Adriana S. Franca

Evaluation of untreated coffee husks as potential biosorbents for treatment of dye contaminated waters.

The objective of this work was to propose an alternative use for coffee husks (CH), a coffee processing residue, as untreated sorbents for the removal of methylene blue (MB) from aqueous solutions. The effects of solution temperature, pH, biosorbent dosage and contact time on MB removal were investigated. The experimental adsorption equilibrium data were fitted to both Langmuir and Freundlich adsorption models. The biosorption kinetics was determined by fitting first and second-order kinetic models to the experimental data, with the second-order model providing the best description of MB adsorption onto coffee husks. pH variations did not present a significant effect on MB removal. Evaluation of thermodynamics parameters indicated that the adsorption is spontaneous and endothermic. The experimental data obtained in the present study demonstrated coffee husks to be suitable candidates for use as biosorbents in the removal of cationic dyes.

Microwave heating of foodstuffs

Abstract The temperature distribution in a product submitted to microwave radiation is governed by the interaction and absorption of radiation by the medium and the accompanying transport processes due to the dissipation of electromagnetic energy into heat. Thus, modeling of microwave heating involves coupling the models for microwave power absorption and temperature distribution inside the product. In this study, a model was presented, for which the absorbed microwave power was obtained by solving Maxwells equations and then incorporated as a source term in the transient heat equation. The finite element method was used for discretization of the governing equations. The proposed methodology was then applied to simulate microwave heating of foodstuffs. A comparison of the power distribution obtained by solving Maxwells equation to that by using Lamberts indicated the sample size above which the Lamberts law limit is valid is higher for cylinders compared to slabs. The simulation results showed that microwave heating is significantly dependent on sample size and shape. It was also observed that heating is quite dependent on radiation frequency, and that power absorption and radiation penetration are more effective at lower frequencies than at higher ones. An on/off operating system was simulated and coupled with sample rotation, resulting in more uniform temperature profiles compared to each technique applied separately. Simulation runs were also performed for different materials, resulting in quite different power distributions.

Activated carbons from waste biomass: An alternative use for biodiesel production solid residues

Defective coffee press cake, a residue from coffee oil biodiesel production, was evaluated as raw material for production of an adsorbent for removal of methylene blue (MB) from aqueous solution. Batch adsorption tests were performed at 25 degrees C and the effects of particle size, contact time, adsorbent dosage and pH were investigated. Preliminary adsorption tests indicated that thermal treatment is necessary in order to improve adsorption capacity. Adsorption kinetics was determined by fitting first and second-order kinetic models to the experimental data, with the second-order model providing the best description of MB adsorption onto the prepared adsorbent. The experimental adsorption equilibrium data were fitted to Langmuir, Freundlich and Temkin adsorption models, with the last two providing the best fits. The experimental data obtained in the present study indicated that this type of waste material is a suitable candidate for use in the production of adsorbents for removal of cationic dyes, thus contributing for the implementation of sustainable development in both the coffee and biodiesel production chains.

A preliminary study on the feasibility of using the composition of coffee roasting exhaust gas for the determination of the degree of roast

Variations in the chemical composition profile of the gas evolved during roasting of coffee were qualitatively monitored with the aim of further establishing a chemical criterion for determination of the degree of roast. Simultaneously, the variations in the beans physical properties, such as volume, weight loss, and moisture content, were also monitored. Three hundred grams of coffee were roasted in a lab-scale roaster and the optimum degree of roast was reached in 9 min. The gas evolved during roasting was collected for gas chromatographic analysis. The chromatograms representing the evolution of the gas composition profile showed that a group of compounds will first appear close to the optimum degree of roast time. This indicated the feasibility of using such compounds as chemical descriptors when establishing a scientific criterion for determination of the degree of roast.

Microwave assisted thermal treatment of defective coffee beans press cake for the production of adsorbents

Defective coffee press cake, a residue from coffee oil biodiesel production, was evaluated as an adsorbent for removal of basic dyes (methylene blue--MB) from aqueous solutions. The adsorbent was prepared by microwave treatment, providing a significant reduction in processing time coupled to an increase in adsorption capacity in comparison to conventional carbonization in a muffle furnace. Batch adsorption tests were performed at 25 degrees C and the effects of particle size, contact time, adsorbent dosage and initial solution pH were investigated. Adsorption kinetics was better described by a second-order model. The experimental adsorption equilibrium data were fitted to Langmuir, Freundlich and Tempkin adsorption models, with Langmuir providing the best fit. The results presented in this study show that microwave activation presents great potential as an alternative method in the production of adsorbents.

Chemical characterisation of non-defective and defective green arabica and robusta coffees by electrospray ionization-mass spectrometry (ESI-MS)

The coffee roasted in Brazil is considered to be of low quality, due to the presence of defective coffee beans that depreciate the beverage quality. These beans, although being separated from the non-defective ones prior to roasting, are still commercialized in the coffee trading market. Thus, it was the aim of this work to verify the feasibility of employing ESI-MS to identify chemical characteristics that will allow the discrimination of Arabica and Robusta species and also of defective and non-defective coffees. Aqueous extracts of green (raw) defective and non-defective coffee beans were analyzed by direct infusion electrospray ionization mass spectrometry (ESI-MS) and this technique provided characteristic fingerprinting mass spectra that not only allowed for discrimination of species but also between defective and non-defective coffee beans. ESI-MS profiles in the positive mode (ESI(+)-MS) provided separation between defective and non-defective coffees within a given species, whereas ESI-MS profiles in the negative mode (ESI(-)-MS) provided separation between Arabica and Robusta coffees.

Evaluation of the potential of FTIR and chemometrics for separation between defective and non-defective coffees

The objective of this work was to evaluate the potential of Fourier transform infrared spectroscopy (FTIR) for the discrimination of defective and non-defective coffee beans. Defective (black, immature and sour) and non-defective Arabica coffee beans were submitted to FTIR analysis by transmittance readings employing KBr discs and reflectance readings employing attenuated total reflectance (ATR) and diffuse reflectance (DR) accessories. Multivariate statistical analysis (PCA, clusters) was performed in order to verify the possibility of discrimination between defective and non-defective coffee samples. A clear separation between defective and non-defective coffee beans was observed, based on both PCA and cluster analysis of the reflectance spectra (ATR and DR accessories) and of the first derivatives of the transmittance spectra (KBr discs). Such results indicate that FTIR analysis has the potential for the development of a fast and reliable analytical methodology for the discrimination between defective and non-defective coffee beans.

Modeling and simulation of petroleum coke calcination in rotary kilns

Abstract A one-dimensional mathematical model was developed for the simulation of petroleum coke calcination in rotary kilns. The model is comprised of 14 ordinary differential equations derived from mass and energy conservation principles. The system of equations is solved by a fourth-order Runge–Kutta method. The model predicts, in the axial direction, temperature profiles for the bed of particles, the gas phase and the kiln internal wall. It also predicts the composition profiles for the gas and solid phases. The modeling of the axial flow of the bed includes the rheological characteristics of the particulate system. The results from the simulation of the calcination systems presented better agreement with measured industrial data than other simulation results available in the literature.

FTIR Analysis for Quantification of Fatty Acid Methyl Esters in Biodiesel Produced by Microwave-Assisted Transesterification

Biodiesel was produced by microwave-assisted transesterification of soybean oil with methanol as esterifying agent and sodium methoxide as catalyst. Fourier transform infrared spectroscopy was employed as a fast and reliable analytical technique for the quantification of fatty acid methyl ester content in the produced biodiesel. The quantification was done with the use of a partial least squares model developed based on the infrared spectra obtained. It was shown that microwave irradiation is capable of reducing the reaction time when compared to conventional mechanically stirred reactors used for biodiesel production. In addition, quantification of fatty acid methyl ester content in biodiesel by Fourier transform infrared spectroscopy coupled to multivariate statistics was demonstrated feasible.

Quantitative evaluation of multiple adulterants in roasted coffee by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and chemometrics

The current study presents an application of Diffuse Reflectance Infrared Fourier Transform Spectroscopy for detection and quantification of fraudulent addition of commonly employed adulterants (spent coffee grounds, coffee husks, roasted corn and roasted barley) to roasted and ground coffee. Roasted coffee samples were intentionally blended with the adulterants (pure and mixed), with total adulteration levels ranging from 1% to 66% w/w. Partial Least Squares Regression (PLS) was used to relate the processed spectra to the mass fraction of adulterants and the model obtained provided reliable predictions of adulterations at levels as low as 1% w/w. A robust methodology was implemented that included the detection of outliers. High correlation coefficients (0.99 for calibration; 0.98 for validation) coupled with low degrees of error (1.23% for calibration; 2.67% for validation) confirmed that DRIFTS can be a valuable analytical tool for detection and quantification of adulteration in ground, roasted coffee.