Júlia Graciele Vieira

Synthesis and Characterization of Methylcellulose Produced from Bacterial Cellulose under Heterogeneous Condition

In this work, methylcellulose (MC) was produced from bacterial cellulose (BC), using dimethyl sulfate in a 3 h (MC3h) or 5 h (MC5h) reaction under heterogeneous conditions, with reagent substitution at each hour. MC3h showed a degree of substitution (DS) of 2.26 ± 0.13 and MC5h showed a DS of 2.33 ± 0.05. The two samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), 13C nuclear magnetic ressonance (NMR) and 1H NMR techniques. The FTIR spectra of the BC and MC samples present significant differences in the regions from 3750 to 2750 cm−1 and from 1500 to 750 cm−1, which evidence the methylation of the samples. Solid state NMR spectroscopy of the MC samples was used to identify the 13C NMR signals of substitution at sites C-2, C-3 or C-6 in the glucopyranose units. The modification of bacterial cellulose produced a material with a high DS, determined by three different techniques (chemically and using the liquid 1H and solid 13C NMR spectra). These samples also demonstrate high crystallinity and thermal stability. With the MC samples synthesized in this work, transparent and resistant films were prepared and also a highly porous sponge like material.

Caracterização de membranas assimétricas de acetato de celulose produzidas a partir do aproveitamento do resíduo da palha de milho para uso em ultrafiltração

Cellulose acetates (CA) with different degrees of acetylation were synthesized from cellulose extracted from corn stover. Membranes were prepared for the ultrafiltration process with pure polymers and blend form of CA utilizing a dioxane/acetone system. The membranes were characterized according to their transport properties. The blend form materials presented the best results for application in ultrafiltration experiments. M-TAC/DAC (corn stover triacetate and diacetate) and M-TAC/DAC-Rho (corn stover triacetate and Rhodia diacetate) presented rejection to egg albumin protein of 87.39% and 80.50%, respectively. Thus, MWCO of 45 kDa was determined for these materials.

Comparison between Ultrasound Assisted Extraction and Microwave Digestion in the Determination of Arsenic in Edible Grains

A comparative evaluation of arsenic extraction from grains using ultrasound assisted extraction (UAE) and microwave digestion (MW) was developed. The arsenic determination was carried out using hydride generation coupled to flame atomic absorption spectroscopy (HG-FAAS). The optimal extraction condition indicated for corn was 20% v v of HCl, temperature of 67 °C and sonication time of 30 min. For bean, the optical condition was HNO3 in a 10% v v, temperature of 25 °C and sonication time of 10 min and for soybean it was 30% v v HCl, temperature of 60 °C and time of 10 min. Recovery studies close to 100% in the extraction of spiked samples was achieved. The results obtained were compared with two common extraction methods for arsenic using microwave digestion and the developed methods showed a significant increase in the arsenic recovery from the samples. In the real samples it was found an arsenic concentration of 0.3 μg g. The developed methods proved to be efficient at extracting the arsenic present in the studied grains, being appropriate to evaluate the risk to human consumption.

Utilização de hemiceluloses catiônicas, obtidas a partir do aproveitamento da palha de milho, associadas com tanino para o tratamento de efluentes de lavanderia industrial

Elaine Angélica Mundim Ribeiroa, Fúlvio Rafael Bento de Souzaa, Fábio Augusto do Amarala, Guimes Rodrigues Filhoa,*,#, Raquel Maria Ferreira de Sousaa, Júlia Graciele Vieiraa, Talita Ferreira de Rezende Costaa, José Pedro Thompson Juniora, Rosana Maria Nascimento de Assunçãob e Sheila Cristina Canobrea Instituto de Química, Universidade Federal de Uberlândia, Campus Santa Mônica, 38.400-902, Uberlândia – MG, Brasil Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, Campus do Pontal, 38302-000, Ituiutaba – MG, Brasil

PREPARAÇÃO E CARACTERIZAÇÃO DE MEMBRANAS DE CELULOSE REGENERADA A PARTIR DA CELULOSE EXTRAÍDA DE RESÍDUOS AGROINDUSTRIAIS PARA APLICAÇÃO EM PROCESSOS DE SEPARAÇÃO

The aim of this study was to produce membranes using the adapted cuprammonium method. The cellulose utilized was obtained from recycled agroindustrial residues: sugarcane bagasse, corn stover and soybean hulls. The levels of Cu (II) ions in regenerated cellulose membranes produced with cellulose from bagasse, corn stover and soybean hulls were 0.0236 wt%, 0.0255 wt% and 0.0268 wt%, respectively. These levels were approximately 15 times lower than those observed in previous studies (0.3634 wt%). Cellular viability data show that membranes produced from bagasse cellulose do not present toxicity to the cellular cultures studied. These results demonstrate an evolution in production of regenerated cellulose membranes from agroindustrial residues mainly due to a decrease in the Cu (II) ions level, showing the possibility of application of these systems with improved membranes processing.