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.
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
White and red Brazilian Sao Simao's kaolinite-TiO2 nanocomposites as catalysts for toluene photodegradation from aqueous solutions
(MDPI, 2019) Mora, Lucas D.; Trujillano, Raquel; Rives, Vicente; Pérez Bernal, María Elena; Korili, Sophia A.; Gil Bravo, Antonio; Faria, Emerson H. de; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The presence of volatile organic compounds in groundwater is a major concern when it is used as a drinking water source because many of these compounds can adversely affect human health. This work reports on the preparation and characterization of white and red Brazilian Sao Simao's kaolinite-TiO2 nanocomposites and their use as catalysts in the photochemical degradation of toluene, a significant volatile organic compound. The nanocomposites were prepared by a sol-gel procedure, using titanium bis(triethanolaminate)diisopropoxide as a precursor. Thermal treatments of the nanocomposites led to different polymorphic titania phases, while the clay changed from kaolinite to metakaolinite. This structural evolution strongly affected the photocatalytic degradation behavior-all the solids efficiently degraded toluene and the solid calcined at 400 degrees C, formed by kaolinite and anatase, showed the best behavior (90% degradation). On extending the photochemical treatment up to 48 h, high mineralization levels were reached. The advantage of photodegradation using the nanocomposites was confirmed by comparing the results from isolated components (titanium dioxide and kaolinite) to observe that the nanocomposites displayed fundamental importance to the photodegradation pathways of toluene.
Open Access
Application of industrial wastes from chemically treated aluminum saline slags as adsorbents
(American Chemical Society, 2018) Gil Bravo, Antonio; Arrieta Chango, Ekhine; Vicente, Miguel Ángel; Korili, Sophia A.; Institute for Advanced Materials and Mathematics - INAMAT2
In this study, industrial wastes, which remain after aluminum extraction from saline slags, were used as adsorbents. The aluminum saline slags were treated under reflux with 2 mol/dm3 aqueous solutions of NaOH, H2SO4, and HCl for 2 h. After separation by filtration, aqueous solutions containing the extracted aluminum and residual wastes were obtained. The wastes were characterized by nitrogen adsorption at -196 °C, X-ray diffraction, scanning electron microscopy, and ammonia pulse chemisorption. The chemical treatment reduced the specific surface area, from 84 to 23 m2/g, and the pore volume, from 0.136 to 0.052 cm3/g, of the saline slag and increased the ammonia-adsorption capacity from 2.84 to 5.22 cm3/g, in the case of acid-treated solids. The materials were applied for the removal of Acid Orange 7 and Acid Blue 80 from aqueous solutions, considering both single and binary systems. The results showed interesting differences in the adsorption capacity between the samples. The saline slag treated with HCl rapidly adsorbed all of the dyes present in solution, whereas the other materials retained between 50 and 70% of the molecules present in solution. The amount of Acid Orange 7 removed by the nontreated material and by the material treated with NaOH increased in the presence of Acid Blue 80, which can be considered as a synergistic behavior. The CO2 adsorption of the solids at several temperatures up to 200 °C was also evaluated under dry conditions. The aluminum saline slag presented an adsorption capacity higher than the rest of treated samples, a behavior that can be explained by the specific sites of adsorption and the textural properties of the solids. The isosteric heats of CO2 adsorption, determined from the Clausius-Clapeyron equation, varied between 1.7 and 26.8 kJ/mol. The wastes should be used as adsorbents for the selective removal of organic contaminants in wastewater treatment.
Embargo
Improvement of the adsorption properties of an activated carbon coated by titanium dioxide for the removal of emerging contaminants
(Elsevier, 2019) Taoufik, Nawal; Elmchaouri, Abdellah; Anouar, Fatna; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Three activated carbon coated titanium dioxide composites are evaluated as adsorbents for the removal of three pharmaceutical compounds: clofibric, gallic and salicylic acids from aqueous solutions. These composite materials are characterized by several techniques as SEM, FT-IR, TGA and point of zero charge determination. The adsorption mechanism of acids was investigated and compared to the adsorption on the virgin carbon. The analysis of adsorption isotherms and kinetic properties reveals that the addition of TiO2 increased the adsorption capacities of the initial material. The adsorption kinetics has been studied in terms of pseudo-first and pseudo-second order kinetic models, and the Freundlich, Langmuir, Temkin, Tôth and Sips isotherms models have also been applied to the equilibrium adsorption data. The analysis of results indicated that the adsorption of acids on the activated carbon-titanium dioxide composites is well described by the pseudo-first order kinetic model and the Sips isotherm equation fitted the sorption experimental results better than other models.
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
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.