Fotodegradação de hidrogel de poliacrilamida na presença de substâncias químicas para o uso na agricultura

Abstract

RESUMO Utilizado na agricultura como condicionante do solo, a poliacrilamida, constituinte básico do hidrogel, tem a característica de absorver, por processo físico, água e a estocar para as plantas conforme sua necessidade hídrica. Entretanto, a poliacrilamida sofre degradação de sua cadeia, devido à ação da radiação ultravioleta e de sais presentes no meio, ocasionando a liberação de acrilamida, substância tóxica e não biodegradável. O presente trabalho teve como objetivo avaliar a fotodegradação da poliacrilamida e o efeito de algumas substâncias químicas presentes no solo na degradação desse polímero. Para tanto foi feito o estudo da fotodegradação do hidrogel empregando a técnica Espectroscopia no Infravermelho com Transformada de Fourier (FTIR) de forma a comprovar o grau de degradação do polímero. Avaliou-se também a retenção de água de um Latossolo Vermelho Escuro Distroférrico com presença do gel empregando-se para tal, o método da centrífuga. Os resultados comprovaram que depois de degradada a poliacrilamida teve perda do grupamento amida, indicativo da quebra de cadeia em acrilamida. Além do mais o polímero perdeu suas características de retenção de água, com a modificação das suas redes poliméricas e aspecto de gel.

Durability indicatives of hydrogel for agricultural and forestry use in saline conditions

“…In this case, it is possible to observe that the level of salinity of the hydration solution and/or time are altering the chemical structure of the hydrogel, indicating its degradation. These results confirm that the degradation of the hydrogel evaluated in this study can be accelerated in the presence of hydration solutions containing Ca, Mg salts and therefore potentially by salts contained in soils (Freitas et al, 2019) and over time (Holliman et al, 2005). This degradation occurs without any release of RAm but represents limitations to the hydrogel's durability in the long term.…”

HYDROGEL AND WATER REGIMES IN THE CHLOROPHYLL- A FLUORESCENCE AND GROWTH OF Campomanesia xanthocarpa SEEDLINGS

“…The aerial part/root ratio (APRR) was higher under 75% and 50% WRC, without and with WRP, respectively, and it should be noted that when WRP was added to the substrate, different water regimes, except 50% WRC, returned statistically higher values when compared to the seedlings without hydrogel (Figure 4e). This increase relates to the benefits of WRP for water retention in the substrate (Freitas et al, 2019), demonstrating investment in root biomass due to greater water absorption, contributing to translocation to the aerial part, promoting better physiological indexes and growth characteristics. The seedlings showed higher total dry mass yields under 50% and 100% WRC, both with WRP (Figure 4f), demonstrating the beneficial effect of the hydrogel on the photoassimilate production.…”

“…Water-retaining polymers (WRP), known as hydrogels, have the capacity to absorb water and retain it for use during dry periods (Kalhapure et al, 2016;Silva et al, 2019). The composition base of the hydrogel contains polyacrylamide, which when incorporated into the soil, promotes aeration and drainage improvements and reduces nutrient leaching (Azevedo et al, 2002;Freitas et al, 2019), contributing to root and other vegetative organ growth through the stability of metabolic processes and the prevention of plant dehydration.…”

Superabsorbent polymers in soil: The new microplastics?

“…SAP hydrogels could be analyzed as gel, after (freeze)drying or after flocculation triggered by polyvalent ions or pH changes (Moud, 2022;Anwar et al, 2023). In addition to identifying the polymer itself, FTIR would be further capable of characterizing the degree of polymer degradation (Liang et al, 2018;Freitas et al, 2019) or cation exchange of the polymer framework (Rodionov et al, 2014). Similarly, near-and mid-IR imaging may be applied.…”