Hydrophobic Metals Research Articles

Inorganic synthesis of highly hydrophobic metals containing surface compounds with electron acceptor modifiers: process features

Inorganic synthesis of highly hydrophobic metals containing surface compounds with electron acceptor modifiers: process features

Harvesting water surface energy: self-jumping nanostructured hydrophobic metals

SummaryWater in motion is a significant energy source worldwide, but the surface energy of water is rarely utilized as a power source. In this study, we made metals unsinkable and able to jump out of the water by harvesting the water surface energy. This effect is attributed to the enhanced floating ability of the nanostructures on copper and stainless steel foil surfaces. Sufficiently thin hydrophobic metals can slowly float underwater through air trapping at the surface and then rapidly leap out of the water on contact with the water-air interface. The mechanism is related to the surface energy of the water, which contributes to the 15 mg metals with a power of 0.49 μW experiencing rapid changes in velocity and acceleration at the interface. The conversion of surface energy to eject nanostructured hydrophobic materials from the liquid surface may lead to new solid-liquid separation techniques.

Leaching of hydrophobic Cu and Zn from discarded marine antifouling paint residues: Evidence for transchelation of metal pyrithiones

Leaching of Cu and Zn from a composite of discarded antifouling paint residues ([Cu] = 288 mg g −1; [Zn] = 96 mg g −1) into natural sea water has been studied over a period of 75 h. Total Cu and Zn were released according to a pseudo first-order reaction, with rate constants on the order of 0.3 and 2.5 (mg L −1) −1 h −1, respectively, and final concentrations equivalent to the dissolution of about 8 and 2% of respective concentrations in the composite. Time-distributions of hydrophobic metals, determined by solid phase extraction-methanol elution, were more complex. Net release of hydrophobic Cu was greater in the absence of light than under a sequence of light–dark cycles; however, hydrophobic Zn release was not detected under the former conditions but contributed up to 50% of total aqueous Zn when light was present. These observations are interpreted in terms of the relative thermodynamic and photolytic stabilities of biocidal pyrithione complexes.

Chronic pollution of freshwater bodies: Data on accumulation of pesticides, oil products, and other toxic substances in bottom deposits

The results of studies aimed to assess the information significance of the coefficients of bottom accumulation of hydrophobic organic substances and heavy metals as indicators of pollution of freshwater bodies are presented. It is shown that the same value of the coefficient of bottom accumulation may correspond to different situations in water bodies. Methods for the interpretation of data on the state of water bodies based on the coefficient of bottom accumulation and its components are proposed to reliably determine the level and character of pollution. Chronic pollution of a number of freshwater bodies of the Russian Federation is assessed by data on the accumulation of pesticides, oil products, polycyclic aromatic hydrocarbons, and heavy metals in bottom deposits.

Hydrophilicity of metal surfaces: Silver, gold and copper electrodes

In view of the current controversies about the hydrophilic character of polycrystalline silver and gold, an attempt is made here to clarify the situation by testing physical and electrochemical data using different approaches to the concept of hydrophilicity. Analysis shows that polycrystalline silver, gold and copper are hydrophobic metals. However it is stressed that this conclusion for silver, gold and copper refers to heterogeneous crystalline surfaces, while for other sp metals the hydrophilicity refers to relatively homogeneous surfaces. Recommended values of the work function are proposed for single-crystal surfaces of silver and gold. The validity different correlations between the surface potential of water molecules at the interface and various parameters is discussed for sp metals. The metal hydrophilicity is shown to be independent of the work function value. Moreover, the work function is not simply related to the surface electronegativity.

Effect of the nature of the metal on the dielectric properties of water at the electrode solution interface

Structuring of the liquid usually occurs at the solid/solution interface as a consequence of specific interactions between the two phases [1,2]. As a result, the orientation polarizability of polar molecules is influenced with modification in the apparent dielectric properties of the liquid phase. The orienting effect of the solid surfaces modifications in the liquid to a depth depending on the nature and strength of the interactios. Metal surfaces can be divided into hydrophilic and hydrophobic [3] depending on whether or not they tend to bind water molecules strongly through their oxygen atom with increased dipole alignment perpendicular to the solid surface. Hydrophobic metals exert their orienting effect just on the first monomolecular layer of water. Beyond this layer, the diffuse region exhibits the apparent dielectric behaviour of the bulk liquid. Enhanced apparent permittivity is exhibited by the monomolecular layer of water at hydrophilic metals as compared to the hydrophobic ones. Consistently, the strong structuring of the compact layer is expected to drive similar enhancement also in the apparent permittivity of the diffuse layer. Among the sp (non-catalytic) metals it has been shown [4,5] that Au is the most hydrophobic and Ga the most hydrophilic one. The apparent failure of the Gouy-Chapman theory for the diffuse layer at Ga was first pointed out by Frumkin and Grigoryev [6]. No similar effect is exhibited by any of the other sp metals. Transition metals are on the contrary all strongly hydrophilic. Thus, failure of the Gouy-Chapman theory for these metals may also be predicted. It will be shown that the sole sufficiently reliable results are available [7] for Fe and they give evidence that this may in fact be the case. The difference between Ga and Fe lies in the reduced orientation polarizability of water in the compact layer at Fe compared to the former metal. A possible model will be discussed to explain the above results consistently with conclusions drawn earlier [4] on the basis of independent observations. The structuring of the liquid is expected to give rise to dielectric anisotropy at the interface in the compact layer [8] which can penetrate into the diffuse layer depending on the hydrophilicity of the solid surface. Attempts will be made to relate ionic adsorption on different metals to dielectric anisotropy. The apparent permitivity is also expected to depend on the sign of the charge density of the metal since the surface becomes more hydrophilic the more positive is the charge. The type of solvent-adsorbate interaction is thus expected to depend on the charge sign. This will be discussed on the basis of the asymmetric behaviour observed [9] in the adsorption of neutral molecules on Hg about the potential of zero charge. This effect is expected to increase as the hydrophilicity of the metal increases but data on this aspect are still lacking.

Ionenadsorption an Elektroden in wäßrigen und nichtwäßrigen Elektrolyten

AbstractAdsorption of ions on electrodes in aqueous and nonaqueous electrolytes. This article considers the practical implications of adsorption of electrolyte ions on electrodes and methods for quantitative determination of electrosorption of ions. Adsorbed ions influence the potential drop in the inner Helmholtz layer and thereby modify the rate of charge transfer for redox processes occurring at electrodes, and the chemical reactions ensuing upon charge transfer can be effectively directed by adsorbed ions. Corrosion and its inhibition as well as deposition of metal in electroplating can be influenced by surface‐active ionic additives which are adsorbed. Measurement of differential capacity provides information about the electrosorption of ions and neutral compounds. A knowledge of the zero point of the electrode metal permits clear predictions concerning ion adsorption. Anions are preferentially adsorbed at potentials on the anodic side of the zero point, and cations at potentials that are more negative than the zero point. Surface‐active neutral compounds and lyophobic ions are most strongly adsorbed in a narrow potential range around the zero point. Adsorption of weakly solvated ions on hydrophobic metals (e. g. Au, Hg) is more pronounced than the adsorption of strongly solvated ions on hydrophilic metals (e. g. Ga, Cd, Zn).