Surface chemical property

The carbon surface contains a given number of heteroatoms (O, N, H) in the form of functional groups, similar to the way that heteroatoms appear in organic compounds. The presence of these groups can affect the preparation of carbon-supported catalysts, as they confer the carbon surface acid-base and hydrophilic character. 

The first attempt to clarify the influence of surface functional groups on the catalytic behavior of carbon-supported catalysts was made by Derbyshire et al. 

However, it has to be taken into account that some oxygen groups may not be stable under the heat-treatment conditions (i.e., reduction) to which the catalysts are subjected during the preparation stage to obtain the active phase. If they are acting as anchoring centers for the active phase or for the precursor, their decomposition could lead to sintering of the metal species and a loss of dispersion [20]. 

Although less important than oxygen (at least they have been studied to a lesser extent), nitrogen surface groups also play their role. They can be introduced on 

Despite the fact that the presence of heteroatoms on the carbon surface can induce some types of active phase-support interaction, as discussed above, it is clear that this takes place to a lesser extent that in other common catalyst supports, such as oxides (silica, alumina, titania, ceria, etc.). One clear example is provided in work carried out by Milone et al. [28], in which they investigated the influence of the surface area and the nature of the support on product distribution in the hydrogenation of citronellal (3,7-dimethyl-6-octen-l-al) on Ru supported on silica and carbon. It was found that the main products obtained on the Ru/Si02 catalyst were the unsaturated cyclic alcohols (isopulegols), which were produced via the isomerization of cinonellal on the Si02 surface. However, the main reaction products on Ru/C were the open-chain hydrogenated products (i.e., citronellol, 

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Traditional adsorbents such as sihca [7631 -86-9] Si02 activated alumina [1318-23-6] AI2O2 and activated carbon [7440-44-0], C, exhibit large surface areas and micropore volumes. The surface chemical properties of these adsorbents make them potentially useful for separations by molecular class. However, the micropore size distribution is fairly broad for these materials (45). This characteristic makes them unsuitable for use in separations in which steric hindrance can potentially be exploited (see Aluminum compounds, aluminum oxide (ALUMINA) Silicon compounds, synthetic inorganic silicates). 

J) The extreme fineness of iadividual clay particles, which may be of colloidal size ia at least one dimension. Clay minerals are usually platy ia shape, and less often lathlike and tubular or scroU shaped (13). Because of this fineness clays exhibit the surface chemical properties of coUoids (qv) (14). Some clays possess relatively open crystal lattices and show internal surface colloidal effects. Other minerals and rock particles, which are not hydrous aluminosihcates but which also show colloidal dimensions and characteristics, may occur intimately intermixed with the clay minerals and play an essential role. 

Mixed liberated particles can be separated from each other by flotation if there are sufficient differences in their wettability. The flotation process operates by preparing a water suspension of a mixture of relatively fine-sized particles (smaller than 150 micrometers) and by contacting the suspension with a swarm of air bubbles of air in a suitably designed process vessel. Particles that are readily wetted by water (hydrcmhiric) tend to remain in suspension, and those particles not wetted by water (hydrophobic) tend to be attached to air bubbles, levitate (float) to the top of the process vessel, and collect in a froth layer. Thus, differences in the surface chemical properties of the solids are the basis for separation by flotation. 

Effectiveness of selective adsorption of phenanthrene in Triton X-100 solution depends on surface area, pore size distribution, and surface chemical properties of adsorbents. Since the micellar structure is not rigid, the monomer enters the pores and is adsorbed on the internal surfaces. The size of a monomer of Triton X-100 (27 A) is larger than phenanthrene (11.8 A) [4]. Therefore, only phenanthrene enters micropores with width between 11.8 A and 27 A. Table 1 shows that the area only for phenanthrene adsorption is the highest for 20 40 mesh. From XPS results, the carbon content on the surfaces was increased with decreasing particle size. Thus, 20 40 mesh activated carbon is more beneficial for selective adsorption of phenanthrene compared to Triton X-100. 

In addition, the removal of organic matter and Fe oxides from soils and sediments is common practice as a pretreatment for soils prior to physical, chemical and biological analyses. The effects of the removal of these components on physicochemical and surface chemical properties of soils will be discussed as well. 

In summary, the removal of organic matter and Fe oxides significantly changes the physicochemical and surface chemical properties of soils. Thus, this pretreatment affects the overall reactivity of heavy metals in soils. The removal of organic matter and Fe oxides may either increase or decrease heavy metal adsorption. The mechanisms responsible for the changes in metal adsorption in soils with the removal of organic matter and Fe oxides include increases in pH, surface area, CEC and electrostatic attraction, decreases in the ZPC, shifts of positive zeta potentials toward... 

Garrett WD, Timmons CO, Jarvis NL, Kagarise RE (1963) Constitution and surface chemical properties of sea slicks, part 1, Bay of Panama. Report no. 5925. US Naval Research Laboratory, Washington, DC... 

Hohl, H., L. Sigg, and W. Stumm (1980), "Characterization of Surface Chemical Properties of Oxides in Natural Waters The Role of Specific Adsorption Determining the Specific Charge," in M. C. Kavanaugh and J. O. Leckie, Eds., Particulates in Water, Advances in Chemistry Series, ACS 189, 1-31. 

Simple Models. The surface chemical properties of clay minerals may often be interpreted in terms of the surface chemistry of the structural components, that is, sheets of tetrahedral silica, octahedral aluminum oxide (gibbsite) or magnesium hydroxide (brucite). In the discrete site model, the cation exchange framework, held together by lattice or interlayer attraction forces, exposes fixed charges as anionic sites. 

Electro Capillarity and the dropping Mercury Electrode. The term electro capillarity derives from the early application of measurements of interfacial tension at the Hg-electrolyte interface. The interfacial tension, y, can be measured readily with a dropping mercury electrode. E.g., the life time of a drop, tmax. is directly proportional to the interfacial tension y. Thus, y is measured as a function of y in presence and absence of a solute that is adsorbed at the Hg-water interface this kind of data is amenable to thermodynamic interpretation of the surface chemical properties of the electrode-water interface. 

Shinoda, K., Yamanaka, T., andKinoshita, K. Surface chemical properties in aqueous solutions of non-ionic surfactants octyl glycol ether, a-octyl glyceryl ether and octyl glycoside. J. Phys. Chem., 63(5) 648-650,1959. 

The solid phase of the subsurface is a porous medium composed of a mixture of inorganic and organic natural materials in various stages of development. The surface area and the surface (chemical) properties of the solid phase are major factors that control the behavior of chemicals. 

Classic solid phase substrates used in biotesting, such as microtiter plates, membrane filters or microscope slides, have been the first supports used for NA immobilization in array fabrication [27]. Desired attributes of any DNA array substrate include (i) chemical homogeneity (ii) thermal and chemical stability (iii) ability to control surface chemical properties such as polarity or hydrophobicity (iv) ability to be activated with a wide range of chemical functionalities (v) reproducibihty of the surface modification processes involved (vi) inert with respect to enzymatic activity especially ones involved in DNA manipulation and (vii) ultra-low intrinsic fluorescence. 

Metal ion modified polyimide films have been prepared to obtain materials having mechanical, electrical, optical, adhesive, and surface chemical properties different from nonmodified polyimide films. For example, the tensile modulus of metal ion modified polyimide films was increased (both at room temperature and 200 0 whereas elongation was reduced compared with the nonmodif ied polyimide (i). Although certain polyimides are )cnown to be excellent adhesives 2) lap shear strength (between titanium adherends) at elevated temperature (275 0 was increased by incorporation of tris(acetylacetonato)aluminum(III) (2). Highly conductive, reflective polyimide films containing a palladium metal surface were prepared and characterized ( ). The thermal stability of these films was reduced about 200 C, but they were useful as novel metal-filled electrodes ( ). 

Jambor, J.L. Dutrizac, J.E. (1998) Occurrence and constitution of natural and synthetic fer-rihydrite, a widespread iron oxyhydroxide. Chem. Rev. 98 2549-2585 James, R.O. ElealyT.W. (1972) Adsorption of hydrolyzable metal ions at the oxide-water interface. Ill A thermodynamic model of adsorption. J. Colloid Interface Sci. 40 65-81 James, R.O. Parks, G.A. (1982) Characterization of aqueous colloids by their electrical double layer and intrinsic surface chemical properties. Surface Colloid Sci. 12 119-126... 

Zhang, G.-Y, Zhang, X.-N. Yu,T.-R. (1991) Adsorption of sulfate and fluoride in relation to some surface chemical properties of oxisols. Pedosphere 1 17-28... 

The importance of aluminas is due to their availability in large quantities and in high purity presenting high thermal stability and surface areas (in the 199-259 mVg range and even more). Their pore volumes can be controlled during fabrication and bimodal pore size distributions can be achieved. However, besides these textural aspects, the surface chemical properties of aluminas play a major role, since these are involved in the formation and stabilization of catalytically active components supported on their surfaces. Despite the widespread interest in catalytic aluminas there is still only a limited understanding about the real nature of the alumina surface [44,89,99]. 

Spreadsheets for titration of river sediment with HN03 or NaOH. [Data from M. Davranche. s. Lacour. F. Borders, and J.-C. Bollinger, Determination of the Surface Chemical Properties of Natural Solids" J. Chem. Ed. 2003,80,76.]... 

The surface chemical properties of these adsorbents make them potentially useful for separations by molecular class. However-, the microporc size distribution is fairly broad for these materials. This characteristic makes them unsuitable for use in separations in which steric hindrance can potentially be exploited. 

Despite their overawing complexity, clay minerals are to receive particular emphasis in this book as model systems. They are of high abundance and of key importance in sedimentary and soil systems (63-64), as ceramic materials (65) and as industrial fillers (66) they exhibit essentially all of the generic spectroscopic and surface chemical properties of reactive minerals in general and there are good reasons to believe that many of the spectroscopic and chemical attributes of minerals as a whole may be exaggerated in clays. 

N-doping has already been reported for ACF and activated carbon [150,152], It is well known that the uptake pressure and the shape of the H20 isotherm are functions of both micropore size and surface chemical properties. In this case, however, the influence of micropore size can almost be excluded and the observed difference in the uptake pressure be attributed solely to carbon surface chemistry. It is therefore reasonable to conclude that the inner pore surface of the N-doped carbon is more hydrophilic than that of the undoped one. Since the O content of the former carbon is lower than that of the latter, the above results indicate that in this case the presence of N groups is more effective for H20 adsorption. 

A study that illustrates some of these issues most dramatically is that of Koresh and Soffer [85], already mentioned above (see Section 5.3.2). It is instructive to analyze what the literature says about this key aspect of the electrochemical behavior of carbons possessing different surface chemical properties. So far, this paper has been cited close to 50 times in SCI publications, less than its messages deserve. For example, even though their paper deals specifically with the influence of surface oxides on the electrochemical (impedance) behavior of AC fabrics, Nian and Teng [146] cite... 

Baun, W. L., et al. Pitting Corrosion and Surface Chemical Properties of a Thin Oxide Layer on Anodized Aluminum, in Air Force Materials Laboratory Technical Report 78-128, September... 

Wang, J., V. P. Evangelou, and M. T. Nielsen. 1992. Surface chemical properties of root cell walls from two tobacco genotypes with different tolerance to Mnll toxicity. Plant Phys. 100 496-501. 

Water chemistry and mineral solubility soil minerals and surface chemical properties and their behavior and electrochemistry and kinetics... 

The book consists of two major sections—Principles and Application. Each section covers several major subject areas. The Principles section is divided into the following parts I. Water Chemistry and Mineral Solubility II. Soil Minerals and Surface Chemical Properties and III. Electrochemistry and Kinetics. The Application section also covers several subject areas IV. Soil Dynamics and Agricultural-Organic Chemicals V. Colloids and Transport Processes in Soils VI. Land-Disturbance Pollution and Its Control VII. Soil and Water Quality and Treatment Technologies. Each subject area contains one to three chapters. 

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