Teses em Engenharia de Recursos Naturais da Amazônia (Doutorado) - PRODERNA/ITEC
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/4045
O Doutorado Acadêmico inicou-se em 2006 e pertence ao Programa de Pós-Graduação em Engenharia de Recursos Naturais da Amazônia (PRODERNA) do Instituto de Tecnologia da UFPA (ITEC) da Universidade Federal do Pará (UFPA).
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Item Acesso aberto (Open Access) Controle de qualidade de bauxitas gibbsíticas: predição dos parâmetros AvAl2O3 e RxSiO2 a partir de dados difratométricos por reflexão e transmissão utilizando estatística multivariada(Universidade Federal do Pará, 2021-02-16) MELO, Caio César Amorim de; PAZ, Simone Patrícia Aranha da; http://lattes.cnpq.br/5376678084716817; https://orcid.org/0000-0002-5880-7638Currently, traditional wet chemistry methods are used for quality control of bauxites. Such methods indirectly quantify the gibbsite and kaolinite content as available alumina (AvAl2O3) and reactive silica (RxSiO2), respectively, and they are very costly and time-consuming. In order to achieve a rapid and reliable method to estimate these parameters, as alternative to current wet chemistry methods, in this work it is evaluated the use of multivariate statistics – Partial Least Square Regression (PLSR) on XRD data of Brazilian bauxites. The X-ray diffractograms were collected in the reflection and transmission modes, and the data collected by each of these treatments were compared with respect to the quality of the PLSR models. The method was optimized through Principal Component Analysis (PCA) and Factorial Design of Experiments (DOE), from which it was possible to identify outliers, grouping samples with mineralogical similarities into three clusters (C1, C2 and C3), and obtain optimized parameters for the collection and pre-treatment of diffractograms. The best results were obtained using the reflection mode, reducing the 2θ range to 13º – 34º 2θ, increasing the step size from 0.026º to 0.065º, and using standardized data. These collection conditions, although not ideal for most XRD applications, provided both a better accuracy of the predictive models of AvAl2O3 and RxSiO2 and a reduction in the collection time (~ 40 seconds). The results showed that the precision obtained was within the industrially acceptable limits for the quality control of gibbisitic bauxites (AvAl2O3 = 0.49% and 0.83%, and RxSiO2 = 0.32% and 0.23%, respectively for samples of the groups C1 and C2). The prediction was not satisfactory only for marginal bauxites samples (grouped mainly in C3). XRD by transmission allowed the elimination of the preferential orientation effect, however, the accuracy of the model was acceptable only for C1 samples. Compared to the traditional wet chemistry, the proposed method is significantly faster, easier to implement and perform the analyzes, requires less space and manpower, besides no chemical reagents are needed. In addition, with the implementation of X-ray diffraction in the laboratory of the bauxite and alumina industry, it is possible to follow the mineralogy of the ore that feeds the Bayer process and, therefore, to be aware of how variations in the mineralogical composition can impact the process. It is worth noting that such information is still unknown, controlling only the chemical parameters.Item Acesso aberto (Open Access) Rejeito de caulim e caulim estéril amazônicos como fontes de Si e Al na obtenção de SAPO-34: síntese, otimização, influência de impurezas e aplicação em adsorção de corante(Universidade Federal do Pará, 2021-05-27) PINHEIRO, Darllan do Rosário; PAZ, Simone Patrícia Aranha daKaolin waste from kaolin industry sedimentation ponds for paper and sterile kaolin or flint belonging to the same mine, in the Capim region, in northeastern Pará, were used in the synthesis of the SAPO-34 molecular sieve. The precursor materials and those produced were characterized by: DRX, FRX, TG-DSC-DTG, FTIR, ASEBET and MEV. First, the use of R-metakaolin as a precursor was evaluated, varying the SiO2 / Al2O3 ratio in the formulation of the SAPO-34 molecular sieve. The adjustment in the value of this molar ratio showed a positive effect on the formation of the desired zeolite, which showed formation of the CHA structure, in less time and with good thermal stability. In relation to the use of F-metakaolin, the effect of the amount of SDA and crystallization time (nucleation and crystal growth) on the formation of the CHA structure was evaluated and, later, that zeolitic product formed with less amount of SDA was used for a detail evaluation, in which the influence of Fe and Ti ions type impurities was studied. The results revealed a positive effect of the greater amount of SDA in the formation of SAPO-34 (CHA), but in a shorter time and, consequently, contribution in the Si distribution in the structure. When comparing the zeolitic products derived from F-metakaolin and a high purity kaolinitic pattern, the zeolitic product obtained from the kaolinitic sterile showed thermal resistance where the calcined product's DRX pattern maintained the CHA diffractometric profile, but with reduced crystallinity. It was also observed that before calcination, the zeolitic product obtained with F-metakaolin showed a smaller displacement to a 2θ (º) angle, indicating an increase in the interplanar distance with reference to the d101 plane, possibly due to interferences of the present impurities (Fe and ions). Ti), however after the calcination for decomposition of the SDA this displacement was not evidenced, thus indicating interference of the SDA used. That product considered the best, based on crystallochemical parameters, was used in the performance evaluation in methylene blue adsorption, which showed good adsorption capacity. In the evaluation of the adsorption kinetics, the pseudo-second order model (R2 = 0.998) was the one that best fit the experimental data. The optimization of the synthesis using tailings through the planning of Box-Behnken experiment and response surface methodology. It was concluded that the use of Amazon waste and/or flint kaolin is viable for the production of SAPO-34 zeolite (CHA).