AI Summary & Key Takeaways
AI InsightExperimental results showed release rates of nitrates in buffer solutions ranging from 0.2160–0.5739 μM/min.
📌 3 Key Takeaways
Abstract
Nitrogen is essential to plant growth, yet the ineffective use of nitrate fertilizers causes excess nutrient runoff, increasing eutrophication. Unlike common immediate release fertilizers, this project developed a novel pH-responsive slow-release mechanism for environmentally friendly fertilizers. Specifically, the targeted release is at the pH of typical rainwater (~5.6) to increase nutrient uptake for plants during irrigation and reduce nutrient runoff. Calcium chloride was crosslinked with sodium alginate, potassium nitrate, and crystal violet (CV+) to form fertilizer beads. These were coated with chitosan and sodium tripolyphosphate, enabling for a slow release of nitrates at specific pH’s. CV+ acted as a stoichiometric proxy of nitrate concentrations, which were determined using ultraviolet-visible spectrophotometry. The release of nitrates from the beads, at various pH’s, were measured over 90 minutes with aliquots taken every 5 minutes from 4 different pH (4-7) buffer solutions. Experimental results showed release rates of nitrates in buffer solutions ranging from 0.2160–0.5739 μM/min. The highest rates were found at pH 6 followed closely by pH 5. The beads at pH 6 had the least remaining mole percent of nitrates after 90 minutes (42%). Other groups ranged from 45%-77%. Nitrate release rates aligned with the Higuchi model, suggesting diffusion-controlled release through a crosslinked polymer matrix. The release rates of coated beads were between 723%-6815% greater than uncoated beads (control) with pH 4 having the greatest difference.