Study on the photocatalytic degradation of metronidazole antibiotic in aqueous media with TiO2 under lab and pilot scale

Advanced oxidation process-mediated removal of pharmaceuticals from water: a review of recent advances

Pharmaceutical compounds have raised significant environmental concerns, due to their persistent and non-biodegradable nature. Addressing their presence in the environment has become a priority, leading to the application of various removal treatment techniques. Advanced oxidation processes (AOPs) undoubtedly have emerged as highly effective removal techniques, as evidenced by the growing body of work in this area. This review offers an overview of the recent advances in the development of AOPs for treating pharmaceuticals and their by-products. Current trends and discoveries reported in diverse AOP studies have been scrutinized and are presented. Furthermore, emphasis is placed on the use of TiO2-mediated photocatalysis, which stands out as one of the most explored AOPs for pharmaceutical remediation. Performance aspects of TiO2 photocatalytic treatment are explored and discussed encompassing both commercially available and synthesized TiO2, as well as engineered TiO2-based materials (e.g. activated carbon, polymers, metals and non-metals), all aimed at removal of pharmaceutical compounds from the environment. The review concludes by summarizing key findings and offers insights into directions for future research.

Photocatalytic degradation of NO by MnO2 catalyst: The decisive relationship between crystal phase, morphology and activity

This study investigates the critical relationship between the crystal phase, morphology, and photocatalytic activity of MnO2. The δ-MnO2 nanosheets, characterized by multiple exposed crystal planes forming junctions, exhibit optimized optical and electrical properties. Oxygen vacancy concentrations were observed in the order δ-MnO2 > γ-MnO2 > α-MnO2, with corresponding increases in band gap width from 1.38 eV (δ-MnO₂) to 1.68 eV (α-MnO₂). The δ-MnO2 nanosheets achieved over 80 % NO removal efficiency and effectively suppressed the production of NO2 byproducts, outperforming α-MnO2 nanorods and γ-MnO2 nanospheres. The adsorption energy of O₂ followed the trend δ-MnO2 > γ-MnO2 > α-MnO2, while the adsorption energy of NO was lowest on δ-MnO2, facilitating its interaction with reactive species such as •O2⁻ and •OH. For γ-MnO2, NO directly reacted with •O2⁻. The findings highlight the dependence of MnO2 photocatalytic performance on its crystal phase and morphology, with δ-MnO2 effectively inhibiting photogenerated electron-hole recombination due to its superior properties. This work presents a straightforward approach to designing high-performance transition metal photocatalysts through crystal phase and morphology control, offering valuable insights for future photocatalyst research.

Insight into enhanced tetracycline photodegradation by hematite/biochar composites: Roles of charge transfer, biochar-derived dissolved organic matter and persistent free radicals

The combination of hematite and biochar significantly accelerated tetracycline (TC) removal under visible light irradiation. The kinit of TC removal with Hem/BC-5 reached 0.103 min-1, 3.8 and 6.1 times faster than those with hematite and biochar, attributed to boosting free radicals. The enhanced light absorption and charge transfer helped generate more H2O2 and •OH through 2e- oxygen reduction and direct valence band (VB) oxidation. Persistent free radicals (PFRs) on biochar helped generate H2O2. Biochar as electron shutter facilitated Fe3+/Fe2+ redox cycling and triggered more efficient photo-Fenton reaction. Biochar-derived dissolved organic matter (DOM) helped generate 3DOM*, a reactive intermediate to produce H2O2, •OH, and 1O2. Hem/BC composites have excellent photoactivity for the degradation of TC in different water matrixes under visible light irradiation. The degradation pathway was proposed based on theoretical calculation and detected degradation intermediates. These findings contribute to the development of biochar-based catalysts for organic pollutants removal.

Based on T.E.S.T toxicity prediction and machine learning to forecast toxicity dynamics in the photocatalytic degradation of tetracycline

The integration of photocatalysis and biological treatment provides an effective strategy for controlling antibiotic contamination, which requires precise monitoring of toxicity changes during the photocatalytic process. In this study, nanoscale TiO2 (P25) was employed to degrade tetracycline (TC) under full-spectrum irradiation, with O2 identified as a crucial reactant for the generation reactive oxygen species (ROS). The toxicity simulation results of the degradation intermediates were closely correlated with the predictions of T.E.S.T software. By analyzing the content of intermediates under different experimental conditions, we developed a machine learning model utilizing the random forest algorithm with a correlation coefficient of R2 = 0.878 and a mean absolute error of MAE = 0.02. The model can track the changes of photocatalytic intermediates, in combination with toxicity simulation, which facilitates the prediction of toxicity at different degradation stages, thus allowing selection of the optimal timing of biological treatment interventions.

Distribution and ecological risk assessment of antibiotics in different freshwater aquaculture ponds in a typical agricultural plain, China

Freshwater aquaculture serves as a significant focal point for antibiotic contamination, yet understanding antibiotic distribution across different aquaculture models and stages remains limited. This study evaluated antibiotic pollution in three distinct freshwater aquaculture models: rice-crayfish coculture, fish aquaculture, and crab-crayfish aquaculture, during various aquaculture stages. Of the 33 target antibiotics, 16 antibiotics were detected, with the total concentrations ranging from 111.81 ng/L to 15,949.05 ng/L in water and 10.11 ng/g to 8986.30 ng/g in sediment. Among these antibiotics, erythromycin and lomefloxacin are prohibited for use in Chinese aquaculture. Dominant antibiotics in water included lincomycin, enrofloxacin, and enoxacin, whereas in sediment, oxytetracycline and erythromycin were predominant. Notably, lincomycin emerged as a dominant antibiotic in aquaculture for the first time. The concentrations of these dominant antibiotics were high compared to other aquaculture settings and exhibited elevated ecological risk. Critical periods for antibiotic contamination in water and sediment were found to be incongruent, occurring during the rainy season in July for water and the dry season in October for sediment. Notably, the rice-crayfish coculture model exerts a good effect in reducing antibiotic pollution. Overall, these findings offer valuable evidence for the healthful and sustainable advancement of aquaculture.

An innovative Zn3In2S6/ZnIn2S4 homojunction photocatalyst with enhanced interfacial charge transfer for the highly efficient degradation of tetracycline under visible radiation

The interfacial charge transfer ability is a decisive factor influencing the photocatalytic performance of composite photocatalysts. Compared with heterojunctions that combine two or more semiconductors with different properties, homojunctions that combine two semiconductors with similar properties can accelerate the interfacial charge shift and achieve higher photocatalyticability. In this study, a Zn3In2S6/ZnIn2S4 homojunction photocatalyst (ZIS-5) with a Zn3In2S6 to ZnIn2S4 molar ratio of 5:1 was synthesized by selecting Zn3In2S6 nano-microspheres as the substrate material and growing ZnIn2S4 flocs on the nano-microspheres. The photocatalytic performance of the ZIS-5 homojunction was assessed by using tetracycline (TC) as a typical pollutant. The photocatalytic performance and mineralization rate of the ZIS-5 homojunction were significantly improved compared with those of Zn3In2S6 and ZnIn2S4, and its photocatalytic performance was increased by 10.2% and 20.9%, compared with Zn3In2S6 and ZnIn2S4, respectively, while the mineralization rate was enhanced by 22.78% and 43.28%, respectively. The results of the comparison experiment revealed that the interfacial electron transfer ability of the ZIS-5 homojunction is 1.6 times that of the g-C3N4/ZnIn2S4-5 heterojunction. The density functional theory (DFT) computation and Mott-Schottky plots verified the formation of an internal electric field. The toxicity analysis showed that the ZIS-5 homojunction system effectively reduced the toxicity of TC. This work supplies a valuable route for inventing catalysts with efficient photocatalytic performances.

Carbon defects-enriched NBC-C3N5@CoMn with ultrafast modulation of redox couples for efficient degradation of contaminant

The inefficiency of catalysts in sulfate radical-based advanced oxidation processes (SR-AOPs) is primarily attributed to the sluggish circulation of redox couples. Herein, a carbon defects-enriched NBC-C3N5@CoMn (NCC) was synthesized through a self-assembly approach. The carbon defects within the NCC induce the electron trap effect, thereby facilitating the efficient cycling of redox couples in photo-Fenton-like processes during contaminant degradation. This effect enables the self-regeneration of the NCC catalyst. The reductive redox couples (Co (II) and Mn (II)) are continuously regenerated following the degradation process. Within the NCC, CoMn layered double hydroxides (LDHs) act as primary active sites, promoting the generation of hydroxyl radicals (•OH), sulfate radicals (SO4•-) and singlet oxygen (1O2) through continuous electron gain and loss. Additionally, the internal electric field established within the NCC further accelerates electron transfer. Density Functional Theory (DFT) calculations confirm that the carbon defects-enriched NCC exhibits lower adsorption energies and higher electron transfer efficiencies than carbon defect-deficient NCC. This study introduces a novel photocatalyst with self-regenerating capabilities, presenting an innovative approach to regulate redox couples in SR-AOPs for sustainable degradation.

Synthesis and photodegradation performance of a heterostructure ferromagnetic photocatalyst based on MWCNTs functionalized with (3-glycidyloxypropyl)trimethoxysilane and decorated with tungsten trioxide for metronidazole and acetaminophen degradation in aqueous environments

The presence of metronidazole (MNZ) and acetaminophen (ACE) in aquatic environments has raised growing concerns regarding their potential impact on human health. Incorporating various patterns into a photocatalytic material is considered a critical approach to achieving enhanced photocatalytic efficiency in the photocatalysis process. In this study, WO3 nanoparticles, which were immobilized onto ferromagnetic multi-walled carbon nanotubes that were functionalized using (3-glycidyloxypropyl)trimethoxysilane (FMMWCNTs@GLYMO@WO3), exhibited remarkable efficiency in removing MNZ and ACE (93% and 97%) in only 15 min. In addition, the new visible-light FMMWCNTs@GLYMO@WO3 nanoparticles as a magnetically separable photocatalyst were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), EDS-mapping, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS), high-performance liquid chromatography (HPLC), and total organic carbon (TOC) due to detailed studies (morphological, structural, magnetic and optical properties) of the photocatalyst. In-depth spectroscopic and microscopic characterization of the newly developed ferromagnetic FMMWCNTs@GLYMO@WO₃ (III) photocatalyst revealed a spherical morphology, with nanoparticle diameters averaging between 23 and 39 nm. Compared to conventional multiwall carbon nanotube and WO₃ photocatalysts, FMMWCNTs@GLYMO@WO₃ (III) demonstrated superior photocatalytic activity. Remarkably, it exhibited excellent reusability, maintaining its efficiency over a minimum of five cycles in the degradation of metronidazole (MNZ) and acetaminophen (ACE).

Synthesis and Characterization of Composite WO3 Fibers/g-C3N4 Photocatalysts for the Removal of the Insecticide Clothianidin in Aquatic Media

Photocatalysis is a prominent alternative wastewater treatment technique that has the potential to completely degrade pesticides as well as other persistent organic pollutants, leading to detoxification of wastewater and thus paving the way for its efficient reuse. In addition to the more conventional photocatalysts (e.g., TiO2, ZnO, etc.) that utilize only UV light for activation, the interest of the scientific community has recently focused on the development and application of visible light-activated photocatalysts like g-C3N4. However, some disadvantages of g-C3N4, such as the high recombination rate of photogenerated charges, limit its utility. In this light, the present study focuses on the synthesis of WO3 fibers/g-C3N4 Z-scheme heterojunctions to improve the efficiency of g-C3N4 towards the photocatalytic removal of the widely used insecticide clothianidin. The effect of two different g-C3N4 precursors (urea and thiourea) and of WO3 fiber content on the properties of the synthesized composite materials was also investigated. All aforementioned materials were characterized by a number of techniques (XRD, SEM-EDS, ATR-FTIR, Raman spectroscopy, DRS, etc.). According to the results, mixing 6.5% W/W WO3 fibers with either urea or thiourea derived g-C3N4 significantly increased the photocatalytic activity of the resulting composites compared to the precursor materials. In order to further elucidate the effect of the most efficient composite photocatalyst in the degradation of clothianidin, the generated transformation products were tentatively identified through UHPLC tandem high-resolution mass spectroscopy. Finally, the detoxification effect of the most efficient process was also assessed by combining the results of an in-vitro methodology and the predictions of two in-silico tools.

Aqueous fate of furaltadone: Kinetics, high-resolution mass spectrometry - based elucidation and toxicity assessment of photoproducts

Furaltadone (FTD) is an antibiotic belonging to the nitrofurans group. It has been broadly used in livestock and aquaculture for therapeutic purposes, as well as for stimulating promotion. Although the European Union has imposed restrictions on the use of FTD since 1995 due to concerns regarding its toxicity, in many cases FTD has been excessively and/or illegally applied in productive animals in developing countries, because of its high efficacy and low-cost. Unlike other nitrofuran compounds, the hydrolytic and photolytic behavior of FTD in natural aquatic systems has not been thoroughly investigated. To this end, hydrolysis in different pH values and photolysis in aquatic environment, including lake, river and sea water have been both examined. Hydrolysis was found to have an insignificant impact on degradation of FTD in the aquatic environment relevant pH values, whereas indirect photolysis proved to be the main route of its elimination. The identification of tentative photoproducts (PPs) was performed using ultra high performance liquid chromatography coupled to hybrid LTQ/Orbitrap high resolution mass spectrometry. A possible pathway for photolytic transformation of FTD was proposed. Additionally, in silico simulations were used to evaluate the toxicity such as the mutagenicity of FTD and PPs. Complementary to the low-cost and time-limited simulations, an in vitro method (Vibrio Fischeri bioluminescence) was also used to assess ecotoxicity.

Defective metal-organic framework derived from the waste plastic bottles for rapid and efficient nitroimidazole antibiotics removal

In order to alleviate the pressure on the ecological environment and human health caused by wastewater of nitroimidazole antibiotics and poly(ethylene terephthalate) (PET) plastic waste, we propose a strategy of using defective MIL-68(Al) (d-MIL-68(Al)) derived from waste PET plastic for dimetridazole (DMZ) capture. The resulting d-MIL-68(Al) exhibits an excellent adsorption capacity of 555.6 mg g-1, which is three times of pristine MIL-68(Al) (181.8 mg g-1), demonstrating that the defective structures in d-MIL-68(Al) play a crucial role in the adsorption process. Remarkably, d-MIL-68(Al) can remove nearly 97% of DMZ in the first 10 s, and the removal efficiency reached 99% after adsorption equilibrium, affording a record kinetic rate constant k2 (2.84 g mg-1 min-1). In short, d-MIL-68(Al) possesses both an ultrafast adsorption rate and outstanding adsorption capacity toward DMZ compared with reported adsorbents. Mechanism analysis reveals that the excellent DMZ adsorption performances can be ascribed to the abundant active sites caused by defective structures, as well as the π-π stacking and hydrogen bonding interactions between MOF and DMZ. Hence, d-MIL-68(Al) derived from waste PET plastic is an efficient porous adsorbent for rapid DMZ removal, which not only possesses great potential for wastewater treatment, but also reduces the harmful PET plastic waste, reflecting the concept of sustainable development.

Mn anchored zeolite molecular nest for enhanced catalytic ozonation of cephalexin

The molecular nest structured catalysts have demonstrated better performance than the traditional supported catalysts. However, they have not been tried in antibiotics or other organic pollutants removal from water by advanced oxidation processes (AOPs). Here we synthesized Mn anchored zeolite molecular nest (Mn@ZN) for the catalytic ozonation of cephalexin (CLX), which is the widely used antibiotic and also a refractory pollutant in water. The ozonation catalyzed by Mn@ZN achieves 97% of CLX degradation in only 2 min and a reaction rate constant of 0.2454 L mg^-1·s^-1, which is 79.2 times higher than that of the non-catalytic ozonation. Even after ten cycles, the 0.46Mn@ZN/O₃ still achieves a CLX degradation efficiency higher than 88% in 2 min, presenting an excellent stability. Mn ions stabilized by the molecular nests facilitate Lewis acid sites and oxygen vacancies, providing active sites for O₃ sorption and decomposition into ·O^2- and ¹O₂ through electrons transfer for the radical reaction with CLX. DFT calculation indicates that both the oxygen vacancy formation energy and the O₃ adsorption energy of Mn@ZN are reduced by the Mn species introduction. This study finds a fascinating catalyst of Mn@ZN for the catalytic ozonation of antibiotics, and also a smart design strategy for zeolite confined metals catalysts for water treatment.