Silica coating and photocatalytic activities of ZnO nanoparticles: Effect of operational parameters and kinetic study

Published Date

15 October 2014, Vol.131:158–168, doi:10.1016/j.saa.2014.03.041

Title 

Silica coating and photocatalytic activities of ZnO nanoparticles: Effect of operational parameters and kinetic study

• Author 

• L.F.M. Ismail ^a,,
• M.M. Emara ^b,c
• M.M. El-Moselhy ^b,c
• N.A. Maziad ^d
• O.K. Hussein ^c

• aAl-Azhar University, Faculty of Science (Girls), Chemistry Department, Nasr City, Cairo, Egypt
• bAl-Azhar University, Faculty of Science (Boys), Chemistry Department, Nasr City, Cairo, Egypt
• cScience Center for Detection and Remediation of Environmental Hazards (SCDREH), Al-Azhar University, Nasr City, Cairo, Egypt
• dNational Center for Radiation Research and Technology, Naser City, Cairo, Egypt

Received 5 December 2013. Revised 13 March 2014. Accepted 20 March 2014. Available online 21 April 2014.

Highlights

• •
  Preparation of silica-coating ZnO nanoparticles with core/shell structure.
• •
  Characterization of silica-coating ZnO by XRD, TEM, SEM and EDX.
• •
  The photocatalytic performance of silica-coating ZnO in MB aqueous solution.
• •
  Compared to ZnO the maximum apparent rate constant for silica-coating ZnO is obtained at pH 8.5 (pH 11.5 in case of bare ZnO).
• •
  Adsorption isotherm and kinetics.

Abstract

Silica-coating ZnO nanoparticles were prepared using the hydrothermal method. The prepared nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray Spectroscopy (EDX). It was found that ultrafine core/shell structured silica-coating ZnO nanoparticles were successfully obtained. TEM analysis revealed a continuous and uniform silica coating layer of about 8 nm in thickness on the surface of ZnO nanoparticles. The photocatalytic performance of silica-coating ZnO core/shell nanoparticles in methylene blue aqueous solution was investigated. The effects of some operational parameters such as pH value, nanocatalyst loading and initial MB concentration on the degradation efficiency were discussed. Kinetic parameters were experimentally determined and a pseudo-first-order kinetic was observed. Thus, the main advantage of the coating is the stability of the photocatalysts and the better performance in acidic or alkaline solutions. Compared to ZnO the maximum apparent rate constant is obtained at pH 8.5 (pH 11.5 in case of bare ZnO). Moreover, the Langmuir adsorption model was applied to describe the equilibrium isotherm at different MB concentration. The applicability of the Langmuir isotherm suggests monolayer coverage of the MB onto surface of silica-coating ZnO nanoparticles. The kinetics of the adsorption with respect to the initial dye concentration, were also investigated. The pseudo-first-order and second-order kinetic models were used and the rate constants were evaluated. The kinetic studies revealed that the pseudo-second-order kinetic model better represented the adsorption kinetics, suggesting that the adsorption process may be chemisorption.

Graphical abstract

Keywords

• ZnO
• Core/shell
• Degradation
• Kinetics
• Adsorption

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Scheme 1.

Scheme 2.

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 Table 1

Table 1.

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 Table 2

Table 2.

 Table 3

Table 3.

Fig. 11.

Fig. 12.

 Table 4

Table 4.

Fig. 13.

Fig. 14.

 Table 5

Table 5.

• ⁎ 
  Corresponding author. Tel./fax: +20 226221122.

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Chemical and mechanical changes during photooxidation of an acrylic clear wood coat and its prevention using UV absorber and micronized TiO2

Published Date

July 2013, Vol.98(7):1329–1338, doi:10.1016/j.polymdegradstab.2013.03.029

Title 

Chemical and mechanical changes during photooxidation of an acrylic clear wood coat and its prevention using UV absorber and micronized TiO₂

• Author 

• Boris Forsthuber ^a,,
• Ulrich Müller ^b
• Alfred Teischinger ^c
• Gerhard Grüll ^a

• aHolzforschung Austria, Franz-Grill-Strasse 7, 1030 Vienna, Austria
• bWood K plus – Competence Centre for Wood Composites and Wood Chemistry, St.-Peter-Strasse 25, 4021 Linz, Austria
• cDept. Of Wood Science and Technology, University of Natural Resources and Life Sciences, Gregor Mendel Strasse 33, 1180 Vienna, Austria

Received 20 November 2012. Revised 27 March 2013. Accepted 31 March 2013. Available online 17 April 2013.

Abstract

In this study, we hypothesized that the use of UV absorber of the hydroxy-benzotriazole class (BTZ) and micronized TiO₂ (NTiO₂) as mineral UV screener could stabilize the chemical and mechanical properties of clear wood coatings based on a high T_g/low T_g multiphase acrylic binder dispersion. The photooxidation rates were compared using ATR-FTIR techniques and tension tests. For qualitative and quantitative chemical analysis and correlation to the mechanical properties, multiple linear regression (MLR) was used, which was a suitable method to monitor the chemical changes of the polymeric binder and to investigate the influence of these light stabilizing additives on the photooxidation behavior. The analysis of mechanical properties of the acrylic binder during exposure to Xenon arc light showed that both BTZ and NTiO₂ stabilized the Young's Modulus and the elongation at break during the whole cycle. BTZ showed better results. However, it led to a strong decrease of the initial Young's Modulus whereas NTiO₂ showed no comparable effect. We concluded that BTZ was very efficient in reducing the photooxidation and the accompanied change of the elastic properties of the acrylic binder. NTiO₂ only stabilized the high T_gcomponent of the multiphase acrylic binder whereas the photooxidation of the low T_gcomponent was accelerated. This may be explained by a photocatalytical activity of NTiO₂.

Keywords

Wood coatings

Clear coatings

UV absorber

UV screener

(Meth)acrylates

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Fig. 1.

Fig. 2.

Fig. 3.

 Table 1

Table 1.

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

• *
  Corresponding author. Tel.: +43 1 798262620.
  
  

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The Effects of Filler Loading and Vulcanisation System on Properties of Oil Palm Wood Flour-Natural Rubber Composites

Published Date
Hanafi Ismail

1. School of Industrial Technology Universiti Sains Malaysia 11800 Minden, Penang Malaysia
2. 
   
3. R. M. Jaffri

1. School of Industrial Technology Universiti Sains Malaysia 11800 Minden, Penang Malaysia
2. 
   
3. H. D. Rozman

1. School of Industrial Technology Universiti Sains Malaysia 11800 Minden, Penang Malaysia

Abstract

The effects of oil palm wood flour and vulcanization system on curing characteristics and mechanical properties of oil palm wood flour (OPWF)-natural rubber composites were studied. OPWF loading in the range of 0-50 phr and two vulcanisation systems, conventional vulcanisation (CV) and semi-efficient vulcanisation (semi-EV) were used. Increasing loading of OPWF in the rubber matrix resulted in reduction of tensile strength, tear strength and elongation at break, E  _b, but increased modulus and hardness of the composites. At a similar filler loading, semi-EV composites show better properties. Swelling studies and curing characteristics indicate that the rubber-filler interaction, scorch and cure times decrease with increasing filler loading.

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Effect of Elastomer on Flame Retardancy, Thermal Degradation, and Mechanical Properties of Intumescent Flame-Retardant Polyethylene

Author

Sheng Li

1. 1. Heilongjiang Key Laboratory of Molecular Design and Preparation of Flame Retarded Materials, College of Science, Northeast Forestry University, Harbin 150040, China
   2. 
      
   3. Bin Li

1. 1. Heilongjiang Key Laboratory of Molecular Design and Preparation of Flame Retarded Materials, College of Science, Northeast Forestry University, Harbin 150040, China,  libinzh62@163.com

Abstract

Ethylene—acrylic ester—maleic anhydride (EAEM), as a compatibilizer, has been used to modify a new halogen-free flame retardant linear low-density polyethylene (LLDPE) in this article. Intumescent flame retardants (IFRs) consist of a charring—foaming agent (CFA), ammonium polyphosphate (APP), organic montmorillonite (OMMT) and an antidripping agent. Based on limiting oxygen index values and UL-94 ratings, the IFRs show the effective flame retardancy in the blend of LLDPE and EAEM. Comparative study on the thermal degradation of the composites demonstrates that the IFRs can reduce initial temperature (T _initial) of thermal degradation of the composites, and make the main thermal degradation peak move to the high temperature. CONE results reveal that the IFRs can form a char layer on the surface of the composites and clearly change the decomposition behavior of the IFR-LLDPE/ EAEM composites. Whether OMMT is contained or not in the IFRs, the IFRs show a little effect on reducing tensile strength of the composites. This result is proved by well dispersion of IFRs in the blend observed from scanning electron microscopic images. EAEM is also beneficial for improving the flame retardancy and mechanical properties of the composites.

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http://jep.sagepub.com/content/43/3/257.abstract

Comparative Effect of Foliar Application of Cow Dung, Wood Ash and Benlate on the Disease Initiation and Development of Roselle (Hibiscus sabdariffa L.) Leaf Spot Disease Caused by Coniella musaiensis Var. Hibisci. in Makurdi, Central Nigeria

Published Date

DOI: 10.4236/gep.2016.48003

Author(s)    

K. D. Apeyuan^*, A. O. Nwankiti, H. O. A. Oluma, E. J. Ekefan

ABSTRACT

A study on the comparative effect of cow dung, wood ash and benlate for the control of leaf spot disease of Roselle (Hibiscus sabdariffa L.) was carried out following the preparation and foliar application of the materials on selected Roselle plants of the green and red accessions (Acc₁ & Acc₃) in the field. The cow dung was fermented for 14 days while sour milk was added to wood ash, dissolved and all filtered and labeled. The spraying commenced soon after the plants were thinned to one and was done weekly until after 50% of the plants had flowered. Results showed significant (p = 0.05) difference between benlate, the synthetic fungicide and the bio-fertilizers (cow dung and wood ash) for the two years of the study. Disease severity was significantly lower in the benlate than in the bio-fertilizers. There was no significant difference in yield between the treatments although higher yield was recorded in benlate. Though the bio-fertilizers could not suppress infection, they aided the growth of the plants by boosting luxuriant growth. The result showed that these bio-fertilizers cannot be used as substitute to the synthetic fungicide for the control of this leaf spot disease caused by Coniella musaiensis var. hibisci. However, since they give equally good yield the bio-fertilizers can still be used to minimize the reliance upon use of chemical fungicides.

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