Open Access
Adsorption recovery of Ag(I) and Au(III) from an electronics industry wastewater on a clay mineral composite
(University of Science and Technology Beijing, 2019) Rakhila, Youness; Elmchaouri, Abdellah; Mestari, Allal; Korili, Sophia A.; Abouri, Meriem; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The aim of this work is to investigate the ability of an adsorbent of a clay mineral composite to remove and recover gold and silver ions from wastewater. The composite was prepared by mixing phosphogypsum (PG), obtained from an industrial waste, and a natural clay mineral. The materials were characterized before and after use in adsorption by several techniques. Batch adsorption experiments were carried out, and the effects of the contact time and the pH and temperature of solution on the removal processes were investigated. The optimum pH for the adsorption was found to be 4. The adsorption of these metal ions reached equilibrium after 2 h of contact. The pseudo-first- and the pseudo-second-order kinetic models, as well as the Freundlich and the Langmuir isotherm equations, were considered to describe the adsorption results. The maximum adsorbed amount of 85 mg·g−1 Ag(I) and 108.3 mg·g−1 Au(III) was found. The recovery of the adsorbed gold and silver ions from the adsorbent was also analyzed. Strong acids appeared to be the best desorption agents to recover gold and silver ions. The use of aqua regia gave regeneration rates close to 95.3% and 94.3% for Ag(I) and Au(III), respectively. Finally, the removal of gold and silver ions from an industrial wastewater was tested in batch experiments, and percentage recoveries of 76.5% and 79.9% for Ag(I) and Au(III), respectively, were obtained. To carry out the industrial application of the proposed methodology, an economic viability study is required.
Embargo
A layered titanosilicate AM-4 as a novel catalyst for the synthesis of 1-methoxy-2-propanole from propylene oxide and methanol
(Elsevier, 2019) Timofeeva, Maria N.; Kurchenko, Julia V.; Kalashnikova, Galina O.; Panchenko, Valentina N.; Nikolaev, Anatoliy I.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
In this paper we report for the first time the catalytic properties of the titanosilicate AM-4 in the synthesis of 1-methoxy-2-propanol (PGME) from methanol and propylene oxide (PO). PGME is widely used as a pollution-free solvent and intermediate in the synthesis of propylene glycol methyl ether acetate, the herbicide metolachlor and in other industrial applications. We found that the catalytic properties of AM-4 could be adjusted by treatment with 0.0625–0.25 M HNO3. Increasing the concentration of HNO3 led to a decrease in basicity, which played a critical role in the reaction rate and the selectivity towards PGME. The yield of PGME decreased with increased acid concentration. The maximum conversion of PO (88.4%) and the selectivity towards PGME (92.3%) were found to be in the presence of AM-4 at 110 °C and 8 mol/mol MeOH/PO. Our results suggest that titanosilicate AM-4 has great potential for application in basic catalysis.
Open Access
Microwave-assisted pillaring of a montmorillonite with al-polycations in concentrated media
(MDPI, 2017) González, Beatriz; Pérez, Alba Helena; Trujillano, Raquel; Gil Bravo, Antonio; Vicente, Miguel Ángel; Química Aplicada; Kimika Aplikatua
A montmorillonite has been intercalated with Al3+ polycations, using concentrated solutions and clay mineral dispersions. The reaction has been assisted by microwave radiation, yielding new intercalated solids and leading to Al-pillared solids after their calcination at 500 °C. The solids were characterized by elemental chemical analysis, X-ray diffraction, FTIR spectroscopy, thermal analyses, and nitrogen adsorption. The evolution of the properties of the materials was discussed as a function of the preparation conditions. Microwave treatment for 2.5 min provided correctly pillared solids.
Open Access
Photocatalytic degradation of trimethoprim on doped Ti-pillared montmorillonite
(Elsevier, 2019) González, Beatriz; Trujillano, Raquel; Vicente, Miguel Ángel; Rives, Vicente; Korili, Sophia A.; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2
Montmorillonite pillared with titanium and doped with Cr3+ or Fe3+ has been tested for the photo-degradation of the antibiotic trimethoprim (trimethoxybenzyl-2,4-pyrimidinediamine) under different conditions, namely, in the dark or in UV light, with or without catalyst, finding excellent catalytic performance under photocatalytic conditions. The degradation by-products were preliminary analysed by mass spectrometry. The results suggested that the molecule broke in two halves, corresponding to its two existing rings. The process continued with the breakage of new fragments from the trimethoxybenzene half, these fragments later reacted with the methoxy groups in this part of the molecule, giving species with m/z values higher than that for the starting molecule, and with the breakage of new fragments.
Embargo
Zeolite synthesis from industrial wastes
(Elsevier, 2019) Yoldi Sangüesa, María; Fuentes Ordóñez, Edwin Gustavo; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua, 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.
Open Access
Effect of high pressure on the reducibility and dispersion of the active phase of Fischer-Tropsch catalysts
(MDPI, 2019) Yunes, Simón; Vicente, Miguel Ángel; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The effect of high pressure on the reducibility and dispersion of oxides of Co and Fe supported on -Al2O3, SiO2, and TiO2 has been studied. The catalysts, having a nominal metal content of 10 wt.%, were prepared by incipient wetness impregnation of previously calcined supports. After drying at 60 °C for 6 h and calcination at 500 °C for 4 h, the catalysts were reduced by hydrogen at two pressures, 1 and 25 bar. The metal reduction was studied by temperature-programmed reduction up to 750 °C at the two pressures, and the metal dispersion was measured by CO chemisorption at 25 °C, obtaining values between 1% and 8%. The physicochemical characterization of these materials was completed by means of chemical analysis, X-ray diffraction, N2 adsorption-desorption at -196 °C and scanning electron microscopy. The high pressure lowered the reduction temperature of the metal oxides, improving their reducibility and dispersion. The metal reducibility increased from 42%, in the case of Fe/Al2O3 (1 bar), to 100%, in the case of Fe/TiO2 (25 bar).
Open Access
Synthesis of zeolite a from metakaolin and its application in the adsorption of cationic dyes
(MDPI, 2018) Pereira, Priscila Martins; Ferreira, Breno Freitas; Oliveira, Nathalia Paula; Gil Bravo, Antonio; Korili, Sophia A.; Kimika Aplikatua; Institute for Advanced Materials and Mathematics - INAMAT2; Química Aplicada
The present work reports the synthesis of zeolites from two metakaolins, one derived from the white kaolin and the other derived from the red kaolin, found in a deposit in the city of São Simão (Brazil). The metakaolins were prepared by calcination of the kaolins at 600 ◦C; zeolite A was obtained after alkali treatment of the metakaolins with NaOH. The resulting solids were characterized by powder X-ray diffraction, thermal analysis, scanning electron microscopy, and nitrogen adsorption/desorption at −196 ◦C, which confirmed formation of zeolite A. The zeolites were applied as adsorbents to remove methylene blue, safranine, and malachite green from aqueous solutions. The zeolites displayed high adsorption capacity within short times (between one and five minutes); qt was 0.96 mg/g. The equilibrium study showed that the zeolites had higher adsorption capacity for malachite green (qe = 55.00 mg/g) than for the other two cationic dyes, and that the Langmuir isotherm was the model that best explained the adsorption mechanism.
Open Access
Efficient recovery of aluminum from saline slag wastes
(Elsevier, 2019) Yoldi Sangüesa, María; Fuentes Ordóñez, Edwin Gustavo; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua, PI017 CORRAL
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.
Open Access
Comparative removal of emerging contaminants from aqueous solution by adsorption on an activated carbon
(Taylor & Francis, 2019) Gil Bravo, Antonio; Taoufik, Nawal; García Mora, Ana María; Korili, Sophia A.; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Batch sorption experiments were performed to study the adsorption of six emerging pollutants from aqueous solutions using a commercial granular activated carbon as adsorbent. Caffeine, clofibric acid, diclofenac, gallic acid, ibuprofen and salicylic acid were selected as representative contaminants. The activated carbon was characterized by nitrogen adsorption at 77 K, and through the determination of point of zero charge. The effects of several operational parameters, such as pH, initial concentration of organic molecules, mass of adsorbent and contact time, on the sorption behaviour were evaluated. The contact time to attain equilibrium for maximum adsorption was found to be 40 min. The kinetic data were correlated to several adsorption models, and the adsorption mechanism found to follow pseudo-second-order and intraparticle-diffusion models with external mass transfer predominating in the first 15 min of the experiment. The equilibrium adsorption data were analysed using the Freundlich, Langmuir and Toth isotherm equation models. The similar chemical structure and molecular weight of the organic pollutants studied to make the adsorption capacity of the activated carbon used very similar for all the molecules.
Open Access
Effective degradation of methylene blue in aqueous solution using Pd-supported Cu-doped Ti-pillared montmorillonite catalyst
(Elsevier, 2019) Joseph, Annu; Vellayan, Kannan; González, Beatriz; Vicente, Miguel Ángel; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2
The effluents from the textile, paper and food industries contain organic dyes that are strongly colored and reveal harmful effect on living systems. In order to reduce water pollution, the degradation of dye into non toxic form is desirable. Methylene blue is one such organic dye, discharged from textile industries. In this work, the catalytic degradation of methylene blue was investigated using a montmorillonite supported trimetallic catalyst, prepared by supporting Pd on a Cu-doped Ti pillared montmorillonite. The catalyst exhibited excellent performance to reduce methylene blue, in the presence of NaBH4. The decolorization was appreciable and the results indicated that methylene blue could be successfully decolorized and degraded using the catalyst under room conditions. Almost complete degradation was achieved within 20 min. The results obtained were better than those reported for other catalysts. © 2018 Elsevier B.V.