Navegando por Assunto "Rejeito"

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Acesso aberto (Open Access)
Determinação espectrofotométrica do arsênio em solo da cidade de Santana-AP usando o método do dietilditiocarbamato de prata (SDDC) modificado
(Instituto Nacional de Pesquisas da Amazônia, 2009) PEREIRA, Simone de Fátima Pinheiro; OLIVEIRA, Geiso Rafael Fonseca; OLIVEIRA, Johny da Silva; SILVA, Juliane da Silva e; SOUSA JUNIOR, Pedro Moreira de
Several tons of manganese residues containing arsenic, generated by a mining company, were used as streets landfill in Santana-Ap city. The possibility of exposure of people living in these villages has led to the study of quantification of total arsenic in the soil. After digestion, the levels of arsenic were quantified by molecular absorption spectrophotometry using a hydrides generation automatic system (HG-MAS), dicyclohexilamine/CHCl3 as silver diethyldithiocarbamate (SDDC) solvent and KBH4 as reducer. The method presented good results with sensitivity (ε) of 1.10 104 l.mol-1.cm-1, stability of 2.96 % and other advantages in relation to the official method. The method was applied to the soil standard samples with recoveries of the 98.82 % (n=10). The soil analysis showed that 94.74 % samples showed arsenic concentrations above the value published by CETESB for residential land (50 mg.kg-1) with the average value of 682.96 mg.kg-1, ranging of 48.08 mg.kg-1, at 1,713.00 mg.kg-1 shows that the soil arsenic contamination.
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 da
Kaolin 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).
Acesso aberto (Open Access)
Síntese e caracterização da piroaurita a partir de resíduo de mina de cobre e sua aplicação na adsorção do corante vermelho do Congo
(Universidade Federal do Pará, 2023-03-24) FERREIRA, Rafaela da Silva; RODRIGUES, Elizabeth Maria S.; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568
In this study, the copper flotation tailings extracted from the Sequeirinho pit of the Sossego mine, Carajás region, Southeast of the State of Pará (Brazil), has been used as raw material for the synthesis of Pyroaurite, a potential absorbent of organic dyes. Initially, tailings characterization was performed through X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) techniques. Next, a sample of this characterized material was leached (HCl 1:1 H2O), the obtained solution was filtered and used in the procedures of Pyroaurite synthesis. This solution was kept in the coprecipitation method at constant pH (14) with Mg/Fe molar ratio equal to 6:1, a dripping time of 4 hours, hydrothermal bath of 24 hours at high agitation rate. After, the synthesized Pyroaurite was submitted to characterization by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), Specific Surface Area (ASE) and total pore volume (Wo) techniques. Then, the synthesized Pyroaurite was evaluated for the adsorption process of Congo Red (CR) dye, where 0.025 mg of Pyroaurite were added to 10 mL of CR samples at concentrations of 5, 10, 20, 30, 40, 50 and 80 mg·L-1, respectively. The adsorption results fitted to the Langmuir model (R2 = 0.9614), while the kinetics suggested the pseudo-second order model (R2 = 0.9977). In addition, the temperature of 40ºC showed to be the most pleasant for the adsorption of the CR dye. Finally, the thermodynamic parameters of entropy (ΔSº= 0.0886 kJ·mol-1·K-1) and enthalpy (ΔHº= 8.2999 kJ·mol-1) show that the adsorption process was found to be naturally spontaneous and endothermic.