Kenneth L. Kreuz

Structure-performance relationships of composite membranes: Porous support densification

Abstract Changes in the structure and chemical composition of a composite membrane surface were correlated with changes in the procedure used to prepare the membrane and with resultant changes in performance. Membranes were formed by the interfacial polymerization of a water-soluble multifunctional amine with an organic-soluble crosslinking agent on top of a porous polysulfone support. Scanning and transmission electron microscopy results indicate that with some reactions a dense layer (0.30 μm thick or less) was formed on top of a nodular substructure, and that the dense layer penetrates at least 0.1 μm into the porous support. In some other reactions little or no dense layer was formed on top of the porous support; for these membranes the nodules comprising the surface of the porous support compacted during the heat-curing process. fp]The membranes were used to remove water from a dilute aqueous solution of isopropyl alcohol by reverse osmosis. Performance results indicate that the lack of a generated dense layer decreases the permeate flux through the membrane. It is believed that the dense layer may act as a spacer to prevent densification of the support during heat curing; alternatively, it may favor water retention, which would prevent surface pore densification during the heat curing step.

Characterization of calcium alkylaryl sulfonates containing encapsulated solids

Abstract Several calcium alkylaryl sulfonates containing varying amounts of “encapsulated” inorganic solids were characterized by quasi-elastic light scattering, transient electric birefringence, intrinsic viscosity, and CP/MAS NMR spectroscopy. Aggregate radii of these inverse micellar structures were found to be in the range 50 to 250 A. A simple packing model (amphiphiles surrounding a core of solids) related the experimental data to aggregate structure. Deviation from the model behavior is attributed to the non-uniformity of the aggregate packing.

Rigidity of alkylaryl sulfonate micelles monitored by intrinsic fluorescence probes

Abstract The aggregate behavior of inverted micelles of calcium alkylaryl sulfonates was studied by using the aromatic moieties of these surfactants as intrinsic fluorescent probes. It appears that this approach is applicable to mixtures of aromatic sulfonate types. Internal rotational relaxation times of the intrinsic probes were estimated in the presence of alcohols in heptane and were related to the structural rigidity of micelles formed from various sulfonate preparations. Lower alcohols show marked effects in reducing the apparent rigidity. Methanol, ethanol, and propanol show small but definite differences in their effectiveness in loosening these sulfonate micellar aggregates. The rigidity of micellar aggregates appears to depend on the amount of inorganic basic calcium species in the core.

Selective Solubilization of Polynuclear Aromatics (PNA's) in Aqueous Media

Abstract The use of 2,4,7-trinitrofluoren-9-one (TNF) or a TNF derivative, 9-dicyanomethylene-2,4,7-trinitrofluorene (DTF), as an agent for complexing various aromatics has been well documented (1–4).

Following Inverted Micelle Behavior by Intrinsic Fluorescence Probes

The aromatic moiety of calcium alkarylsulfonates was used as an intrinsic fluorescence probe to follow the behavior of inverted micelles formed by this general type of materials in hydrocarbon media. The rotational relaxation times of the intrinsic probe in different systems were determined from anisotropy decays obtained with a single photon counting system using a UV excitation source at 295 nm, generated by a Spectra-Physics Model 375 synchronously-pumped, cavity-dumped dye laser system coupled with an INRAD frequency doubler. They provide information on the rigidity of sulfonate molecules adsorbed on the surface of basic inorganic materials that are components of the polar core of the inverted micelles.