RESUMEN

Semiconductor-based remediation enables environmentally friendly methods of removing aqueous pollutants. Simply fabricated ZnO modified g-C3N4 composites were utilized as bifunctional adsorptive photocatalysts for orange II removal from aqueous solution through adsorption and photocatalysis processes. The adsorption isotherm data of the g-C3N4 (g-CN) and ZnO modified g-C3N4 (ZCN) composites on orange II solution were better fitted with the Langmuir isotherm compared to the Freundlich isotherm. The maximum adsorption capacity for ZCN-2.5 was slightly higher than that of bare g-CN. According to the adsorption thermodynamics investigation of ZCN-2.5 in orange II solution, the positive values of Gibb's free energy change (ΔG0) suggested a non-spontaneous adsorption process. Furthermore, the negative values of entropy change (ΔS) and enthalpy change (ΔH) indicated the decrement of randomness and exothermic nature during the adsorption process, respectively. The photocatalytic degradation kinetics of g-CN and ZCN composites indicated that the degradation process follows the pseudo-first-order reaction kinetic. The degradation rate of orange II with the ZCN-2.5 composite was 6.67 times higher than that obtained with bare g-CN. Possible adsorption and photocatalytic mechanisms have been proposed.

RESUMEN

Natural enzyme mimics have attracted attention as alternatives to natural peroxidases. Among these, magnetic nanoparticles, especially ferrites, have attracted attention because of their unique electronic and physical structures, which are expected to be applied in various fields, including high-frequency magnetic materials, biomaterials, gas sensors, and semiconductor photocatalysts. The structural properties of the synthesized catalysts were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The prepared CoFe2O4 exhibited a spinel ferrite structure and formed a wood-flake-like bulk structure. In this study, magnetic CoFe2O4 was prepared using a precipitation method as a natural enzyme mimetic. CoFe2O4 showed excellent peroxidase-like activity, as demonstrated by the Michaelis-Menten constant (Km) and the maximum velocity (Vmax). The linear ranges of the calibration curves for H2O2 and glucose were in the range of 0-500 µM, and the detection limits were 1.83 and 5.91 µM, respectively. This analytical method was applied for the determination of glucose in human serum, and the results were satisfactory and consistent with certified values. The performance of this sensor was comparable to or superior to those of several other sensors commonly used for glucose analysis, indicating that its practical application is feasible.

Asunto(s)

Cobalto , Colorimetría , Compuestos Férricos , Cobalto/química , Catálisis , Compuestos Férricos/química , Humanos , Glucemia/análisis , Límite de Detección , Peróxido de Hidrógeno/química , Peróxido de Hidrógeno/análisis

RESUMEN

Oxygen-doped g-C3N4 with pyridine ring (POCN) was synthesized by easily thermal polymerization of urea, pyridine solution, and ammonium acetate to improve photocatalytic hydrogen production. The experimental results indicate that pyridine was incorporated into the tri-s-triazine structure of g-C3N4. The O atoms were modified to g-C3N4 by replacing the N atoms (C-N=C) of the triazine ring. The photocatalytic activity for the hydrogen production rate of optimized POCN was 1018 µmol g-1 h-1, approximately 30 times higher than that of bulk g-C3N4 (CN) under visible light irradiation (λ > 420 nm). The high stability of POCN was confirmed through cycling tests for 30-h, XRD patterns, and SEM images. The pyridine incorporation can significantly enhance surface charge transfer efficiency. The oxygen modification can greatly promote visible light absorption (600 nm) and photogenerated electron-hole pairs separation. This work provides a suitable strategy to synthesize g-C3N4 based on metal-free photocatalysts for highly efficient photocatalytic hydrogen generation performance.

RESUMEN

Graphitic carbon nitride (g-C3N4, abbreviated as g-CN) suffers from low visible-light-responsive photocatalytic efficiency. In this study, aromatic benzene rings and black phosphorus (BP) were successfully incorporated into g-CN photocatalysts (BP/A-CN), resulting in modified materials with improved properties. Structural analysis confirmed the successful integration of aromatic rings and BP into the g-CN framework, indicating the formation of a stable composite. Morphological characterization revealed that the introduction of aromatic rings and BP did not cause any significant changes in the nanosheet-like morphology of the g-CN photocatalysts. To evaluate the photocatalytic hydrogen production activity under visible-light irradiation, various compositions of aromatic benzene rings and BP were investigated. Specifically, the BP/A-CN composite exhibited an enhanced photocatalytic hydrogen production rate (860 µmol g-1 h-1), which was approximately 4.0 times higher than that of g-CN (210 µmol g-1 h-1). The improved hydrogen production rates observed in the modified g-CN photocatalysts can be attributed to several factors. First, the aromatic benzene rings and BP enhanced light absorption, thereby improving the efficient utilization of solar energy. Additionally, the presence of these components in the composite photocatalysts reduced electron-hole recombination, thereby facilitating improved charge transfer and separation efficiencies. Overall, this study demonstrates the potential of incorporating aromatic benzene rings and BP into g-CN photocatalysts for efficient solar energy conversion. These findings contribute to the development of novel photocatalytic materials with enhanced performance and highlight the versatility of g-CN-based composites for various applications in environmental and energy fields.

RESUMEN

The ZnO/g-C3N4 composite was successfully synthesized by a simple one-step calcination of a urea and zinc acetate mixture. The photocatalytic activity of the synthesized composite was evaluated in the degradation of bisphenol E (BPE). The morphology, crystallinity, optical properties, and composition of the synthesized composite were characterized by using various analytical techniques such as scanning electron microscopy (SEM), transmitted electron microscopy (TEM), field emission-electron probe microanalysis (FE-EPMA), nitrogen adsorption and desorption isotherm measurement, Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The degradation rate of BPE with the ZnO/g-C3N4 composite was 8 times larger than that obtained with pure g-C3N4 at the optimal conditions. The excellent photocatalytic activity was attributed to the synergistic effect between the g-C3N4 and ZnO, which enhanced the efficiency of charge separations, reduced the e-/h+ pairs recombination, and increased the visible light absorption ability. The radical scavenger studies indicated that the •O2 - and h+ species were mainly responsible for the degradation of BPE. The stability test suggested the chemical and photostability of the synthesized composite. Two possible photocatalytical mechanisms have been suggested.

RESUMEN

Although WO3 appears to be one of the extensively studied photocatalysts, the low response of pure WO3 in aqueous solution under visible light limits its application remarkably. In this work, the enhancement of the efficiency of WO3 for the visible light-driven photocatalytic oxidation of arsenite was explored using Cu2+ ion and CuO as a co-catalyst. While the addition of Cu2+ was found effective for the suppression of dissolution of WO3, the efficiency of CuO appeared to be slightly lower. Significant improvement of the efficiency for the photocatalytic oxidation of As(III) with WO3 was noted when Cu2+ ions and CuO were added. The optimized conditions were WO3 in the presence of 10 mg L-1 Cu2+ ion and 1 wt% CuO coupled with WO3, respectively. The As(III) concentration of 10 mg L-1 could be lowered to less than 0.1 mg L-1 by the photocatalytic treatment. Acidic pH favours the oxidation of arsenite in the presence of Cu2+ whereas basic pH is suitable with CuO. Characterization techniques such as TEM, XPS, XRD and UV-DRS were used to characterize photocatalysts. The reactive species scavenger tests revealed that the photo-induced holes (h+) play a key role in the photocatalytic oxidation process while the effect of •OH is negligible. It was found that As(III) oxidation rate was remarkably suppressed in the nitrogen atmosphere. A mechanism for enhanced photocatalytic oxidation has been proposed based on the results of the reactive species scavenger tests. This research may contribute to the large-scale As(III) oxidation treatment in the groundwater.

Asunto(s)

Arsenitos , Luz , Oxidación-Reducción

RESUMEN

The photocatalytic reduction of Cr6+ to Cr3+ in an aqueous solution, using 3 wt% Ag/g-C3N4 in the presence of ethylenediaminetetraacetic acid (EDTA), has been investigated here. The photocatalytic reduction of Cr6+ with pure g-C3N4 was very low. The addition of Ag and EDTA can significantly improve the photocatalytic reduction of Cr6+ using g-C3N4. In the presence of EDTA, the efficiency with Ag/g-C3N4 was better than those with Au/g-C3N4 and Cu/g-C3N4. With EDTA, the reduction rate constant increased from 0.0005 for pure g-C3N4 to 0.12 min-1 for 3 wt% Ag/g-C3N4. By increasing the concentration of EDTA from 0 to 500 mg L-1, the reduction efficiency of Cr6+ increased extremely, and the rate constant raised from 0.008 to 0.12 min-1. The optimal EDTA concentration was 500 mg L-1 for the photocatalyst Ag/g-C3N4. The Ag-EDTA complex may be reduced to metallic silver by the conduction band electrons of g-C3N4. The electron-hole recombination was significantly suppressed by the electron trapping of Ag. EDTA may act in by the formation of Cr3+-complex and the separation of Cr3+ from the g-C3N4 surface and by the valence band hole scavenger of g-C3N4. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectra (PL) were used to characterize g-C3N4 and Ag/g-C3N4 nanoparticles. A possible mechanism for photocatalytic Cr6+ reduction has also been demonstrated.

Asunto(s)

Grafito , Luz , Ácido Edético , Grafito/química , Rayos Ultravioleta , Catálisis

RESUMEN

The photocatalyst Ag/Ag2O-modified ZnO, fabricated by a simple one-step calcination method, was applied into the degradation of organic pollutant dibutyl phthalate (DBP). Ag/ZnO and Ag2O/ZnO were prepared as a reference comparison. The prepared catalysts were evaluated by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area measurement, and photoluminescence spectra (PL) and UV-Vis diffuse reflectance spectroscopy (DRS) and electrochemical measurements. After the irradiation with ultraviolet light (352 nm), the solution was sampled and subjected to HPLC to evaluate the degradation efficiency of DBP. Ag/Ag2O/ZnO showed the best results with the excellent degradation of DBP. Ag/Ag2O/ZnO was four times more efficient, relative to zinc oxide alone. According to photocatalyst characterization, the total pore volume of photocatalyst was improved by loading Ag and Ag2O, suggesting an increase in the active sites. Also, the efficient electron transfer of Ag/Ag2O/ZnO was mainly responsible for the enhanced activity. The reaction mechanism for Ag/Ag2O/ZnO was determined to become a Z-scheme. From the radical scavenger tests, the main active species was identified as superoxide radicals. The stability of Ag/Ag2O/ZnO could be confirmed after five cycling reutilization. It was found from the radical scavenger test that •O2 - play an important role as the main reactive species in the photocatalytic degradation of DBP. Consequently, Ag/Ag2O/ZnO with a simple fabrication method seems to become one of the powerful photocatalyst for the photocatalytic degradation of organic pollutant in water.Implications: This study discusses the usefulness of Ag/Ag2O/ZnO composites. This photocatalyst could be an approach to solve the environmental pollution caused by organic pollutants, which is a growing problem all over the world. In addition, the highly efficient photocatalyst Ag/Ag2O/ZnO is an inexpensive and reusable catalyst with great practical potential.Furthermore, to the best of our knowledge, there are very few reports that have examined the combination of Ag, Ag2O and ZnO. In addition, the photocatalytic mechanism has not been understood. Here, we introduce Ag into Ag2O/ZnO to improve the photocatalytic performance and photostability, enhance the activity, and elucidate the mechanism of Ag/Ag2O/ZnO.

Asunto(s)

Contaminantes Ambientales , Óxido de Zinc , Dibutil Ftalato , Superóxidos , Agua , Óxido de Zinc/química

RESUMEN

AIMS/INTRODUCTION: The sodium-glucose cotransporter 2 inhibitor, canagliflozin, reduced kidney failure and cardiovascular events in the Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) trial. We carried out a post-hoc analysis to evaluate the efficacy and safety of canagliflozin in a subgroup of participants in East and South-East Asian (EA) countries who are at high risk of renal complications. MATERIALS AND METHODS: Participants with an estimated glomerular filtration rate of 30 to <90 mL/min/1.73 m2 and urinary albumin-to-creatinine ratio of >300-5,000 mg/g were randomized to 100 mg of canagliflozin or a placebo. The effects of canagliflozin treatment on pre-specified efficacy and safety outcomes were examined using Cox proportional hazards regression between participants from EA countries (China, Japan, Malaysia, the Philippines, South Korea and Taiwan) and the remaining participants. RESULTS: Of 4,401 participants, 604 (13.7%) were from EA countries; 301 and 303 were assigned to the canagliflozin and placebo groups, respectively. Canagliflozin lowered the risk of primary outcome (composite of end-stage kidney disease, doubling of serum creatinine level, or renal or cardiovascular death) in EA participants (hazard ratio 0.54, 95% confidence interval 0.35-0.84). The effects of canagliflozin on renal and cardiovascular outcomes in EA participants were generally similar to those of the remaining participants. Safety outcomes were similar between the EA and non-EA participants. CONCLUSIONS: In the CREDENCE trial, the risk of renal and cardiovascular events was safely reduced in participants from EA countries at high risk of renal events.

Asunto(s)

Canagliflozina/uso terapéutico , Enfermedades Cardiovasculares/prevención & control , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Nefropatías Diabéticas/tratamiento farmacológico , Fallo Renal Crónico/prevención & control , Inhibidores del Cotransportador de Sodio-Glucosa 2/uso terapéutico , Adulto , Albuminuria/sangre , Albuminuria/orina , Asia Sudoriental , Enfermedades Cardiovasculares/etiología , Creatinina/sangre , Creatinina/orina , Diabetes Mellitus Tipo 2/complicaciones , Diabetes Mellitus Tipo 2/metabolismo , Nefropatías Diabéticas/etiología , Nefropatías Diabéticas/metabolismo , Método Doble Ciego , Asia Oriental , Femenino , Tasa de Filtración Glomerular/efectos de los fármacos , Humanos , Riñón/efectos de los fármacos , Fallo Renal Crónico/etiología , Masculino , Persona de Mediana Edad , Modelos de Riesgos Proporcionales , Resultado del Tratamiento

RESUMEN

The photocatalytic reduction of toxic Cr(VI) to non-pernicious Cr(III) using ZnFe2O4/EDTA (ethylenediaminetetraacetic acid) under UV irradiation was evaluated. The reduction of Cr(VI) with bare ZnFe2O4 under UV irradiation was negligible. However, the Cr(VI) in the solution was completely reduced within 3 h after the introduction of EDTA. EDTA could consume valence band holes and could be oxidized by holes into inorganic products. Therefore, photo-generated electrons could be used to reduce Cr(VI) to Cr(III). The effect of concentration of EDTA, ZnFe2O4 photocatalyst dosages, and initial pH on the photocatalytic reduction of Cr(VI) was investigated. The results revealed that the photocatalytic reduction of Cr(VI) accelerated by increasing EDTA concentration and ZnFe2O4 dosage. The present reduction process confirms the pseudo-first-order kinetic reaction. The quasi reduction rate constant increased from 3.5 x 10-4 min-1 to 2.6 x 10-2 min-1 with the increase in initial EDTA concentration from 0 to 1000 mg L-1. The acidic solution is preferable for the photocatalytic reduction of Cr(VI). The entire reduction of Cr(VI) was carried out within 2 h under the optimum conditions with pH 2, 20 mg ZnFe2O4, and 500 mg L-1 EDTA. The formation of [Cr-EDTA]3+ complex may be advantageous to accelerate the Cr(VI) reduction. A probable mechanism for the photocatalytic Cr(VI) reduction was speculated here.

Asunto(s)

Cromo/análisis , Ácido Edético/química , Compuestos Férricos/química , Rayos Ultravioleta , Contaminantes Químicos del Agua/análisis , Zinc/química , Catálisis , Cromo/efectos de la radiación , Cinética , Imanes/química , Nanopartículas/química , Oxidación-Reducción , Fotólisis , Contaminantes Químicos del Agua/efectos de la radiación

RESUMEN

UV-light irradiated photocatalytic reduction of Cr(VI) to Cr(III) in aqueous solution using ZnFe2O4 nanoparticles in the presence of formic acid was reported. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and UV-Vis diffuse reflectance spectroscopy (DRS) were employed to characterize ZnFe2O4 nanoparticles. The photocatalytic activity of pure ZnFe2O4 under UV irradiation was significantly low. However, the Cr(VI) reduction efficiency on nano-sized ZnFe2O4 in the presence of 0.40% formic acid reached 95.4% within 4 h. Herein, the effect of pH, photocatalyst amount, initial concentration of Cr(VI) and formic acid concentration on the photocatalytic reduction of Cr(VI) was investigated. The results indicated that the photocatalytic reduction of Cr(VI) decreased with increase in the initial concentration of Cr(VI), photocatalyst dosage and pH. The reduction rate constant declined from 0.017 min-1 to 0.0023 min-1 with the increase in initial concentration of Cr(VI) from 5 to 25 mg L-1. However, the reduction rate constant sharply increased from 0.000075 min-1 to 0.0127 min-1 with the increase in formic acid concentration from 0.05% to 0.40%. The formic acid could capture the photogenerated holes, and eventually formate (HCOO-) ions could be converted into carbon dioxide radicals (•CO2-). Because of more negative redox potential for •CO2- radicals, Cr(VI) species could easily be reduced to Cr(III) under UV irradiation. The pseudo-first-order kinetic reaction was confirmed for this reduction process. A tenable mechanism for the photocatalytic Cr(VI) reduction has also been demonstrated.

Asunto(s)

Cromo , Nanopartículas , Catálisis , Formiatos , Oxidación-Reducción

RESUMEN

AIM: Our aim was to investigate the effects of add-on canagliflozin with glimepiride dose adjustment or glimepiride dose adjustment on pancreatic beta cell function in patients with type 2 diabetes mellitus and inadequate glycemic control despite stable triple therapy (metformin, teneligliptin, and glimepiride) plus diet/exercise therapy. METHODS: Forty patients on stable triple therapy were randomized to glimepiride dose adjustment without (glimepiride group) or with add-on canagliflozin 100 mg (canagliflozin group) for 24 weeks. The glimepiride dose was adjusted every 4 weeks based on continuous glucose monitoring over the previous 2 weeks according to a prespecified algorithm. After the 24-week treatment period, the patients returned to the pre-intervention regimen for 1 week (wash-out period). Patients underwent 75 g OGTTs at the start of the run-in period and at the end of the wash-out period. The primary endpoint was the change in disposition index (DI). RESULTS: Thirty-nine patients completed the study (canagliflozin, n = 19; glimepiride, n = 20). The change in DI was +5.1% and -11.0% in the canagliflozin and glimepiride groups, respectively, with a between-group difference ratio of 18.0% (P = 0.330). HbA1c, fasting plasma glucose, body weight, and daily-life continuous glucose monitoring-derived parameters improved in the canagliflozin group. Hypoglycemia occurred in 60% (44 episodes) and 70% (79 episodes) of patients in the canagliflozin and glimepiride groups, respectively. The change in DI was significantly correlated with the changes in glycemic control and variability in overall cohort. CONCLUSION: Adding canagliflozin to the triple therapy improved beta cell function by 18%, but it did not reach statistical significance. This study also demonstrated a correlation between the change in DI and glycemic control. As canagliflozin improved both glucose level and variability with relatively lower risk of hypoglycemia compared with glimepiride dose adjustment, adding canagliflozin to the triple therapy may be clinically beneficial. TRIAL REGISTRATION: UMIN000030208/jRCTs051180036.

RESUMEN

The photodegradation and mineralization of the nitenpyrum [(E)-N-(6-chloro-3-pyridylmethyl)-N-ethyl-N'-methyl-2-nitrovinylidenediamine], which is one of the most popular neonicotinoid insecticides, were conducted in the presence of ZnO photocatalyst under solar irradiation. An initial nitenpyrum concentration of 10 ppm was completely degraded in the presence of ZnO after 30 min irradiation, while only 70% degradation was observed in the absence of ZnO. The effect of different parameters, for example, amount of ZnO, initial pH, light intensity, reaction temperature, and irradiation time, on the photocatalytic degradation of nitenpyrum was also evaluated. The drop of total organic carbon (TOC) as a consequence of mineralization of nitenpyrum was observed during the photocatalytic process. The kinetics of photocatalytic degradation followed a pseudo-first order law according to Langmuir-Hinshelwood model, and the rate constant is 0.140 min-1. CO2, chloride, and nitrate ions were observed as the end-products after completing degradation of nitenpyrum. The four kinds of intermediate products were identified by GC-MS during the decomposition of nitenpyrum. In order to investigate the degradation pathway of nitenpyrum, the point charge and frontier electron density at each atom on the molecule were determined using molecular orbital (MO) stimulation. The degradation mechanism was proposed, based on the identified intermediates. The solar photocatalytic degradation method can become an effective technique for the treatment of nitenpyrum-polluted water.

Asunto(s)

Insecticidas , Contaminantes Químicos del Agua , Óxido de Zinc , Catálisis , Neonicotinoides , Fotólisis

RESUMEN

A preconcentration technique with a magnetite-kaolin adsorbent capable of magnetic separation was developed for the determination of rhodium in environmental samples. The magnetite-kaolin nanocomposite was prepared for the preconcentration of rhodium in an aqueous solution prior to an electrothermal atomic absorption spectrometric determination. The detection limit (3S/N) of rhodium was 16 pg mL-1 under the optimum conditions. Even though matrix elements existed in 103 fold excess in aqueous solution, the rhodium adsorption could be not affected by the matrix. The present method could be applied to the determination of Rh in an aqueous solution. The advantages are easy preparation of the adsorbent and fast magnetic separation.

RESUMEN

The photocatalytic degradation of Diazinon under sunlight irradiation is investigated by using the nanosized photocatalyst TiO2. Eight intermediates are detected during the degradation, and the reaction pathway is proposed on the base of their intermediates. The degradation parameters, concerning photocatalyst concentration, temperature, pH, sunlight intensity and irradiation time are optimized. Under the optimal conditions, the photocatalytic degradation of Diazinon can be completed within 60 min. The photodegradation is found to follow the pseudo-first-order kinetic law at a rate constant of 0.068 min-1. The activation energy is 14.7 kJ/mol. The formations of sulphate, phosphate, nitrate and ammonium ions during the degradation are observed. About 83% of the initial N is detected as ammonium and nitrate ions during 50 h of irradiation time.

Asunto(s)

Diazinón , Contaminantes Químicos del Agua , Catálisis , Fotólisis , Luz Solar , Titanio , Agua , Contaminantes Químicos del Agua/análisis

RESUMEN

The development of photocatalysts that efficiently degrade organic pollutants is an important environmental-remediation objective. To that end, we report a strategy for the ready fabrication of oxygen-doped graphitic carbon nitride (CN) with engendered nitrogen deficiencies. The addition of KOH and oxalic acid during the thermal condensation of urea led to a material that exhibits a significantly higher pseudo-first-order rate constant for the degradation of bisphenol A (BPA) (0.0225 min-1) compared to that of CN (0.00222 min-1). The enhanced photocatalytic activity for the degradation of BPA exhibited by the dual-defect-modified CN (Bt-OA-CN) is ascribable to a considerable red-shift in its light absorption compared to that of CN, as well as its modulated energy band structure and more-efficient charge separation. Furthermore, we confirmed that the in-situ-formed cyano groups in the Bt-OA-CN photocatalyst act as strong electron-withdrawing groups that efficiently separate and transfer photo-generated charge carriers to the surface of the photocatalyst. This study provides novel insight into the in-situ dual-defect strategy for g-C3N4, which is extendable to the modification of other photocatalysts; it also introduces Bt-OA-CN as a potential highly efficient visible-light-responsive photocatalyst for use in environmental-remediation applications.

RESUMEN

A new visible-light-responsive tetrahedral ultrathin metal-organic framework nanosheet (UMOFNs)/Ag3PO4 composite photocatalyst with a core-shell structure was readily synthesized by sonication in an organic solvent. Characterization methods for the photocatalyst included X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy. The XRD patterns of the composite photocatalyst before and after visible-light irradiation demonstrated that trace amounts of Ag ions in the composite photocatalyst easily transformed into Ag nanoparticles, which play a role in promoting charge separation at the interface of a heterojunction. The UMOFNs/Ag3PO4 composite photocatalyst showed higher photocatalytic activity for the photodegradation of 2-chlorophenol (2-CP) under visible-light irradiation (>420 nm) than Ag3PO4. The complete degradation of 2-CP was achieved in 7 min using the tetrahedral UMOFNs/Ag3PO4 core-shell photocatalyst, and the apparent reaction rate was approximately 26 times higher than that of pure Ag3PO4. Further, a scavenger experiment showed h+ and O2 •- were the major reactive species involved in the photocatalytic reaction system. This enhanced photocatalytic activity results from the efficient separation of photoinduced electron-hole pairs and the increase of interface area between Ag3PO4, UMOFNs, and the Ag nanoparticles.

RESUMEN

Ag/ZnO nanocomposites are successfully synthesized at different Ag contents through simple, effective, high yield and low-cost mechanochemical combustion technique, with the addition of silver acetate to zinc acetate and oxalic acid mixture. The synthesized materials are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron spectroscopy (SEM), BET surface area analysis, UV - visible diffuse reflectance spectroscopy (UV - DRS) and photoluminescence spectroscopy (PL). It is shown that the prepared nanocomposites are composed of metallic Ag0 and wurtzite ZnO. The photocatalytic performance of different composites is evaluated by the degradation of Famotidine (FMT) under UV irradiation. The results indicate it that the maximum photodegradation rate is obtained with 6 wt% metallic Ag-decorated ZnO, and it is 2.1 times better than that obtained with pure ZnO. The photocatalytic degradation of FMT with Ag/ZnO is affected by various parameters such as calcination temperature and time, doping concentrations and reusability. The Ag/ZnO demonstrates higher activity due to the reduction of electron - hole recombination and Ag0 metal catalyst. The possible photocatalytic degradation mechanism of FMT with Ag/ZnO is estimated from the scavenger test.

Asunto(s)

Acetatos/química , Famotidina/química , Compuestos de Plata/química , Óxido de Zinc/química , Catálisis , Nanocompuestos/química , Ácido Oxálico/química , Fotólisis , Temperatura , Rayos Ultravioleta