Morsyleide de Freitas Rosa

Extraction and characterization of nanocellulose structures from raw cotton linter

This study aimed to characterize nanocellulose extracted from cotton (Gossypium hirsutum) linters. The nanocellulose was subjected to electronic microscopy, thermal analysis, X-ray diffractometry, light scattering, and contact angle. The properties of the nanocellulose are considerably different from the linter. The acidic hydrolyses applied to extract the nanocrystals increased the crystallinity index and the hydrophilicity and decreased the thermal stability. On average, the nanocrystals were 177 nm long and 12 nm wide, with an aspect ratio of 19 when measured by microscopy. The light scattering results were coherent with the crystal dimensions. Cotton linter is a potential source of nanocellulose crystals, particularly to be used in the production of hydrophilic nanocomposites. Extraction of nanocellulose from raw cotton linter does not require pulping.

Effect of fiber treatments on tensile and thermal properties of starch/ethylene vinyl alcohol copolymers/coir biocomposites.

Coir fibers received three treatments, namely washing with water, alkali treatment (mercerization) and bleaching. Treated fibers were incorporated in starch/ethylene vinyl alcohol copolymers (EVOH) blends. Mechanical and thermal properties of starch/EVOH/coir biocomposites were evaluated. Fiber morphology and the fiber/matrix interface were further characterized by scanning electron microscopy (SEM). All treatments produced surface modifications and improved the thermal stability of the fibers and consequently of the composites. The best results were obtained for mercerized fibers where the tensile strength was increased by about 53% as compared to the composites with untreated fibers, and about 33.3% as compared to the composites without fibers. The mercerization improved fiber-matrix adhesion, allowing an efficient stress transfer from the matrix to the fibers. The increased adhesion between fiber and matrix was also observed by SEM. Treatment with water also improved values of Youngs modulus which were increased by about 75% as compared to the blends without the fibers. Thus, starch/EVOH blends reinforced with the treated fibers exhibited superior properties than neat starch/EVOH.

Green coconut shells applied as adsorbent for removal of toxic metal ions using fixed-bed column technology

This study applies green coconut shells as adsorbent for the removal of toxic metal ions from aqueous effluents using column adsorption. The results show that a flow rate of 2 mL/min and a bed height of 10 cm are most feasible. Furthermore, larger amounts of effluent can be treated for removal of single ions. The breakthrough curves for multiple elements gave the order of adsorption capacity: Cu(+2) > Pb(+2) > Cd(+2) > Zn(+2) > Ni(+2). Real samples arising from the electroplating industry can be efficiently handled.

Improvement of polyvinyl alcohol properties by adding nanocrystalline cellulose isolated from banana pseudostems

Cellulose nanocrystals (CNCs) isolated from banana pseudostems fibers (BPF) of the Pacovan variety were used as fillers in a polyvinyl alcohol (PVOH) matrix to yield a nanocomposite. The fibers from the external fractions of the BPF were alkaline bleached and hydrolyzed under acidic conditions (H2SO4 62% w/w, 70 min, 45 °C) to obtain CNCs with a length (L) of 135.0 ± 12.0 nm and a diameter (D) of 7.2 ± 1.9 nm to yield an aspect ratio (L/D) of 21.2. The CNCs were applied to PVOH films at different concentrations (0%, 1%, 3%, and 5% w/w, dry basis). With higher concentrations of CNCs, the water-vapor barrier of the films increased, while the optical properties changed very little. Increasing the concentration of the CNCs up to 3% significantly improved the mechanical properties of the nanocomposite.

Enzymatic esterification of ethanol and oleic acid : a kinetic study

Abstract The formation of ethyl oleate from ethanol and oleic acid using a free or immobilised Rhizomucor miehei lipase as catalyst was evaluated in a biphasic system. Based on a 2 (3) factorial design previously developed [1] , it was possible to study the reaction kinetics. The data obtained indicated that the reaction follows a Michaelis–Menten kinetics and it is described by the ternary complex mechanism. Based on the proposed model, the kinetic constants to the esterification reaction, without considering substrate inhibition, were determined. The kinetic results showed that the free lipase had the same affinity for both substrates ( K m(Et) =1.79 M, K m(Ol) =1.80 M) while the lipase in its immobilised form had higher affinity for oleic acid ( K m,app(Et) =1.20 M, K m,app(Ol) =1.16×10 −8 M). It was also verified that the specificity was higher in the immobilised lipase system ( K s,app(Et) =2.90 mmol h −1 mg −1 M −1 ) than in the free one ( K s(Et) =0.637 mmol h −1 mg −1 M −1 ). Diffusional effects were detected for low ethanol and oleic acid concentrations, when using the enzyme in its immobilised form, and related to the effectiveness factor. The integrated Michaelis–Menten equation coupled to the kinetic constants obtained, accord well with experimental results.

Uso da casca de coco verde como adsorbente na remoção de metais tóxicos

Green coconut shells were treated with acid, base and hydrogen peroxide solutions for 3, 6, 12 and 24 h for removing toxic metals from synthetic wastewater. The removal of ions by the adsorbent treated with 0.1 mol L-1 NaOH/ 3h was 99.5% for Pb2+ and 97.9% for Cu2+. The removal of Cd2+, Ni2+, Zn2+, using adsorbent treated with 1.0 mol L-1 NaOH/3 h, was 98.5, 90.3 and 95.4%, respectively. Particle size, adsorbent concentration and adsorption kinetics were also studied. An adsorbent size of 60-99 mesh and a concentration of 30-40 g/L for 5 min exposure were satisfactory for maximum uptake of Pb2+, Ni2+, Cd2+, Zn2+ and Cu2+ and can be considered as promising parameters for treatment the aqueous effluents contaminated with toxic metals.

Seleção dos indicadores da qualidade das águas superficiais pelo emprego da análise multivariada

Multivariate statistical technique, factor analysis/principal component analysis (FA/PCA), was applied to identify the human activity effects and natural processes on surface water quality in Low Acarau basin, Ceara, Brazil. Water samples were collected in four different campaigns from Feb/2003 to Mar/2004, at seven sampling stations sited in low Acarau watershed. Twenty-five physical, chemical and bacteriological parameters were examined in this study. The FA/PCA allowed the identification of the total variance. The best model was adjusted with four components, explaining 82.1% of the data variance. The first factor was mainly associated with suspended solids defining the erosion process and runoff; that is, a suspended solids component. The second factor was mainly associated with sewage, agricultural runoff and others non-pontual pollution; the third one was defined as an organic component and represents the anthropogenic activites; while the fourth was mainly correlated with soluble salt, expressing the weathering and leaching. Besides, the factorial analysis did not result in data reduction, since 18 of the 25 parameters have been kept to explain 82% of the data variance.

Avaliação da vulnerabilidade ambiental de reservatórios à eutrofização

This work presents a tool to analyze the vulnerability of reservoirs to eutrophication, aiming to subsidize control and remediation actions related with this process. It was analyzed the water basins of Araras, Edson Queiroz and Jaibaras reservoirs, located in the Acarau watershed, Ceara, Brazil. The multi-criteria analyses methodology used, in order to define environmental vulnerability indicators to reservoir eutrophication, considered reservoir sensibility and pressure factors in the water basin responsible for the transport of sediments and nutrients to the reservoir. A Geographic Information System (GIS) with map algebra as major tool was applied to soil use and occupation, declivity and erosion indicators. It was identified high vulnerability to eutrophication in the three mentioned reservoirs because of the waterbasins susceptibility to erosion, high phosphorous load mainly from the extensive cattle raising and low relative depth of the reservoirs.

Pectin extraction from pomegranate peels with citric acid.

Pectins were extracted from pomegranate peels with citric acid, according to a central composite design with three variables: pH (2-4), temperature (70-90°C), and extraction time (40-150min). Fourier transform infrared (FTIR) spectroscopy was used to follow changes in material composition during the main steps of pectin extraction, and also to determine the degree of methyl esterification and galacturonic acid content of pectins produced under different conditions. Harsh conditions enhanced the extraction yield and the galacturonic acid contents, but decreased the degree of methoxylation. The optimum extraction conditions, defined as those predicted to result in a yield of galacturonic acid higher than 8g/100g while keeping a minimum degree of methoxylation of 54% were: 88°C, 120min, pH 2.5. Close agreement was found between experimental and predicted values at the extraction conditions defined as optimum.

A novel green approach for the preparation of cellulose nanowhiskers from white coir

The aim of this work was to optimize the extraction of cellulose nanowhiskers (CNW) from unripe coconut husk fibers (CHF). The CHF was delignified using organosolv process, followed by alkaline bleaching (5% (w/w) H2O2+4% (w/w) NaOH; 50°C, 90 min). The CHF was subsequently hydrolyzed with 30% (v/v) sulfuric acid (60°C, 360 min). The process yielded a partially delignified acetosolv cellulose pulp and acetic black liquor, from which the lignin was recovered. The CNW from the acetosolv pulp exhibited an average length of 172±88 nm and a diameter of 8±3 nm, (aspect ratio of 22±8). The surface charge of the CNW was -33 mV, indicating a stable aqueous colloidal suspension. The nanocrystals presented physical characteristics close to those extracted from cellulose pulp made by CHF chlorine-pulping. This approach offers the additional advantage of extracting the lignin as an alternative to eradication.