Controlled release and mitigation of the volatility of 2,4-dichlorophenoxyacetic acid herbicide using biopolymer microparticles as carriers

Abstract

Herbicides play a crucial role in sustaining crop productivity. However, growing concerns about their impact on both the environment and human health necessitate strategies to improve their effectiveness and suitability. Of particular concern are volatile herbicides like 2,4-dichlorophenoxyacetic acid (2,4-D), which not only pose risks to the environment but also impact neighboring crops. To deal with this, we developed a microparticle system comprising chitosan ionotropically crosslinked with tripolyphosphate anions to encapsulate 2,4-D. Optimization of the biopolymer/herbicide ratio yielded remarkable encapsulation efficiencies (> 95 %) and loading capacities (> 32 %). Characterization analyses revealed interactions between 2,4-D and chitosan, resulting in microparticles (1.7 ± 0.4 µm) with distinct thermal, morphological, and surface charge properties compared to pristine microparticles. In vitro experiments demonstrated pH-dependent release kinetics, with optimal release observed under neutral conditions. A 94 % release was achieved at pH 7 after 37 days, driven by sustainable diffusional processes. This ability to control the release of 2,4-D was pivotal in controlling its volatilization. As demonstrated, the volatilization rate for 2,4-D encapsulated within the chitosan microparticles was found to be 64 times lower compared to the commercial herbicide. This encapsulation approach presents an innovative strategy for regulating the presence of 2,4-D in agricultural settings, effectively tackling its significant volatility concerns.