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The preparation and properties of oxide coatings with immobilized ZSM-5 zeolite obtained by plasma electrolytic oxidation on aluminum support are investigated and discussed. Pure and Ce-exchanged ZSM-5 are immobilized on aluminum support from silicate-based electrolyte in ultra-low duty cycle pulsed direct current conditions. Obtained composite coa...
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Context 1
... activity of Methyl Orange photodegradation is presented in Fig. 5 for all obtained coatings. If the irradiation light photon energy is higher than the band-gap energy of a semiconducting photocatalyst it results in the excitation of electrons from the valance band to the conduction band, thus generating electron-hole pairs. Photogenerated electrons and holes participate in oxidation and reduction ...
Context 2
... since roughness increases while the porosity decreases with PEO processing time, larger, irregularly shaped pores may prevent light, as an immaterial agent, from penetrating towards the active centers positioned deeper inside the composite coatings, leaving only centers close to the surface accessible for photodecomposition of MO. Clearly, Fig. 5 shows that when Ce-exchanged ZSM-5 zeolite is incorporated into oxide coatings, the photoactivity of the obtained coatings increases almost linearly, compared to coatings without Ce. Therefore, the Ce-content could be excluded as the reason for the observed photoactivity decrease. It is also well known that oxygen vacancy defects play ...
Similar publications
The preparation and properties of zeolite-containing oxide coatings obtained by plasma electrolytic oxidation are investigated and discussed. Pure and Ce-exchanged natural (clinoptilolite) and synthetic (13X) zeolites are immobilized on aluminum support from silicate-based electrolyte. Obtained coatings are characterized with respect to their morph...
Citations
... Recently, it has been shown that Ce-loaded zeolite addition to electrolyte improves photoactivity of PEO coatings on aluminum [15][16][17]. Zeolites are crystalline materials known for their three-dimensional framework made of pores and channels resulting in large surface area [18]. The primary building units of zeolites' framework are TO 4 (where T = Si, Al) tetrahedra linked to four neighboring units by oxygen atoms. ...
... ZSM-5 zeolite, purchased from Zeolyst, used in this work has molar ratio Si/Al = 11.5. The purchased NH 4 -ZSM-5 zeolite was transformed to H-ZSM-5 (H 7.68 (H 2 O) 16 [Al 7.68 Si 88.32 O 192 ]) form by calcination at 500 °C for 5 h. Zeolite cavities were loaded with Ce ions using following ion exchange procedure: 5 g of zeolite was suspended in 1 L of 0.003 M Ce(NO 3 ) 3 ·6H 2 O aqueous solution (purity 99%, purchased from Aldrich) and stirred for 7 days at room temperature. ...
... Acidic aqueous solution used in this study was 0.001 M tungstosilicic acid WSiA (H 4 O 40 SiW 12 ·xH 2 O), while the alkaline aqueous solution was 0.01 M Na 2 WO 4 ·2H 2 O (see Table 1). Based on our previously reported results, 1 g/L of ZSM-5 zeolite powder loaded with Ce ions (Ce 3+ ) was added to every electrolyte solution [15][16][17]. During the PEO processing electrolyte solution was agitated with magnetic stirrer to sustain homogeneous distribution of zeolite and to gain better efficiency of cooling. ...
The preparation and characterization of oxide coatings made by plasma electrolytic oxidation (PEO) process on aluminum in two different electrolyte solutions of opposite pH values with addition of Ce-enriched ZSM-5 zeolite are investigated in this paper. The first selected electrolyte solution is highly acidic pH < 3, prepared with tungstosilicic acid (H4O40SiW12), while the second one is made with sodium tungstate (Na2WO4) creating highly alkaline PEO environment with pH > 12. Phase structure, chemical composition, morphology, photoluminescent properties, and photocatalytic activity of deposited oxide coatings are discussed. Properties of PEO coatings are analyzed against processing time revealing dynamics of PEO under defined conditions. Both sets of oxide coatings have similar chemical composition and morphology, but the photocatalytic activity is considerably higher for oxide coatings made in alkaline environment.
