Browsing by Author "Baldo, Arthur P."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Breakthrough Curves for the Continuous Adsorption of Micropollutants on Activated Carbon/Geopolymer MixturesPublication . Baldo, Arthur P.; Silva, Ana P. F.; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Marin, Pricila; Peres, José A.; Gomes, HelderBreakthrough curves are key for designing continuous flow adsorption systems, typically obtained experimentally or through modeling [1]. In this study, a mixture of activated carbon (AC) and geopolymers (GP) was tested in a continuous treatment system for the removal of model contaminants from waters in a single-component system composed of sulfamethoxazole (SMX), acetaminophen (ACT), or gallic acid (GA). In addition, the adsorbent materials were also tested in a multi-component water matrix to evaluate the interactions between adsorbates and adsorbents. Adsorption tests were conducted using 1g of GP and 0.5g of AC, filled with glass beads. The experiments were carried out at room temperature, considering 100 mg/L for all contaminants and natural pH of the solutions. The flow was set to 1 mL/min and controlled by a peristaltic pump. The breakthrough curves are shown in Figure 1. Based on the experimental data, the useful operating times were calculated, assuming that the effluent concentration should not exceed 5% of the initial concentration [2], yielding 228 minutes for ACT, 46 minutes for SMX, and 53 minutes for GA in the multi-component system. A reduction in time was observed when compared to the single-component system due to faster saturation caused by competition for active sites. The useful adsorption capacities were also calculated, with values of 45.7 mg/g for ACT, 9.2 mg/g for SMX, and 10.7 mg/g for GA in the multicomponent system. The overall results indicated that the column was efficient, as the contaminating compounds were removed up to the system breakthrough. In conclusion, this preliminary study suggests that these materials can be effectively combined and applied in tertiary wastewater treatments, as permeable reactive barriers.
- Carbon-Coated Magnetic Catalysts for Enhanced Degradation of Nitrophenols: Stability and Efficiency in Catalytic Wet Peroxide OxidationPublication . Baldo, Arthur P.; Bezerra, Ana J.B.; Silva, Adriano S.; Silva, Ana P. F.; Roman, Fernanda; Çaha, Ihsan; Bañobre-López, Manuel; Deepak, Francis Leonard; Gomes, HelderNitrophenols are persistent organic pollutants that pose serious environmental and health risks due to their toxic and lipophilic nature. Their persistence arises from strong aromatic stability and resistance to biodegradation, while their lipophilicity facilitates bioaccumulation, exacerbating ecological and human health concerns. To address this challenge, this study focuses on the synthesis and characterization of two different types of hybrid multi-core magnetic catalysts: (i) cobalt ferrite (Co-Fe2O4), which exhibits ferrimagnetic properties, and (ii) magnetite (Fe3O4), which demonstrates close superparamagnetic behavior and is coated with a novel and less hazardous phloroglucinol–glyoxal-derived resin. This approach aims to enhance catalytic efficiency while reducing the environmental impact, offering a sustainable solution for the degradation of nitrophenols in aqueous matrices. Transmission electron microscopy (TEM) images revealed the formation of a multi-core shell structure, with carbon layer sizes of 6.6 ± 0.7 nm for cobalt ferrite and 4.2 ± 0.2 nm for magnetite. The catalysts were designed to enhance the stability and performance in catalytic wet peroxide oxidation (CWPO) processes using sol–gel and solution combustion synthesis methods, respectively. In experiments of single-component degradation, the carbon-coated cobalt ferrite (CoFe@C) catalyst achieved 90% removal of 2-nitrophenol (2-NP) and 96% of 4-nitrophenol (4-NP), while carbon-coated magnetite (Fe3O4@C) demonstrated similar efficiency, with 86% removal of 2-NP and 94% of 4-NP. In the multi-component system, CoFe@C exhibited the highest catalytic activity, reaching 96% removal of 2-NP, 99% of 4-NP, and 91% decomposition of H2O2. No leaching of iron was detected in the coated catalysts, whereas the uncoated materials exhibited similar and significant leaching (CoFe: 5.66 mg/L, Fe3O4: 12 mg/L) in the single- and multi-component system. This study underscores the potential of hybrid magnetic catalysts for sustainable environmental remediation, demonstrating a dual-function mechanism that enhances catalytic activity and structural stability.
- 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, HelderWater 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.
- Plastic waste-derived carbon nanotubes: Influence of growth catalyst and catalytic activity in CWPOPublication . Roman, Fernanda; Silva, Adriano S.; Tuesta, Jose L. Diaz de; Baldo, Arthur P.; Lopes, Jessica P.M.; Gonçalves, Giane; Pereira, Ana I.; Praça, Paulo; Silva, Adrián; Faria, Joaquim L.; 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 LDP 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).
- Synthesis and Characterization of Activated Carbons, Geopolymers, and Carbon Nanotubes from Waste-Derived SourcesPublication . Baldo, Arthur P.; Silva, Ana P. F.; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Marin, Pricila; Peres, José A.; Gomes, HelderCircular Economy implies strategies for waste valorization and reuse to produce higher-value products [1]. In this context, exhausted olive pomace, a waste biomass derived from olive industry was used to synthesize activated carbon (AC) through slow pyrolysis, followed by activation with CO2 to optimize the adsorbent's porosity. The pyrolysis furnace was initially maintained under an inert atmosphere with a nitrogen flow rate of 100 NmL/min, considering three different temperature stages reached through the application of a heating ramp of 5ºC/min up to 400°C and 600°C (maintained 1 hour each) and up to 800°C. Activation with CO2 occurs in the first hour at this temperature, followed by 3 hours in a nitrogen atmosphere, completing the process in 9 hours. The geopolymer (GP) was synthesized using 10 g of fly ash, a byproduct of the combustion of municipal solid waste, mixed with an alkaline solution, a mixture of 5,67g of sodium silicate and 2,27g of sodium hydroxide (10M), to initiate the geopolymerization reaction. The synthesis of carbon nanotubes (CNTs) was based on the methodology of Díaz de Tuesta et al. [2], by chemical vapor deposition with plastic waste as the precursor. The results obtained for textural characterization are presented in Table 1. AC showed the highest surface area (527 m²/g) and a pore volume of 0.318 cm³/g, can be advantageous for adsorption, while CNT functions effectively as a catalyst despite its lower surface area. Acid-base characterization showed that AC possesses high basicity (1250 μmol/g), enhancing its ability to adsorb acidic contaminants, while CNT and GP demonstrated balanced acid and basic properties, with point of zero charge (pHpzc) values of 9.86 for AC, 6.9 for CNT, and 7.6 for GP. Elemental analysis (CHNS) revealed that AC contained 63.0% C, 0.8% H, 18.0% O, and 16.4% ash. CNT, in contrast, had a higher carbon content of 92.5% and 6.0% ash.