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This study is the first to propose the use of aluminum saline slag as aluminum source in the synthesis of alumina pillared clays (Al-PILC). Aluminum was extracted from this waste using both alkaline and acid solutions and both were compared for preparation of the intercalation solutions used for the synthesis of Al-PILC. Variations in parameters such as [OH–]/[Al3+], Al/clay (mmol/g), clay/volume solution ratios and temperature were studied in the synthesis processes. The solids obtained were characterized by X-ray diffraction (XRD), N2 adsorption–desorption at −196 °C, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX), which confirmed that the pillaring process was successful. PILC obtained from both acid (Al-PILCAE) and alkaline (Al-PILCBE) extracts were evaluated as adsorbents for three organic pollutants, namely bisphenol A (BPA), 2,6-dichlorophenol (2,6DCP) and triclosan (TCS), in batch mode. The resulting adsorption capacities were compared with montmorillonite (Mt) and an Al-PILC prepared by the conventional method, namely, dropwise addition of an NaOH solution into an aluminum chloride solution (Al-PILCCM). In all cases, the effect of factors such as pH, initial concentration of pollutant, adsorbent dosages and contact time was studied. The kinetic and equilibrium results obtained were evaluated using both pseudo-first- and pseudo-second-order kinetics, and Langmuir, Freundlich and Sips equation isotherms for the equilibrium. The kinetic study showed that the time needed to reach equilibrium was 30, 900 and 510 min for BPA, 2,6DCP and TCS, respectively. Moreover, adsorption data showed that the Al-PILCAE and Al-PILCBE synthesized have excellent potential as adsorbents for 2,6DCP and TCS, removing 98.46% and 98.47% of these compounds, respectively. ; YC thanks the Universidad Pública de Navarra for a pre-doctoral grant (IberusTalent, European Union's H2020 research and innovation program under Marie Sklodowska-Curie grant agreement N° ...

The use of biofuels offers advantages over existing fuels because they come from renewable sources, they are biodegradable, their storage and transport are safer, and their emissions into the atmosphere are lower. Biomass is one of the most promising sustainable energy sources with a wide variety of organic materials as raw material. Chemical, biochemical, and thermochemical methods have been proposed to obtain biofuels from raw materials from biomass. In recent years, a thermochemical method that has generated great interest is hydrothermal liquefaction. In this paper, a brief review of the main sources for liquid biofuels and the synthesis processes is presented, with special emphasis on the production of biofuels using hydrothermal liquefaction by using waste generated by human activity as raw material. ; The authors are grateful for financial support from the Spanish Ministry of Science and Innovation (AEI/MINECO) and the Government of Navarra through projects PID2020-112656RB-C21 and PC034-035 BIOGASOLANA. AG also thanks Santander Bank for funding via the Research Intensification Program.

This work presents the procedure to improve the aluminum extracted from a hazardous waste from the recycling of aluminum, aluminum that could be used in the production of value-added materials, as well as with the generation of non-hazardous waste. The aluminum waste was treated under reflux and stirring with NaOH aqueous solutions taking into account two concentrations (1 and 2 mol/dm3), various times of extraction (1, 2 and 4 h) and 4th consecutive steps of extraction in order to obtain solutions with Al3+. The activation of the waste by milling is also analyzed. After extraction, the solution is filtered to separate an aqueous solution that contain the extracted Al3+ and a residual waste. A maximum of 7.54 g/dm3 of aluminum was extracted in the first step, for a total accumulated of 9.59 g/dm3 of aluminum. The extracted aluminum can be used to synthesize added-value products applied as adsorbents and catalysts. Finally, the residual waste generated was characterized by N2 adsorption at −196 °C, X-ray diffraction, X-ray fluorescence, energy-dispersive X-ray and scanning electron microscopy in order to apply it as in future works adsorbent or catalyst. ; The authors are grateful for financial support from the Spanish Ministry of Economy, Industry and Competitiveness (AEI/MINECO), the European Regional Development Fund (ERDF) and the Government of Navarra through projects MAT2016-78863-C2-1-R and PI017 CORRAL.

Conventional synthesis conditions for each type of zeolite are tabulated and reported by the International Zeolite Association Structure Commission (IZA) and most of them are synthesized from commercial reagents, but they can also be synthesized from industrial by-products rich in Si and/or Al. In zeolite synthesis from wastes, concentration of alkali source, temperature, reaction time, liquid/solid ratio and type of waste determine the textural properties, crystal structure, Si/Al ratio and ion exchange characteristics of the fabricated zeolite and its applications. This work summarizes the main methods that have been developed to synthesize zeolites using industrial wastes as Al and/or Si sources, the parameters of synthesis and the advantages and limitations of each synthesis process. The main characteristics and the applications of these synthetic waste zeolites are also reported. ; The authors are grateful for financial support from the Spanish Ministry of Economy, Industry and Competitiveness (AEI/MINECO) , the European Regional Development Fund and the Government of Navarra through projects MAT2016-78863-C2-1-R and PI017 CORRAL . MY thanks Government of Navarra for technologist recruitment. AG and EGFO also thank Santander Bank for funding through the Research Intensification Program.

This work describes the synthetic procedures developed to obtain zeolite X (NaX), zeolite A (LTA) and sodalite (SOD) using aluminum saline slag waste (AlSSW) as aluminum source in a two-step hydrothermal method involving alkaline extraction of Al, with separation of the residual waste, and hydrothermal treatment at low temperatures and long reaction times. Use of the mother liquor obtained after filtration and separation of the zeolite is also analyzed in the alkaline extraction of Al. The synthetic parameters that determine the type of zeolite, purity, crystallinity, specific surface area, pore size and pore volume include the Si/Al molar ratio, pH, nucleation temperature and time, and crystallization temperature and time. These critical parameters were studied and determined to synthesize NaX, LTA and SOD as individual phases. The materials obtained were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption/desorption measurements at −196 °C. The characteristics of the best zeolites obtained are similar to those of IZA references and the specific surface areas are in the range of commercial ones: NaX ranges from 450 to 500 m2/g and LTA from 250 to 300 m2/g. The results show that it is possible to synthesize zeolites from AlSSW, thus allowing these materials to be applied as promising adsorbents and catalysts. ; The authors are grateful for financial support from the Spanish Ministry of Economy, Industry and Competitiveness (AEI/MINECO), the European Regional Development Fund (ERDF) and the Government of Navarra through projects MAT2016-78863-C2-1-R and PI017-PI039 CORRAL.

This work reports the synthesis of Zinc-Titanium-Aluminum (ZnTiAl) layered double hydroxides (LDH) with various proportions of Al[sbnd]Ti and a Zn/(Al[sbnd]Ti) molar ratio of 3:1 by the co-precipitation method. Two series, made with commercial aluminum (Al) and aluminum extracted from saline slags (Al*), have been considered. Structural characterization and comparison of the two series has been made using powder X-ray diffraction (PXRD), Nitrogen physisorption at 77 K, Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetry measurements. The adsorption capacity of diclofenac and salicylic acid, as examples of emergent pollutants, by the different LDH on batch and fixed-bed column experiments has been analyzed. The effect of various parameters, such as the pH, the initial concentration of pollutant, the mass of adsorbent and the contact time, on the sorption behavior were studied and compared. The contact time to attain equilibrium for maximum adsorption was found to be between 100 and 400 min. The kinetic and equilibrium results were correlated to several adsorption and isotherm equation models. The synthesized materials were more effective in removing diclofenac than salicylic acid, being Zn6Al*2 the hydrotalcite that showed the highest adsorption capacity. The results showed a new application of a material obtained from the valorization of an industrial waste such as aluminum saline slags. ; This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (AEI/MINECO), and the European Regional Development Fund (ERDF) through project MAT2016-78863-C2-R and the Government of Navarra through projects PI017-PI039 CORRAL. LS thanks Universidad Pública de Navarra for a pre-doctoral grant. AG also thanks Santander Bank for funding through the Research Intensification Program.