Hydrophobically modified adsorption isotherm

If a mineral surface becomes hydrophobic as a result of adsorption of a hydrolytic product of the collector, i.e. a nondissociated component, the modified Langmuir isotherm gets the form... 

The unmodified and modified pillared clays, synthesized using amines or with mixed pillars, have an intermediate hydrophylic-hydrophobic character and thus have some potential for the removal of chlorinated hydrocarbons. In Figure 12, the adsorption isotherms of some hydrocarbons on different pillared clays are compared to the adsorption isotherm on Na-montmorillonite (79). In all cases, the adsorption capacity of the mixed Fe-/Zr-PILC is a factor 4 higher than that of the pure Fe-PILC. Besides the adsorption capacity, the isotherm type also changes. 

Adsorption Isotherm Experiment. Crystalline quartz (SlOj) in the form of Berkeley HIN-U-SIL 5 and MIN-U-SIL 30 were supplied by Pennsylvania Glass Sand Corp., whose metal oxide analysis yields 99.72 SiOj. This nonporous powdered solid was acid cleaned with repeated washes of concentrated HCl. Reaction with dlchloro-dimethylsllane converted the very hydrophilic surface of clean SiO to a hydrophobic methylated surface. Covalent bonds are formed with the SiOj surface through elimination of HCl. The Si-OH groups on the quartz surface and the -SiCl groups of the dichlorodlmethylsilane react to produce Si-O-Sl bonds, with the dimethyls of the silane at the newly modified Interface. Surface areas were determined on these powdered solids using the BET (Brunauer, Emmett, Teller) Nj adsorption isotherms measured on a Quantasorb Jr. (Quantachrome). The hydrophilic NIN-U-SIL 5 has a specific surface area of 5.06 m /g. Acid-cleaned HIN-U-SIL 30 has a surface area of 2.16 m /g which decreases to 1.81 m /g upon methylation. 

There continues to be extensive interest in latexes and micellar systems. The structure of acrylic latex particles has been investigated by non-radiative energy transfer by labelling the co-monomers with fluorescent acceptor-donor systems. Phase separations could also be measured in this way. Excimer fluorescence has been used to measure the critical micelle temperature in diblock copolymers of polystyrene with ethylene-propylene and the results agree well with dynamic light scattering measurements. Fluorescence anisotropy has been used to measure adsorption isotherms of labelled polymers to silica as well as segmental relaxation processes in solutions of acrylic polymers. In the latter case unusual interactions were indicated between the polymers and chlorinated hydrocarbon solvents. Fluorescence analysis of hydrophobically modified cellulose have shown the operation of slow dynamic processes while fluorescence... 

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