Photodegradation Of Metronidazole Research Articles

The coupled WO3-AgBr nanocatalyst, part II: Synthesis, characterization, and the boosted photocatalytic activity towards metronidazole in an aqueous solution

The AgBr and WO3 nanoparticles (NPs) were synthesized and coupled, and the coupled AgBr-WO3 binary catalyst, as well as the individual AgBr and WO3 NPs, were then characterized by XRD, FTIR, DRS, and SEM-EDX. XRD results showed the formation of orthorhombic WO3 cubic AgBr crystals. The crystallite sizes of 45, 28, and 45 nm were estimated by the Scherrer formula for the as-prepared AgBr, WO3, and AgBr-WO3 catalysts, respectively. The DRS study estimated band gap energies using both absorption edge wavelengths and the Kubelka-Munk model. The band gap energies of 2.72, 3.06, and 2.92 eV were obtained for the direct electronic transitions of AgBr, WO3, and AgBr-WO3. The ECB (potential position) of AgBr and WO3 were estimated to be 0.01 and 0.52 V, while their EVB values were 2.60 and 3.55 V, respectively. Typical FTIR absorption bands of W‒OH, the W‒O‒W, and AgBr bonds have appeared at 1637 cm−1, 823 (and 766) cm−1, and 1384 cm−1, respectively. The pHpzc of 4 was estimated for the individual and coupled catalysts. In studying the photocatalytic activity of the catalysts in the photodegradation of metronidazole (MNZ) a boosted activity was achieved for the coupled system. This increased activity depends on the maximum AgBr:WO3 mole ratio in a 1:3 mol ratio. Grinding time applied to prepare the coupled catalyst has also varied the photocatalytic activity.

Enhanced activation of sulfite by the iron-citrate complexes under NUV irradiation for metronidazole degradation: Kinetic, degradation mechanism and efficiency in real water

In the present study, a novel approach for the elimination of emerging pollutants through an advanced oxidation process has been developed by combining near ultraviolet (NUV) irradiation with an iron-citrate complex (Fe(III)-Cit) to overcome the defects of the traditional Fe(III)/sulfite system and enhance the activation of sulfite in a neutral aqueous solution. The performance of this system was studied using metronidazole (MTZ) as the target pollutant, and the impact of operational conditions such as initial pH, Fe(III)-Cit complex concentration, sulfite dose, metronidazole concentration and dissolved oxygen were studied. The rate constant of MTZ degradation at natural pH (7.0 ± 0.2) by the Fe(III)-Cit/sulfite/NUV system is over 12.72-times and 13.25-times higher than the sulfite/NUV and Fe(III)-Cit/NUV individual binary systems. The effectiveness of the system was further examined in various real water matrices. The latter proved to be effective in the following order: groundwater > ultra-pure water > > seawater, revealing that it was very effective in the former. Chemical probe experiments indicated that sulfate radicals and hydroxyl radicals were the principal reactive oxygen species involved in the photodegradation of MTZ. Additionally, dissolved oxygen played a crucial role in the reaction. MTZ degradation products were determined by HPLC/MS, leading to the identification of nine different by-products and the proposal of possible degradation pathways. Although further studies are required to better understand this system, this work paves the way for the application of activated sulfite-based processes for environmental remediation without pH adjustment, offering an alternative to the use of conventional oxidants.

Highly Efficient Solar-Light-Driven Photodegradation of Metronidazole by Nickel Hexacyanoferrate Nanocubes Showing Enhanced Catalytic Performances.

Environmental pollution is a complex problem that threatens the health and life of animal and plant ecosystems on the planet. In this respect, the scientific community faces increasingly challenging tasks in designing novel materials with beneficial properties to address this issue. This study describes a simple yet effective synthetic protocol to obtain nickel hexacyanoferrate (Ni-HCF) nanocubes as a suitable photocatalyst, which can enable an efficient photodegradation of hazardous anthropogenic organic contaminants in water, such as antibiotics. Ni-HCF nanocubes are fully characterized and their optical and electrochemical properties are investigated. Preliminary tests are also carried out to photocatalytically remove metronidazole (MDZ), an antibiotic that is difficult to degrade and has become a common contaminant as it is widely used to treat infections caused by anaerobic microorganisms. Under simulated solar light, Ni-HCF displays substantial photocatalytic activity, degrading 94.3% of MDZ in 6h. The remarkable performance of Ni-HCF nanocubes is attributeto a higher ability to separate charge carriers and to a lower resistance toward charge transfer, as confirmed by the electrochemical characterization. These achievements highlight the possibility of combining the performance of earth-abundant catalysts with a renewable energy source for environmental remediation, thus meeting the requirements for sustainable development.

Physical and photo-electrochemical characterization of Ca2Fe2O5 for metronidazole antibiotic degradation under sunlight

This study aims to investigate and describe the properties of the brownmillerite Ca2Fe2O5, synthesized from nitrates precursors. The X-ray diffraction showed that the single phase crystallizes in an orthorhombic symmetry (Space Group: Pcmn) with a specific surface area of 8.16 m2 g−1. The d-d transition of Fe3+: in octahedral coordination gives a direct optical band gap (2.02 eV) as determined by diffuse reflectance spectroscopy in agreement with the brown color of the oxide. The first one is due to the charge transfer O2−: 2p → Fe3+: t2g. This enables the material to exploit a large part of the solar radiation for photocatalytic purposes. The chemical stability of Ca2Fe2O5 is demonstrated over the pH range (5–12). The capacitance-potential plot revealed n-type conduction; a flat band potential of (Efb) 0.40 VSCE and electron concentration (NA) of 8.57 × 1024 m−3 were obtained in Na2SO4 (0.1 M) solution. The intensity-potential (J - E) profile showed electrochemical stability with oxygen intercalation in the layered lattice. The conduction band is more anodic than the level of O2/O2•, allowing the successful oxidation of Metronidazole by •O2− radical under visible light. The photodegradation of Metronidazole (MNZ) was successfully achieved at an initial concentration of 10 mg/L under solar radiation and a photocatalyst dose of 1 g/L at a free pH after 120 min of exposure and obeys a first-order kinetic with a rate constant of (33.7 × 10−3 min−1).

The coupled WO3-AgBr nanocatalyst, part I: Experimental design, kinetics and mechanism studies of the boosted photocatalytic activity towards metronidazole in an aqueous solution

The boosted photocatalytic activity of the coupled AgBr-WO3 nanocatalyst was observed towards metronidazole (MNZ) in an aqueous solution, and to study the simultaneous interaction effects between the influencing variables, experimental design was performed via the response surface methodology approach (RSM). The optimized run included MNZ solution pH: 9, catalyst dosage: 1 g/L, irradiation time: 45 min, and CMNZ: 10 mg/L. The goodness of the model was proven by greater model F-value than F0.05, 14, 15 = 2.42, and smaller lake of fit F-value than F0.05, 10, 5 = 4.74 and also by regression coefficient values of R2: 0.9994, Adjusted R2: 0.9988, Predicted R2: 0.9977. Based on the results obtained in the scavenging agent study, the following trend was suggested for the relative importance of the main four reactive species in MNZ photodegradation: Photoinduced h+> Hydroxyl radicals > Photoinduced e-> Superoxide radicals. The Z-scheme pathway well illustrates the mechanism pathway. The photodegradation kinetics obeyed the pseudo-first-order Hinshelwood model with a rate constant of 0.014 min−1 (t1/2 = 49.5 min). The photodegraded solutions' chemical oxygen demand (COD) confirmed the MNZ mineralization. Based on the COD results, a rate constant of about 0.018 min−1 (t1/2 = 38.5 min) was obtained. Reusing experiments confirmed the excellent stability of the binary catalyst for at least four reusing runs.

Metronidazole photodegradation under solar light with UiO-66-NH2 photocatalyst: Mechanisms, pathway, and toxicity assessment

Metronidazole is a nitroimidazole antibiotic that is increasingly detected in aquatic bodies. Therefore, there is an urgent need to research methodologies to remove this and other antibiotics. One of the alternatives is the application of solar photocatalysis, which requires the use of an efficient photocatalyst. In this work, UiO-66-NH2 was synthesized by a facile solvothermal method and evaluated for the degradation of metronidazole under simulated solar light. The effects of catalyst dosage, initial pH, and metronidazole concentration were discussed, establishing the best operation conditions. In addition, the stability and reproducibility of UiO-66-NH2 activity were also verified. The quenching reaction showed that holes and superoxide radicals coexisted as the main active species, being responsible for the metronidazole degradation. The pathway of metronidazole photodegradation was proposed by means of density functional theory calculations and LC/ESI-MS analysis. It is noteworthy that this study detected for the first time C6H11N3O4, C4H6N2O3, and C4H8N2O4 as metronidazole photodegradation byproducts. ECOSAR toxicity analysis showed that all byproducts were less toxic than the original metronidazole, supporting the potential feasibility of this method for treating water polluted with this antibiotic.

UV/TiO2 photodegradation of metronidazole, ciprofloxacin and sulfamethoxazole in aqueous solution: An optimization and kinetic study

Emerging pharmaceutical ingredients (APIs) like sulfamethoxazole (SMX), metronidazole (MNZ) and ciprofloxacin (CIP) are biopersistent and toxic to the environment and public health. In this study, UV/TiO 2 photodegradation was applied in the degradation of SMX, MNZ and CIP individually and in a mixture. For a 5 mg/L SMX solution, about 97% of SMX was degraded within 360 min, which was reduced to 80% for 80 mg/L of SMX solution at the same TiO 2 dosage and photodegradation time. The maximum removals of MNZ and CIP as individual components were 100% and 89%, respectively at 600 min of photodegradation reaction time. For binary mixtures, the highest removal (100%) was achieved for MNZ and CIP ([MNZ] = [CIP] = 40 mg/L) mixture at 120 min whereas the degradations were 97% and 96% for SMX and MNZ, and SMX and CIP binary mixtures, respectively, even after 600 min of experimental time at the same concentrations. For tertiary mixture, the maximum degradation 99% was observed for (SMX = CIP] = 20 mg/L and [MNZ] = [40 mg/L) at 600 min. The observed reaction rate was 0.01085 min −1 when SMX concentration was 5 mg/L, which decreased to 0.00501 min −1 for SMX concentration of 80 mg/L, indicating decreasing of reaction rate at higher concentration. The results indicate that the UV/TiO 2 process is promising to apply for the treatment of pharmaceutical wastewaters.

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.

Photodegradation and mineralization of metronidazole by a novel quadripartite SnO2@TiO2/ZrTiO4/ZrO2 photocatalyst: Comprehensive photocatalyst characterization and kinetic study

A facile hydrothermal technique was used to prepare a novel quadripartite SnO2@TiO2/ZrTiO4/ZrO2 (STZZ) photocatalyst, and the photocatalytic activity of STZZ was successfully tested in the metronidazole (MNZ) photodegradation under UV irradiation in water. The effects of photocatalyst type, pH, photocatalyst dosage, MNZ initial concentration on the photodegradation of MNZ were also evaluated. The maximum degradation of MNZ was achieved with STZZ photocatalyst at pH = 6.5 with a photocatalyst dosage of 0.07 g L−1 and MNZ concentration of 20 mg L−1. The rate constants of MNZ photodegradation and mineralization processes were 0.017 min−1 (t1/2 = 40.76 min) and 0.066 min−1 (t1/2 = 10.50 min), respectively. The activation energy of the photodegradation process calculated from the Arrhenius equation was 10.6 kJ/mol. A positive ΔG value was obtained for the MNZ photodegradation by the STZZ photocatalyst that contained a positive ΔH and a negative ΔS (−0.2039 kJ/mol).

Synthesis of novel HKUST-1-based SnO2 porous nanocomposite with the photocatalytic capability for degradation of metronidazole

Metal-organic frameworks (MOFs) are crystalline microporous materials that show catalytic activity when used as hosts. Nanostructured materials supported by MOFs show increased catalytic activity and stability. Several steps or templates are vital in the synthesis of MOF composites. However, developing effective and simple MOF synthesis approaches remains challenging. In this study, a simple one-step reaction is described for preparing Nanosized Stannic (II) oxide particles in MOF composites, called nanosized SnO2/MOF-199 (HKUST-1). The SnO2/MOF-199 (30 wt%) exhibited the best degradation efficiency of metronidazole (MZ), SnO2/MOF-199 (5 wt%), SnO2/MOF-199 (10 wt%), SnO2/MOF-199 (20 wt%), and SnO2/MOF-199 (40 wt%). The photocatalyst used in this work is a novel nanocomposite-based compound. The nanocomposite was characterized using SEM, EDX, TEM, XRD, FT-IR, BET, and TG-DTG techniques. Also, PL and DRS analyses were used for the optical-property study of the photocatalyst. Afterward, the synthesized nanocomposite was used for metronidazole (MZ) degradation. The result showed that pH of the solution, irradiation time, time-CMZ interactions, and time-pH interactions remain highly significant in MZ degradation. The most suitable degradation extent was acquired at pH = 3, catalyst dosage = 2 g/L, MZ = 40 mg/L, and irradiation time of 240 min. Between type II-heterojunction and Z-scheme mechanisms, the second case showed the most significant role in MZ photodegradation.

Efficient degradation of metronidazole antibiotic by TiO2/Ag3PO4/g–C3N4 ternary composite photocatalyst in a continuous flow-loop photoreactor

Developing photocatalytic systems by major design to achieve deep degradation of contaminants such as antibiotics to improve environmental conditions is highly desirable. Herein, we reported a facile method to fabrication of composite consisting of g-C3N4 layers and TiO2/Ag3PO4 nanoparticles (TiO2/Ag3PO4/g–C3N4) through calcination and precipitation methods. The as-prepared photocatalyst was used for the photodegradation of metronidazole (MNZ) in a designed continuous flow-loop photoreactor which is equipped with blue light-emitting diodes (LEDs) irradiation based on central composite design (CCD). According to the desirability function, the degradation efficiency of MNZ was also reported to be 97.18% under optimal conditions. The experiments indicated the photocatalytic degradation of MNZ by the as-prepared samples were in the order of TiO2/Ag3PO4/g-C3N4 > TiO2/g-C3N4 > TiO2/Ag3PO4 > TiO2. The strengthened visible-light-driven photocatalytic performance can be assigned to the formation of a Z-scheme system, surface plasmon resonance (SPR) effect, and high charge separation compared to pure and binary samples for degradation of MNZ. Based on trapping results, hydroxyl radicals were the major active radicals in the degradation of MNZ. Besides, the photodegradation pathway of MNZ was clarified via the analysis of intermediate products, and a mechanism of charge-carrier separation for MNZ photodegradation via TiO2/Ag3PO4/g–C3N4 was proposed.

Natural clay loaded Sm2MoO6 nanocomposite, a green catalyst, for multiple applications

In the present work, multiple applications of natural clay loaded Samarium molybdate for photodegradation, sensing and antibacterial activity were analyzed. The clay-based materials have attracted great attention as they show good application prospects for environmental remediation. We developed natural clay loaded Sm2MoO6 (CSm2MoO6) nanocomposite, hydrothermally and characterized by XRD, SEM, HR-TEM, FT-IR and optical studies. XRD pattern of CSm2MoO6 exhibits peaks at 19.60, 27.80, 35.60 and 62.40 corresponding to clay and Sm2MoO6 peaks clearly indicates the formation of natural clay conjugated with Sm2MoO6. SEM image of the natural clay doped CSm2MoO6 nanoparticle shows a homogeneous distribution of spherical Sm2MoO6on nanoflakes of clay material. HR-TEM images reveal that the average particle size is 50 nm. Loading of natural clay material increased the visible absorption of Sm2MoO6 by reducing the band gap from 3.82 to 2.39 eV. Decomposition of 20 ppm of Metronidazole (MNZ) was 95% with 60 mg of CSm2MoO6 in 100 min of visible light illumination. Hydroxyl radicals played the main role for photodegradation of MNZ. Electrochemical analysis revealed that the oxidation peak current of 4-aminophenol has increased with a high potential at pH 6.0 and CSm2MoO6/SPCE electrode has an advantage of low detection limit of 0.005 μM and a long linear range of 2949.72 μM with a sensitivity of 5.29301 μM. The synthesized nanocomposite has a significant bactericidal activity against Bacillus subtilis, Staphylococcus aureus, Proteus mirabilis, Bacteroides fragilis, E. coli and Candida albicans. These results make this green catalyst potential for multiple applications.

Comparison of Ag and AgI-Modified ZnO as Heterogeneous Photocatalysts for Simulated Sunlight Driven Photodegradation of Metronidazole

Ag and AgI-modified ZnO composites (Ag/ZnO and AgI/ZnO) were synthesized in facile ways. The photocatalysts were used for the photodegradation of metronidazole (MNZ) under the irradiation of simulated sunlight. The results of experiments showed that both Ag/ZnO and AgI/ZnO had a specific molar ratio to reach the best performance. Ag/ZnO performed better in the photodegradation of MNZ than AgI/ZnO under the same conditions. The reaction rate constant of AgI/ZnO was less affected by the variation of initial concentration of MNZ or pH values. The main reactive oxygen species of the photocatalytic process are OH, O2− and h+, but the free radicals which play the most critical part differ in Ag/ZnO and AgI/ZnO. Several intermediates were revealed by LC–MS/MS analysis. The stability of the photocatalysts was evaluated by a series of repeated MNZ photodegradation experiments. The results showed that AgI/ZnO had better stability than Ag/ZnO.

Comparative Study Between Metronidazole Residues Disposal by Using Adsorption and Photodegradation Processes onto MgO Nanoparticles

The photodegradation and adsorption processes of metronidazole (MNZ) was conducted utilizing the batch reactor onto magnesium oxide nanoparticles (MgO NP) as the catalyst surface affected by UV radiation, initial concentration of MNZ, pH, catalyst loading, inorganic salts addition, time, and temperature. Chemical composition and morphological properties of the prepared MgO NP can also be portrayed by several techniques such as XRD, EDX, SEM, and TEM, while GC–MS analysis was used to monitor the photodegradation pathway for MNZ molecules. The results indicated that the actual removal of 93.2% of 80 mg/L MNZ present in 25 mL of a solution containing 0.1 mg/L of MgO NP could be distributed as 35.7% for maximum adsorption and 57.5% for degradation efficiency during 180 min. The degradation process is mainly of two steps; dark adsorption experiment, and photocatalytic degradation performance. Hence, Kinetic analyses indicate that adsorption constant estimated in dark conditions is smaller than the adsorption equilibrium constant derived from the Langmuir–Hinshelwood kinetic model through photodegradation of MNZ that follows pseudo-first-order kinetic. The adsorption isotherm result specified that the adsorption nature is chemisorption and fit Langmuir model, as well as thermodynamic results indicated that it is a nonspontaneous and endothermic reaction.

Microwave-assisted preparation of ZnFe2O4@methyl cellulose as a new nano-biomagnetic photocatalyst for photodegradation of metronidazole

In the present study, ZnFe2O4@methyl cellulose (MC) nano-biomagnetic photocatalyst was rapidly prepared based on a microwave-assisted method. FTIR, FESEM, EDS, UV-DRS, XRD, and VSM were performed to characterize the structure of as-prepared ZnFe2O4@MC. The removal efficiency of Metronidazole (MNZ) degradation was 92.65% and 71.12% in synthetic and real samples under optimal conditions, respectively. The removal efficiency of TOC was also reported to be 77.87% under optimal conditions. The kinetic linear models showed that the photocatalytic degradation of MNZ follows either a pseudo-first-order kinetic or the Langmuir-Hinshelwood model. The correlation coefficients (R2) were 0.92, 0.97, 0.99, and 0.94, respectively at 5, 10, 20, and 30 mg/L. The equilibrium adsorption coefficient (KL−H) of the Langmuir-Hinshelwood model and the superficial reaction rate constant (Kc) were 0.633 Lmg−1 and 0.203 mg/L min−1, respectively. The participation of active species such as holes and hydroxyl and superoxide radicals was studied during MNZ photodegradation with organic and inorganic radical scavengers. Finally, the nano-biomagnetic catalyst could be reused for six further runs without remarkable changes in catalytic efficiencies. In this study, we present a new magnetic nanocomposite and a novel strategy for antibiotic removal from aqueous media.

Removal of metronidazole by TiO2 and ZnO photocatalysis: a comprehensive comparison of process optimization and transformation products.

The photodegradation of antibiotic metronidazole (MNZ) was systematically studied and compared by using aqueous suspensions of TiO2 and ZnO catalysts under 100-W UV irradiation. The degradation conditions were optimized using the central composite design and response surface methodology. The optimal photodegradation conditions obtained were at pH 6.0 with 1.5gL-1 of TiO2 (86.10% removal for 50mgL-1 MNZ) and at pH 9.5 with 0.5gL-1 of ZnO (60.32% removal for 30mgL-1 MNZ) after 60-min irradiation at 20°C. The degradation efficiency in the presence of TiO2 was higher than that of ZnO. The participation of active species such as hydroxyl radicals (OH·), holes (h+), and superoxide radicals (O2-·) during MNZ photodegradation over TiO2 and ZnO catalysts was also examined. Experimental results showed that MNZ oxidation was mainly driven by the presence of holes and superoxide radicals. Totally, 10 major intermediates were detected in UV/TiO2 and UV/ZnO photocatalysis of MNZ using LC-QTof/MS system, in which 5 same intermediates were found. The remaining different intermediates led to the variations of degradation pathways of both processes. Moreover, some bigger transformation products than the parent MNZ were detected.

Synthesis of magnetically recoverable Fe0/graphene-TiO2 nanowires composite for both reduction and photocatalytic oxidation of metronidazole

Novel ternary nanocomposite based on nano zero-valent iron (nZVI) and graphene-TiO2 nanowires (Fe@GNW) was successfully synthesized for both reduction and photocatalytic oxidation of metronidazole (MNZ). Fe@GNW exhibits synergetic effects and significant properties, such as facilitating the photogenerated charges separation, enhancing the surface activity of nZVI, improving the adsorbent ability of catalyst, possessing the magnetic property for facile recycling. Due to the formation of micro-graphene-nZVI batteries and heterogeneous photo-Fenton system, Fe@GNW showed a superior activity in removal of MNZ (99.3%) compared with TiO2 nanowires (43.0%) and graphene-TiO2 nanowires (67.6%). Moreover, Fe@GNW retained excellent stability without apparent loss in catalytic activity after five cycles. MNZ removal by Fe@GNW experienced a two-stage process of reduction-adsorption and photocatalytic oxidation, which could be well-described by a revised pseudo-first order kinetics. The decomposition pathways of MNZ were proposed based on the analysis of intermediates. The quenching tests demonstrated that h+ and OH are responsible for MNZ decomposition. New insights into the mechanism of the enhanced reduction and photodegradation of MNZ were proposed.

Preparation and photocatalytic properties of Bi2InNbO7 nanorods obtained by the sol-gel method

The Bi2InNbO7 photocatalyst with rod-like nanostructure was synthesised by a facile sol-gel method, using Bi(NO3)3·5H2O, In(NO3)3·4·5H2O and Nb2O5 as raw materials. The structural, surface morphological, specific surface area and optical properties of the samples have been studied by X-ray diffraction, transmission electron microscopy, ultraviolet-visible absorption spectroscopy, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller surface area measurement. The photocatalytic activity was evaluated for degradation of metronidazole in aqueous solution under visible light irradiation. Different parameters like substrate concentration, catalyst concentration and different pH have been studied. The resulting Bi2InNbO7 nanorods exhibit high crystallinity with 10–50 nm diameters and BET surface area of 33.19 m2/g. It was observed that the photodegradation of metronidazole under visible light in the presence of Bi2InNbO7 nanorods is more efficient than its bulk counterparts. The optimum conditions for the degradation of metronidazole were initial concentration 10 mg/L, catalyst concentration 0.8 g/L and pH 3.

Comprehensive study on enhanced photocatalytic activity of heterojunction ZnS-NiS/zeolite nanoparticles: Experimental design based on response surface methodology (RSM), impedance spectroscopy and GC-MASS studies

In the present work, coupled and supported NiS and ZnS onto the mechanically prepared clinoptilolite nanoparticles (NC) was prepared and characterized by XRD, FTIR, SEM-EDX, X-ray mapping, DRS, BET, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The obtained catalysts were used in photodegradation of metronidazole (MZ). The mole ratio of NiS/ZnS affects the degradation activity of the obtained catalysts so the best activity was obtained for the NZ4-NC (NiS1.0–ZnS5.2/NC, containing 1.0 and 5.2W% of NiS and ZnS, respectively and mole ratio of ZnS/NiS about 4) catalyst. The simultaneous effects of the experimental parameters were studied using central composite design combined with response surface methodology (RSM). Results of CV and EIS have good agreement with photodegradation results, so the coupled NiS-ZnS-NC system with significant enhancement in charge transfer with respect to the monocomponent systems showed the best photodegradation activity. The best degradation extent of MZ was obtained at a run including pH 2, catalyst dose of 3gL−1, 4mgL−1 of MZ at irradiation time of 150min. The high correlation coefficient (R2=0.9883) for the second-order polynomial model, showed that the data predicted using RSM were in good agreement with the experimental results. Change of initial pH of MZ solution from 5.5 to 4.1 during 150min, confirms formation of acidic degradation intermediates.

FATE OF METRONIDAZOLE UNDER SOLAR IRRADIATION

Photodegradation caused by sun irradiation may be of major significance in the natural elimination process of pharmaceuticals and personal care products (PPCPs). The fate of metronidazole (MET) in surface water under solar irradiation was investigated. Several parameters affecting the photochemical degradation rate of MET were investigated, including the initial pharmaceutical concentration, continuous input and the presence of other pharmaceuticals like tinidazole (TNZ) with similar structure to MET as the analogue or amoxicillin (AMX) as non-analogue. The focus of the study was to evaluate the effect of the coexisting pharmaceuticals and continuous input on the photodegradation of PPCPs. The results showed that the photodegradation rate of MET became lower in the presence of TNZ. At the same time, the presence of AMX showed no effect on the photodegradation rate of MET. Besides, to elucidate the effects of continuous input on the photodegradation, a high concentration solution of MET with calculated volume of MET was added repetitively to the reaction solution under solar irradiation for 60 minutes. After 5 times of recovering concentration, the removal of MET decreased from 32.9% to 9.6%. The fact shows that the coexisting pharmaceuticals and continuous input effect on the photodegradation of MET obviously. Therefore, these factors must be taken into account in assessing the fate of PPCPs in the environment. In addition, the kinetic parameters such as quantum yields and rate constants were also determined.