Adsorbentes carbonosos a partir de materiales de desecho de origen industrial: preparación, caracterización y aplicaciones

En la presente Tesis Doctoral se proponer métodos experimentales que permitan el reciclado de materiales de desecho poliméricos (NFU, goma; PET, plástico; CV, plástico/goma) mediante su utilización como materiales de partida en la preparación de materiales carbonosos (MCA) para su empleo en la adsorción de solutos de naturaleza inorgánica y orgánica en disolución acuosa. En el desarrollo del trabajo, la preparación de los MCA se ha llevado a cabo a partir de sistemas de un único componente y de dos o tres componentes por métodos químicos y por métodos físicos. En el primer caso se han utilizado los ácidos HCl y HNO3 y una base como NaOH y en el segundo caso los tratamientos térmicos se han efectuado en atmósfera inerte de N2 y en las atmósferas gasificantes de aire, dióxido de carbono y vapor de agua. Con fines comparativos, como adsorbentes también se han empleado productos comerciales como un negro de carbón, un carbón activado y una fibra de carbono. Los MCA, todos o tan solo algunas muestras seleccionadas, han sido caracterizados en términos de la composición química, textura porosa y química superficial. Como adsorbatos en disolución acuosa se han utilizado iones inorgánicos altamente tóxicos en sistemas de uno y tres componentes (Hg2+, Pb2+, Cr6+, Cd2+) y moléculas orgánicas de gran importancia medioambiental (fenol, p-aminofenol, p-nitrofenol, p-clorofenol y azul de metileno).In this Doctoral Thesis we propose experimental methods that allow the recycling of polymeric waste materials (NFU, rubber, PET, plastic, CV, plastic / rubber) by using them as starting materials in the preparation of carbonaceous materials (MCA) for Its use in the adsorption of solutes of organic and inorganic nature in aqueous solution. In the development of the work, the preparation of MCAs has been carried out from single component and two or three component systems by chemical methods and by physical methods. In the first case the acids HCl and HNO3 and a base like NaOH have been used and in the second case the thermal treatments have been carried out in an inert atmosphere of N2 and in the gasifying atmospheres of air, carbon dioxide and water vapor. For comparative purposes, commercial products such as carbon black, activated carbon and carbon fiber have also been used as adsorbents. MCAs, all or just selected samples, have been characterized in terms of chemical composition, porous texture and surface chemistry. As adsorbates in aqueous solution, highly toxic inorganic ions have been used in one and three component systems (Hg2 +, Pb2 +, Cr6 +, Cd2+) and organic molecules of great environmental importance (phenol, p-aminophenol, p-nitrophenol, p-chlorophenol and Methylene blue).Trabajo patrocinado por: Ministerio de Educación y Ciencia. Proyecto TRA2008-06602-C03-0

Simultaneous adsorption of Cd2+ and reactive dye on mesoporous nanocarbons

High-surface-area mesoporous MgO-templated nanocarbons made with reinforcing fibres from scrap tyres and a bituminous waste as carbon precursors were employed for the simultaneous adsorption of Cd2+ and reactive Cibacron Brilliant Yellow 3G-P dye. A commercial activated carbon (AC) Darco KB-WJ was also used for comparison purposes. The effect of the pH of the solution was studied to establish whether acidic pH favours the adsorption of reactive dye and alkaline pH improves the removal of Cd2+. Because the surface chemistry of the three adsorbents was similar, the focus in this study was directed towards their textural characteristics. It was found that the larger the SBET, the greater the amount of dye removal. The adsorption isotherms corresponding to the commercial AC fitted to the Langmuir-Freundlich model, whereas in the case of the nanocarbons the Langmuir model provided the best fit. The results obtained show that Cd2+ is successfully adsorbed in the presence of the dye due to the ion exchange between the Na+ from the dye and the Cd2+. It was also found that a high total and mesopore volume, and a high SBET played a determinant role in the simultaneous adsorption

Carbonaceous adsorbents from polymers-rubber and plastic wastes for adsorption of methylene blue

Se investiga el desarrollo de adsorbentes carbonosos (AC) a partir de restos de caucho de neumáticos (TR), botellas de plástico de poli(tereftalato de etileno) (PET) y una mezcla industrial de PP (plástico)-EPDM (caucho) (VR) para su uso en el tratamiento de la decoloración del agua. No sólo se utilizaron los tres materiales de partida por separado, sino también mezclas de dos y tres componentes en las proporciones de masa 50/50 y 75/12,5/12,5 para todos ellos. Los CAs se prepararon primero por tratamiento térmico de los materiales a 900°C durante 2 h en N2 y a 850°C durante 2 h en vapor, luego se caracterizaron por difracción de rayos X (XRD), microscopía electrónica de barrido (SEM), adsorción de N2 a -196°C, porosimetría de mercurio, espectroscopía FT-IR y medición del pH del punto de carga cero (pHpzc), y finalmente se probaron como adsorbentes de azul de metileno (MB) en solución acuosa. El rendimiento del proceso de preparación de CAs es significativamente mayor con TR y bastante similar con PET y VR. Aumenta o disminuye significativamente con las mezclas de materiales, presumiblemente debido a la interacción de VR con TR y PET durante dicho proceso. El uso de tales mezclas da lugar a mayores aumentos de la superficie y la porosidad. El SBET es de 675 m2-g-1 para la muestra preparada a partir de la mezcla 50/50 de PET y RV (M3), mientras que es de 248 y 100 m2-g-1 para los productos de la activación por separado de PET y RV en vapor. El pHpzc se sitúa entre 5,8 y 11,1. El efecto favorable también afecta al proceso de adsorción de MB. La constante cinética de pseudosegundo orden es de 2,69-103 g-mol-h-1 y la capacidad de adsorción de Langmuir es de 0,85-103 g-mol-h-1 para M3.The development of carbonaceous adsorbents (CAs) from scrap tyre rubber (TR), poly(ethylene terephthalate) plastic bottles (PET) and an industrial PP (plastic)-EPDM (rubber) blend (VR) for use in the treatment of water discolouration is investigated. Not only the three starting materials separately, but also two- and three-component blends in the mass ratios of 50/50 and 75/12.5/12.5 were used for all of them. The CAs were first prepared by heat treatment of the materials at 900°C for 2 h in N2 and at 850°C for 2 h in steam, then characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), adsorption of N2 at -196°C, mercury porosimetry, FT-IR spectroscopy and measurement of the pH of the zero charge point (pHpzc), and finally tested as adsorbents for methylene blue (MB) in aqueous solution. The yield of the preparation process of CAs is significantly higher with TR and quite similar to PET and VR. It significantly increases or decreases with material mixtures, presumably due to the interaction of VR with TR and PET during such a process. The use of such blends results in greater increases in surface area and porosity. The SBET is 675 m2-g-1 for the sample prepared from the 50/50 mixture of PET and VR (M3), while it is 248 and 100 m2-g-1 for the products of the separate activation of PET and VR in steam. pHpzc is between 5.8 and 11.1. The favourable effect also concerns the adsorption process of MB. The pseudo-second order kinetic constant is 2.69-103 g-mol-h-1 and the Langmuir adsorption capacity is 0.85-103 g-mol-h-1 for M3.Ministerio de Ciencia e Innovación. Proyecto CTM2008-03636 Junta de Extremadura y Fondos FEDER. Ayuda GR18013peerReviewe

Urea coated with oxidized charcoal reduces ammonia volatilization

Urea is the most consumed nitrogen fertilizer in the world. However, its agronomic and economic efficiency is reduced by the volatilization of NH3, which can reach 78 % of the applied nitrogen. The coating of urea granules with acidic compounds obtained by charcoal oxidation has the potential to reduce the volatilization, due to the acidic character, the high buffering capacity and CEC. This work aimed to evaluate the effect of HNO3-oxidized carbon on the control of NH3 volatilization. These compounds were obtained by oxidation of Eucalyptus grandis charcoal, produced at charring temperatures of 350 and 450 ºC, with 4.5 mol L-1 HNO3. The charcoal was oxidized by solubilization in acidic or alkaline medium, similar to the procedure of soil organic matter fractionation (CHox350 and CHox450). CHox was characterized by C, H, O, N contents and their respective atomic relations, by the ratio E4 (absorbance 465 nm) by E6 (absorbance 665 nm), and by active acidity and total acidity (CEC). The inhibitory effect of CHox on the urease activity of Canavalia ensiformis was assessed in vitro. The NH3 volatilization from urea was evaluated with and without coating of oxidized charcoal (U-CHox350 or U-CHox450) in a closed system with continuous air flow. The pH of both CHox was near 2.0, but the total acidity of CHox350 was higher, 72 % of which was attributed to carboxylic groups. The variation in the ionization constants of CHox350 was also greater. The low E4/E6 ratios characterize the high stability of the compounds in CHox. CHox did not inhibit the urease activity in vitro, although the maximum volatilization peak from U-CHox450 and U-CHox350 occurred 24 h after that observed for uncoated urea. The lowest volatilization rate was observed for U-CHox350 as well as a 43 % lower total amount of NH3 volatilized than from uncoated urea

Adsorbentes carbonosos a partir de materiales de desecho de origen industrial: preparación, caracterización y aplicaciones

En la presente Tesis Doctoral se proponer métodos experimentales que permitan el reciclado de materiales de desecho poliméricos (NFU, goma; PET, plástico; CV, plástico/goma) mediante su utilización como materiales de partida en la preparación de materiales carbonosos (MCA) para su empleo en la adsorción de solutos de naturaleza inorgánica y orgánica en disolución acuosa. En el desarrollo del trabajo, la preparación de los MCA se ha llevado a cabo a partir de sistemas de un único componente y de dos o tres componentes por métodos químicos y por métodos físicos. En el primer caso se han utilizado los ácidos HCl y HNO3 y una base como NaOH y en el segundo caso los tratamientos térmicos se han efectuado en atmósfera inerte de N2 y en las atmósferas gasificantes de aire, dióxido de carbono y vapor de agua. Con fines comparativos, como adsorbentes también se han empleado productos comerciales como un negro de carbón, un carbón activado y una fibra de carbono. Los MCA, todos o tan solo algunas muestras seleccionadas, han sido caracterizados en términos de la composición química, textura porosa y química superficial. Como adsorbatos en disolución acuosa se han utilizado iones inorgánicos altamente tóxicos en sistemas de uno y tres componentes (Hg2+, Pb2+, Cr6+, Cd2+) y moléculas orgánicas de gran importancia medioambiental (fenol, p-aminofenol, p-nitrofenol, p-clorofenol y azul de metileno).In this Doctoral Thesis we propose experimental methods that allow the recycling of polymeric waste materials (NFU, rubber, PET, plastic, CV, plastic / rubber) by using them as starting materials in the preparation of carbonaceous materials (MCA) for Its use in the adsorption of solutes of organic and inorganic nature in aqueous solution. In the development of the work, the preparation of MCAs has been carried out from single component and two or three component systems by chemical methods and by physical methods. In the first case the acids HCl and HNO3 and a base like NaOH have been used and in the second case the thermal treatments have been carried out in an inert atmosphere of N2 and in the gasifying atmospheres of air, carbon dioxide and water vapor. For comparative purposes, commercial products such as carbon black, activated carbon and carbon fiber have also been used as adsorbents. MCAs, all or just selected samples, have been characterized in terms of chemical composition, porous texture and surface chemistry. As adsorbates in aqueous solution, highly toxic inorganic ions have been used in one and three component systems (Hg2 +, Pb2 +, Cr6 +, Cd2+) and organic molecules of great environmental importance (phenol, p-aminophenol, p-nitrophenol, p-chlorophenol and Methylene blue).Trabajo patrocinado por: Ministerio de Educación y Ciencia. Proyecto TRA2008-06602-C03-0