ABSTRACT
The synthesis and application of cellulose acetate (CA) from sugarcane bagasse were investigated. Firstly, cellulose was extracted by a sequential treatment with H2SO4 (10% v/v), NaOH (5% w/v), EDTA (0.5% w/V), and H2O2 (5% v/v), and characterized by X-ray diffraction (DRX). After the acetylation of the extracted cellulose, CA was characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA), and was applied in the membrane production. The membranes were analyzed by DSC and atomic force microscopy (AFM), and tested in the flux of water vapor to determinate the best conditions for membrane manufacturing. FTIR analysis proved the replacement of free OH groups by acetyl groups, and the thermal analysis showed that sugarcane bagasse CA possessed thermal properties compared to commercial grade CA. The best conditions to prepare membrane were: 3% (w/v) of polymer/solvent relation, 10min of solvent evaporation time, and 20°C as temperature for the coagulation bath. These results show that CA can be successfully synthesized from sugarcane bagasse and applied in membrane preparation.
ABSTRACT
Sugarcane straw (SCS) is a raw material with high potential for production of cellulose derivatives due to its morphology and structure. The proposal of this work was to synthesize cellulose acetate (CA) and carboxymethylcellulose (CMC) from sugarcane straw cellulose, and applied the CA in the preparation of a membrane. The cellulose extraction was carried out in four steps. Firstly, SCS was treated with H2SO4 (10% v/v) followed by NaOH (5% w/v) treatment. Subsequently, a chelating process was performed before ending the extraction process with chemical bleaching using H2O2 (5% v/v). The extracted cellulose was employed in the obtainment of CA and CMC. The CA presented a degree of substitution (DS) of 2.72. Its FTIR spectrum showed that practically all hydroxyl groups were replaced by acetate groups. The membrane synthesized from CA was dense and homogeneous. The presence of small particles on the top and bottom surfaces decreased the mechanical resistance of the membrane. The CMC presented a low DS (0.4) demonstrating the carboxymethylation reaction was not very effective due to the presence of lignin. These results proved that SCS can be utilized in the synthesis of CA and CMC.
Subject(s)
Carboxymethylcellulose Sodium , Cellulose/analogs & derivatives , Saccharum/chemistry , Carboxymethylcellulose Sodium/chemical synthesis , Carboxymethylcellulose Sodium/chemistry , Cellulose/chemical synthesis , Cellulose/chemistryABSTRACT
Se estudiaron en agar sabouraud dextrosado, muestras obtenidas del conducto auditivo externo de 80 perros y 22 gatos aparentemente sanos. El examen micológico directo y las características morfofisiológicas y bioquímicas, permitieron determinar la presencia de malassezia pachydermatis en el 61,3 porciento de las muestras provenientes de perros y en el 13,6 porciento de los gatos. La susceptibilidad de esta levadura se determinó en medios sólidos, por el método de dilución in vitro frente a soluciones de yodo, timerosal y violeta de genciana. Todas las cepas fueron inhibidas en las siguientes concentraciones: yodo 1,0 g/l; timerosal 0,0125 g/l y violeta de genciana a 0,0078 g/l, lo que representa su dilución comercial diluída 641 veces
