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Plastic waste-derived carbon nanotubes: Influence of growth catalyst and catalytic activity in CWPO

Publication . 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, Helder

Low-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).

2025Journal article

Restricted access

Carbon-Nanotube-Based Superhydrophobic Magnetic Nanomaterial as Absorbent for Rapid and Efficient Oil/Water Separation

Publication . Kudaibergenova, Rabiga M.; Roman, Fernanda; Silva, Adriano S.; Sugurbekova, Gulnar K.

In this work, the simple fabrication of a new superhydrophobic magnetic sponge based on CNTs, NiFe2O4 nanoparticles, and PDMS was investigated. CNTs were synthesized by chemical vapor deposition (CVD) on a nickel ferrite catalyst supported on aluminum oxide (NiFe2O4/Al2O3). The synthesis of nickel ferrite (NiFe) was accomplished using the sol–gel method, yielding magnetic nanoparticles (43 Am2kg−1, coercivity of 93 Oe, 21–29 nm). A new superhydrophobic magnetic PU/CNT/NiFe2O4/PDMS sponge was fabricated using a polyurethane (PU) sponge, CNTs, NiFe2O4 nanoparticles, and polydimethylsiloxane (PDMS) through the immersion coating method. The new PU/CNT/NiFe2O4/PDMS sponge exhibits excellent superhydrophobic/oleophilic/mechanical properties and water repellency (water absorption rate of 0.4%) while having good absorption of oil, olive oil, and organic liquids of different densities (absorption capacity of 21.38 to 44.83 g/g), excellent separation efficiency (up to 99.81%), the ability to be reused for removing oil and organic solvents for more than 10 cycles, and easy control and separation from water using a magnet. The new PU/CNT/NiFe2O4/PDMS sponge is a promising candidate as a reusable sorbent for collecting oil and organic pollutants and can also be used as a hydrophobic filter due to its excellent mechanical properties.

2024Journal article

Open access

Beyond batch experiments: unveiling the potential of bimetallic carbon xerogels for catalytic wet peroxide oxidation of hospital wastewater in continuous mode

Publication . Silva, Adriano S.; Roman, Fernanda; Ribeiro, Rui; Garcia, Juan; Gomes, Helder

Single- and bimetallic carbon xerogels were prepared by incorporating iron and iron-cobalt precursors during their synthesis, respectively, and tested in the catalytic wet peroxide oxidation (CWPO) of ibuprofen spiked into a simulated matrix in batch mode. The bimetallic catalyst outperformed single and non-metallic catalyst by 25 and 85% after 360 min of reaction, at mild temperature (30 °C). The best-performing catalyst was further used to treat hospital wastewater in a CWPO system operating in full continuous mode. Process optimization was carried out considering different catalyst loads, temperatures, and pH. The results obtained showed that the best conditions are initial pH 3, T = 80 °C, and a catalyst load of 35.4 mg cm− 3. Having maintained values of chemical oxygen demand (COD) removals as high as 80% after 24 h of continuous operation, the results herein reported revealed the high potential of the bimetallic carbon xerogel for CWPO of hospital wastewater beyond conventional applications in batch mode. Despite some catalytic deactivation, the bimetallic carbon xerogel still delivered a mineralization degree as high as 55% of the initial total organic carbon (TOC) content of the hospital wastewater in the third 24-h cycle of CWPO in continuous mode of operation with successive catalyst reuse, as opposed to a 73% TOC removal in the first cycle. Therefore, our results open prospects for the implementation of CWPO for hospital wastewater treatment in continuous mode of operation.

2024Journal article

Open access

3D printed photopolymer derived carbon catalysts for enhanced wet peroxide oxidation

Publication . 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, Helder

In 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.

2024Journal article

Open access

Occurrence of micropollutants in surface water and removal by catalytic wet peroxide oxidation enhanced filtration using polymeric membranes loaded with carbon nanotubes

Publication . 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, Helder

Monitoring 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).

2025Journal article

Open access