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Seletividade da Clinoptilolita natural por metais tóxicos em sistemas aquosos
(Universidade Federal de São Carlos, 2004-12-13) Fernández, Juan Carlos Torres; Gubulin, José Carlos
Natural zeolites are the most important inorganic cationic exchangers exhibiting high ion exchange capacity, selectivity and environment compatibility. Heavy metals are well known for toxicity and their disposal is a significant industrial waste problem. The goal of this work was directed to evaluate the selectivity of a purified homo-ionic clinoptilolite mineral for aqueous Pb2+, Zn2+, Cu2+ and Na+ ions at 0,005 eq/L and 303 K, interpreted through the application of empirical thermodynamic models to the zeolite phase (Margules, Van Laar, Wilson) coupled with a well established ion-interaction approach for the electrolyte solution (Pitzer). The present study considered the following stages: (1) adsorbent material: preparation and characterization; (2) aqueous solutions: nitrates of sodium, lead, zinc and copper; (3) equilibration of weighed amounts of homo-ionic clinoptilolite with a series of solutions containing the two competing cations; (4) analysis for aqueous cations by AAE; (5) construction of the equilibrium points; isotherm analysis; (6) test for thermodynamic reversibility; (7) empirical models for the zeolite phase (admitted as a solid solution) jointed to the ion-interaction model chosen for the aqueous solution; (8) equilibrium constant and Gibbs free energy for the ion-exchange reactions; phenomenological interpretation of the thermodynamic parameters obtained by means of the application of empirical models to the zeolite phase. The above procedure was, in the same way, followed for the ternary systems. The results obtained in this work shown that the empirical models adopted for the solid phase coupled to Pitzer s model for the activity coefficients in the electrolyte solution describe successfully the binary ion-exchange equilibria. The calculated equilibrium constant and the corresponding Gibbs free energy for each binary-exchange reaction resulted in a selectivity sequence, at the normality and temperature of this study, easily deduced as: 2 2 2 Pb Na Cu Zn + + + + > > . Besides, the parameters estimated applying the Margules , Van Laar s and Wilson s equations for cations in the solid binary mixture resulted in useful values quantifying adequately the cation zeolite framework interactions, thus, an alternative way to interpret the adsorbent selectivity from the charge and cationic radius effect. The ternary parameters obtained applying multi-component empirical models do not explain properly the non-ideality of ions in a solid mixture containing more than two components. This is in accordance with the results encountered in a number of publications on crystal structure of heulandite-group zeolites: these aluminosilicates are found to contain crystallographically distinct set of sites throughout the exchanger framework and that normally each set of sites is partially populated by the exchanging ions. As a consequence, activity coefficients for a multi-component exchange reaction cannot be predicted from appropriate binary data for a heterogeneous exchanger, since the phenomenological binary coefficients are complicated functions of each site set, population and composition, and both these properties will change on introducing other species of ion in the exchanger. In this sense, and from what were obtained here, is believed that multi-component solid phase nonideality must, at least, be interpreted through the application of statistical thermodynamic models considering the energetic heterogeneity of a number of site set and the charge density of the specific zeolite framework.
O uso do system dynamics em um modelo de apoio a comercialização: uma aplicação à agricultura familiar
(Universidade Federal de São Carlos, 2004-12-13) Faulin, Evandro Jacóia; Azevedo, Paulo Furquim de
The family farmers play an important role in the Brazilian agricultural production. However, even though they occupy a prominent position in the agricultural production in Brazil, there are not management techniques specifically suitable to family farmers. Focusing on commercialization and vertical coordination, this dissertation has as main objective the development of management prescriptions related to procurement and marketing activities undertaken by family farmers. Computational simulation, based on System Dynamics methodology, was the main instrument to support procurement and marketing decisions. Interviews with thirty three vegetables family farmers and five of their main suppliers, all located in the region of São Carlos SP, provided the real data for the design of the computational model. The empirical research revealed that family farmers do not plan procurement and marketing appropriately, although they manage to compete with non-family production. The use of governance structures based on trust seems to be the main cause of their survival and success. The simulation based on System Dynamics helped the design of models that represent and help the decision making related the procurement and marketing by family farmers.
Dispersão dielétrica em materiais ferroelétricos
(Universidade Federal de São Carlos, 2004-12-13) Guerra, José de Los Santos; Eiras, José Antônio; https://lattes.cnpq.br/6653223814715498
In the last decades, the high frequency dielectric response has been one of the most studied issues in the ferroelectricity area. The main dielectric characteristic is the strong dependence of the dielectric parameters (real and imaginary component of the dielectric permittivity) with the measuring frequency (dielectric dispersion). Among them, the perovskite-structured family, such as barium titanate (BaTiO3), pure and modified lead zirconate titanate (PZT and PLZT, respectively), and some others similar compounds can be emphasised. In order to explain such phenomenon some theoretical models have been proposed, nevertheless a major discussion about the true mechanism responsible for the microwave dielectric dispersion remains still open. In this work, a pressurecontrolled sample holder for microwave dielectric measurements is presented. The experimental set-up involves a coaxial line coupled to a pressure-controlled sample holder able to obtain the dielectric characterization as a function of the temperature. On the other hand, the microwave dielectric dispersion process was investigated in the relaxor and normal ferroelectric composítions of lanthanum modified lead titanate ceramics. The obtained results were discussed concerning a damped harmonic oscillator, considering the vibration of the boundaries of the polar regions, independently of their structure, as the mechanism responsible for the high frequency dielectric anomalies (dielectric dispersion and resonance) in ferroelectric systems.
Métodos exatos baseados em relaxação lagrangiana e surrogate para o problema de carregamento de paletes do produtor.
(Universidade Federal de São Carlos, 2004-12-13) Oliveira, Lilian Kátia de; Morabito Neto, Reinaldo
The purpose of this work is to develop exact methods, based on Lagrangean and Surrogate relaxation, with good performance to solve the manufacturer s pallet loading problem. This problem consists of orthogonally arranging the maximum number of rectangles of sizes (l,w) and (w,l) into a larger rectangle (L,W) without overlapping. Such methods involve a tree search procedure of branch and bound type and they use, in each node of the branch and bound tree, bounds derived from Lagrangean and/or Surrogate relaxations of a 0-1 linear programming formulation. Subgradient optimization algorithms are used to optimize such bounds. Problem reduction tests and Lagrangean and Surrogate heuristics are also applied in the subgradient optimization to obtain good feasible solution. Computational experiments were performed with instances from the literature and also real instances obtained from a carrier. The results show that the methods are able to solve these instances, on average, more quickly than other exact methods, including the software GAMS/CPLEX.
Preparação, caracterização e estudos termoanalíticos de bases de Schiff biopoliméricas e seus complexos de cobre
(Universidade Federal de São Carlos, 2004-12-13) Santos, José Estrela dos; Cavalheiro, Éder Tadeu Gomes; https://lattes.cnpq.br/4745280891704797
The present work is divided in three parts. The first part deals with the purification and characterization of commercial chitosan from different suppliers. The second part describes the synthesis and characterization of biopolymeric Schiff bases obtained of chitosan. The Schiff bases were obtained from the condensation chitosan ( DA= 90%) with salicylaldehyde and its 5-bromo, 5-chloro, 5-nitro, 5-methyl, 5-methoxy sallicylaldehyde derivatives in acidic medium. Using the data obtained in the spectra of 1H NMR of the Schiff bases, it was determined the Mean Degree of Substitution ( DS ). The Mean Degree of Substitution ( DS ) ranged from 4.6% to 68.5% depending on the R group. The most substituted Schiff bases (highly DS ) has been used to obtain copper complexes. All the products were characterized by elemental analysis, hydrogen nuclear magnetic resonance (1H NMR) and infrared spectroscopy (IR). SEM photomicrographs was obtained with the purpose of verifying in morphologic changes in the biopolymerics Schiff bases as well as the copper complexes obtained from these bases in relation to starting chitosan. In a third stage, it was investigated the thermal behavior of biopolymerics Schiff bases and with the starting chitosan. An evaluation of the hydration and of thermal decomposition of chitosan and of the biopolymerics Schiff bases was accomplished using Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). The chitosan TG curves under N2 presented two mass losses representing dehydration and decomposition of the polymer. Under air an additional step was observed due to the burnning of carbonaceous material. The biopolymeric Schiff bases decomposed in three steps: dehydration, decomposition and burnning of the carbonaceous residue in air. In both cases the DSC curves agreeded with the thermal events described by the TG curves.
Contribuição ao estudo dos mecanismos envolvidos na aglomeração esférica de sólidos em suspensão
(Universidade Federal de São Carlos, 2004-12-13) Aldeia, Wagner; Giulietti, Marco; https://lattes.cnpq.br/7703659740618915
This work was developed with the objective of to improve the state of the technique of spherical agglomeration of solids in suspension and to promote a progress in the necessary knowledge for its exploration in larger scale. We studied the agglomeration of salicylic acid crystals obtained from the reaction of sodium salicylate and sulfuric acid. The agglomeration was promoted using chloroform as bridging liquid, that was introduced in the solution immediately after the precipitation of crystals, the agglomeration being monitored by measurement of the suspension turbidity. The effect of variables as temperature, flow rate of chloroform feed, agitation and solid concentration on the following product properties were investigated: granulometric distribution, flowability, real and apparent densities, mechanical resistance, residual solvent, porosity and morphology. The results of this study allowed the identification of a new mechanism of agglomeration of solids from suspension and the possibility of controlling the process, in order to provide particles of a great variety of sizes, depending on the average size of the original crystals and according to the requirements of the final product application.
Avaliação da qualidade da água do rio Manguaba, estado de Alagoas, Brasil, com ênfase na comunidade de macroinvertebrados bentônicos
(Universidade Federal de São Carlos, 2004-12-13) Freitas, Liriane Monte; Gessner, Alaíde Aparecida Fonseca; https://lattes.cnpq.br/8465752836529703
The Manguaba river basin is located in the State of Alagoas, Brazil. It has an estimated area of 352 km2 and it drains part of the counties of Novo Lino, Jundiá, Porto Calvo, Japaratinga and Porto de Pedras. Since the riverhead, visible anthropic interferences can be detected. The river crosses rural zones (where sugar-cane crops predominate), as well as urban areas. With the aim of evaluate the environmental conditions of this river, and considering the regional context, this thesis is the first study in the State of Alagoas on benthic macroinvertebrates carried out in fluvial environment. The different anthropic activities developed along the river was the criterium to establish seven stations for collection purposes, that were plotted between 08º59 S - 35º42 W e 09º04 S - 35º22 W. The samples were collected on rainy and dry season, during 2001 and 2002. Samples of superficial water and bottom sediments were used for abiotic analyses. Fauna samples were done to study qualitative and quantitative features. Four higher groups were detected, with 76 taxonomic categories. Chironomidae (Insecta: Diptera), with 28 genera, was the most important among the 44 families identified. Larvae of Chironomidae, Oligochaeta (Tubificidae, Naididae), Hirudinea (Glossiphoniidae) and Mollusca (mainly Thiaridae) overtopped in high density and occurrence. Among Chironomidae Procladius and Chironomus were dominant in the area of the riverhead and Polypedilum (Tripodura) was an important group all along the river. Diversity and evenness indices indicated low to medium values. The similarity analysis and multivariate correspondence analysis distinguished the riverhead from the other sampling stations. Among the last ones, the results indicated higher impacts at on the stations near urban areas. This could be confirmed by the faunistic composition of taxonomic groups known as tolerant.
Mini-fábrica: uma nova proposta de arranjo produtivo e organizacional híbrido em uma empresa do setor eletroeletrônico.
(Universidade Federal de São Carlos, 2004-12-13) Rotta, Ivana Salvagni; Grün, Roberto; https://lattes.cnpq.br/6028266827740491; https://lattes.cnpq.br/1366592110711803
This thesis is concerned to the structure of a productive and organizational arrangement the mini-factory (MF) and its related concepts. A local subsidiary of an electronics multinational corporation was analysed, considering the main characteristics of the mini-factory. The thesis analysed the initial project for the mini-factory, its planning and implementation, the main changes and adaptations along the years, and the way that the mini-factory concept is used more recently by the company. The thesis also analysed the mini-factory impacts and contributions for the work groups and the qualification processes, focusing both people and organization. A case study research was developed, including interviews and data research, considering three distinctive periods of study. The variety of data collected supported the analysis of several important characteristics of the company and the way it works. The main results of this thesis show that the arrangement studied, called mini-factory by the company, is, actually, a new hybrid productive and organizational arrangement, that integrates characteristics of the mini-factory original concept with the related concepts. The results indicate that the adaptation processes, made during the years by the company, developed an arrangement different from those described by the other companies and even by the literature. These identified characteristics had been crucial for the good results achieved by the company and, nowadays, it is considered an example for the other subsidiaries of this multinational corporation.