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Carbon-based materials were tested as methanogenic boosters to enhance the anaerobic treatment slaughterhouse wastewater, which included an organic xerogel (OX) doped with graphene oxide, a peach stone carbon (PSC), and a monolithic whey carbon (MWC). Enhanced treatment by the carbon-based boosters was evident in terms of organic matter removal and methane production rate, which was globally reflected on a superior methanogenic conversion efficiency as compared to the unamended control. OX appeared as the best methanogenic booster increasing up to 77 % and 12 % the methane production rate and organic matter removal, respectively. The obtained results suggest that hydrolysis and acidification of the complex wastewater were the limiting steps during the treatment of this industrial effluent. This observation is consistent with the higher production of ammonium, derived from protein hydrolysis, which occurred in bioreactors amended with carbon-based materials, as compared to the unamended control. Several changes in the relative abundance of key microbial taxa occurred; particularly, members of the bacterial families Synergistaceae and Anaerolineaceae, as well as the archaeal Methanolinea and Proteiniclasticum genera, increased significantly in the presence of OX. The synthesized materials are proposed to improve the performance of anaerobic treatment systems dealing with complex wastewaters.

Novel customised carbon monoliths with a high specific surface area were synthesised by carbonisation plus activation of dehydrated whey powders, a biomass byproduct of the dairy industry. The whey powders were casted directly by pouring them into a desired mould. After a pseudo-sintering process promoted by the self-reaction of the whey components (mostly lactose and whey proteins) at moderate temperatures (ca. 250 °C), 3D porous carbons were obtained. The process did not require any binder or external overpressure to prepare the 3D porous carbons. Upon thermal activation with CO2 or chemical activation with H3PO4 and KOH, the shape of the monolithic structure was preserved after the development of a microporous network (SBET up to 2400 m2/g). Both thermal and chemical activation had little effect on the macroporosity of the monoliths. Activation of these 3D carbons had to be performed with care to avoid heterogeneous skin/core activation and/or overactivation. Highly porous monoliths (SBET of 980 m2/g; open porosity of 70%) with outstanding compressive strength (10 MPa) could be obtained by thermal activation (CO2) of whey monoliths at 850 °C for 1.5 h. Additionally, the use of whey as a precursor provided the carbon monolith with a relatively high nitrogen content (ca. 3 wt.%).

Carbon-based materials have been shown to enhance anaerobic digestion processes by promoting direct interspecies electron transfer in methanogenic consortia. However, little is known on their effects during the treatment of complex substrates, such as those derived from protein-rich wastewaters. Here, organic xerogels (OX) are tested, for the first time, as accelerators of the methanogenic activity of an anaerobic consortium treating a synthetic protein-rich wastewater. Three OX with distinct pore size distribution (10 and 1000 nm for OX-10 and OX-1000, respectively) and structural conformation (graphene oxide integration into OX-10-GO polymeric matrix) were synthesized. OX-1000 promoted the highest methane production rate (5.21 mL/g*h, 13.5% increase with respect to the control incubated without OX) among the synthesized OX. Additionally, batch bioreactors amended with OX achieved higher chemical oxygen demand (COD) removal (up to 88%) as compared to the control, which only showed 50% of COD removal. Interestingly, amendment of bioreactors with OX also triggered the production of medium-chain fatty acids, including caprylate and caproate. Moreover, OX decreased the accumulation of ammonium, derived from proteins hydrolysis, partly explained by their adsorption capacities, and probably involving their electron-accepting capacity promoting anaerobic ammonium oxidation. This is the first time that OX were successfully applied as methanogenic accelerators for the anaerobic treatment of synthetic protein-rich wastewater, increasing the methane production rate and COD removal as well as triggering the production of medium chain fatty acids and attenuating the accumulation of ammonium. Therefore, OX are proposed as suitable materials to boost the efficiency of anaerobic systems to treat complex industrial wastewaters.

In this work, unsupported Pd aerogel catalysts were synthesized for the very first time by using microwaves as a heating source followed by a lyophilization drying process and used towards formic acid electro-oxidation in a microfluidic fuel cell. Aerogels were also made by heating in a conventional oven to evaluate the microwave effect during the synthesis process of the unsupported Pd aerogels. The performance of the catalysts obtained by means of microwave heating favored the formic acid electro-oxidation with H2SO4 as the electrolyte. The aerogels' performance as anodic catalysts was carried out in a microfluidic fuel cell, giving power densities of up to 14 mW cm-2 when using mass loads of only 0.1 mg on a 0.019 cm2 electrode surface. The power densities of the aerogels obtained by microwave heating gave a performance superior to the resultant aerogel prepared using conventional heating and even better than a commercial Pd/C catalyst.

Whey, the main by-product of the dairy industry, is proposed as a sustainable binder for the production of extruded activated carbon. Coconut shell char was mixed with controlled quantities of either rehydrated whey powders or partially dehydrated liquid whey. After extrusion, extrudates were dried, and carbonised or activated under N2 or CO2 atmosphere, respectively. A comprehensive study of the effect of different parameters including binder proportion, coconut shell char particle size and carbonisation temperature was carried out. The composition of whey prompted Maillard reactions boosted with temperature that conferred a resin-like behaviour to the binder. Quality parameters of the resulting extrudates were their ball-mill hardness, real and bulk densities. All whey-bound pellets retained their original shape after the high temperature treatment. The hardness of those whey extrudates was particularly remarkable considering the biomass origin of this binder. The carbonisation temperature had little effect in the hardness or densities of the carbon pellets. The best pellet formulation comprised the use of coconut shell char powders with particle sizes < 212 µm, in mixtures having a 7/3 char/dry whey mass ratio. The properties of the pellets obtained after the activation of such pellets were comparable to those of commercial activated carbon extrudates. The use of partially dehydrated liquid whey rather than re-hydrated dry whey rendered very similar results. The alkalinity of the binder made the resulting activated carbons adequate for H2S removal at room temperature. An economic estimation of the process placed whey in a practical position within the binder market.

The presence of moderate concentrations of impurities in the nickel-plating baths generates failures on the coated pieces. This situation entails the necessity of replacing the electroplating bath, which implies the generation of large volumes of wastewater with metallic species and high quantity of sludge. For this reason, the adsorption of the principal impurities of nickel-plating baths of an industry was analyzed in this work. Particularly, the removal of Zn2+ was studied in more detail since the presence of this metal in the baths generates black spots on the coated pieces. Different commercial materials were used as adsorbents and Zn2+ adsorption studies were carried out using both standard solutions and industrial water from the nickel-plating baths. All the adsorption tests were performed in batch systems under constant agitation and the quantification of the impurities was made by ICP-MS analysis. The bone char (BC) was an efficient adsorbent for the removal of the principal impurities of nickel-plating baths. The use of molecular simulation tools helped to understand the preferences of the hydroxyapatite (the principal component of bone char) for different metallic ions present in the industrial waters. According to both the experimental adsorption and molecular simulation results, hydroxyl and phosphate groups of bone char are responsible of the adsorption of impurities of nickel-plating baths.

The synthesis of resorcinol–formaldehyde (RF) xerogels is versatile enough to provide materials with custom pore size distributions in the meso-/macroporous range. Specifically, seven xerogels were synthesised by changing the pH of the same RF solution, from pH 3 to pH 6. The resulting materials presented meso-/macroporous size distributions with average pore sizes from < 5 to 510 nm, as determined by Hg intrusion and N2 adsorption. Most of the RF xerogels had very similar geometric densities, except for the gels obtained at the two highest pH values, which were more dense. Both flexural and uniaxial compression tests were carried out to determine the dependence of strength and stiffness on the porosity of the xerogels. The results followed a power-law relationship between the mechanical properties and the density of the materials. However, two series of RF xerogels were found to fit such law independently, with the gels obtained at the three most acidic pH values (pH 3–4) showing unexpectedly high compression moduli. Further characterisation of the xerogels microstructure revealed the existence of rod-like microstructures that would bear most loads during the compression tests. These microstructures would act as struts that, once broken, would cause the catastrophic failure (bursting) of the xerogel.

The simultaneous removal of phosphate and aluminum from water was studied on iron-modified activated carbons. Methods such as oxidation with HNO3, impregnation and co-precipitation of iron were used to modify a commercial coconut activated carbon and to obtain seven different modified carbons. The physicochemical properties of selected samples were studied by different analytic methods such as FT-IR spectroscopy, SEM/EDX analysis and X-ray diffraction. Adsorption studies of phosphate and aluminum from water in single and binary systems were performed in bath systems with constant agitation at 30 °C and different values of pH. Particularly, the sample obtained by Oxidation-Impregnation-Drying procedure (CCOFeTB) contains 3.80% of iron in amorphous phase according to the EDX and XRD analysis, respectively. Additionally, this sample showed the best adsorption performance achieving an adsorbed amount of phosphates of 23.33 mg/g at pH 2 in single system. In binary systems, it was observed a synergistic effect in the adsorption of both species (phosphate and aluminum) and the principal adsorption mechanism is related to electrostatic interactions according with the results of molecular simulation.

Extensive studies on the correlation between synthesis variables and the final properties of resorcinol-formaldehyde carbon gels have been performed. This knowledge allows us to obtain carbon gels with analogous mean pore sizes and porosity from different combinations of synthesis variables. However, although the materials exhibit these similar characteristics, their behaviors may be very different in certain applications. Since the distribution and connectivity of the polymeric clusters are strongly affected by variables such as the amount of water and methanol in the precursor solution, it seems that the pore tortuosity and thus the permeability of the materials are also dependent on these factors. Further analysis of a series of carbon gels with the apparent same porosity shows how an increase in the amount of water or a suitable combination of methanol content and the pH of the precursor solution used for the polymerization process generate less tortuous pore structures. This allows us to attain even finer tuning of the porous structure of RF carbon gels either to reduce pressure drop or to increase the residence time of solutes in separation processes.

A series of xerogels with a properly designed porous structure and surface chemistry have been synthesized and evaluated as a host structure to promote the nucleation and growth of methane hydrates. Organic xerogels (OGs) have been synthesized from resorcinol-formaldehyde mixtures using a sol-gel approach and microwave heating. These xerogels are hydrophilic in nature and possess designed meso/macrocavities in the pore size range 5–55 nm. Carbon xerogels (CGs) have been synthesized from their organic counterparts after a carbonization treatment at high temperature. Interestingly, the carbonization process does not alter/modify substantially the porous network of the parent xerogels, while developing new micropores. Under water-supplying conditions, the two types of xerogels exhibit a large improvement in the methane adsorption capacity compared to the pure physisorption process taking place in dry conditions (up to 200% improvement), and associated with a significant hysteresis loop. These excellent values must be associated with the promoting effect of these xerogels in the water-to-hydrate conversion process. The comparison of OGs and CGs as a host structure anticipates that surface chemistry, total pore volume and pore size are critical parameters defining the extent and yield of the methane hydrate formation process.

[ES] Procedimiento para la obtención de aeroqeles metálicos, aeroqeles así obtenidos y usos de los mismos. La presente invención se refiere a un procedimiento para la preparación de un aerogel metálico basado en: a) la reducción de las sales metálicas para la formación de nanopartículas, b) seguida por el ensamblaje de las nanopartículas en redes tridimensionales para la obtención del hidrogel (gelación) y c) finalmente el secado del hidrogel para obtener el aerogel final, utilizándose un calentamiento por microondas durante las etapas de reducción y gelación. La invención también se refiere al aerogel obtenido por este procedimiento, así como al uso del mismo como electrocatalizador., [EN] Procedure for obtaining metallic aeroqeles, aeroqeles thus obtained and their uses. The present invention refers to a procedure for the preparation of a metallic aerogel based on: a) the reduction of metallic salts for the formation of nanoparticles, b) followed by the assembly of the nanoparticles in three-dimensional networks to obtain the hydrogel (gelation) and c) finally drying the hydrogel to obtain the final aerogel, using microwave heating during the reduction and gelation stages. The invention also refers to the aerogel obtained by this process, as well as its use as an electrocatalyst.

Six carbon materials were obtained from the carbonisation of resorcinol/formaldehyde xerogels. All carbon xerogels (CXs) showed essentially the same microporosity but differed in their meso- or macroporosity, covering a wide interval of average meso- or macropore sizes from 10 nm to 3000 nm. The graphitisation of the CXs was heterogeneous, as detected by X-ray diffraction. The relative amount of the amorphous, turbostratic and graphitic carbon phases on the graphitised xerogels was different depending on the pore size of the CXs. Crystalline parameters such as interlayer spacings (d002) and crystallite sizes along the c-axis (Lc) were calculated from the different contributions and were also found to depend on the pore size of the parent CXs. Transmission electron microscopy and Raman spectroscopy analyses helped to identify nanostructures that could be assigned to the three carbon components of the graphitic xerogels. The occurrence of most of these nanostructures was compatible with a solid-phase transformation of the amorphous precursor. The electrical conductivity of the graphitised xerogels also depended on their original pore size, with values ranging from 2 S cm−1 for the materials with a 10 nm pore size to 18 S cm−1 for the materials with bigger pore sizes.

A new porous carbon structures made by sintering whey powder in a mold at 150ºC and subsequent carbonization and/or activation are described. These porous carbon structures represent a step beyond simple activated carbon monoliths, as they can take the shape of any mold and machined if necessary. These carbon materials have a porosity that can reach up 70%, made up of a system of hierarchical and interconnected pores, which gives them a high permeability. Furthermore, they have a much higher mechanical strength than other porous carbon monoliths.

La presente invención se refiere a un monolito conformado de carbono obtenido a partir de polvo de lactosuero, a su procedimiento de obtención y a sus usos como andamio para su uso en ingeniería de tejidos celulares, como filtro de gases o líquidos, como tamiz molecular, como soporte de catalizador o como catalizador. La presente invención se engloba en el campo de los materiales de carbono y de la valorización de residuos industriales.

[EN] The present invention relates to a porous shaped carbon monolith obtained from lactoserum powder, to the method for obtaining it and to its uses as scaffolding in cell tissue engineering, as a gas or liquid filter, as a molecular sieve, as a catalyst medium or as a catalyst. The present invention falls within the field of the carbon materials and of industrial waste recovery, [ES] La presente invención se refiere a un monolito conformado de carbono obtenido a partir de polvo de lactosuero, a su procedimiento de obtención y a sus usos como andamio para su uso en ingeniería de tejidos celulares, como filtro de gases o líquidos, como tamiz molecular, como soporte de catalizador o como catalizador. La presente invención se engloba en el campo de los materiales de carbono y de la valorización de residuos industriales, [FR] La présente invention concerne un monolythe constitué de carbone obtenu à partir de poudre de lactosérum, son procédé d'obtention, et ses utilisations comme structure pour une utilisation en ingénieurie des tissus cellulaires, comme filtre de gaz ou de liquides, comme tamis moléculaire, comme support de catalyseur ou comme catalyseur. La présente invention concerne le domaine des matériaux de carbone et de la valorisation des résidus industriels

A series of xerogels with a properly designed porous structure and surface chemistry have been synthesized and evaluated as a host structure to promote the nucleation and growth of methane hydrates. Organic xerogels (OGs) have been synthesized from resorcinol-formaldehyde mixtures using a sol-gel approach and microwave heating. These xerogels are hydrophilic in nature and possess designed meso/macrocavities in the pore size range 5–55 nm. Carbon xerogels (CGs) have been synthesized from their organic counterparts after a carbonization treatment at high temperature. Interestingly, the carbonization process does not alter/modify substantially the porous network of the parent xerogels, while developing new micropores. Under water-supplying conditions, the two types of xerogels exhibit a large improvement in the methane adsorption capacity compared to the pure physisorption process taking place in dry conditions (up to 200% improvement), and associated with a significant hysteresis loop. These excellent values must be associated with the promoting effect of these xerogels in the water-to-hydrate conversion process. The comparison of OGs and CGs as a host structure anticipates that surface chemistry, total pore volume and pore size are critical parameters defining the extent and yield of the methane hydrate formation process.

The adsorption of cytochrome c in water onto organic and carbon xerogels with narrow pore size distributions has been studied by carrying out transient and equilibrium batch adsorption experiments. It was found that equilibrium adsorption exhibits a quasi-Langmuirian behavior (a g coefficient in the Redlich-Peterson isotherms of over 0.95) involving the formation of a monolayer of cyt c with a depth of ∼4 nm on the surface of all xerogels for a packing density of the protein inside the pores of 0.29 g cm–3. A load-dependent surface diffusion model (LDSDM) has been developed and numerically solved to fit the experimental kinetic adsorption curves. The results of the LDSDM show better fittings than the standard homogeneous surface diffusion model. The value of the external mass transfer coefficient obtained by numerical optimization confirms that the process is controlled by the intraparticle surface diffusion of cyt c. The surface diffusion coefficients decrease with increasing protein load down to zero for the maximum possible load. The decrease is steeper in the case of the xerogels with the smallest average pore diameter (∼15 nm), the limit at which the zero-load diffusion coefficient of cyt c also begins to be negatively affected by interactions with the opposite wall of the pore.

Four carbon xerogels (CXs) were used to study the effect of the average pore size (APS) on the adsorption and activity of cytochrome c (cyt c). Pore size distributions of the CXs were relatively narrow with APSs covering the whole mesoporosity range (5, 15, 30 and 55 nm), as determined by mercury porosimetry. Selected techniques verified that all carbons were identical in terms of composition and surface chemistry. The best APS for cyt c adsorption (in terms of capacity) was 30 nm, with loadings of 180 mg of protein (g of support)−1. The CX with APS of 15 nm also hosted high amounts of cyt c, followed by the material with 55 nm. The CX with 5 nm APS did not adsorb cyt c. The pH of adsorption had little effect on the final amount adsorbed, thus stressing the hydrophobic nature of the protein/carbon surface interaction. The activity of the resulting materials towards the ABTS oxidation was similar regardless the amount of cyt c adsorbed on their surface/pores. Their performance in successive cycles of re-use was different depending on the carbon support; xerogels bearing APSs ≥15 nm presented an increasing activity with increasing the number of cycles.