Development and employment of slow-release pendimethalin formulations for the reduction of root penetration into subsurface drippers

Preparation and Characterization of Pendimethalin Microcapsules Based on Microfluidic Technology

Microencapsulation of pesticides is a promising attempt to reduce environmental pollution and prevent the active ingredients from the interference of external factors. In this paper, pendimethalin microcapsules were prepared by the interfacial polymerization of 4,4-methylenediphenyl diisocyanate (MDI) and ethylenediamine (EDA) based on microfluidic technology. Effects of the microchannel structure, reaction temperature, surfactant type, and fluid flow rates were investigated and evaluated. The results showed that pendimethalin microcapsules prepared under suitable conditions had a smooth surface, good monodispersity, a high encapsulation efficiency (96.7%), and excellent thermal stability. The size and morphology control of microcapsules were realized by adjusting the flow rates of the continuous phase and the hydrophilic monomer EDA aqueous solution. The release of pendimethalin had a sustained release characteristic that was closely related to the morphology of microcapsules. Compared with the pendimethalin emulsifiable concentrate, pendimethalin microcapsules exhibited outstanding herbicidal activity in the weed control experiments. Therefore, pendimethalin microcapsules with tunable properties were successfully obtained from the microfluidic device and showed great potential in agricultural applications.

Sorption and desorption of pendimethalin alone and mixed with adjuvant in soil and sugarcane straw

Sugarcane straw may work as a physical barrier for pre-emergent herbicides and interact with their molecules, increasing sorption process. Adjuvants may change herbicides dynamics in the environment and improve their efficiency for weed control. The objective of this work was to evaluate sorption and desorption of pendimethalin alone and in mixture with adjuvant in soil and sugarcane straw. Sorption experiments were performed using pendimethalin alone and in mixture with vegetable oil with herbicide solution concentrations ranging between 2.5 and 40 μg mL^-1 for both conditions. Sorption distribution coefficient (K_d) for soil was 18.48 mL g^-1 using pendimethalin alone. K_d value was not determined when pendimethalin was in mixture with adjuvant due to the complete retention of the herbicide in the soil regardless of the initial aqueous phase concentration. Sugarcane straw sorption experiment had K_d values corresponding to 355.52 and 27.24 mL g^-1 for pendimethalin alone and in mixture with adjuvant, respectively, indicating the addition of vegetable oil may significantly decrease pendimethalin retention in the straw and could improve weed control. Besides all desorption coefficients were higher than the respective sorption coefficients, which means that the sorption process may be considered irreversible.

Interfacial assembly of mussel-inspired polydopamine@Ag core-shell nanoparticles as highly recyclable catalyst for nitroaromatic pesticides degradation

With the abundant use of pesticides in agriculture and grassland farming, water contamination unavoidably occurs due to the leaching of pesticide residues into environment. Now, most of the research on degradation of nitroaromatic pesticides residues has focused on nano catalysis-based method, however, effective post-reaction separation and recycling of the tiny nanocatalysts is also a significant technological challenge to be addressed. Herein, we report a simple and versatile strategy for the construction of efficient and recyclable catalysts of polydopamine (PDA)@Ag/polystyrene (PS) films for degradation of pesticides based on multi-purpose PDA microspheres inspired by mussel adhesion. The PDA not only functioned as a scaffold, a reductant as well as a stabilizer for the formation and dispersions of Ag NPs in situ, but also served as an adhesive layer between the nanocatalysts and the substrate. The obtained PDA@Ag/PS films were evaluated for the first time against the catalytic degradation of pendimethalin. Most importantly, the recovery of catalysts can be easily realized by simply pulling out PS substrate from the reaction mixture and the catalytic activity of the nanofilms was found to be equally efficient for seven catalytic cycles. Considering their excellent catalytic activity and recyclability in the degradation of nitroaromatic pesticides, the PDA@Ag/PS films have great potential applications in the fields of environment protection, soil contamination remediation, and sewage treatment. Also, by virtue of the remarkable reducing and stabilizing ability and adhesive versatility of PDA, this approach can be extended to the deposition of various metals and semiconducting NPs, which can be stably anchored on a diverse range of solid substrates regardless of physiochemical and morphology.

Porous epoxy phenolic novolac resin polymer microcapsules: Tunable release and bioactivity controlled by epoxy value

Microcapsules (MCs) prepared with diverse wall material structures may exhibit different properties. In this study, MCs were fabricated with three kinds of epoxy phenolic novolac resins (EPNs), which possessed unique epoxy values as wall-forming materials by interfacial polymerization. The effects of the EPN types on the surface morphology, particle size distribution, encapsulation efficiency, thermal stability as well as release behavior and bioactivity of the MCs were investigated. In all three samples, the MCs had nearly spherical shapes with fine monodispersities and sizes in the range of 7-30 μm. Scanning electron microscopy (SEM) images showed that some small pores (ranging from 50 nm to 400 nm) appeared on the microcapsule surfaces and that the porosity decreased with an increasing of epoxy value. The X-ray diffractometer (XRD) analysis indicated that the cured EPN shells had larger degrees of crosslinking with higher epoxy values, leading to better thermal stabilities. Moreover, the release rate of the core material (pendimethalin) decreased with an increasing of epoxy value and thus resulted in a lower herbicidal control efficacy. The results of our research will enhance the potential application of EPNs as smart wall-forming materials to prepare porous MCs for controlled release.