Micellar-Enhanced Ultrafiltration Using a Plant-Derived Surfactant for Dye Separation in Wastewater Treatment

Surfactants Accelerate Isotope Exchange-Based 18F-Fluorination in Water

Radiochemical yields (RCYs) of isotope exchange-based ¹⁸F-fluorination of non-carbon-centered substrates in water are rationally enhanced by adding surfactants, which increases both the rate constant k and local reactant concentrations. Among 12 surfactants, the cationic surfactant cetrimonium bromide (CTAB) and two nonionic surfactants (Tween 20 and Tween 80) were selected for their superior catalytic effects, namely, electrostatic effects or solubilization effects. For a model substrate, bis(4-methoxyphenyl)phosphinic fluoride, the ¹⁸F-fluorination rate constant (k) increased up to 7-fold, while its saturation concentration rose up to 15-fold due to micelle formation, encapsulating 70-94% of the substrate. With 30.0 mmol/L CTAB, the required ¹⁸F-labeling temperature of a typical organofluorosilicon prosthesis ([¹⁸F]SiFA) decreased from 95 °C to room temperature, achieving an RCY of 22%. For an E[c(RGDyK)]₂-derived peptide tracer with an organofluorophosphine prosthesis, the RCY in water at 90 °C achieved 25%, correspondingly increasing the molar activity (A_m). After high-performance liquid chromatography (HPLC) or solid-phase purification, the residual selected surfactant concentrations in the tracer injections were well below the FDA DII (Inactive Ingredient Database) limits or the LD50 in mice.

Influence of Solute Size on Membrane Fouling during Polysaccharide Enrichment Using Dense Polymeric UF Membrane: Measurements and Mechanisms

Fouling mechanisms associated with membrane-based polysaccharide enrichment were determined using a dense ultrafiltration (UF) membrane. Dextran with different molecular weights (MWs) was used as a surrogate for polysaccharides. The influence of dextran MW on fouling mechanisms was quantified using the Hermia model. Flux data obtained with different dextran MWs and filtration cycles were plotted to quantify the more appropriate fouling mechanisms among complete pore blocking, standard pore blocking, intermediate pore blocking, and cake filtration. For 100,000 Da dextran, all four mechanisms contributed to the initial fouling. As the filtration progressed, the dominant fouling mechanism appeared to be cake filtration with a regression coefficient (R²) of approximately 0.9519. For 10,000 Da, the R² value for cake filtration was about 0.8767 in the initial filtration. Then, the R² value gradually decreased as the filtration progressed. For 6000 Da, the R² values of the four mechanisms were very low in the initial filtration. However, as the filtration progressed, the R² value for cake filtration reached 0.9057. These results clearly show that the fouling mechanism of dense UF membranes during polysaccharide enrichment can be quantified. In addition, it was confirmed that the dominant fouling mechanism can change with the size of the polysaccharide and the duration of filtration.