marbofloxacin. DFT calculations reveal a positive relationship between degradation rate and Fukui index (ƒ0) of main carbon atoms in seven fluoroquinolones. This study sheds light on the existence of electron migration channels at Z-scheme heterojunction interface to ensure sufficient photoinduced carrier transfer, and reveals the influence of pollutant structure on photolysis rate.

Advanced photocatalytic materials based degradation of micropollutants and their use in hydrogen production - a review

The use of pharmaceuticals, dyes, and pesticides in modern healthcare and agriculture, along with expanding industrialization, heavily contaminates aquatic environments. This leads to severe carcinogenic implications and critical health issues in living organisms. The photocatalytic methods provide an eco-friendly solution to mitigate the energy crisis and environmental pollution. Sunlight-driven photocatalytic wastewater treatment contributes to hydrogen production and valuable product generation. The removal of contaminants from wastewater through photocatalysis is a highly efficient method for enhancing the ecosystem and plays a crucial role in the dual-functional photocatalysis process. In this review, a wide range of catalysts are discussed, including heterojunction photocatalysts and various hybrid semiconductor photocatalysts like metal oxides, semiconductor adsorbents, and dual semiconductor photocatalysts, which are crucial in this dual function of degradation and green fuel production. The effects of micropollutants in the ecosystem, degradation efficacy of multi-component photocatalysts such as single-component, two-component, three-component, and four-component photocatalysts were discussed. Dual-functional photocatalysis stands out as an energy-efficient and cost-effective method. We have explored the challenges and difficulties associated with dual-functional photocatalysts. Multicomponent photocatalysts demonstrate superior efficiency in degrading pollutants and producing hydrogen compared to their single-component counterparts. Dual-functional photocatalysts, incorporating TiO2, g-C3N4, CeO2, metal organic frameworks (MOFs), layered double hydroxides (LDHs), and carbon quantum dots (CQDs)-based composites, exhibit remarkable performance. The future of synergistic photocatalysis envisions large-scale production facilitate integrating advanced 2D and 3D semiconductor photocatalysts, presenting a promising avenue for sustainable and efficient pollutant degradation and hydrogen production from environmental remediation technologies.

Insight into the catalytic performances of Fe0@chitosan/cellulose green hybrid structure for enhanced photo-Fenton's oxidation of levofloxacin toxic residuals: Pathway and toxicity

A green hybridized structure of Fe0 painted chitosan/cellulose base (Fe0@CS/CF) has been developed using cellulose extracted from sugarcane bagasse along with reduction agents sourced from Khaya senegalensis leaves. The composite was assessed as an affordable, powerful, and multifunctional catalyst for enhancing the degradation of Levofloxacin (LVX) remnants within water supplies via photo-Fenton's interactions. Using a dosage of 0.5 g/L, the Fe0@CS/CF blend demonstrated noteworthy catalytic qualities, resulting in the complete photo-Fenton's degradation of LVX at a level of 25 mg/L after 40 min. However, the complete diminution of organic carbon (TOC) occurred only after 100 min, suggesting the presence of significant intermediate residues. The identified intermediate chemicals and confirmed hydroxyl radicals as the main oxidizer suggest that the degradation pathway involves carboxylation/decarboxylation, hydroxylation, demethylation, and oxidation of quinolone rings. The toxicity properties of untreated LVX solutions and their subsequent oxidized byproducts were assessed by evaluating their inhibiting impact on Vibrio fischeri over various durations. The samples that experienced partial oxidation at initial testing demonstrated a higher level of toxicity in comparison to the parent LVX. However, the sample that was treated for 100 min demonstrated substantial biological safety and a non-toxic nature. The blend of ingredients has a synergistic impact that enhances the uptake, Fenton's, photocatalytic, and photo-Fenton's characteristics of the hosted Fe0 nanoparticles.

Boosting the photocatalytic activity of g-C3N4 via loading bio-synthesized Ag0 nanoparticles and imidazole modification for the degradation and mineralization of fluconazole

The emergence of fluorinated organic compounds in the pharmaceutical, agrochemical, and textile industries has led to a potential increase in the environmental issues and health problems. Herein, a modified heterojunction of bio-synthesized Ag nanoparticles (Ag0 NPs) immobilized on imidazole-modified graphite carbon nitride (Im/g-C3N4) as a suitable support (Ag0/Im/g-C3N4) was hydrothermally synthesized and studied for the photocatalytic removal of the most widely used antifungal organo-fluorine compound-fluconazole (FCZ). The optical properties were thoroughly investigated in the present study, and it was observed that the proposed modification to g-C3N4 has led to the shifting of conduction and valance band edge position (for g-C3N4, -0.73 and 1.54 eV and for ICA, -1.14 and 1.28 eV), narrowing of band gap energies, i.e., 2.01 eV, and reduced charge recombination rate. The external and internal surface morphologies were scrutinized through FE-SEM and HR-TEM analyses. Functionalities and potential crystallinity were investigated using FTIR and XRD techniques. The elemental state and composition of the composite were analyzed via XPS. The obtained results substantiate the intended modifications in the ICA composite. The photocatalyst Ag0/Im/g-C3N4 (ICA) was able to degrade 95.74% of FCZ with a high degradation rate (k1) of 0.0289 min-1 within 2-h of the solar illumination experiment. The overall degradation process was observed to be governed by a pseudo-first-order kinetic model. Detailed parameters such as effects of ions, pH (optimized pH 4, highest degradation rate k1 =0.039 min-1), dissolved organic matter (DOM), and optimization of catalysts dosage were studied. The major reactive oxygen species (ROS) was identified as super-oxide radicals (O2●-). The HR-MS and COD-TOC analysis were used to evaluate the degradation and mineralization of FCZ forced by ICA catalysts. The ICA catalyst was found to be stable and reusable for up to five cycles suggesting towards its potential towards the mitigation of environmental pollutants.

Engineering highly dispersed AgI nanoparticles on hierarchical In2S3 hollow nanotube to construct Z-scheme heterojunction for efficient photodegradation of insecticide imidacloprid

Increasing the exposure of active sites and improving the intrinsic activity are necessary considerations for designing a highly efficient photocatalyst. Herein, an In2S3/AgI stable Z-scheme heterojunction with highly dispersed AgI nanoparticles (NPs) is synthesized by the mild self-templated and in-situ ion exchange strategy. Impressively, the optimized In2S3/AgI-300 Z-scheme heterojunction exhibits superior photodegradation activity (0.020 min-1) for the decomposition of insecticide imidacloprid (IMD), which is extremely higher than that of pure In2S3 (0.002 min-1) and AgI (0.013 min-1). Importantly, the three-dimensional excitation-emission matrix (3D EEMs) fluorescence spectra, high-resolution mass spectrometry (HRMS), the photoelectrochemical tests, radical trapping experiment, and electron spin resonance (ESR) technique are performed to clarify the possible degradation pathway and mechanism of IMD by the In2S3/AgI-300 composite. The enhanced photocatalytic performance is attributed to the highly dispersed AgI NPs on hierarchical In2S3 hollow nanotube and the construction of In2S3/AgI Z-scheme heterojunction, which can not only increase active site exposure, but also improve its intrinsic activity, facilitating rapid charge transfer rate and excellent electron-hole pairs separation efficiency. Meanwhile, the practical application potential of the In2S3/AgI-300 composite is systematically investigated. This study opens a new insight for designing catalysts with high photocatalytic performance through a convenient approach.

Environment-friendly organic coordination design of Z-scheme heterojunction N-BOB/BiOIO3 for efficient LED-light-driven photocatalytic and electrochemical performance

As the climate seriously changes, ecofriendly nanomaterials have attracted tremendous interest in renewable energy as photocatalysis. Herein, we designed a new green bismuth-based Z-scheme Bi2O22+ slabs coordinate with 2-aminoterephthalic acid (N-BOB)/BiOIO3 through a simple anion exchange and postsynthetic hydrothermal reaction. FTIR, XRD, FESEM and TEM were employed to characterize the functional groups, structure, and morphologies. UV-DRS revealed the difference in band energy of the N-BOB and N-BOB/BiOIO3. Toward Rh B, TC and CIP degradation tests, 1-N-BOB/BiOIO3 manifests the best photocatalytic degradation (52.3%, 63.6% and 30.2%) efficiency. Also, 1-N-BOB/BiOIO3 possesses high durability in photocatalytic reactions and can inhibit 32.3% of bacterial growth. The results indicate that the synergistic effect between surface amine groups and Z-scheme heterojunction harvests light absorption to increase solar-to-energy (STE) efficiency, accelerate the charge separation, and increases the active sites with high photoredox potential, thus improving the photocatalytic performance. ROS scavenging tests further elucidated that photogenerated holes and hydroxyl radicals play a critical role. In addition, the surface amine groups and benzene rings can be utilized for supercapacitors and other multidisciplinary applications. 0.5 N-BOB/BiOIO3/GO impressively showed 5 times higher specific capacitance than pure GO electrode. We hope this work provides new sight into designing green nanomaterials to relieve environmental pollution and leave behind a clean future for the next generation.

Degradation of Levofloxacin by a green zero-valent iron-loaded carbon composite activating peroxydisulfate system: Reactivity, products and mechanism

In this study, a green zero-valent iron-loaded carbon composite (ZVI-SCG) was synthesized using coffee grounds and FeCl3 solution through two-steps method, and the synthesized ZVI-SCG was used in the activation of peroxydisulfate (PDS) to degrade Levofloxacin (LEX). Results revealed that ZVI-SCG exhibited a great potential for LEX removal by adsorption and catalytic degradation in the ZVI-SCG/PDS system, and 99% of LEX was removed in the ZVI-SCG/PDS system within 60 min. ZVI-SCG/PDS system showed a high reactivity toward LEX degradation under realistic environmental conditions. Also, the ZVI-SCG/PDS system could effectively degrade several quinolone antibiotics including gatifloxacin, ciprofloxacin and LEX in single and simultaneous removal modes. A potential reaction mechanism of LEX degradation by ZVI-SCG/PDS system was proposed, SO4•-, HO•, O2•- and 1O2 involved in radical and non-radical pathways took part in catalytic degradation of LEX by ZVI-SCG/PDS system, but HO• might be the main reactive species for LEX degradation. The possible degradation pathway of LEX was also proposed based on the identified ten intermediate products, LEX degradation was successfully achieved through decarboxylation, opening ring and hydroxylation processes. The potential toxicity of LEX and its oxidation products decreased significantly after treatment. This study provides a promising strategy of water treatment for the antibiotics-containing wastewater.

Construction of Co3O4 anchored on Bi2MoO6 microspheres for highly efficient photocatalytic peroxymonosulfate activation towards degradation of norfloxacin

Dissolved antibiotics have been a research subject due to their widespread presence and potential threats in drinking water treatment. To enhance the photocatalytic activity of Bi₂MoO₆ for the degradation of norfloxacin (NOR), the heterostructured Co₃O₄/Bi₂MoO₆ (CoBM) composites were synthesized by employing ZIF-67-derived Co₃O₄ on Bi₂MoO₆ microspheres. The as-synthesized resultant material 3-CoBM by 300 °C calcination was characterized by XRD, SEM, XPS, transient photocurrent techniques, and EIS. The photocatalytic performance was evaluated by monitoring different concentrations, NOR removal from aqueous solution. Compared with Bi₂MoO₆, 3-CoBM exhibited the better adsorption and elimination capacity of NOR due to the combined effect between peroxymonosulfate activation and photocatalytic reaction. The influences of catalyst dosage, PMS dosage, various interfering ions (Cl^-, NO₃^-, HCO₃^-, and SO₄^2-), pH value, and type of antibiotics for application removal were also invested. By activating PMS under visible-light irradiation, 84.95% of metronidazole (MNZ) can be degraded within 40 min, and NOR and tetracycline (TC) can be completely degraded using 3-CoBM. Degradation mechanism was elucidated by quenching tests in combination with EPR measurement, and the degree of activity of the active groups from strong to weak is h⁺, SO₄^-•, and •OH, respectively. The degradation products and conceivable degradation pathways of NOR were speculated by LC-MS. In combination of excellent peroxymonosulfate activation and highly enhanced photocatalytic performance, this newly Co₃O₄/Bi₂MoO₆ catalyst might be a promising candidate for degrading emerging antibiotic contamination in wastewater.

Ag2CO3-Based Photocatalyst with Enhanced Photocatalytic Activity for Endocrine-Disrupting Chemicals Degradation: A Review

Endocrine-disrupting chemicals (EDCs) in the aquatic environment have garnered a lot of attention during the past few years. Due to their toxic behavior, which interferes with endocrine functions in both humans and aquatic species, these types of compounds have been recognized as major polluting agents in wastewater effluents. Therefore, the development of efficient and sustainable removal methods for these emerging contaminants is essential. Photocatalytic removal of emerging contaminants using silver carbonate (Ag2CO3)-based photocatalyst is a promising process due to the unique characteristics of this catalyst, such as absorption of a larger fraction of the solar spectrum, wide band gap, non-toxicity, and low cost. The photocatalytic performance of Ag2CO3 has recently been improved through the doping of elements and optimization variation of operational parameters resulting in decreasing the rate of electron–hole pair recombination and an increase in the semiconductor’s excitation state efficiency, which enables the degradation of contaminants under UV or visible light exposure. This review summarized some of the relevant investigations related to Ag2CO3-based photocatalytic materials for EDC removal from water. The inclusion of Ag2CO3-based photocatalytic materials in the water recovery procedure suggests that the creation of a cutting-edge protocol is essential for successfully eliminating EDCs from the ecosystem.

Electron flux at the Schottky junction of Bi NPs and WO3-supported g-C3N4: an efficient ternary S-scheme catalyst for removal of fluoroquinolone-type antibiotics from water

Recently, global-scale attempts have been conducted to develop clean technologies and affordable materials to remediate pharmaceutical contaminants of water resources that are resistant to the biodegradation. In line with global efforts, this study reports a facile method to fabricate Bi nanocrystals in situ decorated on WO₃ nanoplates and its composite with graphitic carbon nitride (WO₃/Bi/g-C₃N₄) for photocatalytic degradation of fluoroquinolone-type antibiotics (ciprofloxacin and ofloxacin). The designed ternary S-scheme WO₃/Bi/g-C₃N₄ composite material was fully characterized by physicochemical and electrochemical analysis. Depositing the cost-effective and earth-abundant Bi nanocrystals onto WO₃ via a facile reduction route has been shown to increase the boosting of electron flux at their interface (Schottky junction). The S-scheme separation is confirmed by the calculation of band positions and the analysis of photogenerated hydroxyl radicals and holes. The complete removal of contaminants was obtained over the WO₃/Bi/g-C₃N₄ photocatalyst after 90 min under visible light irradiation. The present work would provide a rational route for developing Bi NP-based photocatalysis to replace metallic Au, Pt, and Ag NPs.

MOFFeCo/B-CN composites achieve efficient degradation of antibiotics in a non-homogeneous concurrent photocatalytic-persulfate activation system

We synthesized an M_FeCoB_0.4CN_x% (MOF-Fe/Co nanosheets/boron-doped g-C₃N₄) composite catalyst for enhancing the concurrent photocatalytic-persulfate activation (CPPA) system and achieved efficient degradation of antibiotics. The role of MOF-Fe/Co is to activate persulfate, while boron-doped g-C₃N₄ can generate photogenerated electrons for the reduction of Co³⁺/Fe³⁺ to enhance the regeneration of the active center. The rate constant for Tetracycline degradation by the CPPA system was 4.74 and 7.54 times higher than the photocatalytic and persulfate-activated systems, respectively. This composite was shown to be practical and economically viable for antibiotic degradation. The degradation behavior was explored based on experiments, and molecular orbitals and Fukui functions were obtained by density functional theory calculations. Mechanisms were investigated using reactive oxygen species trapping studies and electron spin resonance, and the process was explained in terms of the charge population and electron density difference of MOF-Fe/Co nanosheets. The CPPA system is an ecologically benign technology for removing antibiotic-related risks to the environment and human health.

Cost-effective Bi2WO6 for efficient degradation of rhodamine B and tetracycline

The morphology-controlled synthesis of nanostructured photocatalysts by an environmentally friendly and low-cost method provides a feasible way to realize practical applications of photocatalysts. Herein, Bi2WO6 (BWO) nanophotocatalysts with mulberry shape, sheet-like, and round-cake morphologies have been successfully synthesized through a highly facile solvothermal process by simply adjusting the solvothermal temperature or utilizing selective addition of ethylene glycol as an orientation agent without using strong acids and bases and/or hazardous chemicals. The ratio of ethylene glycol and glacial acetic acid can affect the morphology and oxygen vacancy content of BWO, thereby influencing the photocatalytic performance. The photocatalytic activity of the as-prepared samples was evaluated by degradation of rhodamine B (RhB) and tetracycline under visible-light irradiation. The results indicated that all the BWO samples exhibited morphology-associated photocatalytic activity, and the sheet-like structure of BWO obtained via solvothermal treatment at 120 °C with ethylene glycol and glacial acetic acid ratio of 1:3 achieved the maximum specific surface area and possessed abundant oxygen vacancies, exhibiting outstanding photocatalytic activity for degradation of RhB and tetracycline. The degradation rate of RhB reached 100% within 20 min. To the best of our knowledge, this value is one of the most remarkable values for pristine BWO photocatalysts. Radical capture experiments demonstrated that hydroxyl radicals (·OH) play major roles compared with electrons (e-) and holes (h+) in the photocatalytic degradation process. A possible mechanism for the photocatalytic degradation of pollutants was proposed to better understand the reaction process. We believe that the more economical, efficient and greener methodology can provide guidance to develop highly efficient photocatalysts with favourable morphology and structure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10854-022-09654-z.

Ceftriaxone sodium degradation by carbon quantum dots (CQDs)-decorated C-doped α-Bi2O3 nanorods

A novel carbon quantum dots decorated C-doped α-Bi₂O₃ photocatalyst (CBO/CQDs) was synthesized by solvothermal method. The synergistic effect of adsorption and photocatalysis highly improved contaminants removal efficiencies. The ceftriaxone sodium degradation rate constant (k) of CBO/CQDs was 11.4 and 3.2 times that of pure α-Bi₂O₃ and C-doped α-Bi₂O₃, respectively. The interstitial carbon doping generated localized states above the valence band, which enhanced the utilization of visible light and facilitated the separation of photogenerated electrons and holes; the loading of CQDs improved the charge carrier separation and extended the visible light response; the reduced particle size of CBO/CQDs accelerated the migration of photogenerated carriers. The •O₂ ^- and h⁺ were identified as the dominant reactive species in ceftriaxone sodium degradation, and the key role of •O₂ ^- was further investigated by NBT transformation experiments. The Fukui index was applied to ascertain the molecular bonds of ceftriaxone sodium susceptible to radical attack, and intermediates analysis was conducted to explore the possible degradation pathways. The toxicity evaluation revealed that some degradation intermediates possessed high toxicity, thus the contaminants require sufficient mineralization to ensure safe discharge. The present study makes new insights into synchronous carbon dopping and CQDs decoration on modification of α-Bi₂O₃, which provides references for future studies.

Constructing 2D/2D ultrathin Ti3C2/SnS2 Schottky heterojunctions toward efficient tetracycline degradation

In this article, a novel 2D/2D ultrathin Ti₃C₂/SnS₂ Schottky heterojunctions have been prepared via a facile hydrothermal process. The properties of the heterojunction were fully characterized. The photocatalytic degradation performance of composites was examined by photo-degradation of tetracycline hydrochloride (TC-HCL) under visible light irradiation. Compared with single SnS₂, 3% Ti₃C₂/SnS₂ displayed the better performance, the removal rate of TC-HCL reached 87.7% and the kinetic rate constant (k) of the optimal 3% Ti₃C₂/SnS₂ composite was about 2.7 times of that of bare SnS₂. The improved photocatalytic activity of Ti₃C₂/SnS₂ is ascribed to the formation of 2D/2D Schottky heterojunction, which promotes the spatial charge separation and increases the surface reactive sites.

A Study of the Degradation of LEV by Transparent PVA/NCD-TiO2 Nanocomposite Films with Enhanced Visible-Light Photocatalytic Activity

In recent years, antibiotics (such as levofloxacin (LEV)) have been detected widely in the environment. Semiconductor photocatalysis has been recognized as a promising technology for removing pollutants in the environment. In this work, nitrogen and carbon codoped titanium dioxide nano-catalyst (NCD-TiO2) was immobilized in polyvinyl alcohol (PVA) matrix to form PVA/NCD-TiO2 films through solution casting and thermal treatment, which exhibited good photocatalytic efficiency for LEV degradation. The results showed that about 42% LEV can be degraded after 2 h in the presence of PVA/NCD-TiO2 nanocomposite film (the weight ratio of NCD-TiO2 to PVA is 8% and thermal treatment is 120 °C) under visible light. Moreover, possible pathways of photocatalytic degradation of LEV according to the detected intermediates are proposed, which provide insight into the degradation mechanism of LEV by using PVA/NCD-TiO2 photocatalytic films. Finally, the synthesized PVA/NCD-TiO2 films exhibited excellent reusability and stability in photocatalysis. This work provides fundamental support for the design of a high-stability, excellent photocatalyst for practical application.

Novel insights into the mechanism of periodate activation by heterogeneous ultrasonic-enhanced sludge biochar: Relevance for efficient degradation of levofloxacin

In this study, a novel heterogeneous ultrasonic (US)-enhanced sludge biochar (SBC) activated periodate (PI) system was established and explored for the rapid removal of levofloxacin in the aqueous environment. This study focused on the mechanisms of US-enhanced SBC co-activation of PI for levofloxacin degradation. The results indicated that US and SBC exhibited a remarkable synergistic reinforcing activation effect on PI compared to single PI activation systems. The SBC/US/PI system achieved approximately 95% of levofloxacin removal, 51.5% of TOC removal, and 22% of dechlorination rate within 60 min with virtually no heavy metals released into the water matrix. In addition, the acute ecotoxicity of the solutions treated with the SBC/US/PI system was substantially reduced. The presence of IO₃^•, ^•OH, ¹O₂ and O₂^•- were identified in the SBC/US/PI system using quenching experiments and EPR technology while ^•OH and ¹O₂ were the predominant reactive species. Mechanistic studies have suggested that the cavitation effect of ultrasonic improved the dispersion and mass transfer efficiency of SBC and accelerated the desorption process of SBC. Possible pathways of levofloxacin degradation were proposed. This study provides a novel and promising strategy for the efficient removal of emerging contaminants such as antibiotics from the water matrix.

Effective photodegradation of rhodamine B and levofloxacin over CQDs modified BiOCl and BiOBr composite: Mechanism and toxicity assessment

In this contribution, carbon quantum dots (CQDs) modified 3D-flower like BiOX (X = Cl, Br, I) photocatalyst were successfully prepared via a facile mechanical compounding method. The crystal structure, surface composition, morphologies, optical properties and photocatalytic activities were investigated in detail. The photocatalytic activity of the as-obtained photocatalyst were evaluated by degradation of rhodamine B (RhB) and Levofloxacin (LEV) under near IR-UV-vis light irradiation, the CQDs/BiOX composite displayed enhanced photocatalytic activity as compared with individual BiOX materials. The CQDs/BiOX composite had the outstanding light harvesting and electron transfer ability because of the ordered ultrathin nanosheet structure of the BiOX, the formation of metal Bi under photoinduction, and the synergistic effects between CQDs and pure BiOX. Antibacterial activity and effects on Rye seeds growth of the LEV degradation intermediate were also researched. Reactive-species-trapping experiments exhibited that h⁺ and O₂^- were the active reactive species during photodegradation process. This work provided an effective and simple strategy for designing QDs modified Bi-rich oxyhalides in organic pollutant containing wastewater treatment.

Rational design of Ag2CO3-loaded SGO heterostructure with enhanced photocatalytic abatement of organic pollutants under visible light irradiation

The photocatalytic activity of semiconducting silver carbonate was restricted by the lower stability and fast recombination rate of photogenerated electron-hole pairs. Sulfur-doped graphene oxide (SGO) is used as a cocatalyst for improving the photocatalytic activity of Ag₂CO₃ by reducing the recombination rate. A simple precipitation method was used for the modification of silver carbonate. The chemical, physical, optical, and electrochemical properties of the modified photocatalyst was characterized by XRD, SEM, TEM, UV-vis DRS, XPS, CV, impedance, and amperometry. The fabricated SGO-Ag₂CO₃ composite was successfully degraded various organic pollutants such as methylene blue (MB), rhodamine B(RhB), methyl orange (MO), tartrazine, and thiram with augmented mineralization. The optimization of weight percentage of the developed binary composite with 0.5% SGO-Ag₂CO₃ showed enhanced photocatalytic degradation and followed pseudo-first-order kinetics with rate constant 0.126. More than 90% of degradation efficiency of the pollutants within a short time promises the binary heterostructure for future industrial applications. The excellent stability and reproducibility of the composite opened a new route in the treatment of wastewater.

Preparation of non-polluting Tb-doped mesoporous carbon nitride photocatalyst and study on the efficacy and mechanism of degradation of antibiotics in water

Given that the biological treatment of antibiotic wastewater can easily induce resistant bacteria, the photocatalytic degradation of antibiotics is considered as a better method for treating antibiotic wastewater. Therefore, the ability to remove Tylosin (TYL) and Tetracycline (TC) in aqueous solution using rare earth element Tb-doped g-C₃N₄ under simulated natural solar radiation was investigated. A series of rare earth Tb³⁺ doped mesoporous g-C₃N₄ were successfully prepared by nitric acid treatment and Tb(NO₃)₃·5H₂O samples showed significantly higher degradation efficiency for TYL and TC than pure g-C₃N₄. Leaching toxicity experiments were carried out on the catalyst using chard seeds and demonstrated negligible toxicity of the leachate from the catalyst. The structure, elemental state, optical properties, morphology, and photogenerated carrier separation of the prepared xTCN catalysts were characterized by XRD, XPS, UV-Vis DRS, TEM, and PL. The results show that Tb doping enhanced the photocatalytic activity of the g-C₃N₄ catalyst by narrowing the band gap while improving the light-trapping ability; The separation and transport rate of photogenerated carriers were significantly increased after Tb doping. Finally, a simple, efficient, and non-polluting Tb-doped carbon nitride photocatalyst is successfully developed in this paper.

Efficient degradation of orange II by core shell CoFe2O4-CeO2 nanocomposite with the synergistic effect from sodium persulfate

Novel core shell CoFe₂O₄-CeO₂ (CoFe-Ce) nanocomposite was synthesized and investigated as an efficient photocatalyst to activate sodium persulfate (Na2S2O8, PS) for orange Ⅱ (OⅡ) degradation. The CoFe-Ce nanocomposite was successfully designed and synthesized by a facile hydrothermal reaction followed by calcination and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), and vibrating sample magnetometer (VSM). Compared with pure CoFe₂O₄ and CeO₂, the photocatalytic efficiency of CoFe-Ce nanocomposite was significantly improved. Under the irradiation of visible light, the catalytic degradation efficiency of orange II could reach to 98.5% within 60 min. Additionally, the as-prepared material could be recycled for at least five times using magnetic separation ability of the nanocomposite, and during the cycling the dye degradation rate was almost unchanged. The active species produced during the degradation were studied by classical quenching experiments, and the different types of free radicals produced in the system were further confirmed by electron paramagnetic resonance (EPR) spectroscopy. This novel nanocomposite is expected to have potential application for degradation of organic pollutants in wastewater by utilizing solar energy.

Sono-photo hybrid process for the synergistic degradation of levofloxacin by FeVO4/BiVO4: Mechanisms and kinetics

A novel FeVO₄/BiVO₄ heterojunction photocatalyst was synthesized by hydrothermal method. The FeVO₄/BiVO₄ nanostructures were characterized by XRD, SEM, XPS, UV-vis, and photoluminescence spectroscopy. The effects of catalyst dosage, contaminant concentration, initial hydrogen peroxide (H₂O₂) concentration, and pH value on the degradation of levofloxacin were investigated and several repeated experiments were conducted to evaluate the stability and reproducibility. The optimized process parameters were used for mineralization experiments. Reactive oxygen species, degradation intermediates, and possible catalytic mechanisms were also investigated. The results showed that the sonophotocatalytic performance of the FeVO₄/BiVO₄ heterojunction catalyst was better than that of sonocatalysis and photocatalysis. In addition, the Type II heterojunction formed by the material still had good stability in the degradation of levofloxacin after 5 cycles. The possible degradation pathway and mechanism of levofloxacin by sonophotocatalysis were put forward. This work develops new sono-photo hybrid process for potential application in the field of wastewater treatment.

A novel electrochemically enhanced homogeneous PMS-heterogeneous CoFe2O4 synergistic catalysis for the efficient removal of levofloxacin

A novel electrochemically enhanced homogeneous-heterogeneous catalytic system was constructed by placing the prepared heterogeneous catalyst (CoFe₂O₄/NF) in parallel between the anode and the cathode for peroxymonosulfate (PMS) activation to remove levofloxacin (LVF) in this work. Over 90% of LVF could be effectively removed by the constructed system after 40 min's degradation. And the electrical energy consumption was only 2.51 kWh/m³, which was lower than 54.5% of the traditional electrochemical advanced oxidation process. Besides, the system broadened the response range of pH and overcame the inhibitory effect of alkaline conditions on degradation. These activities were mainly due to the high generation ability of free radical (SO₄^·-, ·OH and O₂^·-) and non-radical (¹O₂). And the SO₄^·- was found to be the main radical for LVF degradation. The high SO₄^·- generation ability was demonstrated to be resulted from the dual effects of synergy of CoFe₂O₄/PMS and enhancement of electrochemistry in EC/CoFe₂O₄/PMS system. In detail, electrochemistry could effectively promote the continuous circulation of Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺ redox cycles on the surface of CoFe₂O₄ to enhance the activation of PMS, thereby generating SO₄^·-. This work can provide a promising and cost-effective approach to construct highly efficient organic pollutant degradation system.

Encapsulation of spinel CuCo2O4 hollow sphere in V2O5-decorated graphitic carbon nitride as high-efficiency double Z-type nanocomposite for levofloxacin photodegradation

In this study, spinel CuCo₂O₄ (CCO) with a hierarchical hollow sphere morphology was encapsulated in V₂O₅-decorated ultra-wrinkled graphitic carbon-nitride (VO-UCN) for the first time via a facile glycerol-assisted solvothermal method in the interest of developing a novel high-efficiency double Z-type nano-photocatalyst (denoted as VO-UCN@CCO). The remarkable physicochemical features of the as-prepared nano-photocatalysts were verified using diverse characterization techniques including TGA, XRD, FT-IR, FE-SEM, TEM, BET, UV-vis DRS, PL, EIS, and transient photocurrent techniques. Herein, VO-UCN@CCO nanocomposite was employed for the photodisintegration of levofloxacin (LVOF) antibiotic under visible-light irradiation and the impact of certain operative reaction system variables was explored in an effort to optimize the photocatalytic capability. The 40% loading of CCO in VO-UCN@CCO nanocomposite was found to display maximum photocatalytic performance (about 95%) for LVOF photodecomposition, which was 9.3, 6.6, and 13.8 times greater when compared with pristine VO, UCN, and CCO, respectively. A high capability was observed for as-prepared photocatalyst during reusability tests and near 90% degradation efficiency was obtained in the sixth run. The complete mineralization of LVOF was achieved by the VO-UCN@CCO photocatalyst process after 300 min of reaction. An excellent synergy factor towards the degradation of LVOF was obtained for VO-UCN@CCO compared to each of its components alone. This peculiar design is envisaged to provide new inspirations for ameliorating the photocatalytic decontamination of tenacious and non-biodegradable species present in real wastewater.

A critical review on relationship of CeO2-based photocatalyst towards mechanistic degradation of organic pollutant

Nanostructured photocatalysts commonly offered opportunities to solve issues scrutinized with the environmental challenges caused by steep population growth and rapid urbanization. This photocatalyst is a controllable characteristic, which can provide humans with a clean and sustainable ecosystem. Over the last decades, one of the current thriving research focuses on visible-light-driven CeO₂-based photocatalysts due to their superior characteristics, including unique fluorite-type structure, rigid framework, and facile reducing oxidizing properties of cerium's tetravalent (Ce⁴⁺) and trivalent (Ce³⁺) valence states. Notwithstanding, owing to its inherent wide energy gap, the solar energy utilization efficiency is low, which limits its application in wastewater treatment. Numerous modifications of CeO₂ have been employed to enhance photodegradation performances, such as metals and non-metals doping, adding support materials, and coupling with another semiconductor. Besides, all these doping will form a different heterojunction and show a different way of electron-hole migration. Compared to conventional heterojunction, advanced heterojunction types such as p-n heterojunction, Z-scheme, Schottky junction, and surface plasmon resonance effect exhibit superior performance for degradation owing to their excellent charge carrier separation, and the reaction occurs at a relatively higher redox potential. This review attends to providing deep insights on heterojunction mechanisms and the latest progress on photodegradation of various contaminants in wastewater using CeO₂-based photocatalysts. Hence, making the CeO₂ photocatalyst more foresee and promising to further development and research.

Facile synthesis of MOF-808/AgI Z-scheme heterojunction with improved photocatalytic performance for the degradation of tetracycline hydrochloride under simulated sunlight

The MOF-808/AgI Z-scheme heterojunction expanded the light absorption range and promoted the separation of electron–hole pairs, thus enhancing the photocatalytic activity.

Engineering an oxygen-vacancy-mediated step-scheme charge carrier dynamic coupling WO3−X/ZnFe2O4 heterojunction for robust photo-Fenton-driven levofloxacin detoxification

Schematic representation of the photo-Fenton degradation of levofloxacin under solar-light illumination.

Effective promotion of g-C3N4 photocatalytic performance via surface oxygen vacancy and coupling with bismuth-based semiconductors towards antibiotics degradation

In this research, the potential of bismuth chromate (BCO), a new bismuth-based semiconductor belongs to the family of Bi₂XO₆ (X = Mo, W, or Cr), was introduced by a novel 1D/2D structure consist of BCO nanobelts and N₂-freezed ultra-wrinkled graphitic carbon nitride (N-CN) nanosheets. To enhance intimate contact between BCO and N-CN (BCO/N-CN composite), surface oxygen vacancy (V_O) was created as an efficient electron transfer highway using a simple alkaline-treatment-assisted method. Various characterization techniques, including XRD, FT-IR, EPR, FE-SEM, TEM, BET, DRS, PL, EIS, and photocurrent transient analyses were conducted to elucidate the physicochemical aspects of catalysts. The synthesized catalysts were subjected to levofloxacin (LVFX) photodegradation and optimum conditions were found under LED irradiation. Under optimum conditions, about 92.5% of LVFX was catalytically degraded over V_O-rich BCO/N-CN heterojunction after 120 min of reaction, which was 2.3 folds higher than that of V_O-free composite. The obtained heterojunction maintained superior performance after five consecutive runs with no noticeable changes in the XRD and FT-IR patterns, demonstrating the high stability of synthesized nanocomposite. Thus, the proposed interfacial engineering in this study opens new insight for ameliorating the insufficient interfacial contact between components of heterojunctions. This study not only presents a new bismuth-based photocatalyst for antibiotic degradation but also sheds light on the charge migration behavior in favor of efficient Z-type heterojunction.

Photocatalytic performance and interaction mechanism of reverse micelle synthesized Cu-TiO2 nanomaterials towards levofloxacin under visible LED light

The degradation performance of Cu-TiO₂ nanomaterials towards levofloxacin (LFX) antibiotic was investigated under an environmentally benign visible LED light source. Cu-TiO₂ nanomaterials were prepared using the reverse micelle sol-gel method with different copper content ranging from 0.25 to 1.0 wt% concerning titania. Characterization of Cu-TiO₂ samples was performed by XRD, TEM, UV-Vis, BET, ICP-MS, FTIR and XPS techniques. 0.5 wt% Cu-TiO₂ showed crystallite size below 6 nm, surface area (69.85 m²/g) and significant visible light absorption capacity. Both Cu¹⁺ and Cu²⁺ are formed in lower Cu-doped TiO₂ samples, whereas only Cu²⁺ is present in higher Cu-doped TiO₂ samples as evident in XPS analysis. 0.5 wt% Cu-TiO₂ has shown the optimum photocatalytic degradation of 75.5% under 6 h. of a visible light source. FTIR analysis of LFX adsorbed Cu-TiO₂ materials indicated the pollutant-catalyst interaction, where the declining trend was observed in photocatalytic degradation efficiency for higher Cu-doped TiO₂ samples due to copper-LFX complex formation. Copper-LFX complexes are formed due to the presence of Cu²⁺ in higher Cu-doped TiO₂ nanomaterials, which might have hindered the photocatalytic activity under visible light. Effects of initial pollutant concentration, catalyst loading and visible light intensity on the degradation of LFX are studied. Photocatalytic degradation pathways of LFX using best performing Cu-TiO₂ material were also proposed based on the LC-MS analysis.

Natural and engineered clays and clay minerals for the removal of poly- and perfluoroalkyl substances from water: State-of-the-art and future perspectives

Poly- and perfluoroalkyl substances (PFAS) present globally in drinking-, waste-, and groundwater sources are contaminants of emerging concern due to their long-term environmental persistence and toxicity to organisms, including humans. Here we review PFAS occurrence, behavior, and toxicity in various water sources, and critically discuss their removal via mineral adsorbents, including natural aluminosilicate clay minerals, oxidic clays (Al, Fe, and Si oxides), organoclay minerals, and clay-polymer and clay‑carbon (biochar and graphene oxide) composite materials. Among the many remediation technologies, such as reverse osmosis, adsorption, advanced oxidation and biologically active processes, adsorption is the most suitable for PFAS removal in aquatic systems. Treatment strategies using clay minerals and oxidic clays are inexpensive, eco-friendly, and efficient for bulk PFAS removal due to their high surface areas, porosity, and high loading capacity. A comparison of partition coefficient values calculated from extracted data in published literature indicate that organically-modified clay minerals are the best-performing adsorbent for PFAS removal. In this review, we scrutinize the corresponding plausible mechanisms, factors, and challenges affecting the PFAS removal processes, demonstrating that modified clay minerals (e.g., surfactant, amine), including some commercially available products (e.g., FLUORO-SORB®, RemBind®, matCARE™), show good efficacy in PFAS remediation in contaminated media under field conditions. Finally, we propose future research to focus on the challenges of using clay-based adsorbents for PFAS removal from contaminated water due to the regeneration and safe-disposal of spent clay adsorbents is still a major issue, whilst enhancing the PFAS removal efficiency should be an ongoing scientific effort.

Water-soluble manganese porphyrins as good catalysts for cipro- and levofloxacin degradation: Solvent effect, degradation products and DFT insights

Synthetic manganese porphyrins (MnPs), in the presence of oxidants, were employed for the degradation of fluoroquinolone antibiotics. Ciprofloxacin (CIP) and levofloxacin (LEV) degradation by iodosylbenzene, iodobenzene diacetate, H₂O₂ and meta-chloroperbenzoic acid using water-soluble MnP catalysts yielded thirteen and nine products, respectively, seven of which have been proposed for the first time. The MnP catalysts have demonstrated the ability to degrade these antibiotics to a high degree (up to 100% degradation). The structures of the degradation products were proposed based on mass spectrometry analysis, and density functional theory calculations could confirm how the substituent moieties attached to the basic chemical structure of the fluoroquinolones influence the degradation reactions. CIP has been shown to be a more reactive substrate towards the porphyrinic catalysts tested because of its three-membered ring. However, the catalysts could almost completely degrade LEV, highlighting the ability of these porphyrins to act as catalysts to degrade environmental pollutants.

Efficient removal of levofloxacin from different water matrices via simultaneous adsorption and photocatalysis using a magnetic Ag3PO4/rGO/CoFe2O4 catalyst

A magnetic Ag₃PO₄/rGO/CoFe₂O₄ ternary catalyst was firstly prepared and used for removing levofloxacin (LVF) from different water matrices via simultaneous adsorption and photocatalysis. Compared with Ag₃PO₄ and Ag₃PO₄/CoFe₂O₄, Ag₃PO₄/rGO/CoFe₂O₄ shows a superior adsorption-photocatalysis performance for LVF elimination since rGO component not only improves the adsorption ability but also enhances the charge separation efficiency of the catalyst. About 90.7% of LVF in distilled water (10 mg/L) was removed by the ternary catalyst after adsorption for 0.5 h and photocatalysis for 1.0 h, and the removal of LVF performed well in the pH range of 3.51-9.47. Singlet oxygen (¹O₂) was the major reactive oxygen species for LVF degradation in Ag₃PO₄/rGO/CoFe₂O₄ system under visible light, as confirmed by the quenching experiments and ESR study. Based on the detected intermediates in the photocatalytic process, the possible LVF degradation pathways were well-established. As-synthesized Ag₃PO₄/rGO/CoFe₂O₄ can also efficiently remove LVF from the different real water matrices (river water, lake water and secondary effluent) via simultaneous adsorption and photocatalysis. Moreover, magnetic Ag₃PO₄/rGO/CoFe₂O₄ can be easily recovered and effectively reused for the removal of LVF in actual water bodies.