Initial Metronidazole Concentration Research Articles

PW12/Fe3O4/biochar nanocomposite as an efficient adsorbent for metronidazole removal from aqueous solution: Synthesis and optimization

The growing occurrence of antibiotics in aquatic environments has emerged as a notable environmental issue given their potential detrimental impacts on ecosystems and the well-being of individuals. Therefore, there is a pressing need to develop effective strategies for removing antibiotics from wastewater. Herein, PW12/Fe3O4/biochar nanocomposite as a highly efficient adsorbent was synthesized to remove metronidazole (MNZ) antibiotic from wastewater through a sustainable and environmentally friendly approach. Simple surface modifications, such as chemical and physical modification with acid and base, as well as adding polyoxometalate were employed to enhance the adsorption of MNZ. The physical and chemical characteristics of the adsorbent were extensively analyzed using several techniques as follows, Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET), and transmission electron microscopy (TEM). Experimental results demonstrated a significant increase in the efficacy of MNZ removal when the adsorbent surface was modified with polyoxometalate (H3PW12O40) compared to magnetic biochar (MBC). This improvement favors the pore-filling mechanism, electrostatic, H-bonds, and π-π interactions. To optimize the operating parameters for MNZ removal, response surface methodology (RSM) was employed using Design Expert software, considering the pH of a solution, initial pollutant concentration, adsorbent amount, and contact time. The results revealed that when the conditions were ideal (pH ∼1, initial concentration of MNZ at 5 mg/L, adsorbent amount of 0.6 g/L, and contact time of 60 minutes), the removal efficiency and the adsorption capacity reached 94.28 % and 78.45 mg/g, respectively. The analysis of isotherm and kinetic experiments revealed that the adsorption mechanism followed the Freundlich isotherm and pseudo-second order kinetic models, respectively. Furthermore, the adsorbent demonstrated excellent efficiency and reusability, with a removal efficiency of over 90 % even after four cycles, highlighting its potential and economic viability as an adsorbent for metronidazole removal.

Fast and efficient removal of metronidazole from aqueous solution using graphene oxide (GO) supported nitrogen (N) doped zinc oxide (ZnO) nanoparticles

This work focused on the preparation of ZnO nanoparticles through modifications by nitrogen incorporation (N-ZnO NPs) and thereafter immobilized them on graphene oxide (GO) nanosheets to form GO-N-ZnO nanocomposites, followed by its application for the removal of metronidazole (MNZ) antibiotic from aqueous solution by effective adsorption and visible light driven photocatalysis. The structural, functional, surface morphology and optical properties of the synthesized samples were investigated by numerous techniques. In the comparative study of catalytic degradation of MNZ, GO-N-ZnO demonstrates 96.6% removal efficiency from aqueous solution by adsorption and photocatalysis under visible light irradiation and corresponding degradation kinetics have been studied. Thereafter, effects of initial concentration of MNZ and GO-N-ZnO catalyst dosages have been investigated. Scavengers test reveals that superoxide radicals are responsible for such fast improved degradation. A possible explanation is provided for such fast improved degradation of MNZ by GO-N-ZnO catalyst. The reusability and stability tests demonstrate that as prepared GO-N-ZnO can be used up to fourth consecutive cycles with satisfactory removal efficiency (88.4%) and retains its crystal structure. Finally, microbiological assay showed that the degraded MNZ aqueous solution has diminished capacity to inhibit bacterial growth compared to the control MNZ solution. These results describe the potential of environmental-friendly GO-N-ZnO catalyst for remediation and long-term reusability.

Hydrothermal-assisted synthesis of Sr-doped SnS nanoflower catalysts for photodegradation of metronidazole antibiotic pollutant in wastewater promoted by natural sunlight irradiation.

In this study, we report a facile hydrothermal synthesis of strontium-doped SnS nanoflowers that were used as a catalyst for the degradation of antibiotic molecules in water. The prepared sample was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible absorption spectroscopy (UV-Vis). The photocatalytic ability of the strontium-doped SnS nanoflowers was evaluated by studying the degradation of metronidazole in an aqueous solution under photocatalytic conditions. The degradation study was conducted for a reaction period of 300 min at neutral pH, and it was found that the degradation of metronidazole reached 91%, indicating the excellent photocatalytic performance of the catalyst. The influence of experimental parameters such as catalyst dosage, initial metronidazole concentration, initial reaction pH, and light source nature was optimized with respect to metronidazole degradation over time. The reusability of the strontium-doped SnS nanoflowers catalyst was investigated, and its photocatalytic efficiency remained unchanged even after four cycles of use.

Investigation of the adsorption and degradation of metronidazole residues in agricultural wastewater by nanocomposite based on nZVI on MXene

Metronidazole is a widely used antibiotic with powerful antimicrobial properties, but its presence in water can be detrimental to aquatic life and human health. To address this issue, we developed a novel composite material, zero-valent iron nanoparticles on alkalized Ti3C2Tx nanoflakes (NZVI/Ti3C2Tx), using an in-situ growth technique, aiming to efficiently adsorb and degrade metronidazole from aqueous solutions. The incorporation of Ti3C2Tx in NZVI/Ti3C2Tx resulted in enhanced dispersion, stability, and reactivity of NZVI. Our study demonstrated that NZVI/Ti3C2Tx exhibited the highest metronidazole removal efficiency (95.80%) within just 10 min of reaction time, outperforming NZVI and Ti3C2Tx alone. To optimize the removal process, we investigated the influence of various parameters on the degradation of metronidazole by NZVI/Ti3C2Tx, including the NZVI/Ti3C2Tx ratio, initial metronidazole concentration, pH, and reaction temperature. The highest removal rate was achieved with an NZVI/Ti3C2Tx ratio of 2:1 after 90 min of reaction time. As the initial concentration and pH of metronidazole increased, the removal efficiency decreased, while higher reaction temperatures improved the removal efficiency. Kinetic studies revealed that the degradation of metronidazole by NZVI/Ti3C2Tx followed a modified second-order parameter pseudo-first-order kinetic model, highlighting the effective reduction reaction. The unique properties of MXene nanosheets and NZVI synergistically contributed to the enhanced removal performance, with NZVI/Ti3C2Tx acting as an efficient adsorbent and reducing agent. Uur findings demonstrate the potential of the NZVI/Ti3C2Tx nanocomposite as an efficient and eco-friendly approach for the removal of metronidazole from agricultural wastewater. The combination of NZVI and Ti3C2Tx offers enhanced removal efficiency and stability, making it a promising material for water purification and environmental applications.

Photocatalytic degradation of metronidazole and oxytetracycline by novel l-Arginine (C, N codoped)-TiO2/g-C3N4: RSM optimization, photodegradation mechanism, biodegradability evaluation

Removal of Metronidazole (MNZ) and Oxytetracycline (OTC) from wastewater by the prepared (C, N codoped)-TiO2/g-C3N4 (Graphitic carbon nitride) was examined. l-Arginine (C, N codoped)-TiO2 and l-Arginine (C, N codoped)-TiO2/g-C3N4 photocatalysts were successfully synthesized through the sol-gel method, and optimal ratio of l-arginine:TiO2, as well as l-arginine/TiO2:g-C3N4, was determined by a kinetic study of photodegradation process. The maximum photocatalytic removal rate (0.062 min−1 for MNZ removal) was observed using 1% l-Arginine-TiO2/g-C3N4 (1:1) under visible light illumination, 2.2 and 12.4 times greater than those of 1% l-Arginine-TiO2 and pure TiO2, respectively. l-Arginine (1%)-TiO2/g-C3N4 (1:1) (co-doped-TCN) was investigated using X-ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), Photo-luminescence (PL), and Differential Reflectance Spectroscopy (DRS) as the best-performing photocatalyst. Response surface methodology (RSM) was used to study the effect of co-doped-TCN dosage (0.5–1.0 g/L), pH of simulated wastewater (4–10), initial concentration of MNZ and OTC (50–100 mg/L), and irradiation time (30–90 min for MNZ and 20–40 min for OTC) on removal efficiency of the antibiotics. Also, their optimum values were determined by RSM. The treated pharmaceutical wastewater showed high biodegradability features with 5-day biological oxygen demand/chemical oxygen demand (BOD5/COD) of 0.51 and 0.46 after 40 and 100 min reaction for OTC and MNZ, respectively. The order of reactive species responsible for the photodegradation of pollutants was •O2─> •OH > h+>1O2. The effect of inorganic anions showed that all anions decreased the removal efficiency of both antibiotics in order of NO3─> Cl─ >SO42─>HPO42─ >HCO3─ for MNZ and NO3─> SO42─ > Cl─ >HPO42─ >HCO3─ for OTC. Also, introducing different oxidants improved the photocatalytic removal efficiency with the order of H2O2>K2S2O8> KBrO3.

Application of Ti-based mixed metal oxide electrodes towards electrochemical mineralization of Metronidazole: Evaluation of influencing factors and removal by-products

BackgroundThe treatment of Metronidazole (MTZ) as a persistent pharmaceutical waste in the water is a significant challenge. To reduce the adverse effect of MTZ in water, we tested a novel SiO2-incorporated MMO-Ti/IrO2-Ta2O5 electrode via the electrochemical oxidation (EO) method. MethodsThe electrode was characterized by scanning electron microscopy, energy dispersive spectrum, atomic force microscopy, and cyclic voltammetry analyses. Structural characterization results were represented high resistance, compact surface, and better electrocatalytic properties for Ti/IrO2-Ta2O5-SiO2 electrode. The influence of critical operational parameters, including applied current density, initial pH, initial concentration of MTZ, and electrolysis time, was detected on electrocatalytic removal efficiency. Significant findingsIt was recognized that the high electrocatalytic power of SiO2-incorporated MMO-Ti/IrO2-Ta2O5 electrode gives a high amount of •OH during the removal process. At optimum conditions (pH = 7, J = 200 mA/cm2, [MTZ]0 = 40 mg/L, t = 80 min), 98.76% MTZ removal efficiency was achieved. Besides, comparison analysis was performed with SiO2-incorporated MMO-Ti/IrO2-Ta2O5 electrode and Ti/IrO2-Ta2O5, so results point out the higher total organic carbon removal of about 78.90% and 54.30% with SiO2-incorporated MMO-Ti/IrO2-Ta2O5 than Ti/IrO2-Ta2O5, respectively. Furthermore, MTZ removal intermediates formed during the electrocatalytic oxidation process were identified by the gas chromatography–mass spectrometry technique.

Electrochemical degradation of metronidazole-containing wastewater using Ni-foam as an electrode

This study uses commercially available Ni-foam (NiF) as an anode for the electrochemical degradation of metronidazole (MNZ) in the aqueous phase. The electrode was characterized by Scanning electron microscopy to analyze the 3D layered crisscross network structure of NiF, which facilitates an electrochemical activity for MNZ degradation. Crystalline phases were analyzed by XRD, and metal oxidation states were analyzed by XPS for the characterization of NiF. Electrochemical oxidation tests were performed using NiF electrodes for the degradation of MNZ in the aqueous phase. Various experiments were conducted to study the effect of process parameters, such as current density, initial concentration of MNZ, solution pH, etc., on MNZ degradation. Cyclic voltammetry study confirmed that Ni present in NiF favored through electrochemical oxidation of MNZ at potential; Experimental data exhibit that a higher removal rate of MNZ was attained under the optimized condition (initial concentration: 100 ppm; pH: 5; current density: 40 mA/cm2) in the 180 min electrolysis time and ICE was 23 % initially and then decreased with time. The stability of NiF as an electrode was accessed through an accelerated service lifetime test and repeated cyclic test of the used electrode after regeneration, indicating the NiF can be used up to 10 cycles without significant loss in removal % efficiency of MNZ.

Environmentally friendly loading of palladium nanoparticles on nanoporous PET track-etched membranes grafted by poly(1-vinyl-2-pyrrolidone) via RAFT polymerization for the photocatalytic degradation of metronidazole.

Nanoporous track-etched membranes (TeMs) are highly versatile materials that have shown promise in various applications such as filtration, separation, adsorption, and catalysis due to their mechanical integrity and high surface area. The performance of TeMs as catalysts for removing toxic pollutants is greatly influenced by the pore diameter, density, and functionalization of the nanochannels. In this study, the synthesis of functionalized poly(ethylene terephthalate) (PET) TeMs with Pd nanoparticles (NPs) as catalysts for the photodegradation of the antibiotic metronidazole (MTZ) was methodically investigated and their catalytic activity under UV irradiation was compared. Before loading of the Pd NPs, the surface and nanopore walls of the PET TeMs were grafted by poly(1-vinyl-2-pyrrolidone) (PVP) via UV-initiated reversible addition fragmentation chain transfer (RAFT)-mediated graft copolymerization. The use of RAFT polymerization allowed for precise control over the degree of grafting and graft lengths within the nanochannels of PVP grafted PET TeMs (PVP-g-PET). Pd NPs were then loaded onto PVP-g-PET using several environmentally friendly reducing agents such as ascorbic acid, sodium borohydride and a plant extract. In addition, a conventional thermal reduction technique was also applied for the reduction of the Pd NPs. The grafting process created a surface with high-sorption capacity for MTZ and also high stabilizing effect for Pd NPs due to the functional PVP chains on the PET substrate. The structure and composition of the composite membranes were elucidated by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, thermogravimetry, contact angle measurements and energy dispersive X-ray (EDX), X-ray photoelectron (XPS) and Fourier transform infra-red (FTIR) spectroscopies. The effects of different types of reducing agents, pH, the amount of loaded catalyst and MTZ concentration on the MTZ catalytic degradation efficiency of the obtained composites were investigated. The efficiency of the catalyst prepared in the presence of ascorbic acid was superior to the others (89.86% removal at 30 mg L-1 of MTZ). Maximum removal of MTZ was observed at the natural pH (6.5) of the MTZ solution at a concentration of 30 mg per L MTZ. The removal efficiency was decreased by increasing the catalyst dosage and the initial MTZ concentration. The reaction rate constant was reduced from 0.0144 to 0.0096 min-1 by increasing the MTZ concentration from 20 to 50 mg L-1. The photocatalyst revealed remarkable photocatalytic activity even after 10 consecutive cycles.

Peracetic acid activation by natural chalcopyrite for metronidazole degradation: Unveiling the effects of Cu-Fe bimetallic sites and sulfur species

In this work, we reported the effective activation of PAA by natural chalcopyrite (CuFeS2) to eliminate metronidazole (MTZ) for the first time. The influence of PAA concentration, CuFeS2 dosage, initial pH, initial MTZ concentration, and water matrix on MTZ decontamination was examined. The effective MTZ degradation (83.92%) was achieved after 30 min under conditions of 460 μM PAA, 4 g L−1 CuFeS2, and initial pH 3. CuFeS2 exhibited satisfactory recyclability after five cycles. Hydroxyl radical (OH), organic radicals, and ferryl ion species were proved to exist in the synergistic system based on the scavenging and probe tests, and electron paramagnetic resonance spectrograph, and OH contributed mainly to the MTZ degradation. As expected, surface-bonded Cu(I) and Fe(II) were verified as the main active sites, and surface-bonded Cu(I) had a more significant effect than that of surface-bonded Fe(II). The sulfur atoms of CuFeS2 could capture protons to form sulfur vacancies, facilitating the exposure of active sites. More importantly, the rich reductive sulfur species in CuFeS2 could enhance the regeneration of active sites. In addition, major degradation products of MTZ were identified by mass spectrometry, and their toxicity was assessed. The study proposed a new method for combining natural chalcopyrite and peracetic acid for water treatment.

Facile synthesis of Z-scheme ZnO-nanorod @ BiOBr-nanosheet heterojunction as efficient visible-light responsive photocatalyst: The effect of electrolyte and scavengers

A series of Z-scheme 3D ZnO@BiOBr photocatalysts were prepared by the hydrothermal method. The morphology of BiOBr facing the surface of the ZnO nanorods was controlled under regulating the proper experimental conditions. The photocatalysts were characterized by XRD, FT-IR, FE-SEM, TEM, BET-BJH, UV–vis DRS and PL analyses. The ZnO@BiOBr composites showed the highest photodegradation ability of metronidazole (MTZ), which was about 9.75 and 3.54 times higher than those of the pure ZnO and BiOBr, respectively. In addition, the Z-scheme ZnO@BiOBr photocatalysts indicated high stability after four cycles of MTZ photoreduction. The optimal values of the operating parameters were determined by the Box-Behnken design (BBD) with irradiation time = 112 min, pH = 6, initial MTZ concentration = 20 ppm, and catalyst dose 0.5 g/l. The maximum total organic carbon (TOC) degradation efficiencies in the presence of 3D ZnO@BiOBr reached 76.7% at the optimum conditions. The maximum MTZ removal efficiency was 87.72%. The photodegradation of MTZ by a binary composite followed the first-order kinetics. In addition, the effects of adding inorganic ions at different concentrations on the degradation of MTZ were investigated. Based on the trapping experiments, OH• and O2–• improved the photodegradation process.

Enhanced degradation of metronidazole by cobalt doped TiO2/sulfite process under visible light

The degradation of metronidazole (MNZ) by cobalt doped TiO2 activation of sulfite has been studied in this work. The Co-TiO2 was synthesized using a sol–gel method and characterized by TEM, EDS, DRS, XPS and EPR. The catalytic stability was tested by consecutive reuses. Up to 94% of MNZ was removed after 18 min reaction with Co-TiO2 and sulfite dosage being 0.1 g/L and 5 mM, respectively. The influencing parameters, such as the initial concentration of MNZ (0.03–0.2 mM), sulfite dosage (1–10 mM), catalyst dosage (0.1–0.8 g/L) and pH (2–12) were examined. The MNZ removal was pH-dependent with an optimal pH of 7.0. The presence of halides and nitrite could inhibit the process effectively. The reaction mechanisms were explored by radical quenching experiments and EPR measurements, and investigated by the XPS spectra of the catalysts before and after reactions. The formation of Co-SO3 complex and the Co2+–Co3+–Co2+ redox processes on the surface of the catalyst were crucial for sulfite activation. Compared to other Co species/persulfate processes, Co-TiO2/sulfite/LED combined the advantages of TiO2 photocatalysis and activation of sulfite with transition metal. The study suggests a novel and promising process for the treatment of antibiotics in water.

Synthesis of Fe3O4@activated carbon to treat metronidazole effluents by adsorption and heterogeneous Fenton with effluent bioassay

Metronidazole (MNZ), widely used to treat human bacterial infections, enters surface water and groundwater through sewage effluent that endangers the aqueous environment. In this study, MNZ is removed from real and synthetic wastewater through adsorption and heterogeneous Fenton processes. The Fe3O4 magnetic-activated carbon (AC) nanocomposite (Fe3O4@AC) was synthesized by coprecipitation and characterized by Fourier transform infrared spectroscopy, Field emission scanning electron microscope, Energy dispersive spectroscopy, Brunauer–Emmett–Teller, X-ray powder diffraction and Vibrating sample magnetometer analyzes. MNZ removal efficiency was studied under the influence of several parameters such as pH (3–11), Fe3O4@AC dose (0.1–1 g/L), H2O2 concentration (5–30 mmol/L), initial MNZ concentration (5–30 mg/L), contact time (5–60 min) and temperature (20–60 °C). Bioassay of treated effluents was evaluated by the germination index. Fe3O4@AC was synthesized with high magnetic strength (43.48 emu/g) and large surface area (210.95 m2/g) at nanoscale with a pseudo spherical structure. The maximum MNZ removal efficiency from real and synthetic wastewater by adsorption was 73.77% and 97.6% at pH 7, respectively; whereas, 74.75% and 98.03% at pH 5, respectively, was obtained by the heterogeneous Fenton process. MNZ adsorption is an exothermic process, it follows pseudo-second order kinetics, Langmuir and Freundlich isotherms. Whilst, MNZ oxidation follows pseudo-first order kinetics. Finally, the MNZ removal efficiency during the recovery and regeneration of Fe3O4@AC nanocomposite in the adsorption and heterogeneous Fenton processes was 86.88% and 78.34%, respectively. Bioassay results showed significant reductions in effluent toxicity after treatment with both processes. Clearly, the Fe3O4@AC nanocomposite produced a high efficiency in the treatment of wastewater containing antibiotics.

G–C3N4 induced acceleration of Fe3+/Fe2+ cycles for enhancing metronidazole degradation in Fe3+/peroxymonosulfate process under visible light

In this study, a Fe3+/g-C3N4 hybrid catalyst system was proposed to activate peroxymonosulfate (PMS) for the metronidazole (MNZ) photocatalytic degradation. The two catalysts, Fe3+ and g-C3N4, exhibited an obvious synergistic effect in the photocatalytic degradation process. When 1 mM PMS, 0.04 mM Fe3+ and 0.05 g L−1 g-C3N4 were applied, the rate constant of the Fe3+/g-C3N4/PMS/LED process at 0.07288 min−1 is around 3.6 to 6.8 times faster than that of Fe3+/PMS/LED and g-C3N4/PMS/LED processes at 0.0198 and 0.01076 min−1, respectively. Under visible light, electron transfer from photo-activated g-C3N4 to Fe3+, resulting in the continuous regeneration of Fe2+ in the system, which ensures non-stopping production of radicals for MNZ degradation. UV–visible spectra were used to confirm the regeneration of Fe2+. In addition, EPR tests were used to identify the reactive oxygen species involved in the reaction system. Typically, the effects of various operation parameters, including the catalyst dosage, PMS dosage, initial concentration of MNZ and initial pH were examined. This work provided a new idea of promoting pollutant degradation by accelerating Fe3+/Fe2+ redox through semiconductor, which could help to use the catalyst more effectively for wastewater treatment and/or chemical industries.

Removal of metronidazole antibiotic from aqueous solution by ammonia-modified activated carbon: adsorption isotherm and kinetic study

Abstract This article was aimed at investigating the removal of metronidazole (MNZ) from aquatic solutions by modified activated carbon (MAC) with amine groups. The effect of various parameters on the adsorption rate such as the initial pH, adsorbent dose and initial concentration of MNZ and contact time were scrutinized. MAC was characterized by Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller techniques. The obtained results illustrated that under the optimum conditions (pH = 3, contact time = 50 min, initial MNZ concentration = 5 mg/L and MAC dose = 0.5 g/L), the maximum adsorption efficiency was 95%. Furthermore, the kinetic studies indicated the applicability of the pseudo-second-order kinetic model, whereas the adsorption isotherm fitted well with the Freundlich model (0.996), and the maximum adsorption capacity was 66.22 mg/g. The SBET and the total pure volume of MAC were 706.92 m2/g and 0.532 cm3/g, respectively. Also, the regeneration tests demonstrated that MAC had good stability after five cycles (73%). It can be concluded that MAC, as an effective adsorbent, has a high ability to remove MNZ from aqueous solutions.

Synthesis and Application of Chitosan–Graphene Oxide and Titanium-Dioxide Coated Granular Activated Carbon Composites for Adsorptive and Photocatalytic Removal of Antibiotics

The main aim of this study was to remove a model antibiotic, that is, metronidazole (MET), using TiO2 coated on granular activated charcoal (GAC–TiO2) and graphene oxide (GO) embedded in chitosan (CS) by adsorption and photocatalysis. Analyses including scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Fourier transform Ramen spectroscopy, X-ray diffraction, and the BET method, along with batch adsorption and photocatalysis results, were used to compare the performance of composites. The ultraviolet C (UVC)/CS–GO system (99.4%) showed higher MET removal compared with UVC/GAC–TiO2 (97.4%) at 10 mg L−1 initial MET concentration; however, the total organic carbon reduction was greater in the GAC–TiO2 system (78.4%) than in the CS–GO system (72.3%). After 120 min, the UVC/GAC–TiO2 and UVC/CS–GO systems showed maximum MET removal rates of 0.0561 and 0.04 min−1, respectively. By contrast, batch adsorption experiments indicated that CS–GO has approximately 20 times greater MET adsorption capacity than GAC–TiO2. Furthermore, CS–GO was found to be superior in MET removal than GAC–TiO2 in a reusability study (i.e., for 15 treatment cycles), owing to higher adsorption capacity. Overall, the results indicate that CS–GO could be a potential composite for continuous photocatalytic experiments in the framework of emerging contaminant removal.

Starch and powdered activated carbon amended alginate-biomass beads for metronidazole and bulk organic matter removal: Synthesis, optimization, reaction kinetics and reusability

In this work, biomass immobilized alginate beads were amended with various ratios of starch (0–20%) and powdered activated carbon (PAC: 0–0.1%), and optimum compositions were shortlisted based on simultaneous removal of metronidazole (MNZ) and organic matter from synthetic wastewater. MNZ removal of greater than 80% was achieved for initial MNZ concentration of 1 ppm in 3d with optimum PAC (0.1%) and starch (5%) ratios. The presence of additional carbon substrate (i.e., dextrose) had improved the MNZ removal efficiency. Subsequently, the experiments were conducted with alginate beads amended with 0.1% PAC (A1-C2), 5% starch (A1-S1) and combination of 0.1% PAC and 5% starch (A1-S1-C2) The MNZ removal by PAC and starch amended beads was found to follow the second-order and first-order kinetics, respectively. Compared to starch amended beads, average MNZ, organic carbon and nitrogen removal efficiencies of PAC amended beads were higher by 12%, 32% and 5%, respectively. Moreover, reusability study had shown better stability of PAC (8 cycles) compared to starch (3 cycles). When starch and PAC were added together, the removal efficiencies were better than starch but lower than PAC except in the case of ammonia removal. Among the shortlisted beads, A1-C2 was found to perform best in MNZ, TOC and ammonia removals. PAC addition improved MNZ removal efficiency and the MNZ removal rate. The involvement of both adsorption and biodegradation were established in MNZ removal in all types of beads by FTIR and LC-MS analysis, respectively. However, simultaneous and rapid removal of MNZ along with organic carbon by adsorption paired with subsequent biodegradation demonstrate the applicability of A1-C2 for the treatment of PPCP laden wastewaters.

Synthesis of ZnFe2O4@Uio-66 nanocomposite for the photocatalytic degradation of metronidazole antibiotic under visible light irradiation.

The online version contains supplementary material available at 10.1007/s40201-021-00713-x.

Ultrasound-assisted decomposition of metronidazole by synthesized TiO2/Fe3O4 nanocatalyst: Influencing factors and mechanisms

This study focused on the facile preparation of TiO2/Fe3O4 catalyst prepared by the sol-gel approach as an efficient catalyst for decomposition and mineralization of metronidazole (MTN) in TiO2/Fe3O4/US process. FE-SEM, EDX, VSM, FTIR and XRD analyses were used to characterize the catalyst. The results confirmed the formation of TiO2/Fe3O4 catalyst with the average crystallite size of 32.4 nm. The influence of various factors such as solution pH, catalyst dose, initial MTN concentration and ultrasonic (US) power was examined on MTN decomposition. Also, the effect of various scavengers and inorganic anions was evaluated. In addition, mineralization of MTN, intermediates, reusability and stability tests of catalyst was also investigated. The removal efficiency of MTN by TiO2/Fe3O4 assisted ultrasonic was higher than of pure TiO2 and Fe3O4 nanoparticles. Under the optimal conditions (TiO2/Fe3O4 dosage = 1.0 g L−1, pH = 5.0, initial MTN content = 10 mg L−1, US power = 40 W and time = 90 min), 97.5% of MTN was removed. The scavenging studies expressed that •OH radicals were the main active species in the process. The GC–MS analysis showed that MTN was firstly decomposed into aromatic and aliphatic intermediates in the first stage of the reactions and then mineralized to CO2, H2O and inorganic ions. The removal efficiency of 91.2% for COD and 73.6% for TOC approved the efficient mineralization of MTN solution. The low leakage value of Fe and high reusability of the catalyst (within six consecutive cycles) indicated that TiO2/Fe3O4 had a high stability and reusability and makes it a promising catalyst for efficient degradation of antibiotics in the practical applications.

Photocatalytic performance of a nickel ferrite/chitosan/bismuth(III) oxyiodide nanocomposite for metronidazole degradation under simulated sunlight illumination

Pharmaceutical waste is a source of dangerous pollutants that can be carcinogenic to humans. Therefore, the removal of these residues from wastewater is a priority in environmental engineering. In this study, we evaluated the performance of a FeNi3/chitosan/BiOI nanocomposite as a photocatalyst for metronidazole (MTZ) degradation under simulated sunlight. The morphological and structural properties of the nanocomposite were determined using advanced characterization techniques including X-ray diffractometry, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, diffuse reflectance spectroscopy, and vibrating-sample magnetometry analyses. The kinetics of MTZ degradation and the effect of physicochemical parameters such as pH (3–11), reaction time (5–200 min), initial MTZ concentration (10–30 mg/L), and catalyst dosage (0.005–0.1 g/L) on the MTZ degradation process were studied. The applied treatment process achieved 100% MTZ degradation under the following conditions: pH = 7, FeNi3/chitosan/BiOI dose = 0.04 g/L, MTZ concentration = 20 mg/L, and reaction time = 200 min. The used catalyst can be regenerated and reused six times with only slight losses in its activity. The final by-products of MTZ degradation were mineralized products. Therefore, the FeNi3/chitosan/BiOI nanocomposite used in the present study for MTZ removal is a promising practical catalyst.

Synthesis, characteristics, and photocatalytic activity of zinc oxide nanoparticles stabilized on the stone surface for degradation of metronidazole from aqueous solution

Background: The presence of antibiotics such as metronidazole in wastewater even at low concentrations requires searching for a suitable process such as advanced oxidation process (AOP) to reduce the level of pollutants to a standard level in water. Methods: In this study, zinc oxide (ZnO) nanoparticles were synthesized by thermal method using zinc sulfate (ZnSO4 ) as a precursor, then, stabilized on stone and was used as a catalyst, in order to degrade metronidazole by photocalytic process. Effective factors on the removal efficiency of metronidazole including the initial metronidazole concentration, contact time, pH, and 0.9 gL-1 ZnO stabilized on the stone surface were investigated. Results: The X-ray diffraction (XRD) studies showed that the synthesized nanomaterials have hexagonal Wurtzite structure. Also, scanning electron microscopy (SEM) analysis revealed that the average crystalline size of the synthesized ZnO particles was in the range of 1.9-3.2 nm. The spectra represented a sharp absorption edge at 390 nm for ZnO nanoparticles corresponding to band gap of 3.168 eV. The BET-BJH specific surface area of the synthesized ZnO nanoparticles was 25.504 m2 /g. The EDS spectrum of ZnO nanoparticles showed four peaks, which were identified as Zn and O. The maximum removal efficiency was 98.36% for the synthetic solution under a specific condition (pH = 11, reaction time = 90 minutes, ZnO concentration = 0.9 gL-1, and the initial concentration of metronidazole = 10 mgL-1). The photocatalytic degradation was found to follow pseudo-first-order degradation kinetics. Conclusion: Therefore, the ZnO nanoparticles synthesized by thermal decomposition are suitable and effective photocatalytic materials for degradation of pharmaceutical contaminants.