Percorrer por autor "Natal, Ana Paula S."
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- A comprehensive mechanical and physico-chemical characterization of fly ash-based geopolymersPublication . Silva, Ana P. F.; Natal, Ana Paula S.; Oliveira, Isaac; Bezerra, Ana J.B.; Baldo, Arthur P.; Silva, Adriano S.; Diaz de Tuesta, Jose Luis; Peres, José A.; Ferreira, Débora; Gomes, Helder T.This work focuses on developing a predictive optimization method for geopolymer concrete, addressing both mechanical strength and water absorption. Despite numerous formulations proposed in the literature, no systematic method has been established to evaluate these properties simultaneously. This research addresses this gap by employing a Design of Experiments approach to systematically explore the effects of key variables such as NaOH molar concentration, sodium silicate-to-sodium hydroxide ratio, and alkaline solution-to-fly ash ratio. After 28 days, geopolymer concrete exhibits competitive compressive strength (geopolymer concrete: 25 MPa, reference Ordinary Portland concrete: 27 MPa), and after 365 days, its compressive strength surpasses that of traditional Ordinary Portland concrete (geopolymer concrete: 56 MPa, reference Ordinary Portland concrete: 27 MPa). Moreover, through Response Surface Methodology, an optimization model indicates that geopolymer concrete compressive strength can reach up to 64 MPa, with a strong influence from the alkaline solution-to-fly ash ratio. Additionally, the materials were characterized in terms of crystalline phases, surface chemistry, thermal stability, and surface area to gain a deeper understanding of the behaviour of these materials.
- Enhancing single and multi-component adsorption efficiency of pharmaceutical emerging contaminants using bio waste-derived carbon materials and geopolymersPublication . Silva, Ana P. F.; Baldo, Arthur P.; Silva, Adriano S.; Natal, Ana Paula S.; Bezerra, Ana J.B.; Tuesta, Jose L. Diaz de; Marin, Pricila; Peres, José A.; Gomes, Helder T.Water contamination with pharmaceuticals like acetaminophen (ACT), sulfamethoxazole (SMX), and phenolic compounds such as gallic acid (GA), have become a global concern. These contaminants are persistent environmental pollutants that threaten aquatic life and human health. Adsorption is recognized as an efficient and low-cost solution to tackle water pollution. In this study, the efficiency of three adsorbents—activated carbon (AC), geopolymer (GP), and carbon nanotubes (CNT) prepared from solid wastes for the removal of ACT, SMX, and GA by adsorption is assessed. AC, GP and CNT are synthesized from real wastes to address solid waste management needs. Physisorption confirmed AC superior BET surface area (527 m2 g 1), followed by CNTs (66 m2 g 1) and GPs (30 m2 g 1), allowing to achieve the highest adsorption capacity: 126.8 mg g 1 for ACT, 54.9 mg g 1 for SMX, and 151.5 mg g 1 for GA, with respective breakthrough times of 314, 66, and 68 min. Kinetic and isotherm adsorption models are fitted for all pair pollutant-adsorbent reaching 33 equations to accurately predict adsorption process, concluding that pseudo-second-order kinetic and Freundlich model best fit experimental data, demonstrating a strong adsorbent-adsorbate affinity. The findings suggest that these sustainable materials offer promising solutions for treating contaminated water.