ABSTRACT
A geopolymer foam was synthesized for the evaluation of its capacity for fast retention and slow release of potassium in water. The base matrix of the geopolymer binder was obtained by mixing metakaolin, sodium silicate, and sodium hydroxide solutions. A factorial design of experiments (DOE) was applied to analyze the effect of adding hydrogen peroxide, aluminum powder, soybean oil, and iron ore flotation tailing on the water absorption and compressive strength of the geopolymer samples. The best-performing samples were characterized and evaluated for morphological aspects, chemical stability in different pH ranges, optimal adsorption time, and the ability to release potassium in the water. The inclusion of hydrogen peroxide was not a statistically significant factor at the 95% confidence level. The inclusion of aluminum powder and oil increased the water absorption, whereas the addition of tailing decreased it. The addition of soybean oil and tailing contributed positively to the compressive strength, but the addition of aluminum powder caused its reduction. The tailing addition not only increased the porous samples compressive strength but also prevented large cracks in their structure. The optimized response of 63 wt % of water absorption and 6 MPa of compressive strength was achieved by adding 0.05% of Al-powder, 1.5% of soybean oil, and 20% of tailing on the geopolymer binder. This sample exhibited 72% open porosity, a maximum adsorptive capacity of q = 5.7 mg/g, and chemical stability at pH > 4. Adsorption stabilized after 9 h of contact with water. Kinetics modeling suggested that the concentration gradient and chemical reactions probably drove potassium adsorption. The potassium release step was possibly controlled by the concentration gradient. After 60 days, the water solution released only 28% of absorbed potassium.
ABSTRACT
In this work, samples of Fe mining tailings from the collapsed Fundão Dam, Brazil, which were retained by the Candonga hydroelectric power plant, were characterized by various techniques. Quartz, hematite, kaolinite, and goethite were identified as the main phases present. The composition, homogeneity, and relatively low (~1%) organic matter content indicate potential for usage of these tailings in civil constructions. The next step of this work is to investigate such applications. If their feasibility is confirmed, the goal is to use this material for construction in the areas affected by the Fundão Dam rupture. This use will lead to positive socio-environmental impacts in these regions, where tailings still need to be removed and damaged infrastructure needs to be repaired. Integr Environ Assess Manag 2020;16:636-642. © 2019 SETAC.
Neste trabalho, amostras do rejeito de mineração de ferro, proveniente do rompimento da barragem de Fundão e retidas pela usina hidroelétrica de Candonga, foram caracterizadas por diversas técnicas. Quartzo, hematita, caulinita e ghoetita foram identificadas como as principais fases presentes no rejeito. A composição, homogeneidade e teor de matéria orgânica relativamente baixo, cerca de 1%, indicam uso potencial deste material em construção civil. O próximo passo deste trabalho é investigar tais aplicações. Se a viabilidade for confirmada, o objetivo é utilizar esse material para obras nas áreas afetadas pelo rompimento da barragem de Fundão. Isso contribuirá para reduzir os impactos socioambientais nessas regiões, as quais ainda necessitam da remoção do rejeito e de reparos na infraestrutura danificada. Integr Environ Assess Manag 2020;16:636-642.
Subject(s)
Disasters , Rivers , Brazil , Environmental Monitoring , MiningABSTRACT
In this study, non-radioactive iodine was incorporated in two types of biodegradable hydroxyapatite-based porous matrices (HA and HACL) through impregnation process from sodium iodine aqueous solutions with varying concentrations (0.5 and 1.0 mol/L) . The results revealed that both systems presented a high capacity of incorporating iodine into their matrices. The quantity of incorporated iodine was measured through Neutron Activation Analysis (NAA). The porous ceramic matrices based on hydroxyapatite demonstrated a great potential for uses in low dose rate (LDR) brachytherapy.
Materiais cerâmicos porosos à base de compostos de fosfatos de cálcio (CFC) vêm sendo estudados e desenvolvidos para várias aplicações biomédicas tais como implantes, sistemas para liberação de drogas e fontes radioativas para braquiterapia. Dois tipos de matrizes porosas biodegradáveis de hidroxiapatita (HA e HACL) foram avaliadas em termos da capacidade de incorporação de iodo em suas estruturas. Resultados revelaram que as matrizes porosas a base de hidroxiapatita apresentaram alta capacidade de incorporar iodo em sua estrutura. A quantidade de iodo foi mensurada através da técnica de Análise por Ativação Nêutronica (AAN). As matrizes cerâmicas porosas à base de hidroxiapatita demostraram ter grande potencial para aplicação em braquiterapia de baixa taxa de dose (LDR - Low Dose Rate).
