Adsorption of aflatoxin B1 by different antimycotoxin additives: bentonite, clinoptilolite, and beta-glucans extracted from yeast cell wall.

The present study aims to evaluate and compare antimycotoxin additives (AMAs) composed of bentonite (AMA 1), clinoptilolite (AMA 2), and beta-glucans extracted from yeast cell wall (AMA 3), with respect to their ability to bind Aflatoxin B1 (AFB1) using the isothermal models of Freundlich, Langmuir, and BET. The additives were submitted to an in vitro adsorption experiment with AFB1 (0.05-4 mg L-1), using solutions of pH 3 and pH 6, with an inclusion rate of 0.5%, and analyzed by HPLC-MS/MS. At pH 3, for the seven concentrations evaluated, AMA 1 obtained adsorption rates (99.69 to 99.98%) higher (p < 0. 05) than the other AMAs, which were from 82.97 to 88.72% (AMA 2) and from 79.43 to 89.32% (AMA 3). At pH 6, in concentrations of 1, 2, and 4 mg L-1 of AFB1, AMA 1 obtained higher (p < 0.05) adsorption results (97.86 to 99.86%) than AMA 2 (91.98 to 96.12%) and AMA 3 (87.56 to 93.50%). The Freundlich model best fitted the AMA 1 adsorption data. For the other additives, the Langmuir model obtained the best fit, demonstrating qm of 8.6 mg g-1 at pH 3 and 2.3 mg g-1 at pH 6 for AMA 2; and for AMA 3, with qm of 3.4 mg g-1 at pH 3 and 2.3 mg g-1 at pH 6. The isotherm models work as an effective tool to describe the adsorption process whereas the AMA adsorption capacity varies as a function of product composition, pH, and mycotoxin content.

Outstanding adsorption capacity of iron oxide synthesized with extract of açaí berry residue: kinetic, isotherm, and thermodynamic study for dye removal.

Contamination of water by toxic dyes is a serious environmental problem. Adsorbents prepared by an environmentally safe route have stood out for application in pollutant removal. Herein, iron oxide-based nanomaterial composed of Fe(III)-OOH and Fe(II/III) bound to proanthocyanidins, with particles in the order of 20 nm, was prepared by green synthesis assisted by extract of açaí (Euterpe oleracea Mart.) berry seeds from an agro-industrial residue. The nanomaterial was applied in the adsorption of cationic dyes. Screening tests were carried out for methylene blue (MB), resulting in an outstanding maximum adsorption capacity of 531.8 mg g-1 at 343 K, pH 10, 180 min. The kinetics followed a pseudo-second-order model and the isotherm of Fritz-Schülnder provided the best fit. Thermodynamic data show an endothermic process with entropy increase, typical of chemisorption. The proposed mechanism is based on the multilayer formation over a heterogeneous adsorbent surface, with chemical and electrostatic interactions of MB with the iron oxide nanoparticles and with the proanthocyanidins. The high adsorption efficiency was attributed to the network formed by the polymeric proanthocyanidins that entangled and protected the iron oxide nanoparticles, which allowed the reuse of the nanomaterial for seven cycles without loss of adsorption efficiency.

Novel Adsorbent Material from Plinia cauliflora for Removal of Cationic Dye from Aqueous Solution.

The food industry is responsible for the generation of large amounts of organic residues, which can lead to negative environmental and economic impacts when incorrectly disposed of. The jaboticaba peel is an example of organic waste, widely used in industry due to its organoleptic characteristcs. In this study, residues collected during the extraction of bioactive compounds from jaboticaba bark (JB) were chemically activated with H3PO4 and NaOH and used to develop a low-cost adsorbent material for the removal of the cationic dye methylene blue (MB). For all adsorbents, the batch tests were carried out with the adsorbent dosage of 0.5 g L-1 and neutral pH, previously determined by 22 factorial design. In the kinetics tests, JB and JB-NaOH presented a fast adsorption rate, reaching equilibrium in 30 min. For JB-H3PO4, the equilibrium was reached in 60 min. JB equilibrium data were best represented by the Langmuir model and JB-NaOH and JB-H3PO4 data by the Freundlich model. The maximum adsorption capacities from JB, JB-NaOH, and JB-H3PO4 were 305.81 mg g-1, 241.10 mg g-1, and 122.72 mg g-1, respectively. The results indicate that chemical activations promoted an increase in the volume of large pores but interacted with functional groups responsible for MB adsorption. Therefore, JB has the highest adsorption capacity, thus presenting as a low-cost and sustainable alternative to add value to the product, and it also contributes to water decontamination studies, resulting in a zero-waste approach.

Formulation of Novel Composite (Activated Nanoclay/Hydrocolloid of Nostoc sphaericum) and Its Application in the Removal of Heavy Metals from Wastewater.

The removal of heavy metals from wastewater is an environmental challenge which demands the use of environmentally friendly materials that promote a circular economy. This study aimed to apply a novel composite of an activated nanoclay/hydrocolloid in the removal of heavy metals from wastewater. A composite blended under pressure was prepared with spray-dried hydrocolloid derived from Nostoc sphaericum algae and activated nanoclay in an acid medium and 1M NaCl. The composite and components were analyzed through infrared (IR), X-ray (XR), ζ potential, cation exchange capacity (CEC), particle size, and SEM images. The composite was subjected to the adsorption of heavy metals (Pb, As, Zn, and Cd) at pH 4.5 and the removal percentage, kinetics, and adsorption isotherms were evaluated. It was observed that the activated nanoclay and the composite that presented a particle size of around 400 nm significantly increased (p-value < 0.05) the CEC, ζ potential, the functional groups, and chelating components, removing heavy metals above 99% for Pb, As 33%, Cd 15%, and Zn 10%. Adsorption kinetics was adjusted to the pseudo second-order model (R2 > 0.98), and the Langmuir and Freundlich models better represented the sorption isotherm at 20 °C. The formulated composite presents a good ability to remove heavy metals in wastewater.

Storage Conditions and Adsorption Thermodynamic Properties for Purple Corn.

Adsorption isotherms provide insight into the thermodynamic properties governed by food storage conditions. Adsorption isotherms of purple corn of the Canteño variety were evaluated at 18, 25, and 30 °C, for the equilibrium relative humidity (ERH) range between 0.065 and 0.95. The equilibrium moisture (Xe) was determined by the continuous weight-change method. Seven mathematical models of isotherms were modeled, using the coefficient of determination R2, mean absolute error (MAE), and estimated standard error (ESE) as the convergence criterion. Thermodynamic parameters such as isosteric heat (qst), Gibbs Free Energy (ΔG), differential entropy (ΔS), activation energy (Ea), and compliance with the isokinetic law were evaluated. It was observed that the adsorption isotherms presented cross-linking around 75% ERH and 17% Xe, suggesting adequate storage conditions at these values. The GAB and Halsey models reported better fit (R2 > 97%, MAE < 10%, ESE < 0.014 and random residual dispersion). The reduction of Xe from 17 to 7%, increases qst, from 7.7022 to 0.0165 kJ/g, while ΔG decreases considerably with the increase in Xe, presenting non-spontaneous endergonic behavior, and linear relationship with ΔS, evidencing compliance with the isokinetic theory, governed by qst. Ea showed that more energy is required to remove water molecules from the upper layers bound to the monolayer, evaluated using CGAB. The models predicted the storage conditions, and the thermodynamic parameters show the structural stability of the purple corn grains of the Canteño variety during storage.

Protein Adsorption onto Modified Porous Silica by Single and Binary Human Serum Protein Solutions.

Typical porous silica (SBA-15) has been modified with pore expander agent (1,3,5-trimethylbenzene) and fluoride-species to diminish the length of the channels to obtain materials with different textural properties, varying the Si/Zr molar ratio between 20 and 5. These porous materials were characterized by X-ray Diffraction (XRD), N2 adsorption/desorption isotherms at -196 °C and X-ray Photoelectron Spectroscopy (XPS), obtaining adsorbent with a surface area between 420-337 m2 g-1 and an average pore diameter with a maximum between 20-25 nm. These materials were studied in the adsorption of human blood serum proteins (human serum albumin-HSA and immunoglobulin G-IgG). Generally, the incorporation of small proportions was favorable for proteins adsorption. The adsorption data revealed that the maximum adsorption capacity was reached close to the pI. The batch purification experiments in binary human serum solutions showed that Si sample has considerable adsorption for IgG while HSA adsorption is relatively low, so it is possible its separation.

Synthesis of Chitosan-Polyvinyl Alcohol Biopolymers to Eliminate Fluorides from Water.

The fluoride content in groundwater varies depending on geological configuration. Fluoride problems tend to occur in places where these minerals are most abundant in rocks. The objective of the present work was to synthesize four biopolymers based on chitosan-polyvinyl alcohol (Ch-PVA) cross-linked with sodium tripolyphosphate pentabasic (TPP) and ethylene glycol diglycidyl ether (EGDE) and determine their ability to remove fluoride from water. The characterization of the Ch-PVA beads was performed by way of Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The percentage of humidity and the point of zero charge were determined. The Ch-PVA beads showed a surface area of 63.87 m2 g-1, a pore size of 7.6 nm, a point of zero charge of 7.4, and 98.6% humidity. The kinetic adsorption study was adjusted to the pseudo-second-order model and the adsorption equilibrium data were adjusted to the Freundlich adsorption isotherm, showing a maximum fluoride adsorption capacity of 12.64 mg.g-1 at pH 7 and 30 °C, for the beads of Ch-PVA-NaOH-TPP. According to the thermodynamic parameters: -∆Go, +∆Ho and -∆So, fluoride adsorption is spontaneous, endothermic in nature and there is no random energy change in the solid/liquid interface during the adsorption process.

Preparation and evaluation of hydrocalumite-iron oxide magnetic intercalated with dodecyl sulfate for removal of agrichemicals.

The magnetic adsorbent prepared with hydrocalumite-iron oxide (HC/Fe) modified with dodecyl sulfate (DS) was examined for the removal of the agrichemicals atrazine (ATZ) and chlorpyrifos (CPF) from aqueous solution. The adsorbent HC-DS/Fe was characterized by infrared spectroscopy (IR), Raman spectroscopy, X-ray diffractometry (XRD) and atomic absorption spectrometry. The effects of adsorbent dosage, contact time, pH and initial concentration of ATZ and CPF were evaluated. HC-DS/Fe presented a maximum adsorption capacity for ATZ of 4.5 mg g-1 (30 min) and for CPF of 72.9 mg g-1 (210 min) at 25 °C. HC-DS/Fe can be readily removed from the aqueous solution by magnetization because of its magnetic properties. The free energy variation for HC-DS/Fe during the adsorption of the ATZ was -48.78 to -53.91 kJ mol-1 and for the CPF of -55.79 to -59.28 kJ mol-1, suggesting the spontaneity of the adsorption process. The positive value of △H suggests an endothermic process for the interaction of ATZ and CPF by HC-DS/Fe. This adsorbent showed satisfactory results when used in the treatment of a sample of river water, fortified with the agrichemicals chlorpyrifos, atrazine, thiamethoxam and acetamiprid.

Applicability of the Gibbs Adsorption Isotherm to the analysis of experimental surface-tension data for ionic and nonionic surfactants.

The Gibbs Adsorption Isotherm equation is a two-dimensional analogous of the Gibbs-Duhem equation, and it is one of the cornerstones of interface science. It is also widely used to estimate the surface excess concentration (SEC) for surfactants and other compounds in aqueous solution, from surface tension measurements. However, in recent publications some authors have cast doubt on this method. In the present work, we review some of the best available surface tension experimental data, and compare estimations of the SEC, using the Gibbs isotherm method (GIM), to direct measurements reported in the literature. This is done for both nonionic and ionic surfactants, with and without added salt. Our review leads to the conclusion that the GIM has a very solid agreement with experiments, and that it does estimate accurately the SEC for surfactant concentrations smaller than the critical micellar concentration (CMC).

Modelling the effect of temperature on the water sorption isotherms of chitosan films

Abstract The interaction of the water molecules from the environment with foods and other materials can be evaluated using sorption isotherms. Films and biodegradable films are susceptible to changes in their functional characteristics due to adsorbed water. The amount of moisture that biodegradable films can adsorb depends on the temperature, relative humidity of the storage area and chemical composition. Several mathematical models can be used to describe the behavior of sorption isotherms in biodegradable films and some of them have been modified to include the temperature parameter into the equation. In this research, the original and modified BET, GAB, Halsey, Henderson and Oswin models were assessed to determine their suitability describing the behavior of moisture adsorption isotherms of chitosan films at 15, 20, 25 and 30 °C. The modified models of GAB, Oswin and Halsey gave the best fit to the experimental sorption data of the chitosan films, with R2 values higher than 0.97 demonstrating that those models describe better the sorption isotherms at the temperatures studied.

Effect of equilibrium moisture content on barrier, mechanical and thermal properties of chitosan films.

Water molecules modify the properties of biodegradable films obtained from hydrophilic materials. Most studies dealing with thermal, mechanical and barrier properties of hydrophilic films are carried out under one relative humidity (RH) condition. The objective of this work was to evaluate the effect of the moisture content on the thermal, mechanical and barrier properties of chitosan films under several RH conditions. Microclimates, obtained with saturated salt solutions were used for conditioning samples and the properties of the films were evaluated under each RH condition. Chitosan films absorbed up to 40% of moisture at the higher RH studied. The percentage of elongation and the water vapour permeability increased while tensile strength, Young's modulus and glass transition temperature decreased, when the moisture content increased. The results suggest that the water molecules plasticized the polymer matrix, changing the properties when the films were in contact with high RH environments.

Biosorption of cadmium with brown macroalgae.

Sorption experiments for cadmium removal using two brown macroalgae Lessonia nigrescens and Durvillaea antarctica were carried out. Although both types of algae were capable of retaining cadmium, differences in their performance were observed. The optimum pH was 3.7±0.2, and to achieve the equilibrium, 5 days of contact time were necessary for both biosorbents. The maximum experimental uptake obtained was similar for the two biosorbents: 95.3 mg Cd g(-1) by D. antarctica and 109.5 mg Cd g(-1) by L. nigrescens. The Langmuir model described the equilibrium sorption isotherms very well for both biosorbents and the Lagergren pseudo primer order model described the sorption kinetics for L. nigrescens satisfactorily and the Ho and Mckay pseudo second order model for D. antarctica. It was found that cadmium uptake by D. antarctica was faster than by L. nigrescens.

Assessment of cadmium and iron adsorption in sediment, employing a flow injection analysis system with on line filtration and detection by flame atomic absorption spectrometry and thermospray flame furnace atomic absorption spectrometry.

This work presents an evaluation of iron and cadmium adsorption in sediment of the Furnas Hydroelectric Plant Reservatory located in Alfenas, Minas Gerais (Brazil). The metal determination was done employing a flow injection analysis (FIA) with an on-line filtering system. As detection techniques, flame atomic absorption spectrometry (FAAS) for iron and thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for cadmium determinations were used. The developed methodology presented good limits of detection, being 190 µg L(-1) for iron and 1.36 µg L(-1) for cadmium, and high sampling frequency for both metals 144 and 60 readings h(-1) for iron and cadmium, respectively. Both metals obey the Langmuir model, with maximum adsorptive capacity of 0⋅169 mg g(-1) for iron and 7⋅991 mg g(-1) for cadmium. For iron, a pseudo-first-order kinetic model was obtained with a theoretical Q(e)=9⋅8355 mg g(-1) (experimental Q(e)=9⋅5432 mg g(-1)), while for cadmium, a pseudo-second-order kinetic model was obtained, with a theoretical Q(e)=0.3123 mg g(-1) (experimental Q(e)=0⋅3052 mg g(-1)).

Study on Thermodynamics and Adsorption kinetics of Purified endoglucanase (CMCase) from Penicillium notatum NCIM NO-923 produced under mixed solid-state fermentation of waste cabbage and Bagasse

In the current study, one thermostable endoglucanase was purified from Penicillium notatum NCIM NO-923 through mixed solid state fermentation of waste cabbage and bagasse. The molecular weight of the purified enzyme was 55kDa as determined by SDS polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme had low activation energy (Ea) of 36.39KJ mol-1 for carboxymethyl cellulose hydrolysis and the enthalpy and entropy for irreversible inactivation was 87 kJ mol −1 and 59.3 J mol −1 K−1 respectively. The enzyme was quite thermostable with a Tm value of 62.2˚C. The pKa1 and pKa2 of ionizable groups of the active sites were 2.5 and 5.3 respectively. Apparent Km, Vmax and Kcat of the enzyme were found to be 5.2 mg mL-1, 80 U/gds and 322.4 sec-1 respectively. The enzyme showed about 1.4 fold increased activity in presence of 10mM MgSO4. Adsorption of endoglucanase on Avicel at wide pH range was studied at different temperatures. Langmuir type adsorption isotherm at 10˚C showed maximum adsorption strength of enzyme at pH 3.0, which was in a range of optimum pH of the enzyme.

Study on thermodynamics and adsorption kinetics of purified endoglucanase (CMCase) from Penicillium notatum NCIM NO-923 produced under mixed solid-state fermentation of waste cabbage and bagasse.

In the current study, one thermostable endoglucanase was purified from Penicillium notatum NCIM NO-923 through mixed solid state fermentation of waste cabbage and bagasse. The molecular weight of the purified enzyme was 55kDa as determined by SDS polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme had low activation energy (Ea) of 36.39KJ mol(-1) for carboxymethyl cellulose hydrolysis and the enthalpy and entropy for irreversible inactivation was 87 kJ mol (-1) and 59.3 J mol (-1) K(-1) respectively. The enzyme was quite thermostable with a Tm value of 62.2°C. The pKa1 and pKa2 of ionizable groups of the active sites were 2.5 and 5.3 respectively. Apparent Km, Vmax and Kcat of the enzyme were found to be 5.2 mg mL(-1), 80 U/gds and 322.4 sec(-1) respectively. The enzyme showed about 1.4 fold increased activity in presence of 10mM MgSO4. Adsorption of endoglucanase on Avicel at wide pH range was studied at different temperatures. Langmuir type adsorption isotherm at 10°C showed maximum adsorption strength of enzyme at pH 3.0, which was in a range of optimum pH of the enzyme.

Study on Thermodynamics and Adsorption kinetics of Purified endoglucanase (CMCase) from Penicillium notatum NCIM NO-923 produced under mixed solid-state fermentation of waste cabbage and Bagasse

In the current study, one thermostable endoglucanase was purified from Penicillium notatum NCIM NO-923 through mixed solid state fermentation of waste cabbage and bagasse. The molecular weight of the purified enzyme was 55kDa as determined by SDS polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme had low activation energy (Ea) of 36.39KJ mol-1 for carboxymethyl cellulose hydrolysis and the enthalpy and entropy for irreversible inactivation was 87 kJ mol 1 and 59.3 J mol 1 K1 respectively. The enzyme was quite thermostable with a Tm value of 62.2C. The pKa1 and pKa2 of ionizable groups of the active sites were 2.5 and 5.3 respectively. Apparent Km, Vmax and Kcat of the enzyme were found to be 5.2 mg mL-1, 80 U/gds and 322.4 sec-1 respectively. The enzyme showed about 1.4 fold increased activity in presence of 10mM MgSO4. Adsorption of endoglucanase on Avicel at wide pH range was studied at different temperatures. Langmuir type adsorption isotherm at 10C showed maximum adsorption strength of enzyme at pH 3.0, which was in a range of optimum pH of the enzyme.

INFLUENCIA DEL pH SOBRE LA ADSORCIÓN EN CARBÓN ACTIVADO DE Cd(II) Y Ni(II) DESDE SOLUCIONES ACUOSAS / INFLUENCE OF THE pH ON THE ADSORPTION IN ACTIVATED CARBON OF Cd(II) Y Ni(II) FROM AQUOEOUS SOLUTIONS / INFLUÊNCIA DO PH SOBRE A ADSORÇÃO EM CARVÃO ATIVADO DE Cd(II) E Ni(II) DESDE SOLUÇÕES ACUOSAS

La adsorción de iones Cd(II) y Ni(II) desde soluciones acuosas sobre carbón activado se estudia con diferentes valores de pH. La adsorción de los iones se realiza en dos condiciones de pH de la solución: en la primera el pH varía en el transcurso del proceso a medida que los iones se adsorben y en la segunda el pH se mantiene fijo durante la adsorción. Cuando no se realiza un control en el pH de la solución se observan incrementos en la concentración de los iones hidronio que alcanzan un valor máximo alrededor de pH 4, para los dos iones, y cuyos valores son de 346 mmol mL¹ para el caso de la adsorción de Cd(II) y de 436 mmol mL-1 para el Ni(II). Para todos los valores de pH y las dos condiciones del proceso de adsorción se observa una mayor cantidad de Ni(II) adsorbida con valores entre 0,04 y 0,42 mmol.g-1, mientras que para el Cd(II) la máxima cantidad adsorbida es de 0,16 mmol.g¹. El aumento de los iones hidronio en las soluciones de Cd(II) y Ni(II), en las que no se controla el valor del pH, favorece el proceso de adsorción, en tanto que al mantener un pH fijo en la solución, se obtienen adsorciones menores de los iones.

The Cd (II) and Ni(II) ions adsorption from aqueous solutions on activated carbon is studied to different values of pH. The ions adsorption is carried out under two conditions of pH solution: in the first one, the pH changes in the course of the process as the ions are adsorbed; in the second one, the pH is kept fixed during the adsorption. When the solution is not controlled, the hydronium ions concentration increases, reaching a maximum value around a pH of 4, for both ions, whose values are of 346 mmolmL-1 for the case of the adsorption of Cd (II) and of 436 mmol.mL-1 for Ni(II). For all the pH values and the two conditions of the adsorption process, much more quantity of Ni (II) is adsorbed with values between 0.04 and 0.42 mmol.g-1, while for the Cd (II) the maximum amount adsorbed is 0.16 mmol.g-1. The increase of the hydronium ions in the Cd(II) and Ni(II) solutions, in which the value of the pH is not controlled, helps the process of adsorption, while keeping pH fixed in the solution, ions are adsorbed in a less quantity.

Neste artigo se estuda a adsorção de iones Cd(II) e Ni(II) de soluções aquosas sobre carvão ativado a diferentes valores de pH. A adsorção dos iones se realiza baixo duas condições de pH da solução: na primeira o pH varia em decorrência do processo à medida que os iones se adsorvem; na segunda o pH se mantém fixo durante a adsorção. Quando não se realiza um controle no pH da solução se observam incrementos na concentração de iones hidrónio, que atinge um valor máximo arredor de pH 4, para os dois iones, cujos valores são 346 mmolmL-1 para o caso da adsorção de Cd(II) e 436 mmol.mL-1 para o Ni(II). Para todos os valores de pH e as duas condições do processo de adsorção se observa uma maior quantidade de Ni(II) adsorvida com valores entre 0,04 e 0,42 mmol.g-1, enquanto para o Cd(II) a máxima quantidade adsorvida é 0,16 mmol.g-1. O aumento dos iones hidrónio nas soluções de Cd(II) e Ni(II), nas que não se controla o valor do pH, favorece o processo de adsorção; enquanto ao manter um pH fixo na solução se obtêm adsorções menores dos iones.

Comportamento higroscópico de pós de manga das variedades coité e espada e avaliação das características físico-químicas / Hygroscopic behavior of mango powder of coité and espada cultivar and evaluation of physicochemical characteristics

A manga, embora muito apreciada pelos seus aspectos nutricionais e sensoriais, é altamente perecível e requer técnicas peculiares para sua conservação e comercialização. Nesse contexto, este trabalho teve por objetivos avaliar o comportamento higroscópico dos pós de manga das variedades Coité e Espada por meio das isotermas de adsorção e também analisar as características físico-químicas dessas variedades de manga nas formas in natura e em pó. Os resultados indicaram que os pós de manga não mostraram diferença significativa em relação às características físico-químicas, exceto para o valor de pH. Contrariamente, nas amostras in natura, apenas o pH não apresentou diferença significativa. Entre os modelos matemáticos utilizados para ajuste das isotérmicas de adsorção, o modelo de GAB foi o mais adequado para se ajustar aos dados experimentais, apresentando o teor de água da monocamada (gx100g-1 de matéria seca) de 0,09086 e 0,08857, com erros relativos médios de 6,76 e 2,86 por cento para Coité e Espada, respectivamente. O modelo de Oswin foi o segundo modelo matemático que apresentou valores muito próximos de encaixar o modelo de GAB.

The mango, is much appreciated by its nutritional and sensorial characteristics, but is highly perishable and requires specific techniques for its conservation and marketing. In this sense, this study aimed to evaluate the hygroscopic behavior of powdered mango varieties Coite and Espada cv. using adsorption isotherms and physicochemical characteristics of theses varieties of mango in natura and powder. The results showed that the mango powders didn't show significant difference in relation to physicochemical characteristics, except for the pH value. In contrary, in nature samples only the pH didn´t show significant difference. Among the mathematical models used to fit the adsorption isotherms, the GAB model was the more appropriate to fit the experimental data showing the water content of the monolayer of 0,09086 and 0,08857 (gx100g-1 dry matter) and relative average errors of 6,76 and 2.86 percent for Coité and Espada, respectively. The Oswin model was the second mathematical model that showed very close values to fit the GAB model.

Entalpia de inmrrsión de monolitos de carbón activado en solvente apolar / Immersin enthalppy of activated carbon monoliths in nonpolar solvent / Entlpia de inmerrsión de monolitos de carbon ativado em solvente apolar

En este trabajo se presentan los resultados obtenidos de la calorimetría de inmersión en benceno sobre monolitos de carbón activado tipo disco y panal, que se obtuvieron mediante activación química de cascara de coco con cloruro de zinc a diferentes concentraciones. Adicionalmente, las estructuras fueron caracterizadas por adsorción de N2 a 77 K. Las entalpías de inmersión determinadas se encuentran entre 73,5 y 164,2 Jg-1; con los datos de inmersión se calculó el área accesible y se comparó con el área obtenida mediante adsorción de N2 a 77K, encontrando una buena correlación. En todas las muestras se observó un aumento de la entalpía de inmersión en benceno con el área superficial, igualmente una disminución de la energía característica con el aumento del volumen de poro.

This work presents the results obtained from immersion calorimetry in benzene on activated carbon monoliths disc and honeycomb type that were obtained from coconut shell using chemical activation with zinc chloride at different concentrations. The structures were characterized by adsorption N2 at 77 K. The immersion enthalpies are between 73.5 and 164.2 Jg-1. Using immersion enthalpy data the accessible area was calculated and compared with the area obtained by N2 adsorption at 77K. A good correlation was found. In all the samples was observed an increase in the immersion enthalpy into benzene with the surface area. In addition there was a decrease in the energy characteristic with increasing pore volume.

Neste trabalho se apresentam os resultados obtidos da calorimetría de imersão em benzeno sobre monolitos de carvão ativado tipo disco e panal que se obtiveram mediante activação química de casca de coco com cloreto de zinco a diferentes concentrações. Adicionalmente as estruturas foram caracterizadas por adsorção de N2 a 77 K. As entalpías de imersão determinadas se encontram entre 73,5 e 164,2 Jg-1, com os dados de imersão se calculo o área acessível e se comparo com o área obtida mediante adsorção de N2 a 77K, encontrando uma boa correlação. Em todas as mostras se observo um aumento da entalpía de imersão em benzeno com o área superficial. Ademais se observou uma diminuição da energia característica com o aumento do volume de poro.

Comportamento higroscópico de pós de manga das variedades coité e espada e avaliação das características físico-químicas

The mango, is much appreciated by its nutritional and sensorial characteristics, but is highly perishable and requires specific techniques for its conservation and marketing. In this sense, this study aimed to evaluate the hygroscopic behavior of powdered mango varieties Coite and Espada cv. using adsorption isotherms and physicochemical characteristics of theses varieties of mango in natura and powder. The results showed that the mango powders didn't show significant difference in relation to physicochemical characteristics, except for the pH value. In contrary, in nature samples only the pH didn´t show significant difference. Among the mathematical models used to fit the adsorption isotherms, the GAB model was the more appropriate to fit the experimental data showing the water content of the monolayer of 0,09086 and 0,08857 (gx100g-1 dry matter) and relative average errors of 6,76 and 2.86% for Coité and Espada, respectively. The Oswin model was the second mathematical model that showed very close values to fit the GAB model.

A manga, embora muito apreciada pelos seus aspectos nutricionais e sensoriais, é altamente perecível e requer técnicas peculiares para sua conservação e comercialização. Nesse contexto, este trabalho teve por objetivos avaliar o comportamento higroscópico dos pós de manga das variedades Coité e Espada por meio das isotermas de adsorção e também analisar as características físico-químicas dessas variedades de manga nas formas in natura e em pó. Os resultados indicaram que os pós de manga não mostraram diferença significativa em relação às características físico-químicas, exceto para o valor de pH. Contrariamente, nas amostras in natura, apenas o pH não apresentou diferença significativa. Entre os modelos matemáticos utilizados para ajuste das isotérmicas de adsorção, o modelo de GAB foi o mais adequado para se ajustar aos dados experimentais, apresentando o teor de água da monocamada (gx100g-1 de matéria seca) de 0,09086 e 0,08857, com erros relativos médios de 6,76 e 2,86% para Coité e Espada, respectivamente. O modelo de Oswin foi o segundo modelo matemático que apresentou valores muito próximos de encaixar o modelo de GAB.