Development of bio-based systems as pollutants removal for water remediation

Abstract

In the search of bio-based alternatives to develop systems that can improve water quality, cellulose nanofibril (CNF) were studied as scaffolds for the development of adsorbents for emerging and unregulated pollutants; in particular, the cyanotoxin microcystin-LR. To ensure the capacity of polysaccharides to capture the toxin, modification of the fibrils with β-cyclodextrin (CD) were evaluated in this dissertation. β-cyclodextrin was immobilized directly onto the cellulose nanofibril by epoxy-based reaction and by an indirect adsorption after its immobilization to chitosan following a TEMPO oxidation and EDC/NHS chemistry. A fundamental study on the impact on the adsorption capacity after changing the spatial configuration, the different immobilization approaches, and ratios of chitosan/cyclodextrin were studied using Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). To develop applicable systems with the above-mentioned materials, different three-dimensional structures were generated, characterized, and applied to remove microcystin-LR from controlled samples; the adsorption kinetic of these systems was monitored with High-Pressure Liquid Chromatography (HPLC). Specific, aerogels were generated by solvent exchange (ethanol and tert-butanol) and freeze-drying with the best performing configuration of the epoxy-based immobilized CD on CNF. Meanwhile, the chitosan mediated adsorption was used as coating for hydrogels produced by solubilizing CNF on cold sodium hydroxide/urea and regenerating on acid, and on aerogels from delignified wood (nanowood) air-dried after solvent exchange (ethanol, isopropanol, and octane). Finally, the coated nanowood was tested on lake water from Ogleetree Lake spiked with a known concentration of microcystin-LR.