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En este articulo se presentan unas nuevas estructuras de carbono poroso que pueden fabricarse mediante la sinterizacion de polvo de lactosuero en un molde a 150oC y la posterior carbonizacion y/o activacion. Estas estructuras de carbono poroso representan un paso mas alla de los simples monolitos de carbon activado, ya que pueden adoptar la forma de cualquier molde y mecanizarse si fuese necesario. Estos materiales de carbono tienen una porosidad que puede alcanzar el 70%, constituida por un sistema de poros jerarquizados e interconectados, por lo que presentan una gran permeabilidad. Ademas, poseen una resistencia mecanica muy superior a la de otros monolitos de carbono poroso. Palabras Clave: estructuras de carbono, monolitos, carbono poroso, carbon activado, mecanizado, sinterizacion, lactosuero, lactosuero en polvo

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., Universidad Nacional Autónoma de México (UNAM, PAPIIT grant TA100120 and UNAM, DGAPA Grant Number COIC/DDTPA/064/2020).

We describe how robocasting and carbonisation of partially dehydrated whey, a surplus of the dairy industry, produced 3D porous carbons with custom morphologies. A relatively simple printing device was first used to manufacture 3D structures of whey pastes. The whey pastes behaved as a thermoset polymer when heated hence keeping the original shape of the printed pieces upon carbonisation, albeit an isotropic size reduction (23%) due to thermal shrinkage. The rheological properties of the whey pastes were similar to those of other inks commonly used in direct ink writing, with a shear thinning behaviour and static and dynamic yield stresses that predicted their printability in most robocasting devices. Once the 3D whey structures were printed, a heat-curing process was required to avoid the uncontrolled emission of volatiles that would otherwise distort them. When doing so, 3D lattices of carbon filaments with ca. 500 µm in diameter and ca. 425 µm mesh size were manufactured. The ash content of the carbonised structures, which is related to the salt content of the original whey, was reduced by conventional washing procedures, bringing about 3D hierarchical porous carbons (70% porosity) with modest specific surface areas (500 m2/g) and relatively high compressive strengths (5 MPa)., The authors acknowledge the financial support received from the Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033, Project PID2020–115334GB-I00) and Principado de Asturias (FICYT)-European Union (FEDER) (Project PCTI-Asturias IDI/2021/000015).

Water stress is a current environmental menace mainly driven by over exploitation of aquifers, which is triggering poor water quality with high concentration of minerals in extracted groundwater. Particularly, silica is widespread in natural water supplies due to weathering processes of silicates occurring in contact with water, light, air, and other factors. However, due to groundwater over extraction the concentration of silica has increased during the last years in aquifer reservoirs from Aguascalientes State (México). In this context, it is very important to note that the removal of silica compounds from water is challenging and different methods can be used to avoid embedding problems in different industries. In the present work, the removal of reactive silica from synthetic solutions as well as from real wastewaters from an industrial anodizing process was studied using adsorption and chemical precipitation methods. Twelve commercial materials of different nature were used for adsorption tests, while seven precipitant agents were applied in the precipitation experiments. Adsorption tests were performed in batch systems with constant stirring at 30 °C and at different pH values (7 and 9). Precipitation experiments were carried out in batch systems and the best conditions for silica removal were found using an L

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.

This article belongs to the Special Issue Bio-Inspired Porous Materials and Biomaterials., Porous carbon structures derived from whey powders are described and evaluated as potential scaffolds in bone tissue engineering. These materials have a porosity between 48% and 58%, with a hierarchical pore size distribution ranging from 1 to 400 micrometres. Compressive strength and elastic modulus are outstanding for such a porous material, being up to three times better than those of traditional HA or TCP scaffolds with similar porosities. They also present non-cytotoxic and bioactive behavior, due to their carbon-based composition that also includes some residual mineral salts content., This research was funded by MINECO and MICINN, grant numbers CTQ2017-87820-R and PID2020-115334GB-I00, respectively; and Principado de Asturias–FICYT-FEDER, grant number IDI/2018/000118. Raúl Llamas thanks the Spanish National Research Council (CSIC) for funding received through the Project PIE 202080E276.

Hybrid aerogels from carbon and silica precursors were obtained via a rapid process by microwave heating and the use of catalysts. Due to the varied nature of the precursors, one of the key points in synthesizing these hybrid aerogels is to ensure a homogeneous mixture during the entire synthesis process. It is well known that using microwaves may accelerate some reactions, but our study also evaluated the so-called microwave effect on certain reactions. Another strategy to boost polymerization reactions is the addition of a specific catalyst. The addition of a small amount of aminosilanes to the precursor solution was also evaluated with excellent results. The combination of the two different strategies (i.e., microwave heating and addition of aminosilanes) makes it possible to obtain hybrid aerogels via a rapid process and also to define the final porous properties via the usual synthesis variables (e.g., dilution ratio) in sol-gel synthesis., Authors thanks the financial support received from the Ministerio de Ciencia e Innovación from Spain PCI-2020-112039 (AEI/10.13039/501100011033) and Principado de Asturias–FICYT-FEDER(IDI/2018/000118). SFL is grateful for her research training grant received from the Administración del Principado de Asturias through the “Severo Ochoa” program.

Anodizing wastewater contains principally phosphate (PO43-) anions according to previous studies, but with the purpose to promote water reuse in this type of industry, a complete characterization of wastewater was made to remove other anions and cations also present in significant concentration. Particularly, the adsorption of sodium (Na+), potassium (K+), fluoride (F-), sulfate (SO42-) and phosphate (PO43-) was studied using different sorbents such as: coconut shell activated carbon, bone char, bituminous coal activated carbon, natural zeolite, silica, anionic and cationic exchange resins, a coated manganese-calcium zeolite, coconut shell activated carbon containing iron and iron hydroxide. All sorbents were characterized using FT-IR spectroscopy, potentiometric titration, nitrogen adsorption isotherms at 77 K, X-ray diffraction and SEM/EDX analysis to study the adsorption mechanism. The adsorption studies were performed in batch systems under constant agitation using both standard solutions of each ion and real anodizing wastewater. Results showed that, in general, the adsorption of all anions and cations is higher when mono-component standard solutions were used, since in the anodizing wastewater all species are competing for the active sites of the adsorbent. Na+ present in anodizing wastewater was efficiently adsorbed on coated manganese-calcium zeolite (20.55 mg/g) and natural zeolite (18.55 mg/g); while K+ was poorly adsorbed on all sorbents (less than 0.20 mg/g). Anions such as F-, SO42- and PO43-, were better adsorbed on the anionic resin (0.17, 45.38 and 2.92 mg/g, respectively), the iron hydroxide (0.14, 7.96 and 2.87 mg/g, respectively) and the bone char (0.34, 8.71 and 0.27 mg/g, respectively). All these results suggest that adsorption is a promising tertiary treatment method to achieve water reuse in the anodizing industry., This work was supported by TECNM (7949.20-P), Universidad Nacional Autónoma de México (UNAM, PAPIIT grant TA100120), Ministerio de Economía, Industria y Competitividad, Spain (CTQ2017-87820-R) and PCTI-Asturias/FEDER, Spain, EU (IDI/2018/000118) projects. MC. Acosta-Herrera acknowledges the grant (731286) received from CONACyT. The authors gratefully acknowledge the computing time granted by LANCAD and CONACyT on the supercomputer Yoltla/Miztli/Xiuhcoatl at LSVP UAM-Iztapalapa/DGTIC UNAM/CGSTIC CINVESTAV.

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.

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 authors gratefully acknowledge the financial support received from the Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033) (Project PID2020-115334GB-I00) and Principado de Asturias (FICYT) – European Union (FEDER) (Project PCTI-Asturias IDI/2021/000015).

The removal of tricholoroethylene (TCE) has been investigated in this work through the Fenton-like process using different catalytic materials obtained from metallic by-products of the steel industry. These materials are the slag produced during the transformation of molten pig iron produced in a blast furnace into liquid steel (SLD), the dry particles (or dust) obtained from the bag filters installed in the coking installations to minimize diffuse emissions (POCA) and the dry particles obtained from the liquid sludge from the scrubber (LHA). This study aims to explore the potential of these materials for being used as permeable catalytic barriers to treat groundwater polluted with trichloroethylene (TCE). The wastes used as catalysts were chemically and physically characterized to determine their composition and porosity. The results of this study point out that among the different catalysts used LHA showed the highest catalytic activity to degrade TCE using hydrogen peroxide. Moreover, LHA was the most efficient catalyst using hydrogen peroxide due to its higher stoichiometric efficiency. It is thus concluded that LHA has a high potential to be combined with hydrogen peroxide in permeable catalytic barriers to remove organic compounds from groundwater.

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, The authors gratefully acknowledge the financial support received from the Consejo Superior de Investigaciones Científicas (Project I-LINK1200), Ministerio de Economía, Industria y Competitividad (Project CTQ2017-87820-R) and Principado de Asturias– FICYT-FEDER (Project PCTI-Asturias IDI/2018/000118).

This study presents a new route for the synthesis of carbon gels with a structure that includes aligned fibers of the same material. A modification of the heating process during polymerization of resorcinol and formaldehyde produces a combination of the classical polymeric nodules in carbon gels with arrays of totally aligned fibers. This new morphology, produced through a very simple process, opens up new application possibilities to the already numerous existing ones for carbon gels., We are grateful to the Spanish Ministerio de Economia, Industria y Competitividad (CTQ2017-87820-R) and the Principality of Asturias–FICYT-FEDER(IDI/2018/000118) for their financial support.

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., This work was supported by TECNM (7949.20-P), Ministerio de Economía, Industria y Competitividad, Spain (CTQ 2017-87820-R) and PCTI-Asturias/ FEDER, Spain, EU (IDI/2018/000118) projects. MC. Pérez-Jiménez acknowledges the grant (857757) received from CONACyT. L.A. Ramírez-Montoya thanks CONACyT for a post-doctoral grant (CVU No 330625, 2017).

The conventional carbonisation (450-1000 °C) of whey powders gives totally unexpected results in terms of the mechanical integrity of the resulting carbons. Pieces of different geometries can be easily prepared by pouring the powders loosely into a mould. This green precursor adopts the shape of the predesigned mould at relatively low temperatures (120-150 °C) through the sintering of the whey particles surfaces. The shape of the pre-conformed pieces is preserved at least up to 1000 °C under N2 atmosphere, with a linear shrinkage of ca. 23%. The flexural strength and modulus of the resulting 3-D structured porous carbons are outstanding for a biomass derived carbon monolith, and their abrasiveness exceptionally low, similar to porous monoliths derived from phenolic resins. In addition, carbons obtained at temperatures above 800 °C develop a hierarchical porosity covering from micropores to macropores up to 400 μm granting high permeable structures. It is postulated that the presence of both lactose and whey proteins in whey powders is key for their atypical behaviour during carbonisation.

The integration of 2D graphene sheets into a porous and macroscopic structure is extremely attractive for application in several electrochemical fields. In this regard, for the first time, the synthesis of 3D graphene aerogels is reported by using a rapid, easy, cost-effective, and scalable at industrial level methodology. These aerogels integrate the intrinsic properties of graphene with a high pore volume. To achieve this ultraporous graphene network, resorcinol/formaldehyde polymer with controllable porosity is employed as a binder and a cross-linker material, and a graphene oxide solution provides the graphene building blocks. Two series of materials with and without catalyst for resorcinol/formaldehyde reaction and with different synthesis conditions and graphene contents are studied. The resulting graphene aerogels present low density, large macroporosity, and electrical conductivity values as high as 852 S m−1, with 97.58% of porosity, which is the highest value of electrical conductivity reported so far in the literature for ultralight-weight graphene aerogels., This work was supported by the Ministerio de Economía, Industria y Competitividad from Spain (CTQ2017-87820-R and MAT2016-78155-C2-1-R) and Principado de Asturias—FICYT-FEDER (IDI/2018/000118 and IDI/2018/000170). L.d.S.-G. thanks the Ministerio de Ciencia, Innovación y Universidades for her Juan de la Cierva Formación grant (FJC2018-036746-I).

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., Authors are grateful for the financial support received from the Ministerio de Economia, Industria y Competitividad from Spain (CTQ2017-87820-R) and Principado de Asturias–FICYT-FEDER(IDI/2018/000118). SFL is grateful to the Administración del Principado de Asturias for her research training grant awarded through the “Severo Ochoa” program. LARM thanks CONACYT, Mexico for a post-doctoral grant (CVU No 330625, 2017).

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., This work was supported by TECNM (7949.20-P), Ministerio de Economía, Industria y Competitividad, Spain (CTQ2017-87820-R) and PCTI-Asturias/FEDER, Spain, EU (IDI/2018/000118) projects. MC. Delgadillo-Velasco acknowledges the grant (467325) received from CONACyT. L.A. Ramírez-Montoya thanks CONACyT for a post-doctoral grant (CVU No 330625, 2017).

The thermochemical conversion of biomass through its gasification has been widely explored during the last decades. The generated bio-syngas mixture can be directly used as fuel in thermal engines and fuel cells or as intermediate building block to produce synthetic liquid fuels and/or value added chemicals at large scales. In the present work, the effect of Greek olive kernel (OK) thermal treatment (torrefaction at 300 °C vs. slow pyrolysis at 500 and 800 °C) on the physicochemical characteristics and CO2 or H2O gasification performance of as-produced biochars is examined. Both the pristine OK sample and biochars (OK300, OK500, OK800) were fully characterized by employing a variety of physicochemical methods. The results clearly revealed the beneficial effect of thermal pretreatment on the gasification performance of as-prepared biochars. Α close relationship between the physicochemical properties of fuel samples and gas production was disclosed. Carbon dioxide gasification leads mainly to CO with minor amounts of H2 and CH4, whereas steam gasification results in a mixture containing CO2, CO, H2 and CH4 with a H2/CO ratio varied between 1.3 and 2.3. The optimum gasification performance was obtained for the slowly pyrolyzed samples (OK500 and OK800), due to their higher carbon and ash content as well as to their higher porosity and less ordered structure compared to pristine (OK) and torrefied (OK300) samples., This research has been co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH - CREATE - INNOVATE (project code: T1EDK-01894).

Due to the sulfur dioxide (SO2) negative effects to the environment and human health, its removal is currently of great importance to policy markers and researchers. In this context, the present work had the aim to study the SO2 dynamic adsorption behavior on two activated carbons rich on calcium species. One material prepared directly from peach stone shell (PC) and the other prepared from raw material treated with CaCl2 (PCCa) with the purpose to increase the interaction of sulfur with calcium compounds on the surface and to augment its surface area. The obtained activated carbons were characterized using N2 adsorption at 77 K, IR, XRD and SEM/EDX analysis. PCCa carbon presented the higher adsorption capacity compared with PC material, indicating that the surface area and the increase of calcium groups (Ca(OH)2, CaCO3, CaO) are playing an important role during the adsorption of SO2. Additionally, the results demonstrated that as temperature increases the adsorption capacity decreases. On the other hand, the dynamic studies revealed that the residence time reached at 150 mL min-1 flow-rate was the most efficient for the mass transfer processes. Also, the results demonstrated that the presence of moisture decreases the adsorption capacity due to the presence of water molecules on the adsorbent surface. The dynamic adsorption results were modeled using: the Advection-dispersion model, FANN and the conventional models Thomas and Yan. The results shown that the FANN model was the best to correlate the adsorption breakthrough curves of SO2., This work was supported by Secretaria de Educación Pública de México resources “Apoyo a la incorporación de NPTC” UCOL-PTC-255.

The sol-gel process is a commonly used methodology for producing silica gels with tailored textural properties. However, the full conventional procedure involves several steps and is complicated and time-consuming, preventing production on a large scale. In the present study, as a more practical approach, microwave heating was applied via the acid-base synthesis of different precursor mixtures. By evaluating the effect of microwaves at each synthesis step, optimal pathways were established resulting in considerable time-saving. Mesoporous gels with porosities of around 70 per cent were obtained with a reduction in time consumption of more than 90 per cent compared to conventional methods. Strict control of the production stages has led to a much better understanding of the contribution of each stage to the overall process, making it possible to much more accurately evaluate the effects of applying microwave technology on the final properties of the materials with a view to optimizing their production., The authors gratefully acknowledge the financial support received from the Ministerio de Economía, Industria y Competitividad from Spain (Project CTQ2017-87820-R) and Principado de Asturias–FICYT-FEDER (Project PCTI-Asturias IDI/2018/000118). SFL is also grateful to Administración del Principado de Asturias for her research training grant awarded through “Severo Ochoa” program.

The adsorption of heavy metals on biochars derived from Carya illinoinensis biomass was studied using molecular simulation tools to understand the adsorption mechanism. The experimental conditions to obtain the best performing biochar were determined using a L orthogonal array of the Taguchi method and considering the removal of heavy metals from water as response variable. The studied factors were the mass of precursor, drying temperature, heating rate, maximum temperature of thermal treatment and holding time. Particularly, it was possible to obtain samples of biochar that were very efficient for the removal of Al, Pb, Cd, Cu and Zn from water, using relatively low temperatures of carbonization (200–350 °C) and low processing times (20–50 min). The most influencing factor in the final properties of biochar was the maximum temperature of the thermal treatment. The biochars obtained were rich in oxygen functional groups (carboxylic and phenolic), which favored the removal of heavy metals from water by complexation and ionic exchange mechanisms. According with the data obtained by molecular simulation, the adsorption mechanism of heavy metals was controlled by the dipolar moment of the metallic cations, with Pb being adsorbed more efficiently., This work was supported by TECNM (project 7009.19-P) and Principado de Asturias–FICYT-FEDER (Project PCTI-Asturias IDI/2018/000118). Ing. Silos-Llamas acknowledges the grant (891197) received from CONACyT. Dr. Durán-Jiménez acknowledges the grant 389535 from CONACyT.

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., Authors would like to acknowledge financial support from the MINECO (projects MAT2016-80285-p and CTQ2017-87820-R). Principado de Asturias-FICYT-FEDER (Project PCTI-Asturias IDI/2018/000118) is also acknowledged. L.A. Ramírez-Montoya thanks CONACyT, México, for a post-doctoral grant (CVU No 330625, 2017).

In the present work, the pyrolysis of pecan nut shell was studied using microwave technology at different input power and exposure time. The carbonaceous products were characterized using elemental analysis, potentiometric titration, thermogravimetric analysis, N2 adsorption isotherms at −196 °C and FT-IR spectroscopy. The characteristics of microwave carbonaceous products were compared with carbons prepared by conventional heating and commercial carbons and finally, the interaction of textile dyes with the carbonaceous materials was studied. The results are indicating that it is possible to obtain carbonaceous materials with similar textural parameters in conventional and microwave systems, but for microwave heating the processing times are short (3 min). Also, the exposure time of 2 min of microwave are not enough for the complete depolymerization of the lignocellulosic matrix of the pecan nut shell and significant amount of cellulose and hemicelluloses remain in char after microwave treatment. Finally, all the carbons obtained by microwave heating are microporous materials with a high number of basic groups on their surface and the high molecular size of dyes is controlling the adsorption on these materials.

In the present work the possible surface modification of natural zeolite using cold oxygen plasma was studied. The sample with and without treatment was characterized using nitrogen adsorption isotherms at −196 °C, FT-IR spectroscopy, SEM/EDX analysis and X-Ray Diffraction. Additionally, the two samples were used for the removal of lead and acid, basic, reactive and food dyes in batch systems. The natural zeolite was found to be a mesoporous material with a low specific surface area (23 m2/g). X-ray patterns confirmed that clinoptilolite was the main crystal structure present in the natural zeolite. The molecular properties of dyes and the zeolitic structure were studied using molecular simulation, with the purpose to understand the adsorption mechanism. The results pointed out that only the roughness of the clinoptilolite was affected by the plasma treatment, whereas the specific surface area, chemical functionality and crystal structure remained constant. Finally, adsorption results confirmed that the plasma treatment had no significant effects on the dyes and lead retention capacities of the natural zeolite.

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., The financial support for this research work provided by the Spanish MINECO (CTM2014-56770-R project) and FEDER Funds (GRUPIN14-102 and GRUPIN14-117, Principado de Asturias) is gratefully acknowledged. LARM thanks CONACYT (México) for the award of a post-doctoral grant (CVU No 330625, 2016). We thank Dr. J.B. Parra for his suggestions relating the discussion about the pore size distributions of the materials.

In the present work, it was established a new method for the preparation of bone chars with a double purpose, i.e., the removal of fluoride from water and the antibacterial character. These adsorbents were obtained by doping a commercial bone char with Ag using different reagents. The optimal conditions for the enrichment with silver were established by following the Taguchi method and using as response variable the removal of fluoride from water. Optimal bone chars were thus prepared and they were characterized using FT-IR spectroscopy, SEM/EDX analysis, adsorption isotherms of N2 at −196 °C and X-ray diffraction. All adsorbents were used in the removal of fluoride from water and the antibacterial character was assessed using the technique of total viable count employing standard solutions of Escherichia coli and drinking water. Results clearly indicated that doping of bone chars with silver provides with suitable antibacterial properties, however the fluoride adsorption capacity was not affected by the presence of Ag° on the carbon surface.

The VOC’s adsorption in dynamic systems using three different sorbents (carbonaceous materials) prepared from biomass residue as precursor, was studied. The sorbents were prepared from pecan nut shell (Carya illinoinensis), peach stone shell (Prunus persica) and sawdust (Pinus cembroides), using a L9 orthogonal array of Taguchi method to identify the most important factors in the VOC’s sorbent preparation. To determine the most important characteristic from VOC’s sorbent (i.e. the textural parameters of carbons have more effect in the adsorption of VOC’s than the surface chemistry of the carbon), some specific activating agents were studied (H3PO4, CaCl2 and FeCl3). The obtained samples were characterized using FT-IR spectroscopy, nitrogen adsorption isotherms at 77 K, SEM/EDX analysis and X-ray diffraction. The obtained results indicated that the specific surface and the iron oxides formation (Fe2O3 and Fe3O4) plays the most important role in the adsorption of VOC’s (toluene and 1-butanol considered as model compounds). According with the Taguchi analysis, the precursor and the concentration of the impregnating agent were the most important factors in the synthesis and activation of carbons for the removal of toluene and 1-butanol, respectively. Specifically, the adsorption of toluene was favored by the Fe2O3 formation on the carbon surface of the sample denominated E5, which was obtained by activation of peach stone with FeCl3 (0.1 M) and carbonized at 1000 °C. Additionally, the adsorption capacity of the carbon with high specific surface (654 m2/g) was 102 and 237 mg/g for toluene and 1-butanol, respectively. An adsorption mechanism was proposed so it can be seen that iron species would interact with the VOC’s molecules.

A new macroporous, waterproof and breathable material has been synthetized. The synthesis of these materials consists in a modified version of the classical resorcinol-formaldehyde (RF) xerogels synthesis. This new process includes a further treatment, after the gelation-curing-drying process, with methanol at 240 °C in order to passivate the hydrophilic phenolic groups of the surface of the RF xerogel. It was found that the treatment time strongly depends on the pore size of the xerogels. After reaching a threshold time, the hydrophilic materials become superhydrophobic. It is postulated that the exohedral inner surface of the porous xerogels, different from most porous materials, is responsible for this behavior. Although the materials exhibit a superhydrophobic behavior against liquid water and maintain its waterproofness for a long period of time, they are able to adsorb/desorb water vapor, which makes them also breathable., The authors gratefully acknowledge the financial support of the Ministerio de Economía y Competitividad of Spain, MINECO (Project CTQ2014-54772-P).

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., This work was funded by the PCTI Asturias/FEDER (EU) (Project GRUPIN14-117). LARM thanks CONACYT (México) for a post-doctoral grant (CVU No 330625, 2016).

Electrodes for supercapacitors are commercially produced by mixing active material with a conductive additive and a binder. However, with some polymers such as carbon xerogels the conductive additives can be added during their synthesis in order to enhance interactions between the components of the electrode. In this work the performance in aqueous supercapacitors of a carbon xerogel and carbon black or graphene added during and post synthesis is compared. It was observed that, the more integrated the additive is within the carbon xerogel polymeric structure, the greater the differences in the final performance of the hybrid materials, being the sample with graphene oxide added during the synthesis of the organic gel the one with the best performance throughout the whole range of current densities studied., The authors gratefully acknowledge the financial support received from the Ministerio de Economía, Industria y Competitividad from Spain (Project CTQ2017-87820-R). MCR also acknowledges the support from CSIC (Project I.E. 201880E010).

This work studies the effect of microwaves in the synthesis of carbon adsorbents using pecan nutshell biomass as a precursor in a hybrid multimode microwave cavity avoiding the utilization of chemical activation or susceptors. The dielectric properties were calculated using the cavity perturbation method, and the power distribution of the electromagnetic field inside cavity was obtained by COMSOL Multiphysics. S-350-MW was obtained using at 350 °C and 200 W and it was characterized using elemental analysis, potentiometric titration, FT-IR and nitrogen adsorption isotherms at −196 °C. The adsorption of Pb(II), in single and binary solutions with Cu(II), Cd(II) and Zn(II) in batch systems indicate that the removal of Pb(II) is affected in the presence of Cu(II) due to the competition of these ions as a result of their similarities such as Pauling electronegativity. Finally, the removal of Pb(II) in continuous systems using packed bed columns showed the pH has the most significant effect according to the variance analysis. The finding highlighted the importance of the acidic functional groups in the performance of carbonaceous adsorbents for the removal of Pb(II). Results of this study contribute to the understandings and application of a hybrid heating system and establish the basis of the role of heating processes in the preparation of carbonaceous adsorbents using microwaves. The Pb(II) removal efficiency achieved in this study is significantly higher than the values reported for carbons prepared by using microwave heating which employs susceptors and/or chemical agents reported in literature, demonstrating that it is possible to obtain effective carbon absorbents for the removal of Pb(II) without the use of any additional susceptors or chemical activation., This work was supported by CONACyT under the grant (389535)

Recovery of phosphates from an anodizing industry wastewater was studied by chemical precipitation. Samples of wastewater were selected attending to the highest phosphate concentration observed during 1 year of weekly sampling. Different types of precipitant agents were analyzed in batch systems. Results showed that it is possible to remove 100 % of phosphates when Ca(OH) is used as precipitant agent. The best conditions of precipitation were found following a L orthogonal array design of the Taguchi method. For an initial concentration of phosphates of 4336 mg/L, these best conditions were a Ca/P molar ratio of 5.77, pH 2, stirring time of 15 min and settling time of 1 h. Additionally, it was demonstrated that the factors with more influence in the precipitation of phosphates with Ca(OH) were the pH of the wastewater and the stirring time. When the phosphate removal was performed at pH 6 and 10, hydroxyapatite Ca(PO)(OH) was found in the precipitate, whereas other crystalline hydroxyapatite with a more complex structure (CaNa)(CaNa)(PO)(CO)(OH) was identified in the experiment performed at pH 2. The present study provides valuable information to recover phosphate from industrial effluents., This work was supported by TecNM (project 7009.19-P) and Principado de Asturias–FICYT-FEDER (Project PCTI-Asturias IDI/2018/000118). M.C. Delgadillo-Velasco acknowledges the grant (467325) received from CONACyT.

A new procedure of elimination of Pb 2+ from aqueous solution using carbon adsorbents, in which high amounts of cerussite and hydrocerussite are deposited on the carbon surfaces, is reported. The procedure includes the preparation of carbons from selected lignocellulosic wastes (pecan nut shells and peach stones) by single carbonization and further oxidation with cold oxygen plasma. The materials prior and after the oxidation treatment were characterized using elemental analysis, FT-IR spectroscopy, SEM/EDX analysis, adsorption of N 2 at −196 °C and X-ray photoelectron spectroscopy. The adsorption of Pb 2+ was carried out in batch systems under constant agitation. The formation of cerussite and hydrocerussite on the spent carbon surfaces was confirmed by XRD, SEM/EDX and FT-IR. A Pb 2+ removal mechanism is proposed in which a co-precipitation of lead nitrate and calcium carbonate would render the formation of the lead carbonates. In such mechanism, the occurrence of CaCO 3 on the surface of the adsorbents plays a crucial role. The presence of calcium carbonate on the precursors is understood on the basis of the thermal evolution of calcium oxalate originally present in the biomass. The oxygen plasma treatment helps to expose the calcium carbonate nanocrystals thus improving dramatically the removal capacity of Pb 2+ . Accordingly, retention capacities as high as 63 mg of Pb 2+ per gram of adsorbent have been attained.

Carbons were prepared from peach stones ( Prunus persica ) using different carbonization temperatures (600, 800 and 1000 °C). A selected sample was modified by oxidation using conventional oxidation techniques (thermal treatment in air atmosphere) and with cold oxygen plasma oxidation, under different conditions. Samples were characterized using elemental analysis, FT-IR spectroscopy, nitrogen adsorption isotherms at −196 °C, SEM/EDX analysis, potentiometric titration and XPS analysis. Carbons with and without oxidation were employed in the adsorption of Pb 2+ in aqueous solution. Results obtained indicated that the materials with high contents of acidic oxygen groups were more efficient in the removal of Pb 2+ , values as high as approx. 40 mg g −1 being obtained for the best performing carbon. Textural properties of the original, un-oxidized carbon were significantly altered only after oxidation under air atmosphere at 450 °C. On the other hand, the samples oxidized with plasma show little changes in the textural parameters and a slight increase in the specific surface was observed for the sample treated at high RF power (100 W). Additionally, a significant increment of the oxygen content was observed for the plasma oxidized samples, as measured by XPS.

The adsorption of acid blue 74 (AB74), basic green 1 (BG1) and reactive blue 4 (RB4) on carbons from pine sawdust (Ps) using single carbonization (C-Ps) and modification of Ps with a calcium chloride 1 M (C-Ps-Ca) was studied. Also the effects of the type of adsorbate (acid, basic and reactive dye) on the bioregeneration of exhausted carbons using Pseudomona putida were investigated. Characterization of the samples was performed using Nitrogen adsorption isotherms at 77 K, elemental analysis, FT-IR spectroscopy and SEM-EDX analysis. For this study, the maximum adsorption capacity obtained for the two types of carbons were for C-Ps: 12.8, 4.6 and 51.68 mg g −1 , and for C-Ps-Ca: 38.3, 48.6 and 155.1 mg g −1 , for AB74, RB4 and BG1 dyes respectively. The bioregeneration process showed that is possible to renovate 25% of original adsorption capacity of the carbon C-Ps-Ca, equivalent to the adsorption capacity of C-Ps carbon. Among the dye-loaded adsorbents, the bioregeneration efficiency of C-Ps-Ca using the bacteria Pseudomona putida showed a better capacity for the degradation of BG1 compared with AB74 and RB4. Modelling of the adsorption results using a non-linear regression approach and performing the global minimization showed that both Langmuir and Sips models showed an adequate description of the acid, basic and reactive dyes adsorption.

Microwave-induced pyrolysis of organic wastes has been demonstrated to be a suitable technology for the production of syngas (H2 + CO). However, there is a need for developing alternatives to manage the residual streams from this process. In this short communication, the use of the solid fraction from microwave-induced pyrolysis as a soil conditioner and its ecotoxic effect on the growth of barley and cress plants have been studied. The porous structure of these chars has been found out to be one of the possible factors related to the germination rates. This alternative has resulted to be highly promising since the toxic effect on plants germination was very limited or non-existing regardless of the municipal waste char composition., The research leading to these results has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement n° 311815 (SYNPOL project). D. B. also acknowledges the financial support received from PCTI and FICYT of the Government of the Principado de Asturias.

The application of static magnetic fields during adsorption as an unconventional method for the removal of heavy metals such as Cd2+ and Zn2+ was studied in this work. Two different materials were employed as adsorbents: activated carbon from bituminous coal and bone char. The magnetic characterization of these materials reveals that the activated carbon from bituminous coal is a ferromagnetic material, while the bone char is a paramagnetic material. Both adsorbents were used as received; i.e., no additional modification was employed to alter or improve their magnetic properties. Adsorption studies included adsorption isotherms at 30 °C, at pH 5, and equilibrium times of 72 h. The adsorption results obtained depended on the magnetic nature of both the adsorbent and the adsorbate. It was determined that because of its ferromagnetism (hence, its chemical composition), the activated carbon performed better when an external magnetic field was present during the adsorption process. An increase of 63% and 15% i...

In the present work was studied the adsorption-desorption of heavy metals from aqueous solutions using carbonaceous materials prepared with a technology that combines radiant and microwave heating. Three optimum carbons O-Cu, O-Cd and O-Zn were prepared and characterized using elemental analysis, potentiometric titration, nitrogen adsorption isotherms at − 196 °C, SEM/EDX analysis, and temperature programmed desorption (TPD). The three optimum carbons had very high oxygen contents mainly ascribed to surface functional groups of acidic nature. In contrast, the porosity of the carbons was very limited with specific surface areas being

Laccases from Trametes versicolor have been used for the decolorization of acid and reactive dye solutions. The dyes considered were the acid orange 7 (AO7), acid blue 74 (AB74), reactive red 2 (RR2) and reactive black 5 (RB5). The decolorization of dye solutions was performed in batch systems under constant agitation at 30 °C, using both free laccases and laccases immobilized on a mesoporous carbon obtained from pecan shells. Results obtained pointed out that the biocatalysts tested are more effective in the decolorization of acid dyes (AO7 and AB74), with more than 90% of decolorization percentages attained, than reactive dyes. Furthermore, the laccase used in this study, either freely dissolved or supported on the carbon materials, was inactive towards RB5, which was the larger dye molecule (992 g mol − 1 ). Immobilization of the laccase on the mesoporous carbons brought about a considerable decrease of their activity. However, an enzyme stabilization effect was also observed as the activity of the supported laccase was maintained over a wide pH span. Finally, the combination of spectrophotometric and chromatographic (HPLC) techniques allowed us to get a more precise picture of the influence of adsorption/oxidation mechanisms during the degradation of dyes by the supported enzymes.