Muriel Steele

Functionalized nanoparticle interactions with polymeric membranes

A series of experiments was performed to measure the retention of a class of functionalized nanoparticles (NPs) on porous (microfiltration and ultrafiltration) membranes. The findings impact engineered water and wastewater treatment using membrane technology, characterization and analytical schemes for NP detection, and the use of NPs in waste treatment scenarios. The NPs studied were composed of silver, titanium dioxide, and gold; had organic coatings to yield either positive or negative surface charge; and were between 2 and 10nm in diameter. NP solutions were applied to polymeric membranes composed of different materials and pore sizes (ranging from ≈ 2 nm [3 kDa molecular weight cutoff] to 0.2 μm). Greater than 99% rejection was observed of positively charged NPs by negatively charged membranes even though pore diameters were up to 20 times the NP diameter; thus, sorption caused rejection. Negatively charged NPs were less well rejected, but behavior was dependent not only on surface functionality but on NP core material (Ag, TiO(2), or Au). NP rejection depended more upon NP properties than membrane properties; all of the negatively charged polymeric membranes behaved similarly. The NP-membrane interaction behavior fell into four categories, which are defined and described here.

Understanding dendritic polymer–hydrocarbon interactions for oil dispersion

This study examines the interactions of poly(amidoamine) dendrimers and hyperbranched poly(ethyleneimine) polymers with model linear and polyaromatic hydrocarbons. Large-scale complexations were formed for both types of dendritic polymers hosting the linear but not the polyaromatic hydrocarbon. Furthermore, both types of dendritic polymers exhibited a strong and comparable hosting/dispersion capacity for the polyaromatic hydrocarbon, while the hyperbranched polymers at concentrations below 30 μM showed a consistently higher hosting capacity than the dendrimers for the linear hydrocarbon. Such complexity in hosting capacity of the two types of dendritic polymers is attributed to the more hydrophobic interior and less steric hindrance of the hyperbranched polymers for the partitioning of the hydrocarbons.

Integrating algaculture into small wastewater treatment plants

Algaculture has the potential to be a sustainable option for nutrient removal at wastewater treatment plants. The purpose of this study was to compare the environmental impacts of three likely algaculture integration strategies to a conventional nutrient removal strategy. Process modeling was used to determine life cycle inventory data and a comparative life cycle assessment was used to determine environmental impacts. Treatment scenarios included a base case treatment plant without nutrient removal, a plant with conventional nutrient removal, and three other cases with algal unit processes placed at the head of the plant, in a side stream, and at the end of the plant, respectively. Impact categories included eutrophication, global warming, ecotoxicity, and primary energy demand. Integrating algaculture prior to activated sludge proved to be most beneficial of the scenarios considered for all impact categories; however, this scenario would also require primary sedimentation and impacts of that unit process should be considered for implementation of such a system.