Síntese e caracterização de hidrogéis reticulados com ácido cítrico e álcool polivinílico para uso na agricultura
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Data
2024-12-12
Autores
Orientador
Catto, André Luis
Banca
Borsoi, Cleide
Reisdörfer, Gustavo
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Resumo
Com o aumento da demanda mundial por alimentos, busca-se progressivamente uma agricultura mais sustentável, com a conservação do solo, da água e do meio ambiente, usando técnicas apropriadas, economicamente viáveis e socialmente aceitáveis. Nesse sentido, o uso de hidrogéis é uma alternativa promissora para liberação lenta de água e compostos orgânicos que possam ser incorporados, como óleos essenciais e nanoargilas, resultando em polímeros biodegradáveis hidroretentores e fungicidas. A partir disso, o objetivo desta monografia baseou-se no preparo de hidrogéis com carboximetilcelulose (CMC) e um híbrido de nanoargila montmorilonita sódica (MMT Na+) e óleo essencial de capim-limão (Cymbopogon citratus) para uso na agricultura. Como agentes reticulantes, foram utilizados ácido cítrico em todas as amostras sintetizadas, na concentração constante de 7,5% em relação à quantidade de polímero e, álcool polivinílico (PVA), em concentrações de 0, 0,5, 1,0, 2,5 e 4,0% em relação à massa total de solução. As amostras foram avaliadas quanto às suas propriedades físicas, térmicas, químicas e de hidrofilicidade, além do potencial antifúngico frente aos fungos Fusarium oxysporum e Colletotrichum acutatum. Os resultados da análise de intumescimento realizada em água destilada mostraram alta capacidade de absorção, de até 1646,77% na amostra sem PVA, porém decrescendo ao aumentar a concentração do agente reticulante. Verificou-se também que as amostras com concentrações mais elevadas de PVA apresentaram resultados de fração em gel mais expressivos, de até 95%, indicando um aumento da densidade de reticulação, o que torna o hidrogel mais compactado e menos permeável. A presença de reticulação também é percebida na análise de Espectroscopia de Infravermelho com Transformada de Fourier (FTIR), através das bandas em 1710 e 1570 cm-1, características de ligações éster entre as cadeias dos reticulantes com a CMC. Em meio salino, com sulfato de amônio, os hidrogéis com PVA tiveram maior estabilidade e, na análise termogravimétrica (TGA), apresentaram maior estabilidade térmica nas temperaturas até 300°C. A atividade antifúngica dos hidrogéis apresentou baixos índices de inibição frente aos fungos Fusarium oxysporum e Colletotrichum acutatum, provavelmente devido à baixa concentração usada do óleo essencial de capim-limão. Apesar disso, pode-se concluir que as características dos hidrogéis desenvolvidos são favoráveis à sua utilização na agricultura, sendo biocompatíveis e com grande capacidade de retenção de líquidos, podendo liberá-los de forma controlada.
With the increase in global demand for food, more sustainable agriculture is progressively sought, with the conservation of soil, water and the environment, using appropriate, economically viable and socially acceptable techniques. In this sense, the use of hydrogels is a promising alternative for the slow release of water and organic compounds that can be incorporated, such as essential oils and nanoclays, resulting in water-retaining and fungicidal biodegradable polymers. From this, the objective of this monograph was based on the preparation of hydrogels with carboxymethylcellulose (CMC) and a hybrid of sodium montmorillonite nanoclay (MMT Na+) and lemongrass essential oil (Cymbopogon citratus) for use in agriculture. As crosslinking agents, citric acid was used in all synthesized samples, at a constant concentration of 7,5% in relation to the amount of polymer, and polyvinyl alcohol (PVA), at concentrations of 0, 0,5, 1,0, 2,5 and 4% in relation to the total mass of solution. The samples were evaluated for their physical, thermal, chemical and hydrophilicity properties, in addition to their antifungal potential against the fungi Fusarium oxysporum and Colletotrichum acutatum. The results of the swelling analysis carried out in distilled water showed a high absorption capacity, up to 1646,77% in the sample without PVA, but decreasing when the concentration of the crosslinking agent increased. It was also found that samples with higher concentrations of PVA showed more significant gel fraction results, up to 95%, indicating an increase in crosslinking density, which makes the hydrogel more compacted and less permeable. The presence of crosslinking is also noticed in the Fourier Transform Infrared Spectroscopy (FTIR) analysis, through the bands at 1710 and 1570 cm-1, characteristic of ester bonds between the crosslinker chains with the CMC. In a saline environment, with ammonium sulfate, the hydrogels with PVA had greater stability and, in thermogravimetric analysis (TGA), they showed greater thermal stability at temperatures up to 300°C. The antifungal activity of the hydrogels showed low levels of inhibition against the fungi Fusarium oxysporum and Colletotrichum acutatum, probably due to the low concentration of lemongrass essential oil used. Despite this, it can be concluded that the characteristics of the developed hydrogels are favorable to their use in agriculture, being biocompatible and with a great capacity to retain liquids, being able to release them in a controlled manner.
With the increase in global demand for food, more sustainable agriculture is progressively sought, with the conservation of soil, water and the environment, using appropriate, economically viable and socially acceptable techniques. In this sense, the use of hydrogels is a promising alternative for the slow release of water and organic compounds that can be incorporated, such as essential oils and nanoclays, resulting in water-retaining and fungicidal biodegradable polymers. From this, the objective of this monograph was based on the preparation of hydrogels with carboxymethylcellulose (CMC) and a hybrid of sodium montmorillonite nanoclay (MMT Na+) and lemongrass essential oil (Cymbopogon citratus) for use in agriculture. As crosslinking agents, citric acid was used in all synthesized samples, at a constant concentration of 7,5% in relation to the amount of polymer, and polyvinyl alcohol (PVA), at concentrations of 0, 0,5, 1,0, 2,5 and 4% in relation to the total mass of solution. The samples were evaluated for their physical, thermal, chemical and hydrophilicity properties, in addition to their antifungal potential against the fungi Fusarium oxysporum and Colletotrichum acutatum. The results of the swelling analysis carried out in distilled water showed a high absorption capacity, up to 1646,77% in the sample without PVA, but decreasing when the concentration of the crosslinking agent increased. It was also found that samples with higher concentrations of PVA showed more significant gel fraction results, up to 95%, indicating an increase in crosslinking density, which makes the hydrogel more compacted and less permeable. The presence of crosslinking is also noticed in the Fourier Transform Infrared Spectroscopy (FTIR) analysis, through the bands at 1710 and 1570 cm-1, characteristic of ester bonds between the crosslinker chains with the CMC. In a saline environment, with ammonium sulfate, the hydrogels with PVA had greater stability and, in thermogravimetric analysis (TGA), they showed greater thermal stability at temperatures up to 300°C. The antifungal activity of the hydrogels showed low levels of inhibition against the fungi Fusarium oxysporum and Colletotrichum acutatum, probably due to the low concentration of lemongrass essential oil used. Despite this, it can be concluded that the characteristics of the developed hydrogels are favorable to their use in agriculture, being biocompatible and with a great capacity to retain liquids, being able to release them in a controlled manner.
Descrição
Palavras-chave
agricultura; hidrogel; nanoargila; óleo essencial de capim-limão; ácido cítrico; álcool polivinílico; fungicida; agriculture; hydrogel; nanoclay; lemongrass essential oil; citric acid; polyvinyl alcohol; fungicide
Citação
POZZEBON, Eloisa. Síntese e caracterização de hidrogéis reticulados com ácido cítrico e álcool polivinílico para uso na agricultura. 2024. Monografia (Graduação em Engenharia Química) – Universidade do Vale do Taquari - Univates, Lajeado, 05 dez. 2024. Disponível em: http://hdl.handle.net/10737/4637.