Responsively Soluble Polymers for Purification of Organic and Aqueous Solutions
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abstract
Whether it is industry, agriculture, or just ordinary activities, modern societies in the 21st century produce unwanted waste. In some cases, this waste is concentrated and can be easily dealt with. In still other cases, such waste can be minimized. That was the goal of the prior highly successful collaborations between the Bazzi and Bergbreiter groups that used soluble polymers to minimize chemical waste in homogeneous catalysis. However, waste most often cannot be completely eliminated. Even if it is minimized, unwanted by-products of an industrial or agricultural endeavor or from a modern city often end up in organic or aqueous waste streams in a highly diluted form. Such trace contaminants are often accompanied by other more benign species or, in the case of water, by naturally occurring metal salts or naturally occurring organic compounds. This proposed work will explore new methods that can target and sequester such undesirable trace impurities using the PIsâ expertise in synthetic and polymer chemistry to design new types of sequestering agents. Specifically, this proposed work will produce functionalized polymers that by design target specific metals or specific organic trace species in conventional organic waste streams or in aqueous media. These polymers will be designed and prepared based on past work such that they have phase selective solubility that is triggered by exogenous stimuli like temperature. It is proposed that these new â smartâ materials can be used in new sorts of separation processes that will allow these trace impurities to be sequestered and concentrated. Once sequestered by a polymer, the impurities can be separated as concentrated solutions or solids. By using suitably designed polymeric sequestrants, methods to regenerate the sequestering agents so that they will be reusable can be developed, decreasing the cost and increasing the potential of responsively soluble polymers as tools in addressing real environmental problems. This research will examine several types of trace contamination in organic solutions or water. First, the expertise derived from past collaborative work will be used to prepare soluble end-functionalized polyolefins that can sequester and separate trace metals from organic solutions. There are a variety of procedures for metal sequestration using ion exchange resins, nanoparticles, membrane filtration, bioremediation, and electrochemical treatments, a level of activity that points to the importance and persistence of this problem. Transition metals trace impurities will be specifically targeted since similar trace heavy metals are produced in industrial operations like oil refining. Based on prior experience with recyclable polymer bound catalysts, polymers can be designed with phase selective solubility that changes in response to stimuli like temperature. The resulting changes in solubility will facilitate recovery of the polymer sequestered trace metals in a separable polymeric phase and test the hypothesis that such polyolefins will effectively and efficiently separate and concentrate metal contaminants. Once concentrated, it will be possible to chemically remove the sequestered metals from the polymer sequestrants, regenerating the polymers for further use. Similar procedures using responsively soluble polymers that phase separate from aqueous solutions will be developed to remove trace metals from aqueous solutions. Second, pendent functionalized water soluble polymers that act as phase separable sequestrants for trace organic impurities will be prepared.........
