Surface complexation modelling of Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) adsorption onto kaolinite

Gu, Xueyuan; Evans, L. J.

doi:10.1016/j.gca.2007.09.032

Cited by 219 publications

(75 citation statements)

References 28 publications

(42 reference statements)

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“…Unfortunately, one serious problem with low pH is the acid induced mineral dissolution, 287 which is very hard to circumvent in practice and therefore, the experimental data in low pH range are in 288 bad need. Zn 2+ on montmorillonite (Gu et al, 2010) and around 5.0 for kaolinite (Gu and Evans, 2008 (Fig. 5).…”

Section: Implication For Titration Experiments 263mentioning

confidence: 93%

Acidity of edge surface sites of montmorillonite and kaolinite

Liu

Sprik

et al. 2013

Geochimica et Cosmochimica Acta

194

160

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Acid-base chemistry of clay minerals is central to their interfacial properties, but up to 10 now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles 11 molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of 12 surface groups on (010)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 13 and 1:1-type clay minerals, respectively. It shows that ≡Si-OH and ≡Al-OH 2 OH groups of kaolinite 14 have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each 15 mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of 16 titration curves, indicating that ≡Si-OH and ≡Al-OH 2 OH groups are the major acidic sites responsible to 17 pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is 18 investigated and it is found that Mg substitution increases the pKas of the neighboring ≡Si-OH and ≡Si-19 OH 2 groups by 2~3 pKa units. Furthermore, our calculation shows that the pKa of edge ≡Mg-(OH 2 ) 2 is 20 as high as 13.2, indicating the protonated state dominates under common pH. Together with previous 21 adsorption experiments, our derived acidity constants suggest that ≡Si-O-and ≡Al-(OH) 2 groups are the 22 most probable edge sites for complexing heavy metal cations.

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Section: Implication For Titration Experiments 263mentioning

confidence: 93%

Acidity of edge surface sites of montmorillonite and kaolinite

Liu

Sprik

et al. 2013

Geochimica et Cosmochimica Acta

194

160

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“…So, cations adsorption on siloxane basal surfaces is relatively weak compared with the cases of 2:1 type phyllosilicates (Vasconcelos et al, 2007). In contrast, metal cations can form strong chemical bonds with dangling sites on broken surfaces (Peacock and Sherman, 2005;Gu and Evans, 2008).…”

Section: Introductionmentioning

confidence: 98%

“…For the titration experiments, it has been accepted that the fit "sites" can hardly be assigned to particular surface sites and it is also impossible to distinguish the contributions of different facets (e.g. Bourg et al, 2007;Gu and Evans, 2008;Gu et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Atomic scale structures of interfaces between kaolinite edges and water

Liu

Wang

et al. 2012

Geochimica et Cosmochimica Acta

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This paper reports the atomic scale structures of kaolinite edge surfaces in contact with water. The commonly occurring edge surfaces are investigated (i.e. (0 1 0) and (1 1 0)) by using first principles molecular dynamics (FPMD) technique. For (1 1 0)-type edge surface, there are two different surface topologies (denoted as (1 1 0)-1 and (1 1 0)-2) and they are considered separately.By using constrained FPMD technique, the free-energy changes for the leaving processes of water ligands of O-sheet Al cations have been calculated and thus, the coordination states of those Al cations are determined. The results show that for (0 1 0) and (1 1 0)-2 edges, both the 5 and 6-fold coordination states are possible whereas for (1 1 0)-1 edges, only the 6-fold states are stable. Based on the analyses of H-bonding structures at the interfaces, the surface acid/base reactive sites are illustrated. (1) T-sheet groups are "Si-OH, behaving as both proton donors and acceptors. (2) Bridging oxygen At (0 1 0) and (1 1 0)-2 edges, these sites are inaccessible from the water and thus, they are not effective reactive sites. At (1 1 0)-1 edges, the bridging oxygen atoms are proton accepting sites. (3) O-sheet groups At (0 1 0) and (1 1 0)-2 edges, for 6-fold Al cases, the active surface groups are "Al-(OH)(OH 2 ) and for the 5-fold Al cases, the active surface groups are "Al-(OH). At (1 1 0)-1 edges, the active site is "Al-OH 2 . This study provides fundamental structural properties for understanding the interface chemistry of widely occurring 1:1 type phyllosilicates.

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“…However, the clay fraction in these volcanic soils is dominated by poorly crystalline aluminosilicates such as allophane. Crystalline clay minerals such as smectite and kaolinite are only found in trace amounts in the HA , and Zn adsorption onto kaolinite is likely limited in acidic soil conditions (Gu and Evans, 2008) such as in HA soil (pH 4.8 to 5.3; Table 1). Therefore, interaction between Zn and kaolinite is unlikely to be the main controlling factor on the Zn isotope variations in these soils.…”

mentioning

confidence: 99%