FRBA - Publicaciones en Congresos, Conferencias y Jornadas
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Item Iron nanoparticles based nanofluids for in situ environmental remediation(2023) Crespi, Julieta; Binetti Basterrechea, Gian Franco; Finoli, Agostina Sol; Montesinos, Victor Nahuel; Quici, NataliaThe injection of nanoscale zerovalent iron particles (nZVI) suspensions in the ground is a technology employed for in situ water and soil remediation. Due to its nature, nZVI forming these nanofluids (NFs), tend to agglomerate, but this can be overcome by polyelectrolyte coatings, that also improve their mobility. In this work, stabilization of nZVI with carboxymethylcellulose (CMC) was studied. NFs prepared with CMC (CMC-NSTAR) were compared with non-stabilized NFs (b-NSTAR). First, the stabilization efficiency was evaluated by the analysis of the nanoparticles sedimentation rate. Then, the mobility of stabilized and non-stabilized NFs was studied in columns filled with porous media at laboratory and pilot scale. Finally, NFs reactivity for the removal of aqueous Cr(VI) was tested in batch and columns experiments. In the column experiments, a porous media bed was loaded with NSTAR and then a Cr(VI) solution was injected upwards. CMC-NSTAR showed good mobility at both scales being successfully eluted from the porous media. In the case of b-NSTAR, the accumulation of nanoparticles in the bottom of the column was observed and elution was not achieved. Using b-NSTAR as reactive barrier, a total removal of 15.5 mg Cr(VI)/g Fe was achieved. Better removal rates were found in batch experiments (22.8 mg Cr(VI)/g Fe). Reactivity experiments in batch with CMC-NSTAR showed 39.9 mg Cr(VI)/g Fe removal. In conclusion, the NF was proved to have good transport properties and Cr(VI) removal capacity.Item Iron nanoparticles based nanofluids for in situ environmental remediation(Oscar Pagola (Asociación Argentina de Ingenieros Químicos), 2024) Crespi, Julieta; Binetti Basterrechea, Gian Franco; Finoli, Agostina Sol; Montesinos, Victor Nahuel; Quici, NataliaIn this work, stabilization of commercial nZVI (NANOFER STAR, hereafter NSTAR, provided by NANOIRON s.r.o.) with carboxymethyl cellulose (CMC) was studied. NFs prepared with CMC (CMC-NSTAR) were compared and with NFs prepared without CMC (b-NSTAR). Stabilization was evaluated by sedimentation rate analysis of the nanoparticles in CMC-NSTAR versus b-NSTAR. The mobility of both stabilized and non-stabilized NFs was studied in columns filled with porous media at laboratory and pilot scale. NFs were injected upwards in the column with a peristaltic pump, and the nZVI concentration was monitored with turbidity measurement at the outlet stream. Then, NFs reactivity for the removal of aqueous Cr(VI) was tested in batch and columns experiments. In the batch experiments, 15 mg L-1 Cr(VI) solutions and the NFs were mixed with an orbital shaker, with a Fe:Cr molar ratio = 10. In the column experiments, a porous media bed was loaded with 0.5 g of n-NSTAR and then a 100 mg L-1 Cr(VI) solution was injected upwards.Item Preliminary results of photocatalytic Cr(VI) reduction using TiO2 films grown by cathodic arc deposition: effect of the film thickness and the N-doping(2023-06-08) Kleiman, Ariel; Meichtry, Jorge Martín; Xaubet, M.; Grondona, D.; Litter, Marta Irene; Márquez, AdrianaTiO2 is the most studied photocatalyst for the treatment of pollutants; however, its rather large band gap and the need for a removal step when used as a suspension hinder the wide application of this technology. Immobilized TiO2 films grown by cathodic arc deposition (CAD) have shown superior adhesion to the substrate and activities similar to that of P-25 TiO2 films, the reference photocatalyst, but they still require UV light to be excited [1]. N-doping is a strategy frequently used to extend the TiO2 band gap to the visible range [2], but it has a scarce application on CAD-grown films. In this work, TiO2 CAD films, with and without N-doping, were prepared and tested on the photocatalytic removal of Cr(VI), a priority water pollutant, in the presence of ethylenediaminetetraacetic acid (EDTA) as an organic donor. TiO2 films of different thicknesses: (290 ± 40 nm), (440 ± 40) nm, and (850 ± 70) nm, were deposited by CAD according to a reported method [1]. The doping of the films was performed by plasma immersion ion implantation in a N2 environment. For comparison, P-25 TiO2 films of (280 ± 20) nm and (480 ± 30) nm thicknesses were prepared by dip-coating; thicker P-25 films were not stable. All films were grown over a borosilicate glass substrate. Photocatalytic experiments were performed in thermostatted cylindrical glass cells (T = 25 °C) magnetically stirred and irradiated from the top with a HPA 400S lamp (λ > 320 nm, mean UV irradiance 28 W m-2), equipped with an IR filter. 10 mL of a 0.8 mM Cr(VI) and 1 mM EDTA solution at pH 2 (HClO4) were poured into each cell, and 0.25 mL samples were periodically taken for Cr(VI) quantification by the diphenylcarbazide method; at the end of the experiments, a Cr(III)-EDTA complex in solution was determined by direct spectrophotometry [1]. After 5 h of irradiation, Cr(VI) removals of 58% and 85% were obtained with pure and N-doped 290 nm CAD films, respectively, while for pure and N-doped 440 nm CAD films the corresponding removals were 70% and 85%; with the 280 nm and 480 nm P-25 films, Cr(VI) removals were 81% and 88%, respectively. Although thicker CAD films were more efficient (99% of Cr(VI) removal with 850 nm films), no difference could be appreciated between N-doped and undoped films. Cr(VI) evolution could be adjusted to a pseudo-first-order kinetics. In all cases, Cr(III)-EDTA represented 75% of the reduced Cr(VI), the remaining Cr(III) being retained on the TiO2 surface, [1]. The photocatalytic efficiency increased with the thickness of the films. Although P-25 films showed a higher photoactivity than the CAD films of similar thickness, thicker and more active CAD films can be surely obtained in future works. N-doping increased slightly the photocatalytic activity of the thinnest films.Item Synergetic combination of nano zero-valent iron, ultrasound and carboxylic acids for the removal of aqueous Cr(VI)(2023-06-08) Cancelada, Lucía; Meichtry, Jorge Martín; Destaillats, Hugo; Litter, Marta IreneCr(VI) is a priority pollutant present in wastewater of several industrial processes such as electroplating and leather tanning; it can be also naturally present in groundwater. The usual treatment of Cr(VI) involves its reduction to Cr(III), a far less toxic and mobile species, which can be precipitated from the solution at circumneutral pH values [1]. However, conventional Cr(VI) chemical reductants, such as Fe(II) salts, require large Fe:Cr molar ratios to be efficient, generating the disposal of large amounts of dangerous sludge. Thus, more efficient Cr(VI) reduction treatments are required. In this work, the efficiency of commercial zero-valent iron nanoparticles (nZVI), ultrasound (US), and carboxylic acids (CAs) for Cr(VI) reduction was evaluated. The CAs used were citric acid (Cit) or ethylenediaminetetraacetic acid (EDTA). The experiments were performed with 200 mL of a 0.3 mM Cr(VI) solution at pH 3 and under air bubbling (0.5 L min-1) at 30 °C for 180 min in an ultrasonic reactor (850 kHz, total power input 35 W L-1). NSTAR (Nanoiron®) was used as nZVI, with a 3:1 Fe:Cr molar ratio (the optimal ratio as determined before for N25 nZVI [2]), Cit (0 or 2 mM) or EDTA (0 or 1 mM). In the absence of Cit or EDTA (nZVI alone or nZVI + US), or with Cit or EDTA alone (neither nZVI nor US), Cr(VI) reduction was negligible (≤ 5% of the initial [Cr(VI)]). US + Cit showed a reduction of 49% of the initial [Cr(VI)], while US + EDTA showed a 32% of reduction. On the other hand, nZVI + US + Cit yielded an 88% of Cr(VI) reduction, which was 60% with nZVI + US + EDTA. This indicates a clear synergy within the ternary system (nZVI + US + CAs). In all cases, the evolution of Cr(VI) could be fitted to a zero-order kinetic model , with R2 values higher than 0.94. NSTAR nZVI particles are composed of a zerovalent Fe core surrounded by a protective shield of iron oxides that inhibits Cr(VI) reduction; thus, only the combination of US and CAs can remove this protective shield and enhance Cr(VI) reduction, being Cit more efficient than EDTA. This was reinforced by the monitoring of the evolution of the total Fe concentration in solution, with final values of 0.076, 0.26, and 0.18 mM for the systems nZVI + US, nZVI + US + Cit and nZVI + US + EDTA, respectively, indicating that Cit and EDTA promote the formation of soluble Fe complexes. Besides, in the previous experiments of US without nZVI, Cit also proved to be a better donor than EDTA, probably because it can stabilize to a higher extent intermediate peroxo-Cr(V) compounds [1]. Summarizing, there is a synergy for Cr(VI) reduction in the ternary system nZVI + US + CAs, being Cit more efficient than EDTA.