Browsing by Author "Marin, Pricila"
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- Amphiphilic carbon nanotubes for catalytic wet peroxide oxidation of 4-nitrophenolPublication . Roman, Fernanda; Sanches, Flávia Kim; Díaz de Tuesta, Jose Luis; Marin, Pricila; Machado, Bruno; Serp, Philippe; Silva, Adrián; Faria, Joaquim; Gomes, HelderCarbon nanotubes (CNTs) were synthesized via chemical vapor deposition (CVD) over an AlCoFeO4 catalyst by a sequential feed of ethylene (E, as carbon source) and acetonitrile (A, as nitrogen source). The resulting samples were noted E20 (hydrophobic), E10A10 (amphiphilic), and A20 (hydrophilic), the number referring to the feed time (minutes) of each precursor, as reported elsewhere1. These materials were tested in the catalytic wet peroxide oxidation (CWPO) of 4-nitrophenol (4-NP). The reaction was monitored by HPLC (to determine the concentration of 4-NP and respective intermediates), TOC analyzer, and UV-vis spectrophotometry (to quantify H2O2) (Figure 1). After 8 h of reaction, A20 led to the highest consumption of H2O2 (90%), followed by E10A10 (61%) and E20 (52%). On the other hand, the highest degradation of 4-NP was observed with the amphiphilic E10A10 material (98%) followed by E20 (95%), whereas A20 only led to a removal of 69%. Similar behavior was found when analyzing the formation of reaction intermediates (data not shown), i.e., while A20 resulted in the accumulation of 4-nitrocatechol (4-NTC) and hydroquinone (HQ) E10A10 and E20 led to the total conversion of formed 4-NTC and HQ. This resulted in a lower TOC removal for A20 (37%) than to E10A10 and E20 (53%). Therefore, the amphiphilic E10A10 material is a promising catalyst for the CWPO of 4-NP.
- 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.
- 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.
- 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.
- Selective denitrification of a simulated oily wastewater using Janus-structured carbon nanotubesPublication . Roman, Fernanda; Sanches, Flávia Kim; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Marin, Pricila; Machado, Bruno; Serp, Philippe; Silva, Adrián; Faria, Joaquim; Gomes, HelderCarbon nanotubes (CNTs) bearing a Janus-like structure were synthesized by chemical vapor deposition considering ethylene and acetonitrile as carbon and nitrogen sources. The developed materials were applied as catalyst in the oxidation of 4-nitrophenol (4-NP) dissolved in a biphasic medium (water/2,2,4-trimeylpentane) simulating a contaminated oily wastewater. The CNT prepared using both ethylene and acetonitrile precursors shows a Janus-structure, leading to the highest abatement of 4-NP as well as to the highest removal of TOC, proving to be an alternative towards the removal of lipophilic pollutants from oily effluents, allowing to reclaim the oily phase.
- Selective denitrification of lipophilic pollutants from oily wastewater by peroxidation using Janus-structured amphiphilic carbon nanotubes as catalystsPublication . Sanches, Flávia Kim; Roman, Fernanda; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Marin, Pricila; Machado, Bruno; Serp, Philippe; Silva, Adrián; Gomes, HelderCarbon nanotubes (CNTs) were tested as catalysts in the selective denitrification of 4-nitrophenol (4-NP) from oily wastewater by catalytic wet peroxide oxidation (CWPO). The CNTs were prepared by chemical vapor deposition, feeding sequentially ethylene (E) and/or acetonitrile (A) during different times until 20 min, resulting in samples E20, A20 and E10A10, the number denoting the time feeding of each precursor and the order of appearance of the letter indicating the order of each precursor. The synthesized CNTs were tested in the CWPO of 4-NP in aqueous solutions and in simulated oily wastewater (2,2,4-trimethylpentane and water) at 80 ºC, initial pH 3.5, C4-NP = 1 g L-1, CH2O2 = 3.56 g/L and Ccatalyst = 2.5 g L-1. The catalyst A20 promoted a faster decomposition of H2O2 and a lower degradation of 4-NP in the aqueous system, whereas the catalyst E20 displayed the opposite trend, since E20 was able to remove 99% of the pollutant and A20 only 69% after 8 h of reaction. E10A10 in biphasic L-L media presented the highest conversion of 4-NP after 24 h in the oily phase (51%), followed by A20 (38%) and then E20 (25%). This tendency may be ascribed to the formation of Pickering emulsions by E10A10. The amphiphilic carachteristic of this material ensures a closer contact between the liquid phases, allowing higher mass transfer.
- Selective denitrification of simulated oily wastewater by oxidation using Janus-structured carbon nanotubesPublication . Roman, Fernanda; Díaz de Tuesta, Jose Luis; Sanches, Flávia Kim; Silva, Adriano S.; Marin, Pricila; Machado, Bruno F.; Serp, Philippe; Pedrosa, Marta; Silva, Adrián; Faria, Joaquim; Gomes, HelderThe intense industrial development has resulted in several consequences for human and environmental health, including the increased discharge of oily products in water bodies. Oily products are widely used in industry, often bearing an associated high cost. Finding alternatives to treat oily wastewater aiming at recovering oily and water phases is an approach allowing recovery of products of economic interest. In this work, Janus-like carbon nanotubes (CNTs) were synthesized by varying the feed time of acetonitrile and ethylene, respectively, as nitrogen/ carbon and carbon precursors in a chemical vapor deposition (CVD) approach. The CVD approach allowed the synthesis of completely undoped, completely doped and partially doped CNTs with a Janus structure. The CNTs were then tested as catalysts for the selective oxidation of 4-nitrophenol (4-NP) contained in a simulated oily wastewater (2,2,4-trimethylpentane/water (O/W) = 1:9, volume basis) by catalytic wet peroxide oxidation (CWPO). The CWPO experiments were conducted for 24 h, 80 ◦C, 2.5 g L-1 of catalyst, and the stoichiometric concentration of H2O2 (3.6 g L-1) for the degradation of 4-NP (1 g L-1). The same conditions were kept for experiments conducted under a biphasic system. The catalysts bearing a Janus-like structure were demonstrated to be more effective in CWPO experiments in aqueous-only and biphasic systems for the abatement of 4-NP.
- Selective oxidation of 4-nitrophenol with H2O2 in a biphasic system by janus-like carbon nanotubesPublication . Sanches, Flávia Kim; Roman, Fernanda; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Silva, Adrián; Faria, Joaquim; Machado, Bruno; Serp, Philippe; Marin, Pricila; Gomes, HelderThe use of petroleum-based products has increased drastically with the increase in population, resulting in the deposition of oily products in aquatic systems. It is estimated that for each ton of petroleum that undergoes refinement processes, between 0.5 and 1 ton of oily wastewaters are generated, bearing an oil concentration that may reach 40 g L-1 [1,2]. Hazardous pollutants dissolved both in oily and aqueous phases may also be found in those oily wastewaters [3], hindering their treatment through conventional processes. Furthermore, the oil phase is, in some cases, an added-value product, and its degradation results in economic losses. Thus, the development of processes that allow the removal of hazardous contaminants from oily and aqueous phases, providing an opportunity for recovering both phases, should be advantageous [3]. This work deals with the selective removal of a hazardous compound (4-nitrophenol, 4-NP) from a simulated oily wastewater (2,2,4-trimethylpentane:water = 10:90 v/v) by an oxidative process considering H2O2 as oxidant and amphiphilic Janus-like carbon nanotubes as catalysts. Amphiphilic catalysts were selected since they should present advantages in this process due to their ability to interact with both aqueous and oily compounds and phases [4]
- 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.