Photochemistry of Iron(III) with Carboxylate-containing Polysaccharides for Sustainable Materials
Date of Award
Doctor of Philosophy (Ph.D.)
Alexis Ostrowski (Advisor)
Pavel Anzenbacher (Committee Member)
George Bullerjahn (Committee Member)
Lewis Fulcher (Other)
We present the study of Fe(III)-carboxylate photochemistry of natural polyuronates in aqueous solutions and in soft hydrogel materials with near UV and violet light. Described in this dissertation are the use of Fe(III)-carboxylate photochemistry for sustainable material applications such as surface modifications and controlled plant nutrient delivery.
Quantitative photochemistry of the Fe(III)-alginate system in aqueous solutions was studied using near UV light, and the effect of factors such as alginate composition and solution pH was studied. Degradation of alginate chain with the photochemical reaction was observed by the changes in the solution viscosity. The photochemical reaction seemed to proceed through a radical species and the generation of carbon dioxide anion radical (CO2.-) was identified using Electron Paramagnetic Resonance (EPR) spectroscopy.
We present all polysaccharide hydrogels prepared with agarose and carboxylate group containing pectin which showed photoresponsive behavior. Upon Fe(III) coordination and irradiation with 405 nm LED for various time intervals, these gels changed their pH, mechanical properties, porous structure and swelling properties.
Based on the radical generation phenomenon, studies on polymerization of selected acrylic monomers using this Fe(III)-carboxylate photochemical system was studied. Other than polyuronate based hydrogels, fabrics with introduced carboxylate functionality showed their ability to polymerize acrylic monomers on their surface, and change their physical and mechanical properties with the use of light.
Hydrogel beads prepared with alginate or alginate and other polysaccharide mixtures with Fe(III) showed their ability to absorb phosphate ions from model waste solutions. The solution phosphate concentration dependent phosphate uptake showed a maximum phosphate uptake around 1.5 mgg-1. Phosphate uptake above 1 mgg-1 was seen for a wide pH range of 4.8 - 11.5 due to the strong binding between Fe(III) within the hydrogels and phosphates.
Occurrence of the Fe(III)-carboxylate photochemistry in these hydrogel beads upon exposure to light degraded the hydrogels and released the trapped phosphates into the environment. The release was dependent on the light intensity and the release under dark conditions was negligible. Plant trials conducted in a greenhouse showed these gel beads degrade within couple of weeks and release the nutrients to soil environment slowly compared to conventional chemical fertilizer. Therefore Fe(III)-carboxylate photochemistry can be used for greener material applications as well as wastewater treatment.
Karunarathna, Mudugamuwe Hewawasam Jayan Savinda, "Photochemistry of Iron(III) with Carboxylate-containing Polysaccharides for Sustainable Materials" (2020). Photochemical Sciences Ph.D. Dissertations. 115.