An Electron Paramagnetic Resonance Spectroscopy Investigation of the Retention Mechanisms of Mn and Cu in the Nanopore Channels of Three Zeolite Minerals

Ferreira, Daniel R.; Schulthess, Cristian P.; Amonette, James E.; Walter, Éric

doi:10.1346/ccmn.2012.0600604

Cited by 7 publications

(13 citation statements)

References 19 publications

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“…The adsorption studies showed the selectivity of Na, K, and Ca on those zeolite minerals. Figure 1 illustrates the NISE theory, as well as the inner sphere and outer sphere orientation of the ions as confirmed by previous spectroscopy data (Ferreira et al, 2012a(Ferreira et al, , 2012b. It also shows the process by which Na and Ca exchange proceeds in the different nanopore channels.…”

Section: Resultssupporting

confidence: 80%

“…The NMR and EPR spectroscopy studies (Ferreira et al, 2012a(Ferreira et al, , 2012b confirmed the NISE theory of how monovalent and divalent cations behave in the constrained environments of different zeolite nanopores. The adsorption studies showed the selectivity of Na, K, and Ca on those zeolite minerals.…”

Section: Resultsmentioning

confidence: 55%

“…Evidence in support of the NISE theory has been collected by adsorption envelopes Ferreira and Schulthess, 2011), NMR spectroscopy (Ferreira et al, 2012b), EPR spectroscopy (Ferreira et al, 2012a), and flow calorimetry (this study). All these studies involved zeolites because they have identical chemistry and fixed nanopore dimensions and, therefore, make ideal candidates for elucidating the impact of nanopore dimensions on cation adsorption.…”

Section: Discussionmentioning

confidence: 52%

“…This was, however, an indirect measurement. The predictions of the NISE theory were confirmed with nuclear magnetic resonance (NMR) spectroscopy for Na adsorption (Ferreira et al, 2012b) and electron paramagnetic resonance (EPR) spectroscopy for Mn and Cu adsorption (Ferreira et al, 2012a). Ferreira et al (2012b) conducted a series of NMR scans of adsorbed Na ions on the zeolite minerals zeolite Y, ZSM-5, and mordenite.…”

mentioning

confidence: 79%

“…To investigate the adsorption mechanisms of divalent ions in nanopore channels, Ferreira et al (2012a) performed an EPR study of Mn and Cu on zeolite Y, ZSM-5, and mordenite. The results showed that Mn adsorbed via an outer sphere mechanism on zeolite Y and ZSM-5 and via an inner sphere mechanism on mordenite.…”

mentioning

confidence: 99%

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Calorimetric Evidence in Support of the Nanopore Inner Sphere Enhancement Theory on Cation Adsorption

Ferreira

Schulthess

Kabengi

2012

Soil Science Soc of Amer J

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Soil Chemistry S chulthess and Taylor (2007) proposed a new theory of cation adsorption to describe the adsorption of Na and Ni within zeolite minerals. This theory, called the nanopore inner sphere enhancement (NISE) theory, explains the unusual adsorption selectivity patterns observed for Na and Ni for Na, K, and Ca (Ferreira and. The NISE theory states that ions can dehydrate to fit into confining nanopore channels that are smaller than their hydrated diameters. In such a case, ions with lower hydration energies are more easily stabilized in their dehydrated states on adsorption than ions with higher hydration energies. Accordingly, in certain nanopore channels, monovalent ions are able to outcompete divalent ions because monovalent ions tend to have lower hydration energies than divalent ones (Collins, 1997). While hydration energy generally correlates well with the dehydration potential needed by the NISE theory, there are cases (such as Cu) where ions with high hydration energies can also dehydrate easily (Ferreira et al., 2012b).On zeolite Y, which contained the largest nanopore channels (0.74-nm limiting diameter), Ferreira and Schulthess (2011) observed that all three cations (Na, K, and Ca) adsorbed weakly and in similar amounts. On mordenite, with the smallest nanopore channels (0.26-nm limiting diameter), all three cations adsorbed strongly and in similar amounts. It is important to point out that the monovalent cations competed equally with a divalent cation at equimolar concentrations in these ion exchange reactions, which is very unusual. The most interesting results, however, The nanopore inner sphere enhancement (NISE) theory provides a new theoretical model of cation adsorption within confining nanopore channels. Inside nanopore channels, hydrated ions can dehydrate and more easily adsorb via an inner sphere mechanism. Adsorption data showed that in certain nanopores, weakly hydrated monovalent cations adsorbed more strongly than divalent cations, which tend to be strongly hydrated. Flow adsorption calorimetry is a valuable tool for directly measuring the heats of the ion exchange process and was used to measure the heats of Na and Ca exchange on three zeolite minerals: zeolite Y, mordenite, and ZSM-5. The data collected showed equal and reversible exchange reactions on mordenite but a strong endothermic Na adsorption and weak exothermic Ca adsorption on ZSM-5. On zeolite Y, the calorimetric signal was below the instrument detection limit of 5 to 7.5 mV. These differences coincide with the adsorption mechanisms and relative competitiveness predicted by the NISE theory for these two ions on the three zeolites studied. These data elucidate an exchange reaction where Ca is outcompeted by Na, which is often considered to be a weak background electrolyte.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 55%

Section: Discussionmentioning

confidence: 52%

mentioning

confidence: 79%

mentioning

confidence: 99%

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Calorimetric Evidence in Support of the Nanopore Inner Sphere Enhancement Theory on Cation Adsorption

Ferreira

Schulthess

Kabengi

2012

Soil Science Soc of Amer J

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Nanoconfinement engineering for enchanced adsorption of carbon materials, metal–organic frameworks, mesoporous silica, MXenes and porous organic polymers: a review

Zhou

2021

Environ Chem Lett

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Synthesis and Adsorption Desulfurization Performance of Modified Mesoporous Silica Materials M-MCM-41 (M = Fe, Co, Zn)

Guo

Pan

et al. 2019

Clays and clay miner.

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Adsorption desulfurization is a potential new method for deep desulfurization of fuel oil. The development of adsorbents with high adsorption capacity and selectivity is the core of deep adsorption desulfurization. The adsorption behavior of thiophene in MCM-41 mesoporous materials modified by various metal ions was studied in order to understand the adsorption desulfurization process of molecular sieves. The Fe-, Co-, and Zn-modified MCM-41 materials were prepared using a one-step in situ hydrothermal synthesis method. The modified MCM-41 molecular sieves maintained the mesoporous structure, and the metal ions had specific dispersion on the surface of the molecular sieves. Adsorption of thiophene on the surfaces of molecular sieves had both physical and chemical characteristics. The adsorption desulfurization performance of the modified molecular sieve was superior to that of the pure silica molecular sieve. In the simulated gasoline with sulfur content of 220 μg/g, when the amount of adsorbent used was 100 mg, the adsorptive desulfurization performance tended to be in equilibrium, and the optimum adsorption temperature was 30°C. Fe-MCM-41 and MCM-41 molecular sieves reached adsorption equilibrium after ~60 min, but the desulfurization rate of Co-MCM-41 and Zn-MCM-41 still increased slightly. The kinetic simulation results indicated that the pseudo-second-order kinetics adsorption model described well the adsorption process of thiophene on molecular sieves. The molecular sieve Fe-MCM-41 had the best desulfurization performance with an equilibrium adsorption capacity of 14.02 mg/g and the desulfurization rate was ~90%.

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An Electron Paramagnetic Resonance Spectroscopy Investigation of the Retention Mechanisms of Mn and Cu in the Nanopore Channels of Three Zeolite Minerals

Cited by 7 publications

References 19 publications

Calorimetric Evidence in Support of the Nanopore Inner Sphere Enhancement Theory on Cation Adsorption

Calorimetric Evidence in Support of the Nanopore Inner Sphere Enhancement Theory on Cation Adsorption

Nanoconfinement engineering for enchanced adsorption of carbon materials, metal–organic frameworks, mesoporous silica, MXenes and porous organic polymers: a review

Synthesis and Adsorption Desulfurization Performance of Modified Mesoporous Silica Materials M-MCM-41 (M = Fe, Co, Zn)

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