Browsing by Author "García, Juan"
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- Aplicación de MWNT a aguas residuales de alta carga orgánica mediante CWAOPublication . García, Juan; Gomes, Helder; Serp, Philippe; Kalck, Philippe; Figueiredo, José; Faria, JoaquimUna gran parte de los vertidos residuales que genera la Industria Química. y otras industrias relacionadas con ella, están en forma de corrientes acuosas que, en muchos casos, contienen compuestos orgánicos en una concentración demasiado baja para que su recuperación sea rentable, pero es lo suficiente elevada para constituir una fluente de contaminación importante. La utilización de materiales de carbón como soporte catalítico ha sido ampliamente utilizado en procesos de oxidación húmeda catalítica (CWAO) como un pretratamiento efectivo en el tratamiento de este tipo de efluentes. Los materiales de carbono son utilizados tanto como soportes activos como soportes catalíticos debido a sus características específicas que son principalmente la resistencia a medios ácido/básicos, control de la porosidad y la superficie química y la fácil recuperación de metales mediante la combustión del soporte con el resultado de un bajo impacto medioambiental. El gran impacto de los materiales nanoestruturados se debe a que su gran superficie mejora sus propiedades mecánicas y sus únicas propiedades electrónicas. t abre caminos a una amplia diversidad de nuevas aplicaciones En este contexto, el objetivo principal de este trabajo es ilustrar el potencial que presentan los catalizadores de rutenio soportados en nanotubos de carbono de pared múltiple (MWNT) en la oxidación húmeda catalítica (CWAO) de aguas residuales conteniendo anilina.
- Carbon nanotube supported ruthenium catalysts for the treatment of high strength wastewater with aniline using wet air oxidationPublication . García, Juan; Gomes, Helder; Serp, Philippe; Kalck, Philippe; Figueiredo, José; Faria, JoaquimMulti-walled carbon nanotubes (MWCNT) can be efficiently used as support of ruthenium catalysts for the catalytic wet air oxidation of high strength wastewater containing aniline. Catalysts were prepared using different ruthenium precursors, Ruthenocene [Ru(g5-C5H52], Ruthenium (1,5-cyclooctadiene, 1,3,5-cyclooctatriene) [Ru(cod)(cot)] and Ruthenium trichloride (RuCl3.xH2O), different impregnation methods (excess solution and incipient wetness impregnation) and different MWCNT support surface chemistry (nitric acid oxidized MWCNT-COOH and Na2CO3 ion exchanged MWCNT-COONa). The efficiency of the aniline removal obtained with the catalysts prepared with different precursors decreases in the order [Ru(cod)(cot)] > RuCl3.xH2O > [Ru(g5-C5H52], 100% aniline conversion being obtained after 45 min of reaction with the catalyst prepared with [Ru(cod)(cot)]. The influence of the impregnation technique was found to be negligible, while the use of the MWCNT-COONa support led to increased catalyst performances when compared to that obtained with catalysts prepared with the MWCNT-COOH support. Leaching of ruthenium was observed in all cases, but the use of the precursor [Ru(cod)(cot)] and of the support MWCNT-COONa in the preparation of the catalysts seems to improve their stability. A direct relationship between metal load and catalyst stability was found and attributed to the strength of metal-support interactions.
- Catalytic wet peroxide oxidation in the removal of emerging micropollutantsPublication . Gomes, Helder; Ribeiro, Rui; García, Juan; Frontistis, Zacharias; Mantzavinos, Dionissios; Silva, Adrián; Faria, JoaquimSeveral contaminants of emerging concern (CECs), with negative impact on water security, have been recently identified and quantified in different water sources [1]. Among them, antibiotics are receiving particular attention due to the possible development of antibiotic resistant bacteria and/or resistance genes (ARB&ARG). Conventional urban wastewater treatment plants are unable to cope with most of these compounds, thus allowing their systematic propagation throughout the urban water cycle. The development of efficient and economically viable advanced treatment technologies, able to remove CECs from different water sources, is therefore a top priority in the policy agendas of several countries around the world.
- Editorial - 6th international congress on water, waste and energy management (WWEM-22). 5th international conference on green chemistry and sustainable engineering (GreenChem-22). 2022 international conference on green energy and environmental technology (GEET-22)Publication . Dominguez, Joaquin R.; Nunez-Delgado, Avelino; Gomes, Helder; Augusto, Paulo A.; Varjani, Sunita; García, Juan; Hodaifa, Gassan; Álvarez-Torrellas, SilviaThese were the sixth, fifth, and second editions of a series of biannual academic conferences aimed at creating an international forum for researchers and scientists worldwide to discuss new results regarding the soundest issues related to Water, Waste, Green Chemistry, Green Energy, and Environmental Technologies. Over 330 communications from 27 countries attended these conferences, including 181 posters, 150 selected oral communications, and six plenary talks. Most presentations were based on high-quality original works covering various conference topics. This Special Issue is dedicated to “post-Covid trends and new insights for the physicochemical and biological treatment of wastewaters and soils.”
- Eliminación de contaminantes emergentes mediante adsorción empleando xerogeles de carbónPublication . Álvarez, Silvia; Ribeiro, Rui; Gomes, Helder; Sotelo, José; García, JuanEn la actualidad el número de sustancias quimicas potencialmente peligrosas que pueden lIegar a alcanzar el medio ambiente es muy amplio, por lo que la atención en la investigación de la contaminación dei agua se ha extendido recientemente a lo que se denomina contaminación emergente; es decir, la contaminación causada por sustancias químicas de origen y propiedades muy diversas, en concentraciones muy bajas, y que persisten en las aguas residuales tras el tratamiento de éstas en las plantas depuradoras convencionales.
- 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.
- Estudio cinético en la oxidacion catalítica de anilina con catalizadores de platino soportado en carbon activadoPublication . García, Juan; Gomes, Helder; Figueiredo, José; Faria, Joaquim
- Exploring the activity of chemical-activated carbons synthesized from peach stones as metal-free catalysts for wet peroxide oxidationPublication . Martin-Martinez, Maria; Álvarez-Torrellas, Silvia; García, Juan; Silva, Adrián; Faria, Joaquim; Gomes, HelderPeach stones were used as raw material for the synthesis of activated carbons with different properties. Firstly, peach stones were chemically activated using a 12M H3PO4 solution and carbonized under flowing air (400 °C). The obtained activated carbon, named as PS, is characterized by a high surface development (SBET=1262m2 g−1) and acidic character (pHPZC=4.2). A fraction of PS was further carbonized under N2 atmosphere at 800 °C to remove surface functionalities and to increase its basicity (PS-800). In addition, a Pt catalyst supported on PS (3% w/w Pt/PS) was synthesized by incipient wetness impregnation, resulting in a considerable hydrophilicity increasing. The synthesized materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated solutions of 4-nitrophenol (4-NP, 5 g L−1) during 24 h experiments, conducted at relatively mild operating conditions (T=50–110 °C, pH=3, catalyst load=2.5 g L−1 and [H2O2]0=17.8 g L−1, corresponding to the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP). It was observed that the increase of electron-donating functionalities in PS-800 promotes the generation of reactive HO% radicals, being the activity towards CWPO twice higher than that obtained with the pristine PS. Besides, increasing operating temperature substantially enhances CWPO, finding a 80% of 4-NP removal at 110 °C. On the other hand, despite the sharp increment in H2O2 decomposition due to the presence of Pt particles in Pt/PS catalyst, this decomposition is inefficient in all cases, with a consequent poor pollutant removal. This can be attributed to the recombination of HO% radicals into non-reactive species −scavenging effects, promoted by the hydrophilicity of the catalyst.
- Nanotubos de carbono como suportes para catalisadores de platinaPublication . García, Juan; Gomes, Helder; Serp, Philippe; Kalck, Philippe; Figueiredo, José; Faria, JoaquimDesde a sua descoberta em 19911, que os nanotubos de carbono tem sido amplamente estudados, devido à sua elevada resistência mecânica, excelentes propriedades eléctricas e térmicas e adequação como suporte de catalisadores heterogéneos para reacções em fase líquida2. Neste trabalho pretendeu-se estudar a utilização de nanotubos de carbono de parede múltipla oxidados com HNO3 como suporte na preparação de catalisadores de platina para reacções de degradação oxidativa de compostos orgânicos azotados. Os catalisadores Pt1, Pt2 e Pt3 foram preparados por impregnação em excesso de solução, usando diferentes precursores metálicos, [PtI2(CO)2], H2PtCl6 e [Pt(CH3)2(C8H12)], respectivamente, tendo-se escolhido a reacção de oxidação da anilina como modelo para avaliar a sua eficiência. Na Tabela 1 são apresentados os valores da conversão de anilina (Xanilina), da redução do carbono orgânico total (XTOC) e da selectividade de mineralização total (S), obtidos após 2 h de reacção a 200ºC e 6.9 bar de pressão parcial de oxigénio.
- 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.