Adsorption functional group character

In general, the electrochemical performance of carbon materials is basically determined by the electronic properties, and given its interfacial character, by the surface structure and surface chemistry (i.e. surface terminal functional groups or adsorption processes) [1,2]. Such features will affect the electrode kinetics, potential limits, background currents and the interaction with molecules in solution [2]. From the point of view of electroanalysis, the remarkable benefits of CNT-modified electrodes have been widely praised, including low detection limits, increased sensitivity, decreased overpotentials and resistance to surface fouling [5, 9, 11, 17]. 

The synthesis of phenolic-formaldehyde and melamine-formaldehyde resins in the presence of fumed silica allows obtaining porous organic materials with a differentiated porous structure and surface properties. The pore characteristics of the studied resins in dry state were determined from nitrogen adsorption isotherms. The differences in surface character of the synthesized polymers were estimated satisfactorily by XPS spectra showing the presence of various functional groups. The adsorption/desorption mechanism of water and benzene on the investigated porous polymers was different due to differentiated hydrophobicity of the bulk material. 

It was found (70) that the character of functional groups strongly affected the adsorptivity of substrates in various solvents. The effect of solvents on the relative adsorptivity of unsaturated compounds of a similar type (cyclohexene-1-hexene or 2-methyl-3-butene-2-ol-2-propene-l-ol) was less pronounced than in systems of compounds more differing in their structure (pair olefin-unsaturated alcohol). 

Activated carbons have hydrophobic smfaces with the properly that nonpolar molecules or organic compotmds with a very poor solubility in water such as benzene or toluene are preferably adsorbed. However, small amormts of oxides or functional groups present in the smface can change the hydrophobic character of the adsorbent surface. The capacity of carbonic adsorbents is evaluated by means of benzene adsorption isotherms. 

Differential enthalpies of exchange, plotted as a function of K saturation, exhibit a stepped character (Figure 1 and Table II). This can only reflect different types of adsorption sites on the clay surfaces, the group of sites with the most negative enthalpy... 

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