Title:
Precise Ion Separation by Engineered Polymer Composites for Phosphorous Recovery
Precise Ion Separation by Engineered Polymer Composites for Phosphorous Recovery
Author(s)
Dou, Zeou
Advisor(s)
Xie, Xing
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Abstract
Ionic hydrogels offer sufficient ion selectivity especially within a concentration range comparable to the nutrient level in wastewaters, presenting promising potential for cheap and sustainable solutions to nutrient recovery from wastewater. Therefore the overall objective of this research was to develop and test nutrients, particularly phosphorous, enrichment, recovery, and reuse technologies based on engineered ionic hydrogels, with the specific objectives to: i) investigate the phosphate rejection and enrichment performance of commercial ionic hydrogels through spontaneous water absorbing and reveal the mechanisms driving the selective ion exchange and transport in the swelling hydrogel scaffold; ii) develop advanced composite hydrogels with high ion rejection at the elevated concentration for enhanced enrichment capability; iii) develop green composite hydrogels to recovery and reuse nutrients through adsorption and controlled release.
This research demonstrated phosphate enrichment by negatively charged ionic hydrogels as a self-driven dewatering agent under different conditions. The effects of the pH, ionic strength of the nutrient stream, and the swelling ratio of hydrogels on the rejection of phosphate were investigated. The interactions of anionic hydrogel chains with phosphate and heavy metal ions were elucidated through molecular dynamic simulations.
To further enhance the selectivity of hydrogels, we developed a core-shell polymer composite (CSPC) for effective ion rejection at high concentrations. These flexible and easy-to-use CSPCs exhibit high-capacity and selective water absorption, which presents unique possibilities for recovering valuable resources from waste streams. Extensive characterizations have been done on the nanofilm shell.
Chitosan nanocomposite hydrogel was developed in this research as a controlled release nutrient excipient formula to increase nutrient use efficiency. By introducing elastic and flexible physical crosslinking induced by 2-dimensional (2D) montmorillonite (MMT) nanoflakes into the chitosan hydrogel, highly swellable and degradable chitosan-MMT nanocomposites were fabricated. The chitosan-MMT nanocomposite hydrogel achieved a well-controlled overall fertilizer release in soil. In the meantime, the nanocomposites improved the water retention of the soil, thanks to its excellent water absorbency. Based on chitosan-MMT controlled release formulation, ferric (Fe) salt was added for enhanced phosphate adsorption capability of the composite as a phosphate adsorbent and controlled releaser to bridge recovery from wastewater and reuse in the soil as a fertilizer. Sorption kinetics and isotherm were quantified in batch experiments. Versatile sorption pathways enabled stable capacity across a range of pH. With additional water retaining capability, the P-laden hydrogels can be reused in soil amendment as a controlled release P fertilizer.
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Date Issued
2022-07-29
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Text
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Dissertation