Nanocomposites for controlled delivery of triazinc compounds applied as agricultural pesticides

This research proposed a preparation method for a nanocomposite, able to control the delivery of high quantities of an active compound, inserted on its matrix, in order to prospect an application for the controlled delivery of herbicides. To that, a nanocomposite system was prepared based on the exfoliation of a clay mineral in a continuous starch phase, loading around 50% weight of a model herbicide ametryne. The starch was loaded with 50 to 80% of montmorillonite, dispersed through the starch gelification at 90o C in water. The herbicide was added during the cooling process, at 70o C. The materials were characterized by X-ray diffraction and thermal analyses, where the intercalation of the biopolymer in the clay lamellar structure was observed. The herbicide release showed that the releasing behavior was governed by the starch amount in the nanocomposite, for short periods, and by the clay, in longer periods. It was observed also a synergic effect between the nanocomposite constituents, since the reference materials (produced with starch: ametryne or clay: ametryne) did not showed adequate release behaviors. However, this behavior was shown as governed by physical barriers for the ametryne diffusion, since nuclear magnetic resonance in solid state experiments showed that the starch: ametryne interactions were weak. On the other hand, the starch: clay interactions were shown by the same technique, supporting the synergic behavior of the release. Finally, the nanocomposite system improved the resistance to the UV light attack, reducing the herbicide volatilization under irradiation. This effect was evaluated by mass loss experiments after different irradiation times, compared to infrared spectroscopy measurements.Financiadora de Estudos e ProjetosEste trabalho propôs um método de preparo de um nanocompósito capaz de controlar a liberação de altas quantidades de um composto ativo presente em sua matriz, com a finalidade de prospectar uma aplicação para a liberação controlada de herbicidas. Para tanto, foi proposto um sistema nanocompósito à base de um argilomineral esfoliado em uma matriz de amido, incorporando cerca de 50% em massa de um herbicida modelo, a ametrina. Foram preparados sistemas com teores de 50 a 80% de um argilomineral, a montmorilonita, disperso através da gelificação a 90o C do amido em água, sendo o herbicida adicionado durante o processo de resfriamento, a 70o C. Os materiais foram caracterizados por difração de raios X e análises térmicas, comprovando-se a intercalação do biopolímero com as lamelas do argilomineral. A avaliação da liberação do herbicida demonstrou que o padrão de liberação segue um comportamento governado pela quantidade de amido, em tempos curtos, e pelo argilomineral, em tempos longos. Observou-se ainda um efeito sinérgico entre os componentes, visto que materiais de referência produzidos apenas com amido: ametrina ou argilomineral: ametrina não apresentaram bons comportamentos de liberação. No entanto, observou-se que a liberação é governada principalmente por barreiras físicas para a difusão da ametrina, visto que as interações entre ametrina e amido foram fracas, como avaliado por ressonância magnética nuclear no estado sólido. Por outro lado, as interações do amido com o argilomineral foram confirmadas pela mesma técnica, reforçando o caráter sinérgico de controle da liberação observado. Por fim, o sistema nanocompósito apresentou-se como uma alternativa para reduzir o ataque da luz ultravioleta no herbicida, reduzindo sua volatilização. Esse efeito pôde ser avaliado por experimentos de perda de massa após irradiação, em diferentes tempos, comparados a espectroscopias no infravermelho

Functionalized Charcoal as a Buffering Matrix of Copper and Zinc Availability

ABSTRACT: High copper (Cu) and zinc (Zn) contents in soil can cause phytotoxicity to plants and contaminate surface and groundwater, with negative effects on agriculture and the environment. Functionalized charcoal (OCh) has high cation exchange capacity (CEC) and the ability to adsorb Cu and Zn and control their availability in the soil and water. An adsorption study at two pH levels was carried out to evaluate increasing Cu and Zn sorption capacity provided by the functionalization process of a charcoal. In addition, a kinetics study of competitive and non-competitive adsorption-desorption of Cu and Zn in OCh was also evaluated. The results showed that functionalized charcoal (Ch) increased CEC 8.7 times due to an increase in carboxyl and phenolic groups, without changing its specific surface area. The Cu and Zn kinetics study showed higher interaction of Cu with the OCh, with total adsorption capacity of 53.1 mg g−1. From this amount, only 74.9 % was desorbed. However, competitive adsorption with Zn reduced the total amount of Cu adsorbed and decreased the Cu affinity for organic matter. This study shows the potential use of functionalized charcoal for control of Cu and Zn availability in the soil solution

Smart Fertilization for Tailored Valorization of Tall Wheatgrass Biomass

The perennial grass species Agropyron elongatum, commonly named "tall wheatgrass" (Poacea), has been gaining attention in recent years for its potential as a bioenergy and biorefinery feedstock. A. elongatum is native to southern Europe and Asia Minor, and was introduced to other places in the world as an energy crop, fodder and reclamation grass also marginal sandy soils. Therefore, A. elongatum is an attractive alternative to traditional energy crops such as corn and sugarcane. Improved biomass yield by targeted fertilization in sand using alternative nutrient carriers such as digestate has already been successfully demonstrated earlier and was transferred to the present investigation. One of the key benefits of using A. elongatum for energy and biorefinery applications is its high cellulose content and processability. Depending on the pre-treatment (alkaline or acidic) of the bulk, more than 75% crystalline cellulose and more than 25% lignin can be obtained. As demonstrated earlier, acid pre-treatment even allowed for a direct conversion of 25% of the cellulose into glucose without the need for enzymatic digestion

Mechanochemical Activation of Elemental Sulfur Increases Its Bioavailability in the Forage Species Brachiaria Production

Although sulfur is an essential macronutrient for plants, its supply through elemental S0 is not efficient, demanding its oxidation by soil microbiota before plant uptake. Thus, we demonstrate that a simple reactive mechanochemical route, using anhydrous KOH as a reactant with no need for water addition, can convert S0 to bio-absorbable oxidized forms, leading to residual K+ as a plant nutrient in the final composition. The powdery products obtained by 1 h (S-1 h) or 8 h (S-8 h) milling have been fully converted to HSO3–, SO32–, and SO42–, also suggesting different amounts of these sulfur oxides according to the milling. S-1 h and S-8 h were efficient for S and K fertilization, as probed by the successful growing of the forage crop Brachiaria ssp. in a greenhouse trial, with similar biomass yields observed for K2SO4 (positive control) and superior to S0 + KCl (negative control). These data suggest that the mechanochemical process provides a sustainable route to increase sulfur plant bioavailability, suggesting a simple alternative that can be easily implemented in forage plant production sites such as Brachiaria ssp

Núcleos de Ensino da Unesp: artigos 2007

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Núcleos de Ensino da Unesp: artigos 2008

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq