Skip to main content
ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Stored Product Insect and Engineering Research » Research » Publications at this Location » Publication #427659
Title: Sorption Kinetics and Equilibrium Isotherms of Phosphine Gas into Wheat Kernels

Author
item BUENAVISTA, RANIA MARIE - Kansas State University
item CASADA, MARK - Retired ARS Employee
item PHILLIPS, THOMAS - Kansas State University
item SILIVERU, KALIRAMESH - Kansas State University

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2024
Publication Date: 1/3/2024
Citation: Buenavista, R., Casada, M.E., Phillips, T.W., Siliveru, K. 2024. Sorption Kinetics and Equilibrium Isotherms of Phosphine Gas into Wheat Kernels. Journal of the ASABE. 67(2):363-372. https://doi.org/10.13031/ja.15770.
DOI: https://doi.org/10.13031/ja.15770

Interpretive Summary: Due to increasing resistance among stored-product insect pest populations against phosphine gas, it is critical to improve fumigation practices to effectively kill insects and prolong its use as a fumigant. Among factors that affect phosphine fumigation efficacy, understanding how the gas is absorbed by wheat can help improve the accuracy of modelling studies of phosphine behavior in wheat storage systems. Using a range of phosphine concentrations, from 400 to 2400 parts per million (ppm), mathematical models were generated that accurately predict the absorption of phosphine gas by wheat at different concentrations. These models also allowed researchers to model how much phosphine remained in the air around the wheat, which is important to predicting and improving the efficacy of phosphine fumigations. Overall, these results provide important tools that can be used to predict how much gas needs to be added to maintain an effective concentration of phosphine in the air around wheat, which is especially important for treating resistant insect populations that require higher doses of phosphine.

Technical Abstract: Phosphine (PH3) is the most used fumigant in the U.S. due to its low price, ease of use, and wide accessibility. With the growing concerns of phosphine-resistant insect pests, the sustainability of PH3 as an effective fumigant has been put at risk. Sorption equilibrium data is critical for improving the accuracy of modeling studies for phosphine-wheat fumigation systems and would clarify the PH3 uptake and sorption capacity of wheat. The objectives of this study were to determine the effect of initial concentration (from 400 to 2400 ppm) on the equilibrium concentration for PH3 in wheat kernels and on cumulative and daily PH3 sorption through time. Kinetic data showed the sorption process was time-dependent and occurred in two phases: an initial faster adsorption phase, followed by a phase with a slower sorption rate as the grain and PH3 reached equilibrium. Pseudo-first and pseudo-second order models were fit to PH3 concentrations versus time experimental data. The pseudo-first order model provided better equilibrium estimates and was used for the sorption isotherm analysis. Langmuir, Freundlich, and Redlich-Peterson sorption isotherm models were fit to the plot of equilibrium headspace gas concentration versus sorbed PH3 quantity. All three models had low standard errors of prediction (0.46-0.47). These PH3 sorption kinetics and values of total sorbed quantity at equilibrium are valuable for modeling the rate and maximum quantity of PH3 uptake in wheat.