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15 pags., 7 figs., 5 tabs., The control of chemical, morphological, textural and magnetic properties developed in magnetic activated carbons (MACs) from industrial food waste, was achieved. The process parameters involved in a sustainable and optimized one-step activation route, based on the circular economy model, played an important role and its influence was studied, offering interesting and outstanding results. Magnetite crystals were formed on the MACs surface obtained from 400 °C to 800 °C while other iron species, such as metallic iron and iron carbides, were formed only at 800° C. Acid washing favored the mineral matter removal and the presence of iron species was drastically reduced in acid-washed MACs, mainly the iron species originated at 800 °C. Water-washed MACs presented better magnetic response at high temperatures (confirmed by XRD, FTIR, Raman, Mössbauer spectroscopy and VSM characterization techniques). High BET surface area (≈ 822 m/g) and a large micropore volume (≈ 0.30 cm/g), were reached by acid washed MACs at 800 °C. The obtained MACs were fundamentally microporous, but some mesoporosity was also observed when activating agent/precursor mass ratio (1:1) is used. It can be concluded that a MACs strategic design was reached with the objective of removing specific pollutants in multiple environmental applications., This work was supported by the Plan Nacional, Ministerio de Economía y Competitividad of Spain: PN (MINECO), under the Project CTM2014-58435-C2-1-R.

An unpublished low-cost industrial biomass waste, pomegranate peel, as alternative and sustainable fuel source was studied. A horizontal tubular furnace of original design for conventional and flash pyrolysis was carried out. The bio-char yields from both processes were similar, but the bio-oil and bio-gas yields were higher in flash pyrolysis, depending on the temperature. The bio-char obtained show that it could be used as a fuel (higher heating values ≥ 28.0 MJ/kg) and as a potential precursor of activated carbon. It was also found that the lower temperature of the flash pyrolysis was, the greater the bio-oil yield (∼53%) and that the higher was, the greater the biogas yield (∼50%). The bio-oil from conventional pyrolysis has a predominantly furanic nature and contained significant amounts of the phenols and benzenes. In contrast, the bio-oil from flash pyrolysis is similar to that of “anthracene oil”, both of them being composed mainly of polycyclic aromatic hydrocarbons. The bio-gas obtained by flash pyrolysis is of a higher quality than that obtained by conventional pyrolysis because it has a lower CO2 content (32.4% vs 66.6%) and higher syngas content (CO + H2) (50.8% vs 26.8%). Flash pyrolysis is better in CH4 production (11.6% vs 4.6%).

A novel thermochemical process based on a single step was optimized to obtain magnetic activated carbons from an industrial biomass waste. Anhydrous iron chloride was used as an activating agent and mixed directly with the chestnut shell waste. The effect of the activation temperature (220-800 °C) on the chemical, morphological, textural, and magnetic properties of the materials was studied. The results demonstrated the presence of different iron compounds depending on the activation temperature set as well as their influence on morphological and textural development of the magnetic activated carbons (BET specific surface area, S up to 568 m g, total pore volume, V, up to 0.294 cm g vs 1 m g and 0.007 cm g, respectively, for the raw biomass waste). The techniques employed, especially Mössbauer spectroscopy, showed relative contributions of the different iron compounds (magnetite, maghemite, metallic iron, and so on) in the materials. The higher activation temperature (800 °C) favored the formation of metal Fe and iron carbide. Additionally, the magnetic properties measured by vibrating sample magnetometry confirmed the coexistence of different ferromagnetic phases with the remanent magnetization, M, (up to 3.88 emu/g) and coercivity, H, (up to 140 Oe), being larger as the activation temperature increases. A higher activation temperature favored the development and evolution toward other iron compounds, while at low temperature, 220 °C, the presence of these compounds were null, and their behavior resembled the results obtained for the original biomass waste.

Resorcinol-formaldehyde carbon xerogels were synthesized by means of microwave heating by using precursor solutions with pH values ranging from 3 to 7 and adding various amounts of sodium sulfate, hexadecyltrimethylammonium bromide and Span80. It was found that the amount of additive that can be introduced depends to a large extent on the final pH of the precursor solution. Characterization of the porous structure of the carbon xerogels thus synthesized demonstrated that their porosity was modified by interactions between the additives and the polymeric structure of the xerogels. It is worth noting that carbonaceous materials with a pore size that could not be obtained by merely modifying the pH could be synthesized by adding different types of additive, with the result that a significant improvement of the porous properties of the carbon xerogels was achieved. The addition of sodium sulfate increased the size of the clusters and pores due to repulsive forces created between the additive and resorcinol anions. Hexadecyltrimethylammonium bromide gave rise to a dense branched structure with pores of a small size attributable to forces of attraction between the cations of the additive and resorcinol anions. In contrast, the presence of Span80 in the precursor solution produced a condensation reaction between the resorcinol and the additive, as a result of which the amount of resorcinol available for the sol-gel reaction was reduced., Financial support from the Ministerio de Economía y Competitividad of Spain MINECO (under Projects MAT2011-23733 and IPT-2012-0689-420000) is greatly acknowledged. NRR is also grateful to MINECO for her predoctoral research grant.