Remarkable influence of surface composition and structure of oxidized iron layer on orange I decomposition mechanisms

Montes-Atenas, Gonzalo; Mielczarski, Ela; Mielczarski, J.

doi:10.1016/j.jcis.2005.03.042

Cited by 17 publications

(4 citation statements)

References 38 publications

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“…NZVI has proved to be effective at a laboratory scale in degrading several contaminants, like chlorinated solvents, − perchlorate anions, polychlorobiphenyls (PCBs), and dioxins, which are instead recalcitrant to scrap iron. More recently, metallic iron has resulted in a powerful means to destroy critical functional groups present in anthropogenic compounds, like pesticides , and dyes. − …”

Section: Introductionmentioning

confidence: 99%

“…Several methods have been proposed so far for azo-dye removal from wastewater, including: (i) TiO 2 -mediated photocatalytic processes; − (ii) adsorption on activated carbons; (iii) photoassisted Fenton’s reaction; , (iv) wet air oxidation; and others. , Instead, only a few papers deal with azo-dye degradation in the presence of iron, − among which are a pioneering work by Cao et al and a quite detailed study by Roy et al, both concerning the reactivity in acidic media of a Fe powder and platelet, respectively. Due to its extremely small particle size, involving both large surface area and marked mobility in the fluid phase, NZVI is expected to exhibit high reactivity and is therefore of interest in the degradation of AO7.…”

Section: Introductionmentioning

confidence: 99%

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Reactions of Acid Orange 7 with Iron Nanoparticles in Aqueous Solutions

et al. 2011

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The physicochemical properties of two commercial dispersions of iron nanoparticles were studied, together with their behavior in the room-temperature degradation in basic solutions of Acid Orange 7 (AO7), studied by UVÀvis spectroscopy. In one dispersion (bare-RNIP), water was the solvent, and in the other (M-RNIP) a biopolymer (sodium aspartate) was added (RNIP standing for reactive nanoscale iron particles and M for modified). The features of iron nanoparticles (size, morphology, presence of oxidized phases) were studied both in the dispersions as such and in the corresponding dried powders. A protecting role of the biopolymer was observed, as well as changes in the properties with time (aging). With bare-RNIP, the fraction of Fe 3 O 4 (magnetite) steadily increased with time at the expense of Fe 0 , eventually reaching 99%, and with M-RNIP, the Fe 0 content was higher at any time than with bare-RNIP: aging, however, brought about the formation of the Fe 3+ compound FeOOH besides magnetite. As for AO7 degradation, a similar behavior was observed with the two fresh dispersions: with M-RNIP, degradation was complete in a few minutes, and with fresh bare-RNIP, the same process was basically observed, though at a lower rate. In both cases, successive reactions were observed as a minor feature, for which an interpretation is advanced. Aging of M-RNIP does not prevent the degradation reaction: aging in the absence of the polymer, instead, leads, after 6 months, to an entirely different process, consisting in the mere adsorption through the phenol group of AO7 onto the magnetite external layer of bare-RNIP particles. Further aging of bare-RNIP prevents also this phenomenon. The different behavior of the two dispersions relates to the composition of iron nanoparticles. Reaction with water converts Fe 0 into magnetite. When Fe 0 is present and the thickness of the outer magnetite layer is moderate, AO7 degradation occurs. With a thick outer layer, only adsorption is possible, which does not take place on a fully oxidized surface.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reactions of Acid Orange 7 with Iron Nanoparticles in Aqueous Solutions

et al. 2011

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“…Orange I belongs to the family of azo dyes, which represent around 50% of all dyes used in textile industry [15] – [16] . Because it contains an -N = N- chromophore group, Orange I is highly toxic and causes various diseases [17] – [18] , such as nausea, carcinogen, dermatitis, methemoglobinemia, tumors and allergies [19] – [20] .…”

Section: Introductionmentioning

confidence: 99%

Preparation, Characterization and Application of Magnetic Fe3O4-CS for the Adsorption of Orange I from Aqueous Solutions

Pei

et al. 2014

PLoS ONE

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Fe3O4 (Fe3O4-CS) coated with magnetic chitosan was prepared as an adsorbent for the removal of Orange I from aqueous solutions and characterized by FTIR, XRD, SEM, TEM and TGA measurements. The effects of pH, initial concentration and contact time on the adsorption of Orange I from aqueous solutions were investigated. The decoloration rate was higher than 94% in the initial concentration range of 50–150 mg L−1 at pH 2.0. The maximum adsorption amount was 183.2 mg g−1 and was obtained at an initial concentration of 400 mg L−1 at pH 2.0. The adsorption equilibrium was reached in 30 minutes, demonstrating that the obtained adsorbent has the potential for practical application. The equilibrium adsorption isotherm was analyzed by the Freundlich and Langmuir models, and the adsorption kinetics were analyzed by the pseudo-first-order and pseudo-second-order kinetic models. The higher linear correlation coefficients showed that the Langmuir model (R2 = 0.9995) and pseudo-second-order model (R2 = 0.9561) offered the better fits.

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“…From a kinetic standpoint, the redox potential always follows the mixed potential, if the electrical conductivity of the electrode substrate makes it possible (which in the case of the Eh probe holds) [23]. The irreversible electrochemical theory indicates that this behaviour is also governed by the electrochemical reversibility of each of the redox reactions involved [24,25], which in this case it would be an anodic control [26].…”

Section: Eh and Ph Monitoring During Nash Dosingmentioning

confidence: 99%

Insights on Determining Improved Conditions for Multipurpose Reagent Dosing to Increase Froth Flotation Efficiency: NaSH in Cu-Mo Selective Flotation Case Study

Fernandez,

Montes-Atenas,

Valenzuela

et al. 2024

Minerals

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The assessment of mineral surface hydrophobicity at the industrial scale is a challenge. In some industrial situations, such information is indirectly obtained from other proxy variables. A well-known example of this is observed in the Cu-Mo selective flotation operation, where sodium hydrosulphide is used to change the redox potential and, controlling this value, determine when Cu-sulphide floatability is inhibited. Preliminary experiments indicate that this reagent may also promote the formation of solid precipitates, reducing its impact on the redox potential. This study aims at designing a simple strategy at the laboratory scale to report and quantify NaSH losses due to parallel, irreversible, and/or fast reactions, such as precipitation. Experiments carried out using process water coming from a Cu-Mo selective flotation plant in Chile show that departing from different pH conditions and the addition of hydrosulphide ions effectively triggers the precipitation of specific metal ions, decreasing its availability to reduce the redox potential of the aqueous solution. For this specific case scenario and water quality, around 5% of the NaSH dosed precipitated. An SEM-EDX analysis of the produced solid phase shows that it is composed of mainly iron sulphide and hydroxide, along with other metal hydroxides. More importantly, it was found that dosing the reagent at the same concentration, but in the form of small increments, allows reaching the redox potential more efficiently, reducing to some extent the precipitate production and the unnecessary NaSH consumption in up to 30% of the NaSH dosed. Preliminary 1-D modelling of the process, based on mass transport coupled with reaction mechanisms, provided a first indication of the best dosing conditions for this reagent. The latter is expected to contribute to the development of better and improved reagent dosage technologies in froth flotation environments.

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Remarkable influence of surface composition and structure of oxidized iron layer on orange I decomposition mechanisms

Cited by 17 publications

References 38 publications

Reactions of Acid Orange 7 with Iron Nanoparticles in Aqueous Solutions

Reactions of Acid Orange 7 with Iron Nanoparticles in Aqueous Solutions

Preparation, Characterization and Application of Magnetic Fe3O4-CS for the Adsorption of Orange I from Aqueous Solutions

Insights on Determining Improved Conditions for Multipurpose Reagent Dosing to Increase Froth Flotation Efficiency: NaSH in Cu-Mo Selective Flotation Case Study

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