Using Functionalized Polyolefins as Solvents and Additives to Facilitate Separation and Solubilization

Abstract

Over the past few decades, water pollution has become a grave societal concern. Industrial wastewaters often contain high concentrations of EPA priority pollutants, including phenols and ionic dyes. While there are existing strategies that target the removal of these compounds from water, like tailored solid sorbents and various degradation techniques, development of alternative sequestration schemes that utilize liquid-liquid extractions are also important. We herein detail the use of PAO solvent systems for sequestration of trace organic contaminants from water. PAOs are nontoxic and nonvolatile solvents that may be used as alternatives for conventional alkane solvents. The Bergbreiter research group has extensively studied PAOs as solvents, and we have found that their nonvolatility generally allows for PAO solvent systems to be recyclable over numerous cycles.

An obvious limitation of PAOs is that they are alkanes, and are thus poor solvents for most solutes. Therefore, our experiments began with the development of polymer-bound sequestering agents that were phase-selectively soluble in PAO and did not partition into water. PIB-bound sequestering agents were successfully developed, including PIB oligomers with hydrogen bond donating, hydrogen bond accepting, cationic, anionic, electrophilic, and acidic end groups. Next, we explored the reactivity of unsaturated PAOs. We found that we could functionalize unsaturated PAOs with terminal hydroxyl groups via a hydroboration-isomerization-oxidation reaction. This could be converted into an iodide, and then substituted with various nucleophiles. We were however more successful in utilizing unsaturated PAOs as a substrate for Friedel-Crafts reactions with aromatic species.

We detail the use of PIB-bound sequestering agents for the removal of phenols and dyes from water. We found that PIB-bound imidazoles were highly effective at sequestering phenols from water – including BPA, halogenated phenols, alkylated phenols, and other more acidic and polar phenols. PIB-bound ammonium and imidazolium salts were also discovered to be efficient sequestering agents for the removal of anionic dyes from water. Recycling schemes for the above sequestrants are also discussed.

We also looked to improve the solubility of silica nanoparticles in alkane solvents. To achieve this, we functionalized the surface of native as-received silica nanoparticles. The most successful functionalization scheme involved the silylation of as-received silica nanoparticles with (3-aminopropyl)-triethoxysilane. The pendant amine functional groups were then reacted with electrophilic or acidic PIB-end groups to graft PIB onto the silica nanoparticles. Stable dispersions of silica nanoparticles in alkane solvents like heptane and PAOs were thereby obtained.