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Feasibility of switchable dual function materials as a flexible technology for CO2 capture and utilisation and evidence of passive direct air capture

Merkouri, LP; Reina, TR; Duyar, MS
Química de Superficies y Catálisis


The feasibility of a Dual Function Material (DFM) with a versatile catalyst offering switchable chemical synthesis from carbon dioxide (CO2) was demonstrated for the first time, showing evidence of the ability of these DFMs to passively capture CO2 directly from the air as well. These DFMs open up possibilities in flexible chemical production from dilute sources of CO2, through a combination of CO2 adsorption and subsequent chemical transformation (methanation, reverse water gas shift or dry reforming of methane). Combinations of Ni Ru bimetallic catalyst with Na2O, K2O or CaO adsorbent were supported on CeO2-Al2O3 to develop flexible DFMs. The designed multicomponent materials were shown to reversibly adsorb CO2 between the 350 and 650 degrees C temperature range and were easily regenerated by an inert gas purge stream. The components of the flexible DFMs showed a high degree of interaction with each other, which evidently enhanced their CO2 capture performance ranging from 0.14 to 0.49 mol kg(-1). It was shown that captured CO2 could be converted into useful products through either CO2 methanation, reverse water-gas shift (RWGS) or dry reforming of methane (DRM), which provides flexibility in terms of co-reactant (hydrogen vs. methane) and end product (synthetic natural gas, syngas or CO) by adjusting reaction conditions. The best DFM was the one containing CaO, producing 104 mu mol of CH4 per kg(DFM) in CO2 methanation, 58 mu mol of CO per kg(DFM) in RWGS and 338 mu mol of CO per kg(DFM) in DRM.

Agosto, 2022 | DOI: 10.1039/d2nr02688k

Assessment of construction and demolition wastes (CDWs) as raw materials for the manufacture of low-strength concrete and bases and sub-bases of roads

Garzon, E; Martinez-Martinez, S; Perez-Villarrejo, L; Sanchez-Soto, PJ
Materials Letters, 320 (2022) 132343
Materiales Avanzados


A chemical (XRF) and mineralogical (XRD) characterisation has been carried out, as well as the determination of the main properties, of construction and demolition wastes (CDWs). This waste has been applied as recycled aggregate. The objective was to search for its reuse for the manufacture of concrete and road bases and sub-bases. Chemical analysis revealed the presence of SiO2 (39.13 wt%) and Al2O3 (9.55 wt%) from quartz and some silicates, and gypsum. The content of CaO (21.42 wt%) was associated with calcite and dolomite. The materials' properties have suggested that the particle sizes are not inside the typical interval fixed in the Spanish normative. It can be reused as esplanades or sub-bases of roads and highways, since it is a granular material with a very high California Bearing Ratio (CBR value is 36). It was concluded that the use of CDWs as a substitute of sand for the manufacture of concrete can only be used in percentages lower than 10 wt% producing low-strength concrete.

Agosto, 2022 | DOI: 10.1016/j.matlet.2022.132343

Outstanding MRI contrast with dysprosium phosphate nanoparticles of tuneable size

Gómez-González, E.; Caro, C.; García-Martín, ML; Becerro, AI; Ocaña, M.
Nanoscale, 14 (2022) 11461-11470
Materiales Coloidales


The use of high-field magnets for magnetic resonance imaging (MRI) is expected to experience the fastest growth rate during the present decade. Although several CAs for MRI scanners using high magnetic fields have been reported, they are mostly based on fluoride matrices, which are known for their low chemical stability in aqueous suspensions. Chemically stable MRI CAs for high-field magnets are therefore needed to enable the advances in MRI technique. Herein, we synthesized uniform DyPO4 nanoparticles (NPs) with tuneable sizes between 23 and 57 nm using homogeneous precipitation in butanol. The NPs were successfully functionalized with polyacrylic acid (PAA) and showed good colloidal stability in aqueous suspensions. Chemical stability was also assessed in PBS, showing negligible solubility. The effect of particle size on the transversal relaxivity value (r(2)) was further explored at 9.4 T, finding a clear increase in r(2) with particle size. The r(2) value found for the largest NPs was 516 mM(-1) s(-1), which is, to the best of our knowledge, the highest r(2) value ever reported at 9.4 T for any Dy-based nanometric particles in the literature. Finally, the latter NPs were submitted to biosafety studies after polyethylene glycol (PEG) functionalization. Cell morphology, induction of necrotic/late apoptotic cells, and mitochondrial activity were thoroughly analyzed. The results clearly indicated negligible toxicity effects under the assayed conditions. Short- and long-term in vivo pharmacokinetics of the intravenously injected NPs were assessed by dynamic T-2-weighted MRI and quantitative T-2 mapping, revealing faster liver than spleen uptake, while no accumulation was observed in the kidneys. Finally, no histopathological changes were observed in any of the studied organs, including the liver, kidney, spleen, and lung, which provide further evidence of the biocompatibility of DyPO4 NPs and, therefore, their suitability as bioimaging probes.

Agosto, 2022 | DOI: 10.1039/d2nr02630a

Shepherding reaction intermediates to optimize H-2 yield using composite-doped TiO2-based photocatalysts

Barba-Nieto, I.; Colon, G; Fernández-García, M; Kubacka, A
Chemical Engineering Journal, 442 (2022) 136333
Materiales y Procesos Catalíticos de Interés Ambiental y Energético


Optimization of Pt-promoted TiO2-based is key to promote the photocatalytic production of hydrogen using sacrificial alcohol molecules. Combination of doping and surface decoration of the mentioned base photoactive material is here exploited to maximize hydrogen yield. Using the quantum efficiency parameter, it is shown that the resulting composite system can boost activity up to 7.3 times within the whole methanol:water mixture ratio, yielding quantum efficiencies in the ca. 13-16 % range. The key role of the different components in generating charge carrier species and their use to trigger the sacrificial molecule evolution and control reaction kinetics are examined through an in-situ spectroscopic study. The study unveils the complex reaction mechanism, with generation of C1 to C3 molecules from different carbon-containing radicals, and interprets the physical origin of the huge H2 production enhancement occurring in doped-composite titania-based catalysts.

Agosto, 2022 | DOI: 10.1016/j.cej.2022.136333

Tuning the co-catalyst loading for the optimization of thermo-photocatalytic hydrogen production over Cu/TiO2

Platero, F; Caballero, A; Colon, G
Applied Catalysis A-General, 643 (2022) 118804
Materiales y Procesos Catalíticos de Interés Ambiental y Energético


We have optimized the H-2 production by methanol thermo-photocatalytic reforming in the gas phase using Cu/TiO2 catalyst by tuning metal loading. Metal co-catalyst has been deposited by means of chemical reduction deposition. We have stated that thermo- and thermo-photocatalytic process leads to a notable H-2 production at 200 C. By in-situ FTIR studies we evidenced that formate formation follows a different evolution depending on the reforming experiment. These surface formate would lead to CO formation through dehydration reaction. At higher Cu content the low CO selectivity denote that water-gas-shift reaction would predominate and exalt H-2 yield. Thus, different optimum Cu content is found for each reforming experiment. While for the photocatalytic reforming Cu/TiO2 (2 wt%) is the best catalyst of the series, we should increase the Cu content to Cu/TiO2 (5 wt%) to achieve the optimum performance for thermo-photocatalytic reforming of methanol.

Agosto, 2022 | DOI: 10.1016/j.apcata.2022.118804

Catalytic Upgrading of Biomass-Gasification Mixtures Using Ni-Fe/ MgAl2O4 as a Bifunctional Catalyst

Tarifa, P; Reina, TR; González-Castaño, M; Arellano-Garcia, H
Energy & Fuels, 36 (2022) 8267-8273
Química de Superficies y Catálisis


Biomass gasification streams typically contain a mixture of CO, H-2, CH4, and CO(2 )as the majority components and frequently require conditioning for downstream processes. Herein, we investigate the catalytic upgrading of surrogate biomass gasifiers through the generation of syngas. Seeking a bifunctional system capable of converting CO2 and CH4 to CO, a reverse water gas shift (RWGS) catalyst based on Fe/MgAl(2)O(4 )was decorated with an increasing content of Ni metal and evaluated for producing syngas using different feedstock compositions. This approach proved efficient for gas upgrading, and the incorporation of adequate Ni content increased the CO content by promoting the RWGS and dry reforming of methane (DRM) reactions. The larger CO productivity attained at high temperatures was intimately associated with the generation of FeNi3 alloys. Among the catalysts' series, Ni-rich catalysts favored the CO productivity in the presence of CH4, but important carbon deposition processes were noticed. On the contrary, 2Ni-Fe/MgAl2O4 resulted in a competitive and cost-effective system delivering large amounts of CO with almost no coke deposits. Overall, the incorporation of a suitable realistic application for valorization of variable composition of biomass-gasification derived mixtures obtaining a syngas-rich stream thus opens new routes for biosyngas production and upgrading.

Agosto, 2022 | DOI: 10.1021/acs.energyfuels.2c01452

Structure effect of modified biochar in Ru/C catalysts for sugar mixture hydrogenation

Santos, JL; Sanz-Moral, LM; Aho, A; Ivanova, S; Murzin, DY; Centeno, MA
Biomass & Bioenergy, 163 (2022) 106504
Química de Superficies y Catálisis


This study deals with the production and activation of biochars and their use as supports for a series of ruthenium catalysts for hydrogenation of L-arabinose/D-galactose sugar mixture. The synthesized biochars differ in physicochemical properties and surface chemistry influencing ruthenium metal uptake and dispersion and as a consequence its catalytic behaviour. Selectivity exceeding 95% was observed for both hexitols. The catalytic performance of the prepared Ru supported catalysts is also compared to the already known Ru/activated carbon commercial catalyst.

Agosto, 2022 | DOI: 10.1016/j.biombioe.2022.106504

Recent advances on gas-phase CO2 conversion: Catalysis design and chemical processes to close the carbon cycle

Torres-Sempere, G; Pastor-Perez, L; Odriozola, JA; Yu, J; Duran-Olivencia, FJ; Bobadilla, LF; Reina, TR
Current Opinion in Green andd Sustainable Chemistry, 36 (2022) 100647
Química de Superficies y Catálisis


Chemical CO2 recycling in the gas phase constitutes a straightforward approach for effective CO2 conversion to added-value products like syngas or synthetic methane. In this scenario, some traditional processes such as the dry and bi-reforming of methane, the CO2 methanation and the reverse water-gas shift have gained a renewed interest from the CO2 utilisation perspective. Indeed, these reactions represent flexible routes to upgrade CO2 and their application at an industrial scale could substantially reduce CO2 emissions. The bottleneck for the implementation of these processes at the commercial level is the development of highly active and robust heterogeneous catalysts able to overcome CO2 activation and deliver sufficient amounts of the upgrading products (i.e. syngas or synthetic natural gas) at the desired operating conditions. This review paper gathers the most recent advances in the design of new catalytic formulations for chemical CO2 recycling in the gas phase and constitutes an overview for experts and newcomers in the field to get fundamental insights into this emerging branch of low-carbon technologies.

Agosto, 2022 | DOI: 10.1016/j.cogsc.2022.100647

On the adsorption properties and applications of mixed-linker MOFs based on HKUST-1

Puerto-Rodríguez, M; López-Cartes, C; Ayala, R
Journal of Solid State Chemistry, 312 (2022) 123260
Reactividad de Sólidos


Different mixed-linker MOFs based on HKUST-1 have been successfully synthesized using BtTC (1,2,4,5-benzenetetracarboxylate) and BDC (1,4-benzenedicarboxylate) as modulator ligands. These MOFs maintain the HKUST-1 structure up to 25% and 50% of trimesic acid replacing with BtTC and BDC ligands, respectively. A low percentage of modulator ligand provokes an increasing of the MOF surface area keeping its microporosity whereas a higher content of BtTC induces mesoposority in the samples. The adsorption of moisture ambient or vapour iodine reveals that there is a relation between the surface area and the capacity of adsorption of the samples. However, this relation is not found in the experiments of Congo Red removal from aqueous and ethanol solutions. The pH of the solutions has a significant effect on the adsorption capacity of the samples.

Agosto, 2022 | DOI: 10.1016/j.jssc.2022.123260

One-Dimensional Photonic Crystal for Surface Mode Polarization Control

Mogni, E; Pellegrini, G; Gil-Rostra, J; Yubero, F; Simone, G; Fossati, S; Dostalek, J; Vazquez, RM; Osellame, R; Celebrano, M; Finazzi, M; Biagioni, P
Advanced Optical Materials, (2022) 2200759
Nanotecnología en Superficies y Plasma


Bloch surface waves sustained by truncated 1D photonic crystals (1DPCs) are well known tools for surface-enhanced spectroscopy. They provide strongly confined fields with uniform distribution over a large surface area, a characteristic exploited in standard refractometric sensing. However, their application to polarization-sensitive investigations is not straightforward because the transverse electric (TE) and magnetic (TM) surface modes possess distinct dispersion relations, therefore their relative phase is not conserved along propagation and the polarization state of any wave obtained by combining these modes is ill-defined. In this work, a novel design of a 1DPC is realized in which the TE and TM modes exhibit the same phase velocity over a broadband spectral range and thus their dispersion relations overlap. The capability to simultaneously excite TE and TM modes with a well-defined phase relation allows the generation of surface waves with a controlled polarization state. This paves the way to polarization-resolved surface-enhanced analysis, including, for example, linear and circular dichroism spectroscopy of grafted molecular layers at the photonic crystal surface.

Agosto, 2022 | DOI: 10.1002/adom.202200759

The effect of support surface hydroxyls on selective CO methanation with Ru based catalysts

Martínez, LMT; Muñoza, A; Pérez, A; Laguna, OH; Bobadilla, LF; Centeno, MA; Odriozola, JA
Applied Catalysis A: General, 641 (2022) 118678
Química de Superficies y Catálisis


The aim of this work was to clarify the effect of the support on CO selective methanation with Ru/TiO2 catalysts. TPR, XRD and TEM measurements confirmed that the changes in the activity and selectivity should be ascribed to anatase:rutile ratio, RuO2 +TiO2 solid solution formation, as well as the metal content and the thermal treatment used. All these characteristics result in active and selective catalysts in which the suppression of the reverse water gas shift reaction was observed. The catalytic performance must be explained by both the formation of more active Ru species as a result of support influence and the higher Ru dispersion. The study allows to conclude that for CO activation the role of support surface hydroxyls seems to be determinant for both the activity and selectivity of Ru/TiO2 catalysts.

Julio, 2022 | DOI: 10.1016/j.apcata.2022.118678

Greaseproof, hydrophobic, and biodegradable food packaging bioplastics from C6-fluorinated cellulose esters

Guzman-Puyol, S; Tedeschi, G; Goldoni, L; Benitez, JJ; Ceseracciu, L; Koschella, A; Heinze, T; Athanassiou, A; Heredia-Guerrera, JA
Food Hydrocolloids, 128 (2022) 107562
Materiales de Diseño para la Energía y Medioambiente


Tridecafluorononanoic acid (TFNA), a C6-fluorinated carboxylic acid, was esterified with cellulose at different molar ratios (0:1, 1:1, 2:1, and 3:1) in a trifluoroacetic acid (TFA):trifluoroacetic anhydride (TFAA):CHCl3 (2:1:1, v:v:v) solvent mixture. Free-standing films were obtained for all formulations and are presented as alternatives to composites and blends of paper with fluorinated molecules. Mechanical properties were investigated by tensile tests, and a plasticizer effect of fluorinated chains was observed. Interestingly, the wettability of these new cellulose derivatives was similar or even better than other common cellulose derivatives and fluorinated poly-mers employed in food packaging. Hydrodynamic properties were also improved by addition of TFNA, resulting in materials with water vapor permeability values comparable to other cellulose-based food packaging materials. In addition, films with the higher amounts of TFNA showed the required oil resistance for papers used in food packaging applications, as determined by the Kit Test. Finally, the biodegradation of these C6-fluorinated cel-lulose esters, assessed by biological oxygen demand (BOD) in seawater, was higher than typical bio-based polymers used in food packaging. The bioplastic synthesized at a molar ratio 1:1 (TFNA:cellulose) showed excellent performances in terms of greaseproof, hydrophobicity, ductility, and biodegradability, representing a sustainable alternative to typical plastics used in food packaging.

Julio, 2022 | DOI: 10.1016/j.foodhyd.2022.107562

Insights on Guerbet Reaction: Production of Biobutanol From Bioethanol Over a Mg-Al Spinel Catalyst

Crespo, MAP; Vidal-Barrero, F; Azancot, L; Reina, TR; Campoy, M
Frontiers in Chemistry, 10 (2022) 945596
Química de Superficies y Catálisis


The production of biobutanol from bioethanol by the Guerbet reaction is an alternative pathway to renewable sources. The commercial viability of this green route requires improvements in the process development. This study experimentally examines the influence of operating conditions on the performance of a Mg-Al spinel catalyst prepared from hydrotalcite precursors. This catalyst demonstrates an exceptional performance in the Guerbet reaction with a promising activity/butanol selectivity balance, excellent long-term stability, and very-low-carbon footprint (CO2 generation as by-products is minimal). This study showcases a systematic strategy to optimize the reaction parameters in the Guerbet reaction for biobutanol production using an advanced spinel catalyst. Upon carefully adjusting temperature, pressure, space velocity, and reactants co-feeding, very promising conversion (35%) and butanol selectivity values (48%) were obtained.

Julio, 2022 | DOI: 10.3389/fchem.2022.945596

Steam-enhanced calcium-looping performance of limestone for thermochemical energy storage: The role of particle size

Arcenegui-Troya, J.; Sánchez-Jiménez, PE; Perejon, A; Valverde, JM; Pérez-Maqueda, LA
Journal of Energy Storage, 51 (2022) 104305
Reactividad de Sólidos


Steam injection has been proposed to attenuate the decay of CaO reactivity during calcium looping (CaL) under operating conditions compatible with carbon capture and storage. However, it is yet unknown whether the perceived advantages granted by steam hold under the distinct operating conditions required for the integration of the CaL process as a thermochemical energy storage system in Concentrating Solar Power Plants (CaL-CSP). Here, we study the influence of steam in conditions compatible with a CaL-CSP scheme and assess its impact when injected only during one stage; either calcination or carbonation, and also when it is present throughout the entire loop. The results presented here demonstrate that steam boosts the CaO multicycle performance in a CO2 closed loop to attain residual conversion values similar to those achieved at moderate temperatures under inert gas. Moreover, it is found that the enhancement in multicycle activity is more pronounced for larger particles.

Julio, 2022 | DOI: 10.1016/j.est.2022.104305

Catalytic reforming of model biomass-derived producer gas

Azancot, L; Bobadilla, LF; Centeno, MA; Odriozola, JA
Fuel, 320 (2022) 123843
Química de Superficies y Catálisis


This work includes a complete study of the reaction of reforming a simulated producer gas stream comparing a Ni-based catalyst with another one promoted with potassium to enhance the resistance to coke formation. Although coke deposition is unavoidable in the presence of tars in the stream, the analysis of different reaction parameters revealed that operating at 750 degrees C, weight hourly space velocity (WHSV) of 60 L-1 g(-1) h(-1) and 10-20 vol% of steam is possible to minimize the accumulation of carbon deposits. Moreover, it was demonstrated that the addition of potassium helps to mitigate carbon formation, but a high concentration of steam leads to nickel sintering and/or partial oxidation of metallic nickel. On this basis, it was successfully evidenced that the Ni-K catalyst is an excellent candidate for obtaining clean syngas from producer gas reforming.

Julio, 2022 | DOI: 10.1016/j.fuel.2022.123843

Flame confinement in biomass combustion systems for particles abatement

Ciria, D; Orihuela, MP; Moreno-Naranjo, P; Chacartegui, R; Ramirez-Rico, J; Becerra, JA
Energy Conversion and Management, 264 (2022) 115706
Materiales de Diseño para la Energía y Medioambiente


This work explores the use of open-pore, inert ceramic foams with different pore sizes as particle abatement systems in small biomass combustion systems. Porous foams made of silicon carbide with pore sizes 10 to 60 pores-per-inch were installed in an in-house designed combustion unit operated with wood pellets. Their effects on the temperature distribution inside the chamber, particulate and gases emissions were studied using different airflow rates in the reaction-limited regime (low equivalence ratio) to minimise stoichiometric factors. The influence of pore size, foam position with respect to the flame and space velocity were assessed. The confinement of the flame with inert foams was found to substantially modify the temperature distribution in the combustion chamber, improve the air-fuel mixture, and favour the thermal decomposition of the pellet, leading to a reduction in particulate emissions when compared to free-flame combustion at the same experimental conditions. In general, the amount of particulate matter was found to decrease by up to one order of magnitude as the pore size of the foam was reduced, while the temperature gradient in the combustion chamber was increased. Nitrogen oxides and carbon dioxide emissions were essentially unchanged, irrespectively of the pore size of the foam. It is expected that these values will be improved with longer residence times, as happens in operations with reduced excess air ratios. These results suggest that it is possible to control pollutants derived from domestic heating within the most restrictive current regulations on particulate emissions by integrating flame confinement designs with better operating practices and efficient abatement systems.

Julio, 2022 | DOI: 10.1016/j.enconman.2022.115706

Ultrathin Plasma Polymer Passivation of Perovskite Solar Cells for Improved Stability and Reproducibility

Obrero-Perez, JM; Contreras-Bernal, L; Nuñez-Galvez, F; Castillo-Seoane, J; Valadez-Villalobos, K; Aparicio, FJ; Anta, JA; Borras, A; Sanchez-Valencia, JR; Barranco, A
Advanced Energy Materials, (2022) 2200812
Materiales Nanoestructurados y Microestructura


Despite the youthfulness of hybrid halide perovskite solar cells, their efficiencies are currently comparable to commercial silicon and have surpassed quantum-dots solar cells. Yet, the scalability of these devices is a challenge due to their low reproducibility and stability under environmental conditions. However, the techniques reported to date to tackle such issues recurrently involve the use of solvent methods that would further complicate their transfer to industry. Herein a reliable alternative relaying in the implementation of an ultrathin plasma polymer as a passivation interface between the electron transport layer and the hybrid perovskite layer is presented. Such a nanoengineered interface provides solar devices with increased long-term stability under ambient conditions. Thus, without involving any additional encapsulation step, the cells retain more than 80% of their efficiency after being exposed to the ambient atmosphere for more than 1000 h. Moreover, this plasma polymer passivation strategy significantly improves the coverage of the mesoporous scaffold by the perovskite layer, providing the solar cells with enhanced performance, with a champion efficiency of 19.2%, a remarkable value for Li-free standard mesoporous n-i-p architectures, as well as significantly improved reproducibility.

Julio, 2022 | DOI: 10.1002/aenm.202200812

Albero: An alternative natural material for solar energy storage by the calcium-looping process

Moreno, V; Arcenegui-Troya, J; Sanchez-Jimenez, P; Perejon, A; Chacartegui, R; Valverde, JM; Perez-Maqueda, LA
Chemical Engineering Journal, 440 (2022) 135707
Reactividad de Sólidos


Large-scale thermochemical energy storage (TCES) is gaining relevance as an alternative to current thermal energy storage systems in Concentrated Solar Power plants. Among the different systems, the reversible reaction between CaO and CO2 stands out due to the wide availability and low cost of the raw material: limestone. Direct solar absorption of the storage media would improve the efficiency of solar-to-thermal energy storage due to reduced thermal transfer barriers, but the solar optical absorption of CaCO3 is poor. In this work, we propose the use of a Ca-rich calcarenite sedimentary rock so-called albem as an alternative to limestone. We demonstrate that this reddish material exhibits an average solar absorptance that is approximately ten times larger than limestone. Moreover, the multicycle carbonation/calcination performance under different experimental conditions has been studied by thermogravimetry, and similar values to those exhibited for limestone have been obtained. Besides, the material is cheap (6 Elton), and simulations showed that the use of this material would significantly improve the overall CaL-CSP efficiency at the industrial level.

Julio, 2022 | DOI: 10.1016/j.cej.2022.135707

Photocatalytic oxidation of pollutants in gas-phase via Ag3PO4-based semiconductor photocatalysts: Recent progress, new trends, and future perspectives

Y. Naciri; A. Hsini; A. Bouziani; R. Djellabi; Z. Ajmal; M. Laabd; J.A. Navío; A. Mills; C.L. Bianchi; H.Li; B. Bakiz; A. Albourine
Critical Reviews in Environmental Science and Technology, 52 (2022) 2339-2382
Fotocatálisis Heterogénea: Aplicaciones


Air pollution has become a significant challenge for both developing and developed nations. due to its close association with numerous fatal diseases such as cancer, respiratory, heart attack, and brain stroke. Over recent years, heterogeneous semiconductor photocatalysis has emerged as an effective approach to air remediation due to the ease of scale-up, ready application in the field, use of solar light and ready availability of a number of different effective photocatalysts. To date, most work in this area has been conducted using UV-absorbing photocatalysts, such as TiO2 and ZnO; However, recent studies have revealed Ag3PO4 as an attractive, visible-light-absorbing alternative, with a bandgap of 2.43 eV. In particular, this material has been shown to be an excellent photocatalyst for the removal of many types of pollutants in the gas phase. However, the widespread application of Ag3PO4 is restricted due to its tendency to undergo photoanodic corrosion and the poor reducing power of its photogenerated conductance band electrons, which are unable to reduce O2 to superoxide •O2 −. These limitations are critically evaluated in this review. In addition, recent studies on the modification of Ag3PO4 via combination with the conventional heterojunctions or Z-scheme junctions, as well as the photocatalytic mechanistic pathways for enhanced gas-pollutants removal, are summarized and discussed. Finally, an overview is given on the future developments that are required in order to overcome these challenges and so stimulate further research into this promising field.

Julio, 2022 | DOI: 10.1080/10643389.2021.1877977

Thermal behaviour of the different parts of almond shells as waste biomass

Garzon, E; Arce, C; Callejon-Ferre, AJ; Perez-Falcon, JM; Sanchez-Soto, PJ
Journal of Thermal Analysis and Calorimetry, (2022) 5023-5035
Materiales Avanzados


The main aim of this study is to investigate the thermal behaviour of the different parts of almond shells produced in an almond industry as a waste biomass. For this purpose, several experiments have been conducted under laboratory conditions. After removing the mature almonds, the waste raw materials subject of this study were treated with distilled water (10 min) and separated in several parts. Taking into account their physical characteristics, they were: (a) complete shells: exocarp, mesocarp and endocarp without grinding (Sample C); (b) ground samples of complete shells, sieved under 0.2 mm (Sample M); (c) hard layers of the endocarp (Sample E); (d) internal layers of the endocarp (Sample I); and (e) mature drupes (Sample P) or skin, being constituted by the flexible part of green colour (fresh form) or yellow (after drying). The thermal behaviour of all these sample materials has been investigated using a laboratory furnace, with determination of ash contents and mass loss by progressive heating (120 min of holding time). Elemental and DTA-TG/DTG analyses of selected sample materials have been carried out. Although a complete study can be very complex, a first approach has been performed in this investigation. Results on thermal decomposition of this biomass waste have been presented to emphasize the main differences between sample materials of almond shells. These results have demonstrated the influence of several parameters, such as the particle size, and previous treatments in the thermal behaviour of the different parts of the almond shells, as showed in this investigation. Structural analysis of almond shells allowed to determine lignin, cellulose and hemicellulose. From the lignin content, it has been predicted the higher heating value (18.24 MJkg(-1)) of this waste as by-product of industrial interest. Other linear correlations to calculate this parameter have been applied with similar results in all these samples.

Junio, 2022 | DOI: 10.1007/s10973-021-10940-x