A study on the mechanism of Ca2+ adsorption on TiO2 and Fe2O3 with the usage of calcium ion-selective electrode

Szymanek, Karolina; Charmas, Robert; Piasecki, Wojciech

doi:10.1016/j.chemosphere.2019.125162

Cited by 16 publications

(17 citation statements)

References 67 publications

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“…For Al 2 O 3 the exclusion of the hydrolyzed tetra-species presented in Fig. 5 helped with fitting noticeably as it was in the case of maghemite in the previous paper (Szymanek et al 2020). According to Sverjensky (2006) the adsorption mechanism may depend on ionic strength and solid concentration.…”

Section: Electrokinetic Potentialsupporting

confidence: 55%

“…In this study theoretical investigations were carried out using the 2-pK TLM modeling approach (Yates et al 1974;Davis et al 1978;Sverjensky 2005Sverjensky , 2006 in accordance with our recent paper (Szymanek et al 2020).…”

Section: Methodsmentioning

confidence: 96%

“…The raw materials were subjected to the experiment without further purification. The applied chemicals, the experimental setup and the conditions were the same as described in our previous paper (Szymanek et al 2020).…”

Section: Methodsmentioning

confidence: 99%

“…The surface coverage was calculated by dividing the number of adsorbed calcium ions (in millimoles) by the total number of adsorption sites. The adsorption data for titania and maghemite are taken from the paper by Szymanek et al (2020) (Color figure online) that the enthalpy of this process is close to zero. It follows that calcium adsorption occurs as a result of an increase in entropy in the system during the accumulation of calcium ions at the surface.…”

Section: Ca 2+ Uptake Experimentsmentioning

confidence: 99%

“…Our aim was to examine whether in our systems the same adsorption mechanism could be applied. For this purpose the methods applied in our recent paper (Szymanek et al 2020), i.e. direct potentiometry for monitoring Ca 2+ concentration, ζ-potential measurements, and surface complexation 2-pK TLM (triple-layer model) with the GEOSURF program developed by Sahai and Sverjensky (1998) were used.…”

Section: Introductionmentioning

confidence: 99%

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Investigations of mechanism of Ca2+ adsorption on silica and alumina based on Ca-ISE monitoring, potentiometric titration, electrokinetic measurements and surface complexation modeling

2020

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Research on Ca2+ adsorption onto the mineral surface is of significant importance with regard to geochemical processes. Sverjensky (Geochim Cosmochim Acta 70(10), 2427–2453, 2006) assumed that alkaline earths form two types of surface species on oxides: tetranuclear (> SOH)2(> SO−)2_M(OH)+ and mononuclear > SO−_M(OH)+. To look into the above assumption we investigated calcium adsorption on SiO2 and Al2O3 because they are the most widespread minerals in the environment. We have determined the proton surface charge, electrokinetic potential and metal adsorption as a function of pH. The Ca2+ uptake and concentration in the system were monitored by the calcium ion-selective electrode (Ca-ISE). The Ca-ISE measurements indicated a similar affinity of Ca2+ for both materials despite their differently charged surface, negative for silica and mainly positive for alumina. This may suggest that simple electrostatic interactions are not the primary driving force for calcium adsorption, and that solvation of calcium ions at the surface may be crucial. We have analyzed our experimental data using the 2-pK triple-layer model (2-pK TLM). Three calcium complexes on the mineral surface were reported. Two of them were the same for both oxides, i.e. the tetranuclear ($$>$$ > SOH)2($$>$$ > SO−)2_Ca2+ and mononuclear complexes > SO−_CaOH+. Additionally, minor contribution from >SOH…Ca2+ for silica was assumed. In the case of Al2O3 the hydrolyzed tetranuclear complexes ($$>$$ > SOH)2($$>$$ > SO−)2_CaOH+ at pH > 7.5 occurred based on the modeling results. Two types of surface complexes suggested by Sverjensky allowed for the correct description of proton and calcium uptake for alumina. However, the electrokinetic data excluded hydrolyzed tetranuclear surface species for this oxide.

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Section: Electrokinetic Potentialsupporting

confidence: 55%

Section: Methodsmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Section: Ca 2+ Uptake Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Investigations of mechanism of Ca2+ adsorption on silica and alumina based on Ca-ISE monitoring, potentiometric titration, electrokinetic measurements and surface complexation modeling

2020

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An Efficient High‐Entropy Perovskite‐Type Air Electrode for Reversible Oxygen Reduction and Water Splitting in Protonic Ceramic Cells

Zhou

et al. 2023

Advanced Materials

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Reversible protonic ceramic electrochemical cells (R‐PCECs) are emerging as ideal devices for highly efficient energy conversion (generating electricity) and storage (producing H2) at intermediate temperatures (400–700 °C). However, their commercialization is largely hindered by the development of highly efficient air electrodes for oxygen reduction and water‐splitting reactions. Here, the findings in the design of a highly active and durable air electrode are reported: high‐entropy Pr0.2Ba0.2Sr0.2La0.2Ca0.2CoO3−δ (HE‐PBSLCC), which exhibits impressive activity and stability for oxygen reduction and water‐splitting reactions, as confirmed by electrochemical characterizations and structural analysis. When used as an air electrode of R‐PCEC, the HE‐PBSLCC achieves encouraging performances in dual modes of fuel cells (FCs) and electrolysis cells (ECs) at 650 °C, demonstrating a maximum power density of 1.51 W cm−2 in FC mode, and a current density of −2.68 A cm−2 at 1.3 V in EC mode. Furthermore, the cells display good operational durabilities in FC and EC modes for over 270 and 500 h, respectively, and promising cycling durability for 70 h with reasonable Faradaic efficiencies. This study offers an effective strategy for the design of active and durable air electrodes for efficient oxygen reduction and water splitting.

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The pH dependent surface charging and points of zero charge. IX. Update

Kosmulski

2021

Advances in Colloid and Interface Science

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A study on the mechanism of Ca2+ adsorption on TiO2 and Fe2O3 with the usage of calcium ion-selective electrode

Cited by 16 publications

References 67 publications

Investigations of mechanism of Ca2+ adsorption on silica and alumina based on Ca-ISE monitoring, potentiometric titration, electrokinetic measurements and surface complexation modeling

Investigations of mechanism of Ca2+ adsorption on silica and alumina based on Ca-ISE monitoring, potentiometric titration, electrokinetic measurements and surface complexation modeling

An Efficient High‐Entropy Perovskite‐Type Air Electrode for Reversible Oxygen Reduction and Water Splitting in Protonic Ceramic Cells

The pH dependent surface charging and points of zero charge. IX. Update

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