Zuy M. Magriotis

Biodiesel production by free fatty acid esterification using lanthanum (La3+) and HZSM-5 based catalysts.

In this work the use of the heterogeneous catalysts pure (LO) and sulfated (SLO) lanthanum oxide, pure HZSM-5 and SLO/HZSM-5 (HZSM-5 impregnated with sulfated lanthanum oxide (SO4(2-)/La2O3)) was evaluated. The structural characterization of the materials (BET) showed that the sulfation process led to a reduction of the SLO and SLO/HZSM-5 surface area values. FTIR showed bands characteristic of the materials and, FTIR-pyridine indicated the presence of strong Brønsted sites on the sulfated material. In the catalytic tests the temperature was the parameter that most influenced the reactions. The best reaction conditions were: 10% catalyst, 100°C temperature and 1:5 m(OA)/m(meOH) for LO, SLO, SLO/HZSM-5 and 10% catalyst, 100°C temperature and 1:20 m(OA)/m(meOH) for HZSM-5. Under these conditions the conversions were: 67% and 96%, for LO and SLO, respectively and 80% and 100%, for HZSM-5 and SLO/HZSM-5, respectively. All catalysts deactivated after the first use, but the deactivation of SLO/HZSM-5 was smaller.

Cathodic stripping voltammetric determination of arsenic in sugarcane brandy at a modified carbon nanotube paste electrode

We have developed an eletroanalytical method that employs Cu(2+) solutions to determine arsenic in sugarcane brandy using an electrode consisting of carbon paste modified with carbon nanotubes (CNTPE) and polymeric resins. We used linear sweep (LSV) and differential-pulse (DPV) voltammetry with cathodic stripping for CNTPE containing mineral oil or silicone as binder. The analytical curves were linear from 30 to 110μgL(-1) and from 10 to 110μgL(-1) for LSV and DPV, respectively. The limits of detection (L.O.D.) and quantification (L.O.Q.) of CNTPE were 10.3 and 34.5μgL(-1) for mineral oil and 3.4 and 11.2μgL(-1) for silicone. We applied this method to determine arsenic in five commercial sugarcane brandy samples. The results agreed well with those obtained by hydride generation combined with atomic absorption spectrometry (HG AAS).

Adsorption of etheramine on kaolinite: A cheap alternative for the treatment of mining effluents

The results of laboratory experiments aimed at determining the influence of physicochemical parameters on the adsorption of etheramine (adsorbate) on white, pink and yellow kaolinites (adsorbent) are presented. The adsorption of etheramine was favoured at pH 10.0 under conditions where the initial concentration of etheramine was 200 mg l(-1) and the ratio of adsorbent to volume of etheramine solution was 1:100 g ml(-1). Equilibrium adsorption was attained within 30 min and the efficiencies of removal of etheramine by white, pink and yellow kaolinite were 77%, 80% and 69%, respectively. The adsorption isotherms of the kaolinites were determined under optimum conditions and with adsorbate in the concentration range of 0-4000 mg l(-1). The amounts of etheramine adsorbed per unit mass of adsorbent were 33.03, 34.32 and 23.11 mg g(-1) for white, pink and yellow kaolinites, respectively. The adsorption of etheramine on kaolinites was better fitted to the Langmuir rather than the Freundlich isotherm, and could be explained by a pseudo-second-order kinetic model. It is concluded that kaolinites offer significant potential in the treatment of effluents originating from the processing of lower grade iron ores by froth flotation.

Properties of biochar derived from wood and high-nutrient biomasses with the aim of agronomic and environmental benefits

Biochar production and use are part of the modern agenda to recycle wastes, and to retain nutrients, pollutants, and heavy metals in the soil and to offset some greenhouse gas emissions. Biochars from wood (eucalyptus sawdust, pine bark), sugarcane bagasse, and substances rich in nutrients (coffee husk, chicken manure) produced at 350, 450 and 750°C were characterized to identify agronomic and environmental benefits, which may enhance soil quality. Biochars derived from wood and sugarcane have greater potential for improving C storage in tropical soils due to a higher aromatic character, high C concentration, low H/C ratio, and FTIR spectra features as compared to nutrient-rich biochars. The high ash content associated with alkaline chemical species such as KHCO3 and CaCO3, verified by XRD analysis, made chicken manure and coffee husk biochars potential liming agents for remediating acidic soils. High Ca and K contents in chicken manure and coffee husk biomass can significantly replace conventional sources of K (mostly imported in Brazil) and Ca, suggesting a high agronomic value for these biochars. High-ash biochars, such as chicken manure and coffee husk, produced at low-temperatures (350 and 450°C) exhibited high CEC values, which can be considered as a potential applicable material to increase nutrient retention in soil. Therefore, the agronomic value of the biochars in this study is predominantly regulated by the nutrient richness of the biomass, but an increase in pyrolysis temperature to 750°C can strongly decrease the adsorptive capacities of chicken manure and coffee husk biochars. A diagram of the agronomic potential and environmental benefits is presented, along with some guidelines to relate biochar properties with potential agronomic and environmental uses. Based on biochar properties, research needs are identified and directions for future trials are delineated.

Study of chemical and thermal treatment of kaolinite and its influence on the removal of contaminants from mining effluents

The effects of chemical and thermal treatments on the structure of kaolinite were examined, as well as the influence of those changes upon the removal of etheramine, a cationic collector used in the processing of iron ore. The materials were characterized using XRD, XRF, specific surface area (SBET), FTIR, zeta potential and a test for determination of acid sites. The effects of the treatments on the structure of kaolinite were evaluated using chemometric tools developed from principal components analysis algorithms and hierarchical components analysis. The parameters evaluated in the kinetic study of adsorption were contact time, initial concentration of etheramine, quantity of adsorbent and pH. The adsorption of etheramine in the samples subjected to chemical treatments could be explained by a pseudo-second order model, whilst for the sample subjected to thermal treatment, better fit was with the pseudo-first order model. With regard to adsorption isotherms, it was shown that for the three adsorbents used, adsorption followed the Langmuir model. The maximum quantities adsorbed were 27 mg g(-1), 29 mg g(-1) and 59 mg g(-1), respectively, for the samples subjected to acid, thermal and peroxide treatments. The treatment with peroxide was found to be the most suitable for removal of etheramine.

Comparative analysis of tropaeolin adsorption onto raw and acid- treated kaolinite: Optimization by Response Surface Methodology

The comparative adsorption of Tropaeolin (TP) onto raw kaolinite (RK) and kaolinite submitted to acid treatment (AK) was studied. RK and AK were characterized by zeta potential and energy dispersive X-ray spectroscopy (EDS). The adsorption was investigated using Composite Central Design (CCD) and the parameters evaluated were initial TP solution concentration, quantity of adsorbent and the pH of the solution. The optimized parameters were: initial TP solution concentration of 75 mg L(-1), pH 4 and 0.12 g adsorbent. Kinetic data were evaluated by pseudo-first order, pseudo-second order and Avrami models. The equilibrium adsorption was analyzed by Langmuir, Freundlich and Sips isotherms. The kinetic data were best fitted to the pseudo-second order model. The Sips isotherm model gives the better correlation to predict the adsorption equilibrium. The maximum adsorption capacities were 18.3 mg g(-1) and 23.2 mg g(-1) for RK and AK, respectively. The calculated thermodynamic parameters showed that the process was spontaneous, endothermic and involving the disorganization of the adsorption system for both adsorbents. The desorption step showed that the AK sample was more suitable as an adsorbent.

Experimental Design Methodology to Optimize the Solid Phase Microextraction Procedure Prior to GC/MS Determination of Ethyl Carbamate in Samples of Homemade Cachaça

Seeking to improve the quality of cachaça, the Ministério da Agricultura, Pecuária e Abastecimento (Ministry of Agriculture, Livestock and Supply - MAPA), the body responsible for setting and approving regulations governing the Identity and Quality Standards (PIQs) for distilled sugar cane spirits and cachaça, through the Normative Instruction No. 13 of 2005 included some contaminants such as ethyl carbamate (EC), acrolein, lead, and arsenic that must be evaluated in these drinks. Studies on EC, as well as the methods for its determination, are required to evaluate and determine which factors contribute to the formation of this compound in the beverage. An analytical method using gas chromatography/mass spectrometry (GC/MS) with prior sample treatment by solid phase microextraction (SPME) was developed along with the assessment of the principal validation parameters. These two developments lead to the determination of EC with analytical reliability. The optimization of the extraction step was performed via a factorial design involving the selection of parameters such as extraction time, extraction temperature, salt concentration, desorption time, pH, and the method of extraction. The linear range was 5.0 to 200.0 µg L−1 (R2 = 0.9965) with limits of detection and quantification of 1.5 and 5.0 µg L−1, respectively. The recoveries for samples of cachaça containing 10.0 and 80.0 µg L−1 concentrations of EC were 89% and 93%, respectively. The concentrations of EC in the samples of cachaça examined were well below the limits required by Brazilian law.

Removal of copper in cachaças using clays

Increased production and cachaca consumption has stimulated research regarding its quality. It is known that copper can be harmful to human health when it is in concentrated form in the beverage and is ingested in large amounts. Thus, there is a great concern among researchers and producers about the use of adsorbent substances for the removal of excess copper. The kinetic parameters and the adsorption isotherms for copper on kaolinite were studied to evaluate the physical-chemical quality of the cachaca before and after adsorption. K01, K03 and K04 kaolinites presented a maximum adsorption capacity of 97, 95 and 90%, respectively. The kinetic rates followed the pseudo-first-order model, and the adsorption isotherm was best adjusted to the Freundlich model. All the parameters of the control samples were within the limits required by law, except for the aldehydes and copper. After adsorption with clay, the values for some of the parameters were lower and those of others were not significantly different. It was possible to describe 87% of the data with the first and second principal components of the multivariate analysis, and all the samples were different from the control for the parameters analyzed. Thus, these clays can be used for the removal of copper from cachaca, but further studies are necessary.

Quantification of Arsenic in Sugar Cane Brandy of Minas Gerais Using Carbon Paste Electrode Modified with Carbon Nanotubes

An eletroanalytical method for determination of arsenic in sugar cane brandy using an electrode consisting of carbon paste modified with carbon nanotubes (CNTPE) and mineral oil has been developed. The cyclic (CV) and linear sweep voltammetry modes (LSV) with cathodic stripping were employed for CNTPE containing mineral oil. The analytical curves were linear from 30.0 to 80.0 µg L -1 for LSV. The limit of detection (L.O.D.) was 10.45 μg L -1 and limit of quantification (L.O.Q.) was 34.33 μg L -1 . The developed method was applied to the determination of arsenic in tree commercial sugar cane brandy samples. The results were in good agreement with those obtained by HGAAS, showing that CNTPE containing mineral oil can be successfully employed to the simultaneous determination of arsenic in sugar cane brandy samples.

An alternative method for the simultaneous determination of copper and lead for quality control of sugar cane spirit using a nanotube-based sensor

Um metodo eletroanalitico foi desenvolvido para determinacao simultânea de ions cobre e chumbo em cachaca empregando eletrodo de pasta de carbono modificado com acido ascorbico e nanotubos de carbono (CPE-AaCNT). A tecnica de voltametria de onda quadrada (SWV) com redissolucao anodica foi empregada e otimizada com relacao aos seguintes parâmetros: frequencia (50 Hz), amplitude (100 mV) e incremento de varredura (9 mV). As curvas analiticas apresentaram intervalo linear de 0,09 a 7,00 mg L - 1 para o chumbo e para o cobre. Os limites de deteccao foram de 48,5 e 23,9 µg L - 1 para o chumbo e o cobre, respectivamente. O metodo desenvolvido foi aplicado na determinacao simultânea de chumbo e cobre em cinco amostras comerciais de cachaca. Os resultados apresentaram-se concordantes com os obtidos por F AAS/GF AAS (espectrometria de absorcao atomica com chama/espectrometria de absorcao atomica com forno de grafite) e revelaram que CPE-AaCNT podem ser empregados com exito na quantificacao de cobre e chumbo em amostras comerciais de cachaca.