<b>Formulation and Diffusion Analysis of Nanocellulose-Based Prills for Controlled Release of Pesticide</b>

<p dir="ltr">This work examines the formulation and diffusion behavior of a nanocellulose-based dry pellet, or prill, for the controlled release of pesticide via a scalable low-cost process. Prills were formed from cellulose nanofibrils (CNF), sodium carboxymethylcellulose (CMC), water, a crosslinking cationic multivalent metal salt, and a commercially available liquid form of the pesticide imidacloprid, Quali-Pro Imidacloprid 2F T&O. Aqueous solutions of aluminum chloride hexahydrate, AlCl₃*6H₂O, and calcium nitrate tetrahydrate, Ca(NO₃)₂*4H₂O, were used as crosslinkers, with prills made by adding the crosslinker dropwise to the extrudate, as well as, for the aluminum, rolling the extrudate through a crosslinker bath. After formulation and pelletization, the diffusion behavior of the prills was characterized via testing in stirred water solutions and measurements with UV-Visual spectroscopy, with supplemental information from swelling testing and thermogravimetric analysis. Regression analysis was performed using MATLAB on a number of models to characterize the behavior, such as the Ritger-Peppas model, the Peppas-Sahlin model, and a first-order model. Additionally, a Fickian formula for cylindrical diffusion into a solution of constant concentration was found to fit well when the diffusion coefficient, D, was substituted as D = D₀t^c, where c was found to range from 0.1 – 0.3. Ultimately, it was found that prills loaded with imidacloprid could be reliably produced with reasonably consistent diffusion behavior, that this diffusion behavior was mostly Fickian in nature, that calcium and aluminum prills had similar diffusion on relevant timescales, and that moderation in the use of the crosslinker solution could lead both to lower imidacloprid loss during crosslinking and a slower release. However, as imidacloprid release occurs relatively quickly for agricultural applications, on the order of minutes (~10 minutes to 50% release, 45 minutes to near-equilibrium), the system will require improvement for commercial agricultural viability.</p>