Surface groups chemical indicator adsorption

Chemical methods based on the study of extractant distribution (TBP) on TVEX-TBP resins were used to demonstrate that TBP is adsorbed by the TVEX porous matrix by physical adsorption. Extractant wash-out from the TVEX matrix is an important characteristic for metal extraction applications of solid adsorbents as TVEX since it may influence the physical-chemical properties of the extraction process. Infrared (IR) spectroscopy analysis of TVEX-TPB resins show the absence of shift for stretching frequency of the P = O group in comparison to the stretching frequency assignment for liquid TBP as an indication that TBP is hold by matrix surface due to physical adsorption as was confirmed from the by enthalpy values of TBP distribution from the TVEX matrix of 45.0 0.5 kJ/mol [10]. 

When a more acidic oxide is needed, amorphous silica-alumina as weU as meso-porous molecular sieves (MCM-41) are the most common choices. According to quantum chemical calculations, the Bronsted acid sites of binary sihca-alumina are bridged hydroxyl groups (=Si-OH-Al) and water molecules coordinated on a trigonal aluminum atom [63]. Si MAS NMR, TPD-NH3 and pyridine adsorption studies indicate that the surface chemistry of MCM-41 strongly resembles that of an amorphous sihca-alumina however, MCM-41 has a very regular structure [64, 65],... 

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