Browsing by Author "Steldinger, Hendryk"
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- 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.
- Separation of alkane isomers in a hierarchically structured 3D-printed porous carbon monolithPublication . Henrique, Adriano; Steldinger, Hendryk; Díaz de Tuesta, Jose Luis; Glaesel, Jan; Rodrigues, Alírio; Gomes, Helder; Etzold, Bastian J.M.; Silva, José A.C.Hierarchically structured 3D printed porous carbons monoliths, exhibiting cylinder structures composed of tetragonal cubic centered unit cells, were studied for their applicability in adsorptive pentane (C5) and hexane (C6) alkane isomers separation (linear/branched). Three materials of the same macroscopic shape were employed in the study, which varied in the micro- and mesoporosity by changing the final CO2 activation step: non-activated and activated at 1133 K for 6 and 12 h, respectively. Fixed bed breakthrough experiments were conducted for C5/C6 isomer feed mixtures, covering 373, 423, and 473 K temperatures and total alkane partial pressure up to 50.0 kPa. Results demonstrated that the initial porosity for the non-activated monolith enables the complete separation of linear from their respective branched isomers (slightly adsorbed) via a near molecular sieving effect, showing the following sorption hierarchy order (nC6 > nC5) >> > >> (2MP > 3MP > 23DMB approximate to iC5 > 22DMB). Regarding the CO2-activated monoliths, both showed a completely different picture, being all the alkane isomers adsorbed (much higher loadings) following the sorption hierarchy order: nC6 > 3MP > 2MP > 23DMB > 22DMB > nC5 > iC5. These results indicate that besides enhancing the microporosity and available specific surface area, the pore sieving effect of branched alkanes is lost due to the pore widening during the CO2 activation. The breakthrough data for the non-activated monolith is also numerically fitted with a convenient, dynamic adsorption model.
- Separation of n/iso-paraffins in a hierarchically structured 3D-printed porous carbon monolithPublication . Henrique, Adriano; Zafanelli, Lucas F.A.S.; Aly, Ezzeldin; Steldinger, Hendryk; Gläsel, Jan; Rodrigues, Alírio; Etzold, Bastian J.M.; Silva, José A.C.Hierarchically structured 3D-printed porous carbons monoliths were investigated for their applicability in adsorptive n/iso-paraffin separation. Three materials of the same macroscopic shape were employed, which varied in the micro- and mesoporosity by altering the final CO2 activation step: non-activated and activated at 1133 K for 6 and 12 h, respectively. Chromatographic breakthrough experiments were conducted for pentane and hexane isomer mixtures at industrially relevant separation conditions. Results demonstrated that the initial porosity for the non-activated monolith enables the complete separation of linear paraffins from their branched isomers (slightly adsorbed) via a near molecular sieving effect. The Langmuir isotherm conveniently fitted the adsorption equilibrium data, and a dynamic mathematical model suitably predicted the breakthrough curves. Regarding the CO2 activated monoliths, both showed adsorption towards all alkanes with practically no selectivity between them.