Controlled Release of Imidacloprid from a Lignin Matrix: Water Release Kinetics and Soil Mobility Study

Abstract

Formulations of the insecticide imidacloprid were made using a commercially available pine kraft lignin. The release kinetics of imidacloprid from granules with variation in the loadings of the insecticide and granule sizes were evaluated in water under dynamic flow conditions. The release data were fitted to the generalized model M t /M z = kt n + c, where M t /M z is the percentage of insecticide released at time t, k and c are constants, and n is another constant that indicates the mechanism of release. The results indicated that the release of imidacloprid was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, T 50, was also calculated for the comparison of formulations. The results showed that the formulation with the higher loading of imidacloprid had the higher value of T 50, which means a slower release of the active ingredient. In a related experiment, it was found that as the size of this formulation decreased, the release of the active ingredient was faster. In addition, mobilities of technical and formulated imidacloprid were compared by using soil columns simulating a layered bed system commonly used under a plastic greenhouse. The use of formulated imidacloprid produced a less vertical distribution of the active ingredient compared to the technical product. Sorption capacities of the various soil constituents for imidacloprid molecules were also calculated by using batch experiments. The results obtained were in agreement with those for sorption in dynamic conditions. Keywords: Controlled release; imidacloprid; lignin; leaching

Effect of formulations and treatment methods of nursery boxes applied with insecticide on the behavior of imidacloprid in rice paddy fields

“…Technical information regarding the controlled release formulation of Admire CR was unknown; however, it was reported as an example of the controlled release formulation of imidacloprid that the inactive ingredient in the controlled release formulation was made by adsorptive materials or sorbents, 3,18) which allow active ingredients to be slowly released to water. T 50 (time taken for 50% of the pesticide to be released) of imidacloprid in Admire was less than 1 day and Admire CR was about 20 days, respectively at 25 of imidacloprid in several controlled release formulations was 0.6-6.5 days for lignin-based formulations, 19) 14.6-18.7 hr for alginate-bentonite formulations, 11) 0.9-12 days for lignin formulations, 17) and 7.6-6290 hr for alginate-bentonite-activated carbon formulations.…”

“…[17][18][19] The release rate of active ingredient from granules depended on the characteristics of sorbents, 8,18) sizes of the granules, 16,17,19) loading mass of the pesticide, and physicochemical properties, such as the aqueous solubility and lipophilicity of pesticides. 8,16,18,19,24) The mechanism of dissolution and sorption of imidacloprid for BT and AS treatments in rice paddy fields is elucidated in the Fig.…”

Behavior of nursery-box-applied imidacloprid in micro paddy lysimeter

“…30) Other studies also found the downward movement of imidacloprid in the soil column. 27,33,34) In a paddy lysimeter study, Oi et al found that imidacloprid was not detected in the leachate (<0.2 μg/L), 35) and the concentration of imidacloprid in the 5-30 cm soil layer a er harvesting (about 4 months a er transplanting) was less than 5 μg/kg for both volcanic ash soil and alluvial soil. e residue of imidacloprid in the lysimeter soil pro le before harvesting in the study of Oi et al is unknown and a direct comparison cannot be made with the residue of imidacloprid in the MPL soil prole at 21 DAT in our study; 35) however, the average concentrations of imidacloprid in 5-15 cm were 13.6 and 8.8 μg/kg, respectively, with AS and BT treatment, which is comparable to the above nding of Oi et al (1994) considering the sampling depth and monitored time.…”

“…e reported T 50 of imidacloprid in several controlled release formulations ranged from a few hours to several months depending on the granular size and formulation type. [25][26][27][28] Figure 4a shows the concentrations of imidacloprid in di erent soil layers: 0-2.5 cm, 2.5-5 cm, 5-7.5 cm, 7.5-10 cm, 10-12.5 cm, and 12.5-15 cm in S1 (BT treatment) and S2 (AS treatment) at 21 DAT, respectively. From the top to bottom layer, the concentrations fell exponentially in both S1 and S2.…”

Microencapsulação do pesticida cipermetrina em blendas de P(3HB/PCL): caracterização e ensaio de liberação in vitro

“…Embora existam esforços consideráveis na investigação de vários aspectos de formulações para liberação in vitro de pesticidas, aplicações comerciais permanecem escassas, em função do alto custo de produção em comparação ao uso de granulados no solo [5] . Entre os materiais que podem ser empregados na microencapsulação, encontram-se os polímeros obtidos de fontes naturais como os polihidroxialcanoatos e os poliésteres sintéticos como as policaprolactonas [12,13] . Os polihidroxialcanoatos são poliésteres termoplásticos sintetizados por várias bactérias a partir de fontes renováveis [14] .…”