Docta Complutense :: Browsing by Author "López Delgado, Aurora"

Browsing by Author "López Delgado, Aurora"

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Al-Waste-Based Zeolite Adsorbent Used for the Removal of Ammonium from Aqueous Solutions
(Hindawi Publishing Corporation, 2018) Sánchez-Hernández, Ruth; Padilla, Isabel; López Andrés, Sol; López Delgado, Aurora
This work evaluates the use of a synthetic NaP1 zeolite obtained from a hazardous Al-containing waste for the removal of ammonium (NH4+) from aqueous solutions by batch experiments. Experimental parameters, such as pH (6–8), contact time (1–360 min), adsorbent dose (1–15 g/L), and initial NH4+ concentration (10–1500 mg/L), were evaluated. Adsorption kinetic models and equilibrium isotherms were determined by using nonlinear regression. The kinetic was studied by applying both the pseudo-first-order and pseudo-second-order models. The equilibrium isotherms were analyzed according to two-parameter equations (Freundlich, Langmuir, and Temkin) and three-parameter equations (Redlich–Peterson, Sips, and Toth). The results showed that the NH4+ uptake on NaP1 was fast (15 min) leading to a high experimental sorption capacity (37.9 mg/g). The NH4+ removal on NaP1 was a favorable process that followed the pseudo-first-order kinetic model. The NH4+ adsorption was better described by the Sips (54.2 mg/g) and Toth (58.5 mg/g) models. NaP1 zeolite from Al-waste showed good NH4+ sorption properties, becoming a potential adsorbent to be used in the treatment of contaminated aqueous effluents. Thus, a synergic effect on the environmental protection can be achieved: the end of waste condition of a hazardous waste and the water decontamination.
Caracterización de un nuevo hidroxicloruro de magnesio
(s.n., 1984) López Andrés, Sol; López Delgado, Aurora; García Martínez, O.
Characterization of the Aluminas Formed During the Thermal Decomposition of Boehmite by the Rietveld Refinement Method
(Wiley, 2015-01) Jiménez, Jose A.; Padilla, Isabel; López Delgado, Aurora; Fillali, Laila; López Andrés, Sol
Boehmite synthesized through a sol‐gel route from a nonconventional raw material, as an aluminum waste, was calcined at temperatures between 500 and 1500°C. Quantification of crystalline phases was performed by the Rietveld refinement of the XRD patterns. γ‐Al2O3 is formed at 500°C, and up to 1000°C, is the dominant phase. At temperatures ranging from 1000 to 1400°C, it was observed the appearance of a four‐phase region. The complete transformation into α‐Al2O3 lasts until 12 h at 1400°C or at higher temperatures. The presence of an amorphous phase in calcined samples was confined by direct comparison with a standard of pure α‐Al2O3.
Eco-friendly bench-scale zeolitization of an Al-containing waste into gismondine-type zeolite under effluent recycling
(Elsevier, 2017-09) Sanchez Hernández, Ruth; Padilla, Isabel; López Andrés, Sol; López Delgado, Aurora
The feasibility of developing an eco-friendly bench-scale zeolitization process of NaP1 from an Alcontaining waste and under recycling of effluents was evaluated.Prior lab-scale tests were performed to optimize the synthesis conditions. The mixture of effluents, i.e., mother liquors (ML) from the synthesis and rinse water (RW) from the cleaning step of the zeolites, was recycled several times to study the reduction of raw materials (NaOH and water) and accordingly the reduction of costs. The bench-scale process allows the complete transformation of the waste into NaP1 zeolite, reaching equivalent reaction yields (2.5 ton of zeolite per ton of waste) to the lab-scale process and avoiding the generation of new solid residues. The effect of the recycling of effluents on the physical-chemical properties of the resulting zeolites was investigated. NaP1 zeolite was the only crystalline phase obtained, showing morphological, textural and crystalline characteristics closely similar to NaP1 synthesized from fresh NaOH aqueous solutions and from pure chemical reagents. NaOH and water consumption savings of 80 and 67%, respectively, were obtained, representing a cost reduction around 70%. These results show that the bench-scale process to obtain NaP1 from an Al-waste with recycling of effluents can be a more sustainable alternative compared with the traditional synthesis methods.
Industrial aluminum hazardous waste as a new raw material for zeolite synthesis
(2014) López Delgado, Aurora; Rodríguez Largo, Olga; Padilla Rodríguez, Isabel; Galindo Llorach, Roberto; López Andrés, Sol
In Spain, the secondary aluminum industry is a mature activity which produces 35% of the total aluminum production. This industry generates slag (black dross) with a valuable content of aluminum which is recovered by dry milling processes in the aluminum tertiary industry. The powdered fine solid is trapped in the sleeve filter suction system of the aluminum slag milling process. This solid is considered as a hazardous waste within the 10 03 21 group in the European Waste Catalogue (EWC), because of the very fine grain size (x50 < 50 μm) and the presence of dangerous substances (metallic aluminum, AlN, heavy metals, etc.). The high aluminum nitride content, ranging between 2 and 24%, is remarkable and it releases ammonia gas in the presence of environmental humidity. The aim of this work was to evaluate the complete recovery of the fine powders coming from the sleeve filters in the aluminum tertiary industry, as a zeolite. Two types of zeolite, analcime and NaP were obtained by hydrothermal processes from the aluminum waste and silica as raw materials. Different compositions of wastes and parameters such as time and temperature were assayed to study their effects on the obtained zeolites. The materials were characterized by X-ray diffraction and scanning electron microscopy. Keywords: aluminum hazardous waste, recycling, zeolite, analcime, NaP
Mayenita: Aluminato Cálcico Sintetizado a partir de un Residuo Peligroso de Aluminio
(Sociedad Española de Mineralogía, 2010-09) Gonzalo Delgado, Laura; López Delgado, Aurora; López, Félix A.; López Andrés, Sol
Nickel basic salts as inorganic precursors in the production of nickel
(Springer Netherlands, 1987-06) López Delgado, Aurora; López Andrés, Sol; García Martínez, O.; Millán Pastor, Pilar; Rojas, R.M.
The utilization of some nickel basic salts, nickel hydroxychloride and nickel hydroxynitrate, as inorganic precursors in the obtention of nickel powder, has been studied. When these materials are thermally decomposed in an X-ray high-temperature diffraction chamber, pure nickel is formed as the only compound at about 700°C but if nickel hydroxide is the starting material, small amounts of nickel oxide are always present even if the temperature is raised up to 900" C.
One-step synthesis of NaP1, SOD and ANA from a hazardous aluminum solid waste
(Elsevier, 2016) Sánchez Hernández, Ruth; López Delgado, Aurora; Padilla, Isabel; Galindo Llorach, Roberto; López de Andrés, Sol
NaP1, SOD, and ANA zeolites were synthesized from a hazardous aluminum waste as main aluminosilicate source by a one-step hydrothermal synthesis. This allowed the total transformation of the waste and no other solid residues were produced. The conversion of the waste into zeolites led to yields of ∼2.5 kg of zeolite per kg of waste. Experimental parameters such as stirring, time, temperature, and concentration of alkalizing agent (NaOH solution) were studied to determine the best synthesis conditions. Samples were characterized by different techniques such as XRD, SEM-EDS, FTIR, TG-DTA; textural properties such as BET specific surface area, zeta potential, granulometry and cation-exchange capacity (CEC) were also determined. Temperature and alkali concentration were the parameters with strongest influence in the formation of the different zeolites. Thus, the optimal conditions to obtain NaP1 and ANA were 1 M NaOH solution for 6 h at 120 and 200 °C, respectively, while SOD was prepared at 120 °C for 6 h, using a very much higher alkali concentration (5 M). These zeolites exhibited similar characteristics to those obtained from conventional chemical reagents. Besides, the mother liquor from the synthesis of NaP1 was recycled twice in order to reduce water and alkalizing agent consumption. In this case, the only crystalline phase obtained was NaP1 showing morphological, textural and crystalline characteristics very similar to those of NaP1 prepared from fresh solutions. The results show that the aluminum waste can be transformed into different types of zeolites, considered as value-added materials, with promising adsorption properties.
Recovery of aluminium from a hazardous waste by precipitation as boehmite
(NST. CIENCIAS CONSTRUCCIÓN EDUARDO TORROJA, 2009) Gonzalo Delgado, Laura; López Delgado, Aurora; López Andrés, Sol; López Gómez, Félix Antonio; Alguacil, Francisco José; López, F.A.; Puertas, F.; Alguacil, Francisco José; Guerrero, A.
Boehmite was synthesized by a low temperature hydrothermal procedure, via sol-gel, from an aluminium hazardous waste (AHW). The method consisted of a first stage of acid digestion to solubilize the metal content, and a second stage of gel precipitation in alkaline medium. Several experiments were performed to study the effect of concentration, time and pH not only on the recovery of aluminium but on the purity of boehmite. A nanocrystalline boehmite was obtained as unique phase at pH8. At pH9 boehmite is obtained along with norstrandite. The complete characterization of samples was carried out by XRD, MEB, and TG/DTA. The procedure allows the recovery of 90% of the soluble aluminium content in the waste.
Recycling of hazardous waste from tertiary aluminium industry in a value-added material
(SAGE Publications, 2011) Gonzalo Delgado, Laura; López Delgado, Aurora; López, Félix Antonio; Alguacil, Francisco José; López Andrés, Sol
The recent European Directive on waste, 2008/98/EC seeks to reduce the exploitation of natural resources through the use of secondary resource management. Thus the main objective of this study was to explore how a waste could cease to be considered as waste and could be utilized for a specific purpose. In this way, a hazardous waste from the tertiary aluminium industry was studied for its use as a raw material in the synthesis of an added-value product, boehmite. This waste is classified as a hazardous residue, principally because in the presence of water or humidity, it releases toxic gases such as hydrogen, ammonia, methane and hydrogen sulfide. The low temperature hydrothermal method developed permits the recovery of 90% of the aluminium content in the residue in the form of a high purity (96%) AlOOH (boehmite). The method of synthesis consists of an initial HCl digestion followed by a gel precipitation. In the first stage a 10% HCl solution is used to yield a 12.63 g L-1 Al3+ solution. In the second stage boehmite is precipitated in the form of a gel by increasing the pH of the acid Al3+ solution by adding 1 molL-1 NaOH solution. Several pH values were tested and boehmite was obtained as the only crystalline phase at pH 8. Boehmite was completely characterized by X-ray diffraction, Fourier transform infrared and scanning electron microscopy. A study of its thermal behaviour was also carried out by thermogravimetric/differential thermal analysis.
Síntesis y estudio del hidroxicloruro de niquel NiOHCl, H2O
(s.n., 1984) López Delgado, Aurora; López Andrés, Sol; García Martínez, O.
Study by DTA/TG of the formation of calcium aluminate obtained from an aluminium hazardous waste
(Springer Science Business Media, 2010-03) López Delgado, Aurora; López Gómez, F.A.; Gonzalo Delgado, Laura; López Andrés, Sol; Alguacil Priego, F.J.
A Spanish hazardous waste from tertiary aluminium industry was used as a raw material for the synthesis of calcium aluminate. An amorphous precursor was obtained by a hydrothermal method at different values of pH. The transformation of the precursor in a crystalline aluminate was followed by TG/DTA up to 1300 ºC. At temperatures between 719 and 744 ºC, the precursors evolve towards the formation of C12A7 which becomes CA at circa 1016 ºC. Mass spectrometry coupled to thermal analyser allowed the identification of the decomposition products.
Sustainable Management of Salt Slag
(MDPI, 2022-04-19) Padilla, Isabel; Romero, Maximina; López Andrés, Sol; López Delgado, Aurora
The management of salt slag, a waste from the secondary aluminum industry, is associated with huge environmental concerns due to the risk of atmospheric pollution (emission of toxic gases), groundwater contamination (high salt content that can percolate and cause an increase in salinity) and soil unavailability (large extensions required for disposal). Therefore, the development of a sustainable process for its treatment and recovery is of the utmost importance. In this work, a two-step process for the valorization of salt slag was developed that rendered zeolite as the main added-value product and NaCl and NH3 as byproducts. First, salt slag was hydrolyzed at 90 °C and at a solid/water ratio of 1/3. More than 90% of salt and ~90% of ammonia were recovered. In a second step, the hydrolyzed slag was completely transformed into a NaP zeolite under mild hydrothermal conditions. The zeolite exhibited specific surface area (17 m2 g−1), cation exchange capacity (2.12 meq g−1) and zeta potential (−52 mV) values that represent good characteristics for use in the removal of metal ions from aqueous effluents. The transformation of salt slag into zeolite can be considered a sustainable process with a high contribution to the circular economy.
Synthèse et caractérisation de l'alumine á partir d'un dechet dangereux
(2012-03) Fillali, Laila; Tayibi, H.; López Andrés, Sol; Jiménez Rodríguez, José A.; Padilla Rodríguez, Isabel; López Delgado, Aurora
La dernière Directive Européenne, 2008/98/CE, relative au traitement des déchets a pour objectif la réduction de l’exploitation des ressources naturelles par la gestion des ressources secondaires. Afin d’atteindre cet objectif, cette étude a été menée pour transformer un déchet dangereux, provenant de l´industrie tertiaire de l´aluminium, à alpha alumine (corindon). Le processus développé peut être résumé en deux phases: 1) la obtention de la boehmite (AlOOH) par traitement hydrothermal à basse température; 2) la calcination de la boehmite obtenue à différentes températures (1300, 1400 et 1500ºC) durant 7h. Les échantillons ont été caractérisés par la diffraction des rayons X, fluorescence des rayons X et le microscope électronique à balayage.
Synthesis of alumina based on industrial waste material
(CVR – Centro para a valorização de Resíduos, 2011) López Andrés, Sol; Fillali, Laila; Jiménez Martín, Juan Ángel; Tayibi, H.; Padilla Rodríguez, Isabel; López Delgado, Aurora; Castro, Fernando; Vilhariño, Cándida; Carvalho, Joana
A hazardous waste generated in slag milling process by the aluminium industry was used as a raw material for the synthesis of alumina, α-Al2O3. This waste is considered as hazardous material in the European legislation due to the release of toxic gases (hydrogen, ammonia, methane and hydrogen sulphide) in the presence of water. The process developed in this work allows to obtaining 1 ton of alumina from 4 tons of hazardous waste and generates an inert solid residue consisting principally of spinel, corundum and quartz with possible uses in cements or glass industry. This process consisted of two steps: in the first one, nearly 90% of aluminium present in the waste is recovered as a nanocrystalline boehmite, γ-AlOOH by hydrothermal treatment of the waste. In the second step, the alumina is obtained by calcination of the boehmite at 1400ºC in air. The chemical composition of the alumina obtained consisted of 95% Al2O3, 3.3% Fe2O3, 0.8% SiO2 and other minor oxides to balance.
Synthesis of α-alumina from a less common raw material
(Springer, 2012-07-19) López Delgado, Aurora; Fillali, Laila; Jiménez Rodríguez, José A.; López Andrés, Sol
A nanostructured α-Al2O3 with particle size lower than 100 nm was obtained from a hazardous waste generated in slag milling process by the aluminium industry. The route developed to synthesize alumina consisted of two steps: in the first one, a precursor of alumina, boehmite, γ-AlOOH was obtained by a sol–gel method. In the second step, the alumina was obtained by calcination of the precursor boehmite (xerogel). Calcination in air was performed at two different temperatures, i.e. 1,300 and 1,400 °C, to determine the influence of this parameter on the quality of resulting alumina. X-Ray diffraction patterns and transmission electron microscopy images of calcined powers revealed beside corundum the presence of transition aluminas and some rest of amorphous phase in the sample prepared at 1,300 °C. The increase of the calcinations temperature to 1,400 °C favors the formation of an almost single-phase corundum powder. The transition of θ- to α-Al2O3 was followed by means of infrared spectroscopy, since it is accompanied by the disappearance of the IR band frequencies associated with tetrahedral sites (AlO4 sites), giving rise to a spectrum dominated by Al3+ ions in octahedral sites (AlO6) characteristic of corundum.
The Application of Thermal Solar Energy to High Temperature Processes: Case Study of the Synthesis of Alumina from Boehmite
(Hindawi Publishing Corporation, 2014-01) Padilla, Isabel; López Delgado, Aurora; López Andrés, Sol; Álvarez Aguirre, Marta; Galindo Llorach, Roberto; Vázquez Vaamonde, Alfonso J.
The aim of this paper is to evaluate the feasibility of obtaining alumina from boehmite using a free, clean, and unlimited power source as the solar energy. Boehmite was obtained by hydrothermal treatment of a hazardous waste coming from aluminum slag milling. The waste is considered as a hazardous substance because of it releasing toxic gases (hydrogen, ammonia, methane, and hydrogen sulfide) in the presence of water. The as-obtained boehmite was transformed into alumina, in air atmosphere, using a solar energy concentrator (Fresnel lens). The solar installation provides a power density of 260 W·cm−2 which allows reaching temperatures upper than 1000°C at few minutes of exposure. Tests were performed at different periods of time that ranged between 5 and 90 min. The percentage of transformation of boehmite into alumina was followed by the water content of samples after solar radiation exposure. Samples were characterized by X-ray diffraction, infrared spectroscopy, and thermogravimetry. Metastable aluminas started to appear at 5 min and the crystalline and stable phase corundum at 10 min of solar radiation exposure.
Thermal decomposition of single hydroxychlorides of nickel, copper and cobalto
((s.n), 1985) García Martínez, O.; López Delgado, Aurora; Millán , P.; López Andrés, Sol; Rojas López, Rosa María; Tigeras , P.
The thermal decomposition reactions of Ni(OH)Cl.l½H20 in still air and in nitrogen and β-CO2(OH)3Cl and γ-Cu2(OH)3Cl in nitrogen atmosphere, have been studied by DTA and TG analysis, and the intermediates and final products have been characterized by x-ray diffraction and infrared spectroscop. The thermal evolution ot the above indicated compounds under dynamic vacuum conditions has be en studied with the aid of an x-ray high teaperature diffraction chamber. They reveals that in these conditions, the pure metallic nickel, copper and cobalt can be obtained at comparative low temperature. The infrared spectra of thése hydroxychlorides have been tentatively assigned.
Zero-waste process for the transformation of a hazardous aluminum waste into a raw material to obtain zeolites
(Elsevier, 2020-05) López Delgado, Aurora; Robla Villalba, José Ignacio; Padilla, Isabel; López Andrés, Sol; Romero, Maximina
A potential route to minimize the environmental impact of industrial activities is, among other approaches, the use of hazardous wastes as less-common raw materials for the preparation of other materials. Realistic technologies for waste management should include simple and low-cost processes as well as the nonproduction of new wastes. Thus, the total conversion of a type of hazardous aluminum waste into zeolite was achieved at the pilot-scale (200 l autoclave reactor) under mild hydrothermal operating conditions. In a one-step process, 3.2 tons of zeolite, 76.4 Nm3 of ammonia and 105.9 Nm3 of hydrogen can be produced per ton of aluminum waste. The process does not generate other wastes. The recycling of process effluents (mother liquor and rinse water), along with the process gases capture and its subsequent commercialization, would increase the environmental impact and the economic yield. The obtained Linde type-A zeolite, exhibited structural, textural and morphological characteristics similar to those of zeolites prepared from commercial reagents. A conceptual design for zero-waste process is proposed. The sustainable process developed can contribute to reduce the high environmental impact of aluminum industry waste, and contribute to the circular economy by converting a hazardous waste into a raw material.

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