Browsing by Author "Gomes, Helder"
Now showing 1 - 10 of 331
Results Per Page
Sort Options
- 17 α-Ethinylestradiol degradation in continuous process by photocatalysis using Ag/Nb2O5 immobilized in biopolymer as catalystPublication . Lenzi, Giane G.; Abreu, Eduardo; Fuziki, Maria Eduarda K.; Fidelis, Michel Zampieri; Brackmann, Rodrigo; Díaz de Tuesta, Jose Luis; Gomes, Helder; Santos, Onélia A.A. dosThis study describes the application of Ag/Nb2O5 catalysts, suspension and spheres alginate immobilized for the degradation of 17α-Ethinylestradiol (EE2). The techniques used to characterize the photocatalysts were as follows: X-ray diffraction (XRD), N2 adsorption–desorption analysis (BET), point charge zero charge (PZC), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Different catalyst calcination temperatures were studied by keeping the silver metal loading at 5%. Among the operational conditions analyzed were pH, catalyst concentration, the emitting source of radiation and the inlet flow rate (in continuous operation). The results of the experiments performed initially with the catalyst in suspension revealed that the highest catalytic activity in the degradation of EE2 was the 5%Ag/Nb2O5 catalyst calcined at 973 K, which removed 77.7% of the initial pollutant concentration in 120 min of reaction. The immobilization of the catalyst in alginate spheres resulted in a degradation reduction, being able to degrade 69.2% of the initial EE2 in a batch system. In the continuous system, the immobilized catalyst obtained a total degraded of 37.3%, with a flow rate of 10 L·h−1. Catalyst reuse was promising, even dropping the removal, degrading around 27% of the initial EE2 concentration in the third cycle of use.
- 3D printed photopolymer derived carbon catalysts for enhanced wet peroxide oxidationPublication . Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Henrique, Adriano; Roman, Fernanda; Omralinov, Daria; Steldinger, Hendryk; Gläsel, Jan; Etzold, Bastian J.M.; Silva, José A.C.; Silva, Adrián; Pereira, Ana I.; Gomes, HelderIn this paper, we explore the application of powdered carbon and 3D-printed carbon monoliths prepared by carbonization of a tailored photopolymer. We demonstrate the efficiency of the developed carbonaceous samples in removing paracetamol (PCM) and sulfamethoxazole (SMX), used as model contaminants. Our results demonstrate that carbon samples are active in CWPO, and their catalytic activity is significantly improved by applying nitric acid and urea functionalization methods. The characterization results showed the pure carbon nature of the material (no ashes), their unique structure defects proven by Raman (D/G > 1.8), textural properties (SBET = 291–884 m2/g) and their surface chemistry, which was addressed by pHPZC (2.5–7.5), acidity (312–2375 μ mol gcat 1) and basicity (117–653 μ mol gcat 1) determination and XPS of highlighted materials (N1s = 0–3.51 at.%, O1s = 7.1–15.3 at.%). Using desorption assays, our study reveals the adsorption role for pollutant degradation by CWPO using carbon monolithic samples. At last, we demonstrated the ability of functionalized 3D-printed carbon monoliths to keep degradation of PCM and total organic carbon (TOC) above 85 % and 80 %, respectively, during 48 h in a continuous flow CWPO system. Sulfamethoxazole degradation in continuous system was also studied to validate the catalyst versatility, achieving 81 % and 79 % pollutant degradation and TOC abatement, respectively, during 48 h on stream. The characterization of the recovered catalyst provides further insights into the absence of structural modifications after the reaction, reinforcing the stability and reusability characteristic of the 3D-printed carbon catalyst.
- 3D tuned porous carbon monolith as catalysts in the wet peroxide oxidation of paracetamolPublication . Roman, Fernanda; Steldinger, Hendryk; Díaz de Tuesta, Jose Luis; Henrique, Adriano; Silva, José A.C.; Gläsel, Jan; Etzold, Bastian J.M.; Gomes, HelderIn recent years, many pharmaceuticals have been identified at trace levels worldwide in the aquatic environment [1]. Municipal wastewater treatment plants (WWTPs) are considered the main sources of these pollutants as they are not generally prepared to deal with such complex substances and thus, they are usually ineffective in their removal [1]. Despite the low concentration of drugs contained in those effluents, the presence of pharmaceuticals, even in trace concentrations, affects the quality of water and constitutes a risk of toxicity for the ecosystems and living organisms [1-2]. Consequently, new regulation for micropollutants discharge and monitoring has been issued in Europe (Directive 2013/39/EU). Paracetamol (PCM) deserves particular attention, since it has recently been discovered as a potential pollutant of waters, largely accumulated in the aquatic environment [3]. This work deals with the treatment of PCM, used as a model pharmaceutical contaminant of emerging concern, by catalytic wet peroxide oxidation using carbon-based monoliths (Fig. 1a) as catalysts. Monoliths were prepared by stereolithographic 3D printing of a photoresin, which was later converted into porous carbon by oxidation in air (300 °C, 6 h) and subsequent pyrolysis in N2 (900 °C, 15 min) as described elsewhere [4]. The materials revealed catalytic activity in the CWPO of PCM allowing to reach PCM conversions up to 30% with a residence time of 3.5 min (Fig. 1b).
- 3D-printed activated carbon for post-combustion CO2 capturePublication . Zafanelli, Lucas F.A.S.; Henrique, Adriano; Steldinger, Hendryk; Díaz de Tuesta, Jose Luis; Gläsel, Jan; Rodrigues, Alírio; Gomes, Helder; Etzold, Bastian J.M.; Silva, José A.C.The applicability of 3D-printed activated carbons for their use to CO2 capture in post-combustion streams and the influence of activation conditions on CO2 uptake and CO2 to N2 selectivity were studied. For two monoliths with the same open cellular foam geometry but low and high burnoff during activation, a series of fixed-bed breakthrough adsorption experiments under typical post-combustion conditions, in a wide range of temperature (313 and 373 K), and partial pressure of CO2 up to 120 kPa were carried out. It is shown that the higher burnoff during activation of the 3D printed carbon enhances the adsorption capacity of CO2 and N2 due to the increased specific surface area with sorption uptakes that can reach 3.17 mol/kg at 313 K and 120 kPa. Nevertheless, the lower burnoff time on monolith 1 leads to higher selectivity of CO2 over N2, up to 18 against 10 on monolith 2, considering a binary interaction to a mixture of CO2/N2 (15/85 vol%) at 313 K. The single and multicomponent adsorption equilibrium is conveniently described through the dual-site Langmuir isotherm model, while the breakthrough curves simulated using a dynamic fixed-bed adsorption linear driving force model. Working capacities for the 3D printed carbon with lower burnoff time lead to the best results, varying of 0.15–1.1 mol/kg for the regeneration temperature 300–390 K. Finally, consecutive adsorption-desorption experiments show excellent stability and regenerability for both 3D printed activated carbon monoliths and the whole study underpins the high potential of these materials for CO2 capture in post-combustion streams.
- Activated carbon xerogel-chitosan composite materials for catalytic wet peroxide oxidation under intensified process conditionsPublication . Pinho, Maria; Silva, Adrián; Fathy, Nady; Attia, Amina; Gomes, Helder; Faria, JoaquimDifferent activated carbon xerogels (ACX) and ACX–chitosan composite materials were tested for the removal of the azo dye Orange II (OII) in aqueous solutions, either by pure adsorption or by catalytic wet peroxide oxidation (CWPO). The ACX materials were produced by activation of an organic resorcinol formaldehyde xerogel (RFX), considering different activation procedures: chemical impregnation with H3PO4 at 773 K (ACX-P), chemical impregnation with monoethanolamine at 773 K (ACX–MEA) and alkali activation with KOH at 1073 K using a 1:1 mass ratio of KOH/RFX (ACX-K). The ACX–chitosan composites were produced by oxidation of ACX with oxalic acid followed by treatment with chitosan gel. During screening studies in adsorption and CWPO tests, the composites ACX-K–chitosan and ACX-P–chitosan revealed the best performances among all the tested materials, namely OII removals between 69 and 73% were respectively obtained in CWPO after 150 min (pH 3.0, T = 323 K, material load of 0.2 g L-1, OII concentration of 100 mg L-1 and hydrogen peroxide concentration of 1.18 g L-1). In process intensification conditions, the CWPO process performance increased remarkably when using the ACX-P–chitosan composite. Complete OII removal in 90 min and a TOC removal of 55% in 24 h was achieved by CWPO, while less than 10% of OII was removed by pure adsorption (pH 3.5, T = 353 K, material load of 2.5 g L-1, OII concentration of 4.5 g L-1 and, in CWPO, hydrogen peroxide concentration of 25 g L-1). The superior performance of the ACX–chitosan composite at intensified process conditions was more likely related with the high pollutant/catalyst ratio, which favors a more controllable H2O2 decomposition near the adsorbed pollutant species, thus avoiding parallel parasite reactions involving hydroxyl radicals and leading to a consequent higher efficiency of its usage. These conditions are of major interest in the treatment of highly polluted waste waters.
- Activated carbon xerogels for the removal of azo dyes by adsorption and catalytic wet peroxide oxidationPublication . Ribeiro, Rui; Fathy, Nady; Silva, Adrián; Faria, Joaquim; Gomes, Helder
- Activated carbon xerogels for the removal of the anionic azo dyes Orange II and Chromotrope 2R by adsorption and catalytic wet peroxide oxidationPublication . Ribeiro, Rui; Fathy, Nady; Attia, Amina; Silva, Adrián; Faria, Joaquim; Gomes, HelderActivated carbon xerogels (ACXs) were tested for the removal of azo dyes in aqueous solutions, either by adsorption or by catalytic wet peroxide oxidation (CWPO). Two azo dyes, Orange II (OII) and Chromotrope 2R (C2R), were chosen as model pollutants. The ACXs were produced by activation of an organic resorcinol–formaldehyde xerogel (RFX). Three different activation procedures were carried out producing five distinct ACXs: steam at 1073 K (ACX-S), chemical impregnation with H3PO4 at 773 K (ACX-P) and alkali activation with dry KOH at 973 K (ACX-K), using three different mass ratios of KOH/RFX, namely 1:1 (ACX-K1), 2:1 (ACX-K2) and 4:1 (ACX-K4). The results obtained in the adsorption experiments carried out at pH = 3, T = 303 K, adsorbent load of 0.1 g L 1 and azo dye concentration of 100 mg L 1 show that the interaction between the carbon materials and the anionic dyes is enhanced with the basicity of the carbon surfaces. ACX-K materials, the carbon materials with higher basicity amongst those prepared, exhibit high adsorption performances for the removal of both dyes, namely from over 215 mg g 1 (for adsorption of C2R on ACX-K2 after 150 min) up to 499 mg g 1 (for adsorption of OII on ACX-K4 at the same period of time). Furthermore, with ACX-K materials in CWPO (i.e., using H2O2) increments in the removal of C2R as high as 33%, 24% and 20%, in comparison to the removals obtained by adsorption, where obtained when ACX-K1, ACX-K2 and ACX-K4 were respectively tested at 303 K. Increasing the operating temperature (T = 323 K), the removal increments achieved by CWPO, compared to the removals obtained by adsorption at the same temperature, increase 67%, 59% and 49%, when ACX-K1, ACX-K2 and ACX-K4 were respectively tested. Recycling studies with ACX-K1 puts in evidence the high stability of this catalyst in CWPO, since it was observed, after a first reaction run, that the catalytic activity of this material is not affected by its successive reuse. Increasing the operating temperature (T = 323 K) and the adsorbent load (0.5 g L 1), ACX-K4 is able to completely remove the C2R content by adsorption. In the case of ACX-K1 and ACX-K2, adsorption removals over 97% of the C2R content are attainable.
- Activated carbons functionalized with thiol and sulfonic acid groups for catalytic wet peroxide oxidationPublication . Gomes, Helder; Miranda, Sandra; Sampaio, Maria; Silva, Adrián; Faria, JoaquimActivated carbons are known catalysts for hydrogen peroxide decomposition through a pathway involving the formation of hydroxyl radicals. Thus, it seems logical to take advantage of the strong oxidizing properties of these radicals for the degradation of organic pollutants adsorbed and concentrated on the surface of activated carbons. In a recent work, we established the unprecedented performance of acidic activated carbons functionalized with sulphuric acid in the catalytic wet peroxide oxidation of Chromotrope 2R, an anionic azo dye. In the present work, we explore the influence of the amounts and types of surface groups with sulphur on the catalytic efficiency of the activated carbons.
- Activated carbons prepared from a compost obtained in mechanical biological treatment plants for municipal solid waste processingPublication . Díaz de Tuesta, Jose Luis; Masso, Caroline; Pietrobelli, Juliana Martins Teixeira; Silva, Adrián; Faria, Joaquim; Gomes, HelderActivated carbons (ACs) obtained from different organic wastes have been reported in several works, aiming the valorisation of low-cost useful materials [1]. However, organic wastes typically contain inorganic substances, which can be leached away from the prepared ACs when employed in oxidative aqueous conditions. The current study proposes different strategies to produce ACs from a compost obtained (in excess) during the treatment of the organic fraction of municipal solid waste by anaerobic digestion and maturation in waste management sites.
- Activated carbons treated with sulphuric acid for degradation of trinitrophenol by catalytic wet air oxidationPublication . Gomes, Helder; Katsoni, Athanasia; Faria, Joaquim; Figueiredo, José; Mantzavinos, Dionissios; Silva, Adrián