Browsing by Author "Ovejero, Gabriel"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Enhancement of p-nitrophenol adsorption capacity throughN2-thermal-based treatment of activated carbonsPublication . Álvarez-Torrellas, Silvia; Martin-Martinez, Maria; Gomes, Helder; Ovejero, Gabriel; García, JuanIn this work several activated carbons showing different textural and chemical properties were obtained by chemical and physical activation methods, using a lignocellulosic material (peach stones) as precursor. The activated carbon resulting from the chemical activation, namely as CAC, revealed the best textural properties (S BET = 1521 m 2 g −1 , pore volume = 0.90 cm 3 g −1 ) and an acidic character. It was found that the activated carbon obtained at 300 °C (under air atmosphere, PAC_air), and those synthesized at 750 °C in presence of N 2 flow with bubbling of water/12 M H 3 PO 4 solution (PAC_N 2 (H 2 O)/PAC_N 2 (H 3 PO 4 )), respectively, revealed worse textural properties, compared to CAC. Two functionalization treatments, by using sulphuric acid at boiling temperature (PACS) and nitric acid-urea-N 2 heating at 800 °C (PAC-NUT), were applied to PAC_air, in order to enhance the adsorption ability of the carbon material. Several techniques were carried out to characterize the physical and chemical properties of the obtained carbon materials. The modification treatments had influence on the carbon surface properties, since the nitric acid-urea-N 2 heating treatment led to a carbon material with highly-improved properties (S BET = 679 m 2 g −1 , pH IEP = 5.3). Accordingly, the original and modified-carbon materials were tested as adsorbents to remove 4-nitrophenol (4-NP), assessing batch and fixed-bed column adsorption tests. PAC-NUT carbon offered the best adsorption behavior (q e = 234 mg g −1 ), showing a high ability for the removal of 4-NP from water.
- New insights on the removal of diclofenac and ibuprofen by CWPO using a magnetite-based catalyst in an up-flow fixed-bed reactorPublication . Huaccallo-Aguilar, Y.; Díaz de Tuesta, Jose Luis; Álvarez-Torrellas, Silvia; Gomes, Helder; Larriba, Marcos; Ovejero, Gabriel; García, JuanThis research has been focused on the removal of two anti-inflammatory drugs, diclofenac (DCF) and ibuprofen (IBU), by a continuous catalytic wet peroxide oxidation (CWPO) process using a lab-synthesized nanomagnetic catalyst (Fe3O4/MWCNTs). The central composite rotatable design (CCRD) method was used to study the effect of DCF and IBU concentration (expressed as theoretical oxygen demand (ThOD) between 0 and 52.5 mg L-1) and of the feed stream pH (from 3 to 7) on the removal of total organic carbon (TOC) and the concentration of aromatic compounds (Arm) and total phenolic compounds (TP) by CWPO. It could be observed that DCF was preferably removed from the DCF-IBU aqueous mixture at pH values ranging from 3 to 5. In addition, feed stream pH had a significant effect on the pollutants removal, as well as on TOC, TP and aromatic compounds removal, observing an increasing in the pollutants degradation when feed stream pH decreased from 7 to 3. Quadratic models predicted for response variable, such as TOC, TP and aromatic compounds removal, and their maximum model-predicted removal values were of 90.0, 80.2 and 90.0%, respectively. Finally, as a proof of concept, three environmentally-relevant aqueous matrices, spiked with DCF-IBU mixture, were treated. In this case, relatively high TOC degradation values were found after 20 h reaction time (ca. 57.7, 73.9 and 54.5% in surface water, WWTP effluent and hospital wastewater, respectively). This work deals the first study about DCF-IBU removal in aqueous solution by CWPO, as well as a continuous study using real wastewater that allow to extend the experimental results to a real scenario.
- Removal of antibiotic compounds by adsorption using glycerol-based carbon materialsPublication . Álvarez-Torrellas, Silvia; Ribeiro, Rui; Gomes, Helder; Ovejero, Gabriel; Rodríguez, A.; García, JuanIn the recent past few years, antibiotics have raised a significant concern from the research community, due mainly to the antibiotic resistance generated by metabolites and the continuous release of these drugs to the environment. Adsorption, since it is a non-destructive tertiary technology, has been revealed as one of the most advantageous technique in wastewater treatment processes. Commercial activated carbons usually show high affinity to hundreds of organic and inorganic compounds, since the use of commercial materials is associated to high operation and regeneration costs. So, the preparation of activated carbons from crude glycerol, an abundant feedstock of the biodiesel production, consists of an interesting research focus. The aim of this study is to explore several glycerol-based carbon materials synthesized by partial carbonization in concentrated sulfuric acid solution and further thermal activation for the removal of the antibiotics flumequine (FLQ) and tetracycline (TCN) from water.
- Removal of antibiotic compounds by adsorption using glycerol-based carbon materialsPublication . Álvarez-Torrellas, Silvia; Ribeiro, Rui; Gomes, Helder; Ovejero, Gabriel; García, JuanThis study is focused on the synthesis and application of glycerol-based carbon materials (GBCM200, GBCM300 and GBCM350) as adsorbents for the removal of the antibiotic compounds flumequine and tetracycline from aqueous solution. The synthesis enrolled the partial carbonization of a glycerol-sulfuric acid mixture, followed by thermal treatments under inert conditions and further thermal activation under oxidative atmosphere. The textural properties were investigated through N2 adsorption–desorption isotherms, and the presence of oxygenated groups was discussed based on zeta potential and Fourier transform infrared (FTIR) data. The kinetic data revealed that the equilibrium time for flumequine adsorption was achieved within 96 h, while for tetracycline, it was reached after 120 h. Several kinetic models, i.e., pseudo-first order, pseudo-second order, fractional power, Elovich and Weber–Morris models, were applied, finding that the pseudo-second order model was the most suitable for the fitting of the experimental kinetic data. The estimated surface diffusion coefficient values, Ds, of 3.88 and 5.06 10 14 m2 s 1, suggests that the pore diffusion is the rate limiting step of the adsorption process. Finally, as it is based on SSE values, Sips model well-fitted the experimental FLQ and TCN adsorption isotherm data, followed by Freundlich equation. The maximum adsorption capacities for flumequine and tetracycline was of 41.5 and 58.2 mg g 1 by GBCM350 activated carbon.