Electrokinetic and adsorption characteristics of (hydr)oxides and oxide nanostructures in 1:1 electrolytes

Ермакова, Л. Э.; Sidorova, M. P.; Bogdanova, N. F.; Klebanov, A. V.

doi:10.1016/s0927-7757(01)00734-8

Cited by 11 publications

(5 citation statements)

References 22 publications

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“…Taking the nano-dimensions of the pores of anodic aluminum oxide into consideration, Rocca et al [78,87] had studied the possible effects of such dimensions on both mass transport into the pores and chemical reactivity of the pore walls and reported interesting results. On the basis of typical values of acidity constant for Al-OH groups (pKa 1 = 6.5 for the Al-/Al-OH couple and pKa 2 = 10.9 for the Al-OH/Al-O− couple), their electrokinetic (ζ potential) measurements which showed the PZC value of their unsealed anodic alumina samples to be around 10.5 [87], and the reported point of zero charge (PZC) of aluminum oxyhydroxide which is the range of pH 8.5-9 [281], Rocca et al [87] had concluded that over a wide pH range (pH < PZC, i.e., pH < 10.5) which is within the pH range of most sealing solutions, the surface charge on anodic alumina oxide and inside the nanopores is positive. Hence it is established that the surface of the oxide layer inside the pores is positively charged under sealing conditions (Figure 7).…”

Section: Effect Of the Nano-dimension Of The Pores And The Surface Chmentioning

confidence: 99%

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

2020

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Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones need to be premised on in-depth appreciation of existing technologies, their limitations, and desired ideal products or processes. In the light of these, published literature mostly in the past 30 years on the sealing process; the second highest energy consuming step in aluminum anodization and a step with significant environmental impacts has been critical reviewed in this systematic review. Emphasis have been placed on the need to reduce both the energy input in the anodization process and environmental implications. The implications of the nano-porous structure of the anodic oxide on mass transport and chemical reactivity of relevant species during the sealing process is highlighted with a focus on exploiting these peculiarities, in improving the quality of sealed products. In addition, perspective is provided on plausible approaches and important factors to be considered in developing sealing procedures that can minimize the energy input and environmental impact of the sealing step, and ensure a more sustainable aluminum anodization process/industry.Coatings 2020, 10, 226 2 of 55 sealing methods. Furthermore, the applicability of another hitherto popular sealing process; chromate sealing, is currently limited to essential parts in the aerospace industry due to toxicological, health, and environmental implications traced to Cr(VI) employed in the process [7][8][9][10][11][12][13][14][15][16]. On the other hand, the advantages of another industrially utilized sealing process; the nickel fluoride (cold) sealing process is limited by the toxicity of nickel salts which narrows its range of application, and introduces added costs due to post-sealing wastewater treatments and management [17][18][19][20]. Further efforts at sealing anodized aluminum at temperatures lower than that used in hydrothermal (high temperature) sealing, have led to much variety in the chemical constitution and operating temperatures of sealing baths [21]. On the basis of temperature at which the sealing step is carried out, sealing can be classified into three major categories; high temperature, mid-temperature, and room-temperature or cold sealing. In this work sealing at temperatures from 0 to 40 • C is classified as low temperature sealing, from ≥ 40 • C to 70 • C as intermediate or mid temperature sealing, and sealing at temperatures > 70 • C as high temperature sealing.

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Section: Effect Of the Nano-dimension Of The Pores And The Surface Chmentioning

confidence: 99%

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

2020

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“…The effect of pretreatment of the oxide surface on electrokinetic characteristics is an interesting object for study, because oxide surfaces are increasingly widely used as substrates in the synthesis of oxide nanostructures of other chemical compositions using the method of molecular layer-by-layer deposition from the gaseous phase. In this case, the position of the isoelectric point (IEP) of the modified surface can serve as a criterion determining completeness of substrate surface-group substitution during synthesis. , Therefore, it is especially important to establish the extent of the changes in the characteristics of the original oxide surface under the conditions corresponding to the surface chemical reactions (temperature and additional surface treatment with various agents).…”

Section: Introductionmentioning

confidence: 99%

Characterization and Adsorption Properties of Chemically Modified Sepiolite

Turhan

Turan

Doğan

et al. 2008

Ind. Eng. Chem. Res.

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Modification of sepiolite clay has been performed using triethoxy-3-(2-imidazolin-1-yl)propylsilane in the presence of toluene solution. The modified material was characterized by FTIR spectroscopy, XRD, and simultaneous DTA/TG analysis. It was found that the chemical bonding takes place between the hydroxyl groups and/or oxygen atoms within the structure of sepiolite and the silane group of the triethoxy-3-(2-imidazolin-1-yl)propylsilane by releasing the ethoxy groups to the solvent. Thermal decomposition of natural and modified sepiolites was carried out with a thermogravimetric analyzer. In TG and DTA analysis, during gradual heating in an oxidizing atmosphere, the modified sepiolite was oxidized, giving rise to significant exothermic peaks. The exothermic peak in the temperature range of 200−650 °C depended on the modifier loading and provided evidence of bond formation on the sepiolite surface. For natural sepiolite, a mass loss of 20.43% was observed up to 900 °C, whereas this value increased to 31.90% for modified sepiolite under oxygen atmosphere. Electrokinetic properties of the modified-sepiolite suspensions were also examined as a function of the initial electrolyte concentration and equilibrium pH using a Zeta Meter 3.0 instrument. To determine the adsorption capacity of modified sepiolite for metal ions, the experiments were examined as a function of pH, ionic strength, and temperature. The adsorption capacity of modified sepiolite increased with increasing pH and temperature, but ionic strength was found to have no significant effect. The experimental data were analyzed using the Langmuir and Freundlich adsorption models. Satisfactory agreement between the metal uptake capacities by the modified sepiolite was expressed in terms of the correlation coefficient (R 2). The Langmuir model represented the sorption process better than the Freundlich model, with R 2 values ranging from 0.9603 to 0.9977.

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“…Earlier [13,14,16], we established that 4-5 cycles of MLD reactions are sufficient to obtain Al-oxygen nanostructures on an Aerosil surface and Ti-oxygen nanostructures on a boehmite surface, whose electrosurface properties are similar to those of corresponding bulk oxides. The study of Ti-oxygen nanostructures of different thicknesses ( n = 1-16), which were synthesized on silica substrates under different conditions with the involvement of both silanol and methoxy functional groups, demonstrated that the isoelectric point (IEP) of a nanolayer is intermediate between the pH IEP values of silicon and titanium oxides.…”

Section: Synthesis and Electrosurface Properties Of One-and Two-compomentioning

confidence: 91%

“…The method of molecular layer-by-layer deposition (MLD) from the gas phase allow one to produce one-and multicomponent element-oxygen nanostructures of different thicknesses on solid substrates [1][2][3][4][5][6][7][8][9]. Previously, we studied the electrosurface characteristics of one-component nanostructures synthesized on oxide substrates with the involvement of hydroxy and methoxy functional groups [10][11][12][13][14][15][16]. Data on electrosurface properties of composite (multicomponent) nanostructures are unavailable in the literature.…”

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confidence: 99%

Synthesis and Electrosurface Properties of One- and Two-Component Nanostructures

et al. 2005

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The interest in the study of the formation mechanisms and the structure of electrical double layers (EDL) at oxide-electrolyte solution interfaces is predetermined by both the abundance of oxides in the nature and their use in practice. Recently, thin oxide layers (oxide nanostructures) have been increasingly applied for the production of highly active catalysts, ion-selective field-effect transistors, and other microelectronic devices. The method of molecular layer-by-layer deposition (MLD) from the gas phase allow one to produce one-and multicomponent element-oxygen nanostructures of different thicknesses on solid substrates [1-9]. Previously, we studied the electrosurface characteristics of one-component nanostructures synthesized on oxide substrates with the involvement of hydroxy and methoxy functional groups [10][11][12][13][14][15][16]. Data on electrosurface properties of composite (multicomponent) nanostructures are unavailable in the literature. Therefore, the goal of this work was the synthesis, study, and comparison of electrosurface properties of one-and two-component Al-and Ti-based nanostructures formed as films of different thicknesses on oxide substrates. In addition, colloidal characteristics of element-oxygen nanostructures of different compositions were compared with those of the substrates and corresponding bulk (hydr)oxides.One-and two-component nanostructures were synthesized with the involvement of hydroxy functional groups according to the following reactions (with the reference to a silica substrate):where E = Al or Ti.Samples were prepared in a flow of air, which was preliminarily dried over phosphorous oxide to a residual moisture content of 2 mg/m 3 . The dried air was saturated with either titanium chloride vapor or the vapor of solid aluminum chloride heated to 200°ë . After the excess of hydrogen chloride was removed with the dried air, the reaction product was treated with water vapor at 200°ë until HCl escaped from the reactor. In order to maintain a specified temperature in the reaction zone, a Nichrome wire was used, to which a necessary voltage was applied. The temperature was measured with a thermocouple.Aluminum-and titanium-oxygen nanostructures of different thicknesses, which were set by number n of the cycles of surface reactions (1) and (2), were synthesized on silicon oxide and aluminum hydroxide substrates. Hereafter, these structures are conventionally designated as n Al 2 O 3 / SiO 2 , n TiO 2 / AlOOH, and n TiO 2 /5 Al 2 O 3 / SiO 2 .Aerosil OX-50 (Degussa) (with a specific surface area S 0 = 42.5 m 2 /g, as determined by the BET method using the thermal desorption of argon with chromatographic recording) and a plane-parallel quartz capillary were used as silicon oxide substrates. The plane-parallel capillary was formed by the plates of KU quartz glass whose inner surfaces were preliminarily ground and polished (14th class). The size of asperities on SiO 2 plates did not exceed 0.1 µ m. Capillary length (5.8 cm) was determined by the geometric sizes of an initial pl...

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Electrokinetic and adsorption characteristics of (hydr)oxides and oxide nanostructures in 1:1 electrolytes

Cited by 11 publications

References 22 publications

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance

Characterization and Adsorption Properties of Chemically Modified Sepiolite

Synthesis and Electrosurface Properties of One- and Two-Component Nanostructures

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