Fe(III)-carboxylate photochemistry offers a greener approach to develop advanced polysaccharide-based materials. Hydrogel beads were prepared using a carboxylate containing polysaccharide alginate with the coordination to Fe(III) ions. These hydrogels absorbed phosphates from aqueous solutions due to Fe(III)-phosphate binding. Depending on the polysaccharide composition and pH, these beads showed an average phosphate uptake of 1 mgg<sup>-1</sup> from 800 ppm solutions for the pH range of 4.5 – 9.0. This accounted for ~80% phosphate uptake from the total phosphates in solution. Uptake from dilute solutions with 100 ppm phosphate was ~99%. Studies with mixed ion solutions (phosphate, nitrate and ammonium) and dairy manure showed that the phosphate binding was not affected by the presence of other nutrients or dissolved solids. In addition to phosphates, these gels showed ammonium and nitrate ion uptake of ~30% from 100 ppm solutions.<br/>Upon exposure to light, these Fe(III)-hydrogels showed the expected photochemistry. This photoreaction caused a degradation of the gels. We showed that this can be used to control the release of phosphate ions to plants using light as the release trigger. Plant trials were conducted under greenhouse conditions with tomato plants. Our hydrogel fertilizer system showed controlled release of nutrients compared to a fertilizer solution as well as enhanced growth and tomato fruit formation compared to the controls.<br/>In addition to using the Fe(III)-carboxylate photoreaction for controlled release of nutrients, we showed polymerization of acrylic monomers such as methyl methacrylate and acrylamide can be initiated from this photoreaction. This was used for surface functionalization of polysaccharide hydrogels and materials. Therefore we have shown the use of natural polysaccharides to create hydrogels that can be used for waste water purification, controlled nutrient release for plants as well as a greener approach for photopolymerization of acrylic monomers such as methyl methacrylate.

Fe(III)-carboxylate photochemistry in polysaccharide hydrogels for a green chemistry approach to nutrient recycling and surface modification of materials

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.