scholarly journals Photocatalytic Degradation of Dissolved Phenol by Immobilized Zinc Oxide Nanoparticles: Batch Studies, Continuous Flow Experiments, and Numerical Modeling

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 69
Author(s):  
Michalis V. Karavasilis ◽  
Maria A. Theodoropoulou ◽  
Christos D. Tsakiroglou

In spite of the progress achieved on the photo-catalytic treatment of water streams, there is still a gap of knowledge on the optimization of the performance of continuous-flow photo-reactors. Zinc-oxide (ZnO) nanoparticles were immobilized on Duranit (80% silica + 20% alumina) inert balls with dip-coating and thermal annealing. The immobilized ZnO nanoparticles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, and Raman spectroscopy. To assess the stability and photocatalytic capacity of immobilized ZnO, degradation tests of phenol were performed in batch mode in a 22 W UV-oven with an emission peak at 375 nm by varying the temperature, the initial phenol concentration, and the ratio of photocatalyst mass to initial phenol mass. Continuous flow tests were conducted on two types of annular photo-reactors, made of poly(methyl)methacrylate (PMMA) and stainless steel (STST), equipped with a 6 W UV-lamp with emission at 375 nm, packed with ZnO-coated Duranit beads. Experiments were conducted by recirculating the phenol solution between the annular space of reactor and an external tank and varying the flow rate and the liquid volume in the tank. A one-dimensional dynamic mathematical model was developed by combining reactive with mass-transfer processes and used to estimate the overall reaction kinetic constant with inverse modeling. The results revealed that the ZnO losses might be discernible in batch mode due to the intense stirring caused by the bubbles of injected air, while an insignificant loss of ZnO mass occurs under continuous flow conditions, even after several cycles of reuse; the order of the overall phenol photodegradation reaction is lower than unity; the pseudo-1st order kinetic constant scales positively with the ratio of photocatalyst mass to the initial phenol mass and Peclet number.

2019 ◽  
Vol 11 (2) ◽  
pp. 119 ◽  
Author(s):  
Aisha Shamim ◽  
Tariq Mahmood ◽  
Monis Bin Abid

Nanoparticles are ultrafine structures with dimensions less than 100 nm. Nanoparticles have diverse applications. There are three important methods of fabrication of nanoparticles namely physical, chemical and biological methods. Physical method is a top down strategy for the fabrication of nanoparticles. It is energy intensive and time consuming. A chemical method is simple, but is expensive and requires expensive chemicals with high purity and also involves hazards of contaminations. Biological synthesis is very simple, cheap and environment friendly, requiring no expensive chemicals, temperature and is time saving. Plants and microorganisms are commonly used in this method. These are available everywhere. In the present work we synthesized Zinc Oxide (ZnO) nanoparticles by biological method using Aspargillus niger and zinc chloride (ZnCl2) as precursors. Biogenic synthesis of metallic nanoparticles by fungi is a safe and economical process because of formation of stable and small sized nanoparticles. Fungal biomass secretes proteins which act as reducing and stabilizing agents. The synthesized nanoparticles were characterized by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), UV-Vis (Ultraviolet, Visible) and EDX (Energy Dispersive X-Ray) techniques. Their size was in nm range and morphology of synthesized ZnO NPs was hexagonal. The ZnO nanoparticles are one of the most versatile materials and are used in cosmetics and in Bioenergy production, as a catalyst and as antibacterial material.


2017 ◽  
Vol 16 (10) ◽  
pp. 2331-2339 ◽  
Author(s):  
Shakeel Ahmad Khan ◽  
Sammia Shahid ◽  
Waqas Bashir ◽  
Sadia Kanwal ◽  
Ahsan Iqbal

Purpose: To synthesize, characterize and investigate the antimicrobial properties of pure and manganese-doped zinc oxide nanoparticles.Method: Un-doped and manganese-doped zinc oxide (Mn-doped ZnO) nanoparticles were prepared using co-precipitation method. The synthesized Mn-doped ZnO  nanoparticles were characterized using energy-dispersive x-ray spectroscopy  (EDX), scanning electron microscopy (SEM), and x-ray diffraction (XRD)  spectroscopic techniques. Their band gap energies were measured with ultraviolet-visible (UVVis) spectroscopy, while their antioxidant properties were evaluated by ferric reducing antioxidant power (FRAP), DPPH radical-scavenging, ferric  thiocyanate (FTC) and total phenolic content (TPC) assays. The antimicrobial  activities of the nanoparticles against different bacterial strains were determined using agar diffusion method.Result: Results from XRD, SEM, EDX and UV-Vis analyses demonstrated  successful synthesis of undoped and Mn-doped ZnO nanoparticles as seen in their hexagonal, wurtzite structures. The un-doped and Mn-doped ZnO nanoparticles had average grain sizes of 16.72 nm and 17.5 nm, and band gap energies of 3.585 eV and 2.737 eV, respectively. Significant antibacterial activity was manifested by Mndoped ZnO against E. coli, S. aureus, Klebsiella and B. subtilis, with zones of inhibition (ZOIs) of 13 ± 0.09 mm, 14 ± 0.01 mm, 18 ± 0.07 mm and 20 ± 0.10 mm, respectively. The Mn-doped ZnO nanoparticles also exhibited effective and significant antioxidant potential relative to butylated hydroxytoluene (BHT) and un-doped ZnO nanoparticles.Conclusion: Mn-doped ZnO nanoparticles demonstrate significant antimicrobial and antioxidant activities. Thus, the preparation is a good candidate for further development into therapeutic formulations.Keywords: Mn-doped ZnO, Nanoparticles, Properties, Antioxidant, Antibacterial


Author(s):  
Marta Lígia Pereira da Silva ◽  
Tellys Lins Almeida Barbosa ◽  
Meiry Gláucia Freire Rodrigues

Background: Region-based solutions for water cleaning could be critical to tackle the water challenges faced in enhancing the in the future. Brazilian Primavera clay is cheap, abundant, and an untested material that has the potential to be used for water cleaning. Objective: the objective of the present work was to thermally activate and characterize the Brazilian clay and then determine the potential to remove Cd2+ from an aqueous solution. Methods: Primavera clay was thermally activated at 300 oC and characterized using X ray diffraction, X-ray Spectroscopy Energy Dispersive, and N2 adsorption. Sorption equilibrium was determined using the following experimental conditions: constant pH 4.5, 5 h, and 27 oC. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin isotherms models were applied in order to determine the efficiency of clay used as an adsorbent. Adsorption kinetics was analyzed using the pseudo-second-order kinetic model. Results: In this study, results revealed that even though the heat treatment did not cause profound alterations on the clay structure(smectite) and surface area (78 m2 /g), a pseudo-second-order kinetic constant of 0.5563 mg/g/min was found for the cadmium removal. Conclusion: The mathematical models of the Langmuir and Temkin showed a better fit to the experimental data. A high affinity between the cadmium and the thermally activated Primavera clay was found up to 88 % with removal efficiencies.


2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
N. B. Rithin Kumar ◽  
Vincent Crasta ◽  
B. M. Praveen

The current paper explores the preparation of PVA nanocomposites by doping with zinc oxide (ZnO) nanoparticles using the method of coagulation and solvent casting technique. The dopant zinc oxide nanoparticle is prepared by simple precipitation method and is confirmed by the X-ray diffraction (XRD) studies. The XRD studies explore that the average particle size of the synthesized nanoparticles is 55 nm and show that the crystallinity factor of PVA nanocomposites is influenced by the interaction occurring between the PVA main chain and the ZnO nanoparticle. The FTIR spectroscopy suggests that the formulation of complexes occurring between the dopants and the PVA main chain is due to inter or intra molecular hydrogen bonding. UV-vis spectra explore the dramatic decrease in the optical energy gap of nanoparticles doped polymer composites and the variations of Urbach energy (Eu) related to crystallinity for various dopant concentrations. The mechanical properties of the PVA nanocomposites were explored using universal testing machine (UTM) that reflects that, for x=15% doping concentration, there is an increase in the tensile strength, stiffness, and Young’s modulus, whereas, for x=7.5% concentration, the percentage total elongation at fracture is found to be the maximum. The morphological behavior and homogenous nanoparticle distribution in the composites were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX).


2015 ◽  
Vol 804 ◽  
pp. 7-11
Author(s):  
Suparut Narksitipan ◽  
Thaweedet Awirut

In this research, zinc oxide (ZnO) films were prepared using a wet chemical reaction via a microwave technique. X-ray diffraction techniques (XRD) and energy dispersive x-ray spectroscopy (EDS) were used to study the phases, crystalline structures, chemical compositions and optical properties of the films, respectively. Optical transmittance was also measured through UV-VIS spectroscopy. Surface film morphologies were investigated by scanning electron microscopy (SEM). As a result, a ZnO phase with a hexagonal structure was detected. The EDS spectrum shows that elements of Zn and O were present. The average optical transmittance value for all films was 75% at a wavelength of 370-375 nm, a comparison among the films obtained at different times show a transmittance value slightly higher for films obtained at higher times. A calculation of the energy band gap of ZnO films was estimated to be in the range of 3.31 to 3.35 eV. Additional, the ZnO films showed a smooth surface.


F1000Research ◽  
2022 ◽  
Vol 10 ◽  
pp. 1077
Author(s):  
Gabriel Amani Kaningini ◽  
Shohreh Azizi ◽  
Hlengilizwe Nyoni ◽  
Fhatuwani Nixwel Mudau ◽  
Keletso Cecilia Mohale ◽  
...  

Background: Nanoparticles are globally synthesized for their antimicrobial, anti-inflammatory, wound healing, catalytic, magnetic, optical, and electronic properties that have put them at the forefront of a wide variety of studies. Among them, zinc oxide (ZnO) has received much consideration due to its technological and medicinal applications. In this study, we report on the synthesis process of ZnO nanoparticles using Athrixia phylicoides DC natural extract as a reducing agent.   Methods: Liquid chromatography–mass spectrometry (LC-MS) was used to identify the compounds responsible for the synthesis of ZnO nanoparticles. Structural, morphological and optical properties of the synthesized nanoparticles have been characterized through X-ray diffraction (XRD), Ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).   Results: LC-MS results showed that different flavonoids and polyphenols, as well as Coumarin, an aromatic compound, reacted with the precursor to form ZnO nanoparticles. XRD and UV-Vis analysis confirmed the synthesis of ZnO nanoparticles, with a spherical shape showed in SEM images. The quasi-spherical ZnO crystals had an average crystallite size of 24 nm. EDS and FTIR analysis confirmed that the powders were pure with no other phase or impurity.   Conclusions: This study successfully demonstrated that the natural plant extract of A. phylicoides DC. can be used in the bio-reduction of zinc nitrate hexahydrate to prepare pure ZnO nanoparticles, thus, extending the use of this plant to an industrial level.


2017 ◽  
Vol 14 (2) ◽  
pp. 146-152
Author(s):  
Neha Sharma ◽  
Sanjayay Kumar

In present study, undoped ZnO, Zn0.8Ag0.2O, Zn0.8Al0.2O and Zn0.6Al0.2Ag0.2O samples are synthesized by simple solution method. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX) and UV-visible (UV-Vis) spectroscopy are used to perform the characterization of undoped, doped and codoped samples. XRD analysis is exposed that hexagonal wurtzite crystalline structure obtained for undoped, doped and codoped samples without any extra representation of impurity phases. The crystalline size is when evaluated by using Scherrer, It has 44, 49, 41and 37nm for undoped ZnO, Zn0.8Ag0.2O, Zn0.8Al0.2O and Zn0.6Al0.2Ag0.2O samples. Similarly, the crystalline size and strain are also evaluated by Williamson hall (W-H) and size strain plot (SSP) for the undoped, doped and codoped nanoparticles. The evaluated crystalline size by SSP is three times greater than the result of the scherrer method. The SEM exposes that surface morphology of nanoparticle samples, in this case is the formation of large agglomeration in spherical shape with nanocrystallites of undoped and doped ZnO with apparent and definite boundaries. EDX points out the replacement of Al2+ and Ag+ with Zn2+ in ZnO matrix and consequences in the development of single-phase Zn1−x−yAgxAlyO. The blueshift is shown in UV-Vis absorption spectra because the band gap value increases with the increase in doping, except Ag+ doped ZnO nanoparticles.


2019 ◽  
Vol 15 (2) ◽  
pp. 268-273 ◽  
Author(s):  
Raja Adibah Raja Ahmad ◽  
Zawati Harun ◽  
Mohd Hafiz Dzarfan Othman ◽  
Hatijah Basri ◽  
Muhamad Zaini Yunos ◽  
...  

Biosynthesis of metallic nanoparticles using plants, enzymes, and microorganism have been known as eco-friendly alternatives to conventional physical and chemical methods. Recently, the biological synthesis of nanoparticles has been a keen interest amongst researchers and scientist due to its simple technique, eco-friendliness, non-toxic, inexpensive and potential to perform in antibacterial activity. Thus, in this current work, the synthesis of zinc oxide (ZnO) nanoparticles using reduction agent from fruit extracts of Ananas Comosus is reported. The biosynthesized zinc oxide was characterized using Field Emission Scanning Electron Microscope (FESEM) with Energy Dispersive X-ray analysis (EDX), UV-Vis absorption spectroscopy and X-ray diffraction (XRD). The average size of the nanoparticles was found to be in the range of 30-57nm. The antibacterial activity of ZnO nanoparticles was carried out via agar diffusion method against pathogenic organisms. It is observed that the biosynthesized ZnO in the process has the efficient antibacterial activity. In conclusion, the green synthesis of zinc oxide nanoparticles using the fruit extract of Ananas Comosus is considered as a potential additive to substitute other metal oxides such as silver (Ag) and titanium dioxide (TiO2)but also provide antibacterial effect that able to enhance the nanoparticle performance.


2020 ◽  
Vol 15 (11) ◽  
pp. 1412-1422
Author(s):  
Nishat Arshi ◽  
Y. Prashanthi ◽  
Tentu Nageswara Rao ◽  
Faheem Ahmed ◽  
Shalendra Kumar ◽  
...  

In this study, we report synthesis of Zinc oxide nanoparticles using simple chemical and green methods. The ZnO nanoparticles were synthesized using leaf extract of Azadirachta indica (neem) as reducing agent. The as obtained product was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy dispersive X-ray analysis (EDAX) and TEM techniques. XRD analysis confirms that ZnO nanoparticles were crystalline having hexagonal Wurtzite structure with (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0) and (1 1 2) planes. SEM analyses show that the as synthesized ZnO NPs were in the form of agglomerates and no other impurity peak was found in the EDS. TEM analyses confirm that the size of the nanoparticle was approx. 50 nm. Here in, we investigate the effect of chemical and green synthesized zinc oxide nanoparticles on germination and growth of lycopersicum esculentus (tomato) using petri plate seed germination method in loamy sand soil. The impact of concentration of applied ZnO nanoparticles via green synthesis and chemical methods were analyzed. Results revealed that green synthesized Zinc oxide nanoparticles showed maximum growth of seedling as compared to chemically synthesized Zinc oxide nanoparticles, bulk ZnO and control. After 50 days of tomato growth analysis, it was recognized that ZnO NPs can be a good green synthetic fertilizer by increasing shoot length, wet weight, dry weight and yield over conventional control. Hence, green method is found to be more effective.


2013 ◽  
Vol 685 ◽  
pp. 119-122 ◽  
Author(s):  
Tahseen H. Mubarak ◽  
Karim H. Hassan ◽  
Zena Mohammed Ali Abbas

The application of nanoparticles in the processes of making commercial products has increased in recent years due to their unique physical and chemical properties. Materials whose crystallites, particle sizes are smaller than 100 nm are commonly named nanocrystalline, nanostructured, nanosized materials. There are many methods used for the preparation of nanomaterials. We use is a method which is easy if compared to other methods with the chemicals required for these methods are available and cheap. Nano zinc oxide has been prepared by wet chemical method from zinc nitrate and using sodium bicarbonate as precipitation agent. The resulting nanopowders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM).The particle size measurement using XRD Scherer’s formula calculations confirms that the crystallite size of the ZnO nanoparticles range from 41 to 67 nm and depending on calcinations temperature. SEM micrographs reveals less number of pores with smaller lump size in addition to clearly showing the micro structural homogeneity and remarkably dense mode of packing of grains of ZnO nanoparticles with minimum porosity.


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