Preparação e caracterização de nanocelulose a partir do bagaço de laranja pera
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Data
2019-11-29
Autores
Fernandes, Luana Lima
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As fibras vegetais são cada vez mais estudadas como opção de substituição a polímeros
derivados do petróleo e têm sido avaliadas para aplicações tais como na indústria aeronáutica,
naval, alimentícia, biomedicina, entre outras. O Brasil é um dos maiores produtores de suco
de laranja, produzindo quase 10 milhões de toneladas por ano, gerando grande quantidade de
resíduos. Este trabalho utilizou diferentes tipos de tratamentos químicos visando remover os
componentes amorfos da biomassa a fim de obter a celulose e posteriormente preparar
nanocelulose via hidrólise ácida partindo da celulose branqueada (CB). Os resíduos solúveis
em álcool do bagaço de laranja pera foram removidos através do processo de extração com
álcool etílico (RSA), seguido de duas etapas de branqueamento (1B e 2B) com peróxido de
hidrogênio (30% v/v) em meio alcalino com uma solução de hidróxido de sódio (NaOH) 4%
(m/v), seguida de solução de hidróxido de potássio 5% (m/v) (2B/KOH). Após esses
tratamentos, a partir da celulose branqueada, foram isoladas as nanoceluloses através de
hidrólise ácida com ácido sulfúrico (H2SO4) 64% e 50% em diferentes tempos de reação: 1 e
2h. Após o isolamento as nanoceluloses foram secas de duas formas: estufa a 50°C e por
liofilização. A fibra in natura (IN), RSA, 1B, 2B e 2B/KOH foram caracterizadas através da
análise de composição química, difração de raios X (DRX), infravermelho com transformada
de Fourier (FTIR), termogravimetria (TGA/DTG) e microscopia eletrônica de varredura
(MEV). As nanoceluloses isoladas foram caracterizadas pela técnica de potencial Zeta, análise
de tamanho de partícula, microscopia eletrônica de transmissão (MET), DRX, TGA/DTG e
FTIR. A nanocelulose obtida com ácido sulfúrico 64% e 1 h de reação apresentou o menor
tamanho de partícula (9,48 µm), assim como melhor valor de potencial Zeta (-23,0 mV),
indicando melhor dispersão da suspensão, no entanto, apresentaram tendência de aglomeração
conforme a análise de TEM, valores de razão de aspecto menores em relação às outras
amostras feitas com ácido 50% (L/D = 25). As nanoceluloses secas por liofilização
apresentaram melhores propriedades térmicas (estabilidade térmica 250ºC) e os menores
valores de tamanho de cristalito (1,5 nm), enquanto as amostras secas em estufa a 50ºC
apresentaram os maiores valores de índice de cristalinidade (aproximadamente 95%). Dessa
forma, obteve-se a nanocelulose a partir da celulose branqueada oriunda do bagaço de laranja
pera com boas propriedades térmicas e alto índice de cristalinidade que podem ser utilizadas
em diversas aplicações, como por exemplo, nanocompósitos e filmes para embalagens
Plant fibers are increasingly being studied as an option to replace petroleum-derived polymers and have been evaluated for applications such as aeronautical, marine, food, biomedicine, and others. Brazil is one of the largest producers of orange juice, producing almost 10 million tons per year, generating a large amount of waste. This work uses chemical methods to remove the amorphous components from biomass to obtain cellulose and later nanocellulose using acid hydrolysis. The alcohol insoluble residues from the orange bagasse are removed by the ethyl alcohol extraction process, followed by two bleaching steps with the hydrogen alcohol (30% v/v) in the alkaline solution with sodium hydroxide (NaOH) 4% (w/v), followed by potassium hydrogen solution 5% (w/v) (2B/KOH). After these chemical treatments, the bleached cellulose was obtained, and acid hydrolysis was performed isolating nanocelluloses, by using sulfuric acid (H2SO4) in different concentrations 64% and 50% in different reaction times: 1 and 2 h. After separating, the nanocelluloses were dried in two ways: oven drying at 50ºC and freeze-drying. The fibers in each step were characterized by chemical composition analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), and electron microscopy scanning (SEM).Nanocelluloses were characterized by the potential Zeta technique, particle size analysis, transmission electron microscopy (TEM), XRD, TGA / DTG, and FTIR. The nanocelluloses using a concentration of sulfuric acid as 64% and 1h of reaction resulted in smallest particle sizes (9.48 µm) as well as the best Zeta potential values (-23.0 mV), show better suspension dispersion, however, for cluster analysis of TEM, fiber aspect ratio values in relation to other colors (L/D = 25). As freeze-dried nanocellulose, showed better thermal conditions (thermal stability at 250ºC) and the lowest crystal size values (1.5 nm), however, it is oven-dried at 50ºC with the highest Ic (approximately 95%). Then, a nanocellulose obtained from bleached cellulose from orange bagasse, with thermal characteristics good (thermal stability) and high crystaliniidade index which can be used in various applications such as application in nanocomposites and packaging films
Plant fibers are increasingly being studied as an option to replace petroleum-derived polymers and have been evaluated for applications such as aeronautical, marine, food, biomedicine, and others. Brazil is one of the largest producers of orange juice, producing almost 10 million tons per year, generating a large amount of waste. This work uses chemical methods to remove the amorphous components from biomass to obtain cellulose and later nanocellulose using acid hydrolysis. The alcohol insoluble residues from the orange bagasse are removed by the ethyl alcohol extraction process, followed by two bleaching steps with the hydrogen alcohol (30% v/v) in the alkaline solution with sodium hydroxide (NaOH) 4% (w/v), followed by potassium hydrogen solution 5% (w/v) (2B/KOH). After these chemical treatments, the bleached cellulose was obtained, and acid hydrolysis was performed isolating nanocelluloses, by using sulfuric acid (H2SO4) in different concentrations 64% and 50% in different reaction times: 1 and 2 h. After separating, the nanocelluloses were dried in two ways: oven drying at 50ºC and freeze-drying. The fibers in each step were characterized by chemical composition analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), and electron microscopy scanning (SEM).Nanocelluloses were characterized by the potential Zeta technique, particle size analysis, transmission electron microscopy (TEM), XRD, TGA / DTG, and FTIR. The nanocelluloses using a concentration of sulfuric acid as 64% and 1h of reaction resulted in smallest particle sizes (9.48 µm) as well as the best Zeta potential values (-23.0 mV), show better suspension dispersion, however, for cluster analysis of TEM, fiber aspect ratio values in relation to other colors (L/D = 25). As freeze-dried nanocellulose, showed better thermal conditions (thermal stability at 250ºC) and the lowest crystal size values (1.5 nm), however, it is oven-dried at 50ºC with the highest Ic (approximately 95%). Then, a nanocellulose obtained from bleached cellulose from orange bagasse, with thermal characteristics good (thermal stability) and high crystaliniidade index which can be used in various applications such as application in nanocomposites and packaging films
Descrição
Palavras-chave
Nanocelulose, Bagaço de laranja, Hidrólise ácida, Fibras vegetais, Nanocellulose, Orange bagasse, Acid hydrolysis, Plant fibers, Fibras, Materiais compostos, Hidrólise, Nanocompósitos (Materiais)