Browsing by Author "Baldo, Arthur Pietrobon"
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- Innovative permeable reactive barriers for the elimination of contaminants of emerging concern from effluents of wastewater treatment plantsPublication . Baldo, Arthur Pietrobon; Gomes, Hélder; Marin, PricilaRapid industrialization and urbanization have led to significant environmental challenges, particularly the contamination of water bodies by contaminants of emerging concern (CECs) due to insufficient tertiary treatment in wastewater treatment plants (WWTPs). Pharmaceuticals like acetaminophen (ACT) and sulfamethoxazole (SMX), as well as phenolic compounds like gallic acid (GA), are persist and bioaccumulate, posing risks to water quality. This study explores the development of permeable reactive barriers (PRBs) using eco-friendly materials: geopolymers (GP), activated carbon (AC), and carbon nanotubes (CNT), sourced from waste. Integrating these materials into PRBs aligns with circular economy principles, providing a sustainable solution to reduce exposure to contaminated water. Elemental analysis revealed that AC contained 63.0% carbon, while CNT exhibited a higher carbon content of 92.5%. The GP analysis indicated substantial calcium and silicon content, and structural analysis via X-ray diffraction (XRD) identified key crystalline phases, predominantly calcite. Functional characterization using Fourier-transform infrared spectroscopy (FT-IR) confirmed the presence of hydroxyl and carbonyl groups in AC and notable C–O bonds in CNTs. Additionally, acid-base characterization demonstrated AC's high basicity (1250 μmol/g), enhancing its capacity to adsorb acidic compounds. Morphological studies using SEM and TEM illustrated the heterogeneous structure of GP and the arrangement of CNTs, including iron nanoparticles, from the synthesis process. BET analysis revealed AC’s superior specific surface area (527 m²/g) and pore volume (0.313 cm³/g) compared to CNT (66 m²/g) and GP (30 m²/g), enhancing its adsorption capacity. Equilibrium analysis revealed that the Freundlich model effectively described the adsorption process, indicating favorable conditions and a strong affinity between adsorbates and adsorbents. The maximum adsorption capacities of AC were determined using the Langmuir model, with values of 112.19 mg/g for ACT, 40.25 mg/g for SMX, and 314.27 mg/g for GA. Kinetic studies confirmed that all materials followed a pseudo-second-order model, achieving equilibrium within approximately 50 minutes. Continuous flow experiments validated the batch adsorption results, showing the effective performance of AC and GP, with breakthrough capacities of 126.85 mg/g for ACT, 54.93 mg/g for SMX, and 151.53 mg/g for GA. Breakthrough times were recorded at 314 minutes for ACT, 66 minutes for SMX, and 68 minutes for GA. The multi-component system exhibited similar behavior, although saturation occurred earlier.
- Occurrence of micropollutants in surface water and removal by catalytic wet peroxide oxidation enhanced filtration using polymeric membranes loaded with carbon nanotubesPublication . Silva, Adriano S.; Zadra Filho, Paulo Cesar; Ferreira, Ana Paula; Roman, Fernanda; Baldo, Arthur Pietrobon; Rauhauser, Madeleine; Díaz de Tuesta, Jose Luis; Pereira, Ana I.; Silva, Adrián; Pietrobelli, Juliana Martins Teixeira; Kalmakhanova, Marzhan; Snow, Daniel D.; Gomes, HelderMonitoring campaigns of contaminants of emerging concern (CECs) in surface waters is of utmost importance in evaluating the anthropogenic impact on riparian ecosystems. Beyond identifying pollutants and threats, treatment solutions are also needed to mitigate the adverse effects caused by polluted water discharged into the environment. For years, grab samples have been used to assess water quality, but the results can be misleading since contaminants are not always found due to the low and highly variable concentrations at which they are present in these matrices. Even in such small concentrations, the contaminants can be harmful to aquatic life. Therefore, for about three months, passive samplers were used to monitor the presence of pharmaceuticals in river water up- and downstream the discharge of a wastewater treatment plant (WWTP). Passive samplers were extracted, analyzed and the results were used to identify possible pollution composition and potential sources. Our campaign enabled the identification and quantification of 28 contaminants and showed that 27 increased in amount after WWTP discharge entered the river. The statistical analysis revealed the correlation between the pollutants, showed the oscillation in their amounts, and enabled the identification of specific pollutant groups that deserve attention for treatment, such as antibiotics and antidepressants. Moreover, an innovative catalytic wet peroxide oxidation (CWPO) intensified filtration process was investigated as a possible water treatment solution, using composite polymeric membranes loaded with carbon nanotubes (CNTs). Sulfamethoxazole (SMX) was selected as a model pollutant, and 85–90 % removals were achieved in continuous flow mode during 8 h (equivalent to 2255–2315 mg m-2 h-1).
- Plastic waste-derived carbon nanotubes: Influence of growth catalyst and catalytic activity in CWPOPublication . Roman, Fernanda; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Baldo, Arthur Pietrobon; Lopes, Jéssica Paula Marim; Gonçalves, Giane; Pereira, Ana I.; Praça, Paulo; Silva, Adrián; Faria, Joaquim; Bañobre-López, Manuel; Gomes, HelderLow-density polyethylene (LDPE) was used in this work to grow carbon nanotubes (CNTs) by chemical vapor deposition (CVD) over catalysts based on Ni, Fe and Al, synthesized either by co-precipitation (C) or wet impregnation (I) methods, with CNT yields in the range of 16–33 %. The morphology of the CNTs was directly influenced by the route used for the CVD catalyst synthesis, with co-precipitation-derived CVD catalysts resulting in CNT samples with curly walls. CNTs were purified with H2SO4 (10–50 wt.%) to remove attached metal particles. All synthesized materials (CVD-catalysts, as-synthesized CNTs, and purified CNTs) were tested as catalysts in the catalytic wet peroxide oxidation (CWPO) of paracetamol (PCM), chosen as a model pharmaceutical compound. Removals of 100 % of PCM in 8 h and 71 % of total organic carbon (TOC) in 24 h were achieved, with an H2O2 consumption efficiency of 76 % in 24 h for purified CNT (CNT@NiFeAl-C-P). The same CVD-catalyst (NiFeAl-C) was used to grow CNTs using real LDPE waste, and it was tested under the same reaction conditions, resulting in a PCM and TOC abatement of 90 % and 65 %, respectively. The synthesis of CNTs using LDPE waste was a good alternative, given the environmental benefits associated with its reintroduction into the economic cycle as a material with higher value than initially (upcycling).
- Response surface method-driven design of experiments for the synthesis of fly ash-based geopolymers in the gallic acid optimized removal from wastewaterPublication . Silva, Ana P. F.; Natal, Ana Paula Silva; Baldo, Arthur Pietrobon; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Marin, Pricila; Peres, José A.; Gomes, HelderThe growing need for sustainable wastewater treatment solutions has led to exploring alternative materials to explore large-scale and reliable technologies. This study focuses on optimizing the synthesis of geopolymers based on fly ash using a Box-Behnken experimental design to enhance their adsorption efficiency for phenolic compounds, as gallic acid model pollutant which are widely found in wastewater leaching from landfills. Fifteen geopolymer samples were synthesized, characterized, and tested for adsorption performance. Various techniques were employed, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy. The optimization process highlighted the significance of the Si/Al mass ratio, NaOH molar concentration, and Na₂SiO₃/NaOH as variables in the geopolymers production. Geopolymer samples demonstrated significant adsorption capacities, with GP_2.0_10_2.5 achieving a maximum adsorption capacity of 75.8 mg g-1. Kinetic studies indicated that the pseudo-first-order model best described the adsorption process. At the same time, equilibrium data fitted well with both Langmuir and Freundlich isotherms, with GP_2.0_10_2.5 showing the best fit for the Langmuir model. These findings reveal the potential of geopolymers derived from fly ash as cost-effective adsorbents in wastewater treatment, promoting the reuse of industrial waste within the framework of a Circular Economy.