"Formulation and Diffusion Analysis of Nanocellulose-Based Prills for Controlled Release of Pesticide " 

Benjamin Kipp, MSE PhD Candidate 

Advisor: Professor Jeffrey Youngblood

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ABSTRACT

The effective usage of pesticides is crucial to addressing an ever-growing global food need, with an estimated 40% of the annual loss to worldwide crop production being caused by pests. Often, however, only a small portion of the pesticide applied reaches the target organisms, so sufficient pest control requires the repeated applications of large amounts of pesticide. This in turn results in increased pesticide in the environment, higher cost of pest control, and the possible development of pest resistance. Controlling the release of pesticide helps treat this issue: by putting the pesticide in a capsule or matrix that it slowly releases from, target organisms have more time to take up the pesticide before it leaches into the environment, while the molecule itself reduces contact by non-target organisms and improves resistance to photodegradation—ultimately resulting in less pesticide being necessary.

Nanomaterials, with high surface area and high adsorption efficiency, are key candidates for this; however, commercial application of many of those examined thus far would be difficult given their high cost and complexity of synthesis. We instead focus on a more scalable and lower cost solution, using wood-based nanocellulose and readily available cationic metal salts. In this process, cellulose nanofibrils (CNFs) and sodium carboxymethylcellulose (NaCMC) are shear-mixed with Quali-Pro Imidacloprid 2F, a commercially available pesticide formulation, to form a highly concentrated (~15%) paste. This paste is then shaped by extrusion and crosslinked by a multivalent metal cation, e.g. Ca2+ or Al3+, before being dried into solid prills loaded with pesticide. This seminar discusses the development process of these prills and the characterization of them and their diffusion properties, ultimately examining prills crosslinked with calcium nitrate (Ca(NO3)2) and aluminum chloride (AlCl3). For the aluminum chloride, we additionally compare the usage of two crosslinker application processes—one where the aluminum solution is added dropwise to the cellulose extrudate, and one where the extrudate is rolled through a crosslinker bath. UV-Visual spectroscopy is used to measure prill diffusion in water over time, from which the appropriateness of different possible models of the diffusion behavior can be compared, and used to determine parameters such as the diffusion coefficient via regression analysis in MATLAB when possible. Thermogravimetric analysis (TGA) and examinations of prill physical behavior are used for key supplemental information such as prill composition and wet radius. We ultimately determine that the system shows promise, but will likely require improvements for appreciable wide-scale viability.