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Abstract  

Residual oil sludges represent an environmental problem in the oil industry and need a proper destination in order to allow sustainable industrial processes when exploring natural resources. In the present paper, the influence of the water content on the oil sludge pyrolysis process was studied by thermal analysis. A method using thermogravimetry on calcined mass basis was developed to estimate the water content of oil sludges. The water present in the sludge vaporizes during the first thermal processing stage, interfering in the initial process of the organic components pyrolysis and increasing the total oil sludge pyrolysis enthalpy. By quantitative differential thermal analysis (DTA) it can be seen that the water content of the sludge may significantly affect the thermal balance of its industrial pyrolysis process.

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Abstract  

During the last years, the demand for biofuels has increased significantly. In Brazil, a production of 1 billion liters of biodiesel was produced by the end of 2007, due to its obligatory use in the composition of the diesel for vehicle use. In this production, a hundred thousand tons of glycerol are produced as by-product, for which alternative uses are needed. As glycerol has already been studied by other conventional characterization methods in the past, thermal analysis has been used mostly for characterization of sub ambient temperature properties of glycerol. In this paper, thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA) were used for its thermal characterization above room temperature. Thermal stability was determined from experimental data, which show that even in air, only a very small part of the volatilized glycerol is burned out. A thermogravimetric quantitative method was developed to determinate the water content of glycerol–water mixtures, which also was used to quantify the water impurity in pro-analysis samples of glycerol, showing compatible results with those obtained by Karl Fischer method.

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Journal of Thermal Analysis and Calorimetry
Authors: Marilda Vianna, Jo Dweck, Frank Quina, Flavio Carvalho, and Claudio Nascimento

Abstract  

This study investigates the sorption of toluene and naphthalene by a sodium bentonite (BFN), an organoclay (WS35) and by their respective iron oxide hydrate composites Mag_BFN and Mag_S35. The organic matter content of WS35 and Mag_S35, determined by thermogravimetry, was used to obtain their organic matter sorption coefficients, which show that they are effective sorbents to remove organic contaminants from water, with a higher selectivity for naphthalene than for toluene sorption. The main iron oxide phase present in Mag_BFN and Mag_S35 is maghemite (γ-Fe2O3), which allows these sorbents to be separated from the effluent by a magnetic separation process after use.

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Journal of Thermal Analysis and Calorimetry
Authors: Marilda Vianna, Jo Dweck, Frank Quina, Flavio Carvalho, and Claudio Nascimento

Abstract  

Commercial bentonite (BFN) and organoclay (WS35), as well as iron oxide/clay composite (Mag_BFN) and iron/oxide organoclay composite (Mag_S35) were prepared for toluene and naphthalene sorption. Mag_BFN and Mag_S35 were obtained, respectively, by the precipitation of iron oxide hydrates onto sodium BFN and S35 clay particles. The materials were characterized by powder X-ray diffraction (XRD), X-ray Fluorescence (XRF), and TG and DTA. From XRF results and TG data on calcined mass basis, a quantitative method was developed to estimate the iron compound contents of the composites, as well as the organic matter content present in WS35 and Mag_S35.

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Partially exchanged organophilic bentonites

Part I. characterization by thermal analysis on calcined mass basis

Journal of Thermal Analysis and Calorimetry
Authors: Jo Dweck, Emerson Paes Barreto, Sergio Meth, and Pedro Mauricio Büchler

Abstract

Using a sodium bentonite (VCNa) as substrate differently exchanged organophilic clays were obtained by reaction with hexadecyltrimethylammonium (HDTMA) chloride, at increasing reacting ratios (R) from 20 to 120 meq/100 g of clay (VC20–VC120). The sodium bentonite was previously synthesized from a Verde Claro policationic bentonite (VC) from Bravo, Paraiba State, Brazil. From the thermogravimetric (TG) and derivative thermogravimetric (DTG) analyses of these clays on calcined mass basis and from TG and DTG curves data of VCNa clay, a method was developed to estimate the mass fraction of the exchanged cation present in each organophilic clay (M org), as a function of R. When all sodium cations of VCNa are exchanged by HDTMA, the obtained organophilic clay presents a maximum value for M org. From this value and TG and DTG curves data of VC and VCNa clays, the cation exchange capacity of the original VC bentonite can be estimated.

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Abstract

Over the past years, the production of biodiesel has significantly increased in Brazil due to its obligatory use in the composition of diesel for vehicle use. As a result, in the most ordinary processes, a hundred thousand tons of glycerol is produced as by-product per 1 billion liters of biodiesel. Glycerol has already been widely studied. Nonetheless, the quantity produced today demands new proposals for uses, such as a fuel. In this aim, the authors studied the kinetics of the thermal processing of glycerol. In this research, thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) were used to provide the experimental data. Kinetic parameters were calculated by Kissinger method for the global process observed during the heating of the samples from the room temperature up to 600 °C, both in open and in sealed crucibles (with a little hole). Kinetic data were also determined at different isoconversion conditions during heating, by applying Ozawa–Flynn–Wall and Blazejowski methods to TG data. Results show that glycerol heated from 30 to 600 °C, under normal pressure, does not experience simple volatilization. The activation energies calculated at different conversion degrees by these methods show that only volatilization occurs when the mass loss of glycerol is lower than 40% and that for higher conversion degrees, partial thermal decomposition and/or dissociation of glycerol are occurring as well. These facts are also confirmed by the volatilization enthalpies estimated using another method developed by Blazejowski based on Van’t Hoff equation.

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Partially exchanged organophilic bentonites

Part II. Phenol adsorption

Journal of Thermal Analysis and Calorimetry
Authors: Emerson Paes Barreto, Mariana Santos Lemos, Isabelle Bulhoes Aranha, Pedro Mauricio Büchler, and Jo Dweck

Abstract

Phenol is a pollutant that has caused many problems even when present in low concentrations and still represents an environmental problem with difficult solution. This paper presents a study of phenol adsorption by organophilic clays, obtained from aVerde Claro bentonitic clay, from Bravo, Paraíba State, Brazil, at different partial cation exchange degrees with hexadecyltrimethylammonium (HDTMA) chloride, at increasing reacting ratios, from 20 to 120 mmol/100 g of clay, which were characterized in a previous paper. By using Freundlich isotherms obtained for each case, which presented the best correlation coefficients with experimental data, it can be seen that for equilibrium concentrations up to 0.53 mmol L−1 of phenol, the adsorptive capacity decreases for organophilic bentonites obtained at cation exchange degrees higher than 80 mmol/100 g of clay. This indicates that in these cases, the higher is the exchange by organic cation, the higher is the difficulty for the phenol diffusion and sorption in the interlayer space of the organophilic clays. For higher equilibrium concentrations, the maximum adsorption occurs for the organophilic bentonite obtained at 100 mmol/100 g of bentonite exchange.

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Early stages hydration of high initial strength Portland cement

Part I. thermogravimetric analysis on calcined mass basis

Journal of Thermal Analysis and Calorimetry
Authors: Alex Neves Junior, Romildo Dias Toledo Filho, Eduardo de Moraes Rego Fairbairn, and Jo Dweck

Abstract

Thermogravimetry (TG) and derivative thermogravimetry (DTG) were used to analyze the early stages of hydration of a high-initial strength and sulphate resistant Portland cement (HS SR PC) within the first 24 h of setting. The water/cement (W/C) mass ratios used to prepare the pastes were 0.35, 0.45, and 0.55. The hydration behavior of the pastes was analyzed through TG and DTG curves obtained after different hydration times on calcined cement mass basis to have a same composition basis to compare the data. The influence of the W/C ratio on the kinetics of the hydration process was done through the quantitative analysis of the combined water of the main hydration products formed in each case. TG and DTG curves data calculated on calcined mass basis of all the results were converted to initial cement mass basis to have an easier way to analyze the influence of the W/C ratio on the free and combined water of the different main hydrated phases. The gypsum content of the pastes was totally consumed in 8 h for all cases. A significant part of the hydration process occurs within the first 14 h of setting and at 24 h the highest hydration degree, indicated by the respective content of formed calcium hydroxide, occurs in the case of the highest initial water content of the paste.

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Abstract

Two catalyst wastes (RNi and RAI) from polyol production were considered as hazardous, due to their respective high concentration of nickel and aluminum contents. This article presents the study, done to avoid environmental impacts, of the simultaneous solidification/stabilization of both catalyst wastes with type II Portland cement (CP) by non-conventional differential thermal analysis (NCDTA). This technique allows one to monitor the initial stages of cement hydration to evaluate the accelerating and/or retarding effects on the process due to the presence of the wastes and to identify the steps where the changes occur. Pastes with water/cement ratio equal to 0.5 were prepared, into which different amounts of each waste were added. NCDTA has the same basic principle of Differential Thermal Analysis (DTA), but differs in the fact that there is no external heating or cooling system as in the case of DTA. The thermal effects of the cement paste hydration with and without waste presence were evaluated from the energy released during the process in real time by acquiring the temperature data of the sample and reference using thermistors with 0.03 °C resolution, coupled to an analog–digital interface. In the early stages of cement hydration retarding and accelerating effects occur, respectively due to RNi and RAl presence, with significant thermal effects. During the simultaneous use of the two waste catalysts for their stabilization process by solidification in cement, there is a synergic resulting effect, which allows better hydration operating conditions than when each waste is solidified separately. Thermogravimetric (TG) and derivative thermogravimetric analysis (DTG) of 4 and 24 h pastes allow a quantitative information about the main cement hydrated phases and confirm the same accelerating or retarding effects due to the presence of wastes indicated from respective NCDTA curves.

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