Examinando por Autor "Arencibia, Amaya"

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Amino functionalized mesostructured SBA-15 silica for CO2 capture: Exploring the relation between the adsorption capacity and the distribution of amino groups by TEM
(Elsevier, 2012) Sanz, Raúl; Calleja, Guillermo; Arencibia, Amaya; Sanz-Pérez, Eloy S.
The distribution of amino groups on amino-functionalized SBA-15 materials for CO2 adsorption was studied by Transmission Electron Microscopy (TEM) in combination with a staining technique using RuO4 in order to analyse the influence of the aminated organic chains location on the CO2 adsorption properties. Mesostructured aminofunctionalized SBA-15 materials were obtained by co-condensation, grafting and impregnation using aminopropyl, AP (N), ethylene-diamine, ED (NN), diethylenetriamine, DT (NNN) and polyethyleneimine, PEI, as functionalizing agents. CO2 adsorption isotherms of functionalized samples at 45 ºC showed that both the adsorption capacity (mg CO2/g ads) and the efficiency of amino groups (mol CO2/mol N) depend on the functionalization technique and the amount of organic compound used. While samples synthesized by co-condensation showed negligible CO2 uptake and efficiency, adsorbents prepared by grafting and impregnation presented significant CO2 adsorption capacities but a dissimilar efficiency. Key differences in the location of aminated chains explained the performance of CO2 capture for every adsorbent, being grafted samples the adsorbents where amino groups were better distributed, favouring the CO2 diffusion trough the whole structure.
Aqueous heavy metals removal by adsorption on amine-functionalized mesoporous silica
(ELSEVIER, 2009) Aguado, José; Arsuaga, Jesús M.; Arencibia, Amaya; Lindo, Montaña; Gascón, V.
Amino functional mesoporous silica SBA-15 materials have been prepared to develop efficient adsorbents of heavy metals in wastewater. Functionalization with amino groups has been carried out by using two independent methods, grafting and co-condensation. Three organic moieties have been selected to incorporate the active amino sites: aminopropyl (H2N-(CH2)3-), [amino-ethylamino]-propyl (H2N-(CH2)2-NH(CH2)3-) and [(2-aminoethylamino)-ethylamino]-propyl (H2N-(CH2)2-NH-(CH2)2-NH(CH2)3-). Materials have been characterized by XRD, nitrogen sorption measurements and chemical analysis. We have found that all materials preserve the mesoscopic order and exhibit suitable textural properties and nitrogen contents to act as potential adsorbents. Metal removal from aqueous solution has been examined for Cu(II), Ni(II), Pb(II), Cd(II), and Zn(II); adsorption performances of materials prepared by the two functionalization methods have been compared. In addition, copper adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for some selected materials. Aqueous Cu(II) adsorption rates show that the overall process is fast and the time evolution can be successfully reproduced with a pseudo-second order kinetic model. Whole copper adsorption isotherms have been obtained at 25ºC. Significant maximum adsorption capacities have been found with excellent behavior at low concentration.
Combination of immobilized TiO2 and zero valent iron for efficient arsenic removal in aqueous solutions
(2021) Raez, Julia; Arencibia, Amaya; Segura, Yolanda; Arsuaga, Jesús M.; López-Muñoz, María José
The photocatalytic removal of arsenic from aqueous solutions was investigated using titania (TiO2) immobilized on a glass support, both bare and combined with synthesized metallic iron nanoparticles (nZVI) or commercial microscale iron (ZVI). Three procedures, namely dip-coating, rotational coating, and sponge coating, were tested for achieving the immobilization of TiO2. The photocatalytic activity of the semiconductor films under UV-irradiation after cumulative coatings was evaluated for 10 mg L−1 aqueous As(III), which was entirely oxidized to As(V) with all settings within 90 and 180 min. Titania immobilized by dip-coating was found to be the most effective as it showed the faster kinetics. The reuse of immobilized TiO2 was also investigated, detecting no changes in the photocatalytic activity after five consecutive reactions. The addition of commercial ZVI particles to the immobilized TiO2 system did not bring about significant changes in the kinetics for As(III) oxidation at the three pH values investigated, i.e., 5, 7, and 9. By contrast, the addition of nZVI not only led to a faster depletion of As(III) compared to bare titania but also the removal of As(V) from the solution to concentrations below 10 μg L−1, the upper limit recommended by the World Health Organization for human consumption. The role of iron species in the arsenic removal process with both [ZVI + immobilized-TiO2] and [nZVI + immobilized-TiO2] systems was further investigated by performing adsorption and irradiation experiments without titania. It was inferred that within the pH range evaluated, the minor corrosion of the ZVI surface, even under UV irradiation, restricts the production of reactive oxidizing species and the generation of sites for arsenic species adsorption. By contrast, adsorption should be the main process responsible for the overall diminution of As(III) and As(V) species in solution attained upon nZVI addition, promoted by the increase of the external oxides/hydroxides layer on iron nanoparticles. Nevertheless, it might be also considered a certain contribution of UV-generated oxidant species formed in nZVI to the photocatalytic oxidation performance of titania.
Efficient amine-SBA-15-type adsorbents for treatment of water containing trace levels of Pb(II) and Cd(II)
(2019) Gascón, Victoria; Arencibia, Amaya; Arsuaga, Jesús M.
Efficient aqueous As(III) removal by adsorption on thiol-functionalized mesoporous silica
(2020) Arencibia, Amaya; López-Gutiérrez, María S.; Arsuaga, Jesús M.
Evaluation of nZVI for the degradation of atrazine in heterogeneous Fenton-like systems at circumneutral pH
(Elsevier, 2021) Plaza, Jorge; Arencibia, Amaya; López-Muñoz, María José
The requirement of acidification for the successful of the Fenton processes in water treatment has promoted the search for new strategies to work at pH close to neutrality. With this objective, in this work the use of nZVI has been evaluated for the oxidative elimination of 10 mg L−1 of atrazine at circumneutral pH with nZVI/UVA, nZVI/H2O2, and nZVI/H2O2/UVA systems. While UVA irradiation of sole nZVI was ineffective for degrading the herbicide, the addition of H2O2 boosted up the reaction, with the nZVI/H2O2/UVA system attaining the highest degradation rate. The inhibition of the reaction upon addition of tert-butanol as scavenger pointed out the significant role of hydroxyl radicals in the atrazine oxidation. The characterization of fresh and spent samples, carried out by XRD, SEM, TEM, and nitrogen adsorption-desorption experiments, confirmed the presence of ferric oxidized compounds responsible of the heterogeneous photo-Fenton-like reactions. On the basis of the degradation products determined by high performance liquid chromatography (HPLC), a scheme of atrazine degradation pathways in the ZVI/H2O2/UVA system was proposed in which the reaction is mainly initiated by alkylic oxidation rather than dechlorination. Finally, the effect on the atrazine oxidation rate of the water constituent species was analyzed in different water matrices (pure, supply, simulated and secondary effluent real water). Considered individually, Cl−, SO42−, HCO3−, and DOC, showed a moderate inhibitory effect on atrazine degradation kinetics, but their combination could explain the significant decrease of efficiency detected in the real secondary effluent water compared to less complex matrices.
Influence of synthesis conditions on mercury adsorption capacity of propylthiol functionalized SBA-15 obtained by Co-condensation
(ELSEVIER, 2008) Aguado, José; Arsuaga, Jesús M.; Arencibia, Amaya
Thiol functionalized mesoporous silicas for aqueous mercury removal by adsorption have been synthesized by co-condensation of 3-mercaptopropyltrimetoxysilane (MPTMS) and tetraethoxysilane (TEOS) in acidic medium with the block copolymer Pluronic 123 as structure directing agent. The influence of two synthesis parameters, the time of TEOS prehydrolysis and the molar ratio x = MPTMS / (MPTMS + TEOS), on both the textural properties and mercury adsorption capacities have been investigated. Materials were characterized by low-angle XRD, nitrogen adsorption-desorption, 29Si NMR, TGA-DTA, transmission electron microscopy and elemental chemical analysis. Adsorbents are mostly mesostructured SBA-15 type silicas with suitable textural properties for mercury adsorption and exhibit thermal stability up to at least 285ºC. The amount of propylthiol incorporated to the materials is in accordance with the MPTMS / TEOS proportion in the synthesis medium (up to 4.1 mmol of S per gram of adsorbent). We have found that it is neccessary to employ a minimal amount of TEOS in order to preserve the mesoporous structure in the resulting material when a high quantity of propylthiol groups is incorporated. Prehydrolysis of silica precursor (TEOS) for 45 minutes before MPTMS addition leads to succesful results. Longer prehydrolysis times can improve the textural and structural properties of materials but the amount of propylthiol incorporated and the mercury adsorption capacity are not superior. Experimental isotherms show that materials are efficient adsorbents of mercury at low aqueous concentration with maximum adsorption capacity as high as 4.1 mmol of Hg(II) per gram of adsorbent.
Optimization of thermal exfoliation of graphitic carbon nitride for methylparaben photocatalytic degradation under simulated solar radiation
(The Royal Society of Chemistry, 2023-04) Plaza, Jorge; Arencibia, Amaya; López-Muñoz, María José
Previous studies have shown that the exfoliation of graphitic carbon nitride (g‐C3N4) is essential to obtain materials with good photocatalytic properties. However, in most works the influence of the exfoliation variables were investigated in an unsystematic way by changing the levels of one factor at a time. In this work, a full factorial design 32 was employed to evaluate the influence of temperature and time used in the thermal exfoliation of bulk g‐C3N4 obtained from urea (bulk‐U) on the photocatalytic performance for 5 mg L−1 methylparaben degradation under simulated solar radiation. Based on the thermal stability of the starting bulk‐U the levels of the design were set in the range 400 to 450 oC for temperature and 2 to 6 h for time. The results showed an enhancement of the photocatalytic activity with the increase of both factors, obtaining the maximum response at T = 450 °C and t = 6 h. An economic evaluation at laboratory scale including the main costs derived from the synthesis stage and the photocatalytic degradation procedure was also performed comparing all the exfoliated materials. The total expenses could be minimized without compromising a good photocatalytic activity with the material obtained by exfoliation of bulk‐U at 450 oC for 2 h. A detailed characterization of the materials was carried out by XRD, FTIR, adsorption‐desorption of N2, UV‐Vis DR, and PL spectroscopy. It was inferred that the enhancement of the photocatalytic performance induced by the thermal exfoliation was mainly related to the consequent increase in the surface area and the improvement in the separation of photogenerated charge pairs derived from the unpacking of the stacked layers.
Use of graphitic carbon nitrides as solar-light-driven photocatalysts for the reduction of p-nitrobenzoic acid
(Elsevier, 2024) López-Timoner, Rubén; Arques, Antonio; Amat, Ana María; Plaza, Jorge; Arencibia, Amaya; López-Muñoz, María-José
he use of graphitic carbon nitrides (g-C3N4) as photocatalysts for the reduction of p-nitrobenzoic acid (PNBA) under simulated sunlight has been investigated. The photocatalysts were synthesized through the thermal polymerization of melamine and urea. The effects of the g-C3N4 precursor employed in the synthesis, the thermal exfoliation treatment, the addition of sacriﬁcial agents, and the pH conditions were evaluated. It was found that the presence of carboxylic acids as sacriﬁcial electron donors was required to attain the photocatalytic reduction of PNBA, while amines or alcohols did not lead to any activity for this purpose. Furthermore, it was observed that the precursor used in the synthesis of graphitic carbon nitride had a slight inﬂuence on the photocatalytic ac-tivity, whereas the thermal treatment of the bulk g-C3N4 materials exhibited a favourable effect. The best results were obtained upon addition of oxalic acid at pH = 3 using the carbon nitride exfoliated materials, achieving in these conditions the complete removal of PNBA after ca. 60 min of irradiation. Time resolved proﬁles of p- aminobenzoic acid (PABA) agree with an initial reduction of PNBA to form this compound, followed by oxidation of PABA by reactive oxygen species formed in the reaction medium.