Meso- and macroporous silica-based arsenic adsorbents: effect of pore size, nature of the active phase, and silicon release

Angotzi, Marco Sanna; Mameli, Valentina; Cara, Claudio; Borchert, Konstantin B. L.; Steinbach, Christine; Boldt, Regine; Schwarz, Dana; Cannas, Carla

doi:10.1039/d1na00487e

Cited by 16 publications

(17 citation statements)

References 98 publications

(162 reference statements)

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“…Concerning the secondary silicon pollution (Table S5), the comparison between As III and As V tests reveals that the phenomenon is limited in the case of the As III species, and the silicon release is mainly affected by the pH, probably due to a weaker interaction of arsenite with the sorbent. On the contrary, the Si release observed for the As V removal tests indicated that arsenate species play a crucial role, as already observed in a previous study [39], beyond a pH effect.…”

Section: Effect Of the Ph In The As V And As Iii Test Removal By Fe Iii -Based Sorbentssupporting

confidence: 68%

“…The comparison between Comp and the bare silica matrix (Figure S1), reveals a decrease of 10% of surface area and 11% of pore volume in the first one, as expected after the impregnation process. The PSD is instead centered, for both samples, at about 8 nm, suggesting the formation of isolated NPs inside the pores in spite of a uniform layer [39,60,61]. a, b, and c: cell parameters; D XRD 1 and D XRD 2 : crystallite sizes; D TEM 1 and D TEM 2 : particle sizes; S BET : surface area; V p : pore volume; D p : pore diameter.…”

Section: Figurementioning

confidence: 99%

“…The silica-iron oxide composite (Comp) was prepared from porous silica adapting a method from the literature [39]. Briefly, at 35 • C, 4.6 g of pluronic 123 (P123) and 7.7 g of Na 2 SO 4 were dissolved in 135 g of 0.02 M acetic acid-sodium acetate buffer solution at pH = 5 for 16 h to form a homogeneous milky mixture under stirring.…”

Section: Synthesis Of the Sorbentsmentioning

confidence: 99%

“…Indeed, the ideal advantage in dispersing an active phase in porous silica may reflect higher chemical and mechanical stability and the possibility to modify the silica walls with other kinds of functional groups and/or active inorganic phases [35,68]. Conversely, one should evaluate the cost of producing such sorbents and the possible issues related to secondary silicon pollution [39]. As reported in Table S4, silicon was found after the adsorption tests, with concentrations that increase with the pH.…”

Section: Effect Of the Ph In The As V And As Iii Test Removal By Fe Iii -Based Sorbentsmentioning

confidence: 99%

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As(III, V) Uptake from Nanostructured Iron Oxides and Oxyhydroxides: The Complex Interplay between Sorbent Surface Chemistry and Arsenic Equilibria

et al. 2022

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Iron oxides/oxyhydroxides, namely maghemite, iron oxide-silica composite, akaganeite, and ferrihydrite, are studied for AsV and AsIII removal from water in the pH range 2–8. All sorbents were characterized for their structural, morphological, textural, and surface charge properties. The same experimental conditions for the batch tests permitted a direct comparison among the sorbents, particularly between the oxyhydroxides, known to be among the most promising As-removers but hardly compared in the literature. The tests revealed akaganeite to perform better in the whole pH range for AsV (max 89 mg g−1 at pH0 3) but to be also efficient toward AsIII (max 91 mg g−1 at pH0 3–8), for which the best sorbent was ferrihydrite (max 144 mg g−1 at pH0 8). Moreover, the study of the sorbents’ surface chemistry under contact with arsenic and arsenic-free solutions allowed the understanding of its role in the arsenic uptake through electrophoretic light scattering and pH measurements. Indeed, the sorbent’s ability to modify the starting pH was a crucial step in determining the removal of performances. The AsV initial concentration, contact time, ionic strength, and presence of competitors were also studied for akaganeite, the most promising remover, at pH0 3 and 8 to deepen the uptake mechanism.

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Section: Effect Of the Ph In The As V And As Iii Test Removal By Fe Iii -Based Sorbentssupporting

confidence: 68%

Section: Figurementioning

confidence: 99%

Section: Synthesis Of the Sorbentsmentioning

confidence: 99%

Section: Effect Of the Ph In The As V And As Iii Test Removal By Fe Iii -Based Sorbentsmentioning

confidence: 99%

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As(III, V) Uptake from Nanostructured Iron Oxides and Oxyhydroxides: The Complex Interplay between Sorbent Surface Chemistry and Arsenic Equilibria

et al. 2022

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“…Various silica-based composites with good performances in the removal of heavy metal ions, or oxyanions, have been lately reported. 24 − 28 Among them, selective and efficient adsorption of arsenic ions by the amino-functionalized silica, 24 , 25 surface-ion imprinted silica, 26 or quaternary amine-functionalized silica 28 have been reported in the last decade. Porous silica has been used as a suitable host for numerous functional polymers, such as anionic hydrogels, 29 anion exchangers, 30 and amidoxime ligands.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Arsenic Removal from Aqueous Solutions Using Amidoxime Resin Hosted by Mesoporous Silica

Humelnicu

Ignat

Dinu³

et al. 2022

ACS Omega

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The paper reports on the performances of cross-linked amidoxime hosted into mesoporous silica (AMOX) in the removal of As(III) and As(V). The optimum pH for sorption of As(III) and As(V) was pH 8 and pH 5, respectively. The PFO kinetic model and the Sips isotherm fitted the best the experimental data. The thermodynamic parameters were evaluated using the equilibrium constant values given by the Sips isotherm at different temperatures and found that the adsorption process of As(III) and As(V) was spontaneous and endothermic on all AMOX sorbents. The spent AMOX sorbents could be easily regenerated with 0.2 mol/L HCl solution and reused up to five sorption/desorption cycles with an average decrease of the adsorption capacity of 18%. The adverse effect of the co-existing inorganic anions on the adsorption of As(III) and As(V) onto the sorbent with the highest sorption capacity (AMOX3) was arranged in the following order: H 2 PO 4 – > HCO 3 – > NO 3 – > SO 4 2– .

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Experiments‐Guided Modeling of MCM‐41: Impact of Pore Symmetry on Gas Adsorption

Carta

Cara

Cannas

et al. 2022

Adv Materials Inter

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by combining sol-gel synthesis with a proper surfactant templating agent. The latter was not a single solvated organic or inorganic species, but a self-assembled surfactant array. Three main mesophases are typically produced, namely, the cubic MCM-48, the lamellar MCM-50, and the hexagonal MCM-41. The latter is characterized by a regular 2D hexagonal array (P6mm space group symmetry) of highly uniform parallel non-interconnected channels, with the pore diameter depending on the specific templating agent. Compared to the other members of the M41S mesoporous family, MCM-41 has a higher thermal stability, and it is easier to prepare, thus attracting greater attention. [1,12] The ordered pore architecture of MCM-41 can be clearly observed through transmission electron microscopy (TEM) [2,13] and assessed through low-angle X-ray diffraction (LA-XRD) techniques or small-angle x-ray scattering (SAXS). [2] Overall, porosity can be as high as 80%, with the pore walls composed of amorphous silica. [1] The analysis of the N 2 adsorption isotherms according to the Brunauer-Emmett-Teller (BET) theory [14] is widely employed to estimate the Specific Surface Area (SSA), which is typically >700 m 2 g -1 . [11] Analysis of the same adsorption isotherm through the Barrett-Joyner-Halenda (BJH) model [15] is the typical choice to determine the pore size distribution (PSD). However, other approaches are available to retrieve these textural details, which are more recent and have a more rigorous physical base, such as the Density Functional Theory (DFT), allowing the determination of both the SSA, the pore volume, and the PSD. [16] The former models and theories have been recently questioned. [17] Computer calculations and simulations are able to unveil the microscopic details and the energetic aspects of the interaction between the guest molecules and the solid surface. Adsorption capacity, selectivity, diffusivity, and so on, can be investigated at the microscopic level under different pressure, temperature and humidity, so to obtain fundamental information to tailor material synthesis and functionalization to meet specific goals. Computational approaches can be used to complement the experiments, but also to possibly predict the system behavior, and to save time and resources on the laboratory bench. To this aim, the preparation of a 3D model that matches the characteristics of the real sample and that is able to reproduce the macroscopic behavior, as seen by the experiments, is crucial. Mesoporous materials cannot be modeled as simple flat surfaces or slits. At Among mesoporous ordered silica-based materials, MCM-41 is widely employed in both experimental and computational investigations of gas adsorption. Specific surface area and pore size distribution are typically obtained by analyzing the N 2 adsorption isotherm. To this aim, different models and theories are available, and which one is more accurate is under debate. On the computational side, the in silico model ought to match the characteristics of real samples and reproduc...

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Meso- and macroporous silica-based arsenic adsorbents: effect of pore size, nature of the active phase, and silicon release

Abstract: Arsenic pollution in ground and drinking water is one of the major problems worldwide due to the natural abundance of arsenic by dissolution from ground sediments or mining activities as...

Cited by 16 publications

References 98 publications

As(III, V) Uptake from Nanostructured Iron Oxides and Oxyhydroxides: The Complex Interplay between Sorbent Surface Chemistry and Arsenic Equilibria

As(III, V) Uptake from Nanostructured Iron Oxides and Oxyhydroxides: The Complex Interplay between Sorbent Surface Chemistry and Arsenic Equilibria

Optimization of Arsenic Removal from Aqueous Solutions Using Amidoxime Resin Hosted by Mesoporous Silica

Experiments‐Guided Modeling of MCM‐41: Impact of Pore Symmetry on Gas Adsorption

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