Calcium-zinc and calcium-cadmium exchange in suspensions of various types of clays

Bladel, R. Van; Halen, Henri; Cloos, P.

doi:10.1180/claymin.1993.028.1.04

Cited by 50 publications

(26 citation statements)

References 6 publications

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“…Heavy metals are sorbed by this clay mineral via complexation on surface hydroxyl groups at the edges and via cation exchange at the negatively charged surface of the crystallites. The capacity of montmorillonite for surface complexation is considerably smaller than for electrostatic interactions, Only at high pH values and trace concentrations of heavy metals does specific sorption dominate (Van Bladel et al, 1993). The negative surface charge of montmorillonite is caused by isomorphous substitution within the 2:1 layer.…”

Section: Introductionmentioning

confidence: 99%

Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

Matthes

Madsen

Kahr

1999

Clays and clay miner.

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Abstract--The sorption of Cd, Cu, Pb, and Zn ions by Na-rich bentonite, AI and Zr-pillared Na-rich bentonite (A1-MX80, Zr-MX80), the uncalcined hydroxy-intercalated precursors (HA1, HZr-MX80), and commercial Al-pillared bentonite EXM 534 was investigated. Experiments were conducted in ultrapure water and artificial leachate with varying pH. The experiments were performed over periods to 30 wk. Sorption characteristics were described with one and two-site Langmuir isotherms. The non-exchangeable quantities of heavy metals were determined by fusion of the sorbents after ion exchange with ammonium acetate.The sorption of Cd, Cu, Pb, and Zn by bentonite was dominated by cation exchange. In artificial leachate, the sorption was reduced due to competition with alkali and alkaline-earth cations. The sorption of Cu, Zn, and Pb at pH 4.9 and Cd at pH 6.9 by A1 and Zr-hydroxy-intercalated and pillared MX80 was governed also by cation exchange. In contrast, the sorbed quantities of Zn at pH 6.9 exceeded the cation exchange capacity (CEC) of HA1, HZr, A1, Zr-MX80, and EXM 534 and were partially nonexchangeable. The increase of the sorption of Zn with pH and its independence of the ionic strength of the solution at neutral pH suggest a complexation of Zn ions to surface hydroxyl groups of the intercalated A1 and Zr-polyhydroxo cations and pillars. This complexation is the dominating sorption mechanism. Removal of dissolved Zn from solution with time is attributed to surface precipitation. Al-hydroxy and pillared bentonites are considered potential sorbents of Zn ions from neutral pH aqueous solutions, such as waste waters and leachates.

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Section: Introductionmentioning

confidence: 99%

Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

Matthes

Madsen

Kahr

1999

Clays and clay miner.

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“…The adsorption of various heavy metals by smectites has received considerable attention in the past. The adsorption of Cd (Egozy, 1980;lnskeep & Baham, 1983;Van Bladel et al, 1993), Co (Egozy, 1980), Cr (Rengasamy & Oades, 1978;Brindley & Yamanaka, 1979;Carr, 1985;Dubbin et aI., 1994), Cu (Inskeep & Baham, 1983), Hg (Blatter, 1973), Pb (Griffin & Au, 1977), and Zn (Asher & Bar-Yosef, 1982;Van Bladel et al, 1993) are among those metats that have received the most attention. Most of the above-mentioned work, however, has focused only on equilibrium studies or adsorption mechanisms.…”

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confidence: 99%

Sorptive capacity of montmorillonite for hydroxy-Cr polymers and the mode of Cr complexation

Dubbin

Goh²

1995

Clay miner.

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A B S T RA C T: Separate montmorillonite suspensions were treated with CrC13 to give seven Cr(III) concentrations. Each suspension was then titrated with 0.1 N NaOH to give a NaOH/Cr 3+ molar ratio of 2.5. Montmorillonite was an effective sorbent for hydroxy-Cr species up to 1200 cmol(+)/kg; above that concentration, sorption continued, though less efficiently. However, N2-BET specific surfaces and cation exchange capacity measurements indicated that the montmorillonite could sorb significantly more than 1200 cmol(+)/kg. There was virtually no exchangeable Cr in any of the clays, suggesting that this element was covalently bonded to the siloxane surface. Infrared spectroscopy revealed a vibration at 1015-1020 cm -1 in the Cr clays which was not present in the control. This new absorption band was attributed to an attenuation of the Si-O al vibration caused by inner-sphere complexaOon of the interlayer Cr with the siloxane oxygen. Because Cr was strongly held and efficiently sorbed, montmorillonite was shown to be an effective sorbent for hydroxy-Cr polymers.Expandable layer silicates have been proposed as sorbents for both organic and inorganic contaminants. In their native state, clays hold hydrated inorganic cations which give the clay surface a hydrophilic character. In this initial condition, the clays are ineffective sorbents for poorly water soluble organic contaminants. The native inorganic cations on the exchange sites must first be replaced with a variety of organic cations to form organoclays that, unlike native clay, are effective sorbents for removing organic contaminants from water (Boyd et al., 1988;Jaynes & Boyd, 1991).Effective adsorption of inorganic cations, on the other hand, does not require any modification of the clay; the cations readily sorb to the unaltered colloid surfaces. The adsorption of various heavy metals by smectites has received considerable attention in the past. The adsorption of Cd

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“…In this respect, clay minerals may fix metals through ionic exchange (Gaines and Thomas 1953;Van Bladel et al 1993;Gorgeon 1994) or surface complexation (Goldberg and Glaubig 1986;Zachara et al 1988;Stadler and Schindler 1993). This property is at the basis of geochemical barriers against diffuse aquatic pollutions such as observed 1) in suspended matters from wastewaters and polluted rivers (Helios-Rybika and Kyziol 1991;Viraraghavan and Kapoor 1994;Bertin and Bourg 1995), 2) in soils near smelter complexes (John et al 1975;Nwankwo and Elinder 1979) or 3) in sediments from settling basins, near motorways (Hewitt and Rashed 1992;Lee et al 1996).…”

Section: Introductionmentioning

confidence: 99%

“…Metals sorption by clays has been studied by numerous authors (Farrah et al 1980;Tiller et al 1984;Hirsch et al 1989;Halen et al 1991;Van Bladel et al 1993;Siantar and Fripiat 1995;Helios Rybicka et al 1995). The various approaches grade from empirical to theoretical studies with special reference to the thermodynamic treatment of ionic exchange.…”

Section: Introductionmentioning

confidence: 99%

Hard and Soft Acid-Base Model Applied to Bivalent Cation Selectivity on a 2:1 Clay Mineral

Auboiroux

Melou

Bergaya

et al. 1998

Clays and clay miner.

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Abstract--We applied the hard and soft acid-base (HSAB) model Harsh 1990a, 1990b) to bivalent cation exchange on a purified Ca-montmorillonite. As a result, a satisfactory model is proposed to describe the gradual selectivity of exchange with Ca for 4 of the 6 metals studied (Cd, Cu, Pb, Zn). The selectivity is predicted as a function of the differences of electronegativity and softness of the metals. The deviation of Ni and Co data from the predicting model is interpreted in terms of hydration (Ni and Co being the most strongly hydrated ions). The fitting parameters of the model, et and 13, are related to the electronegativity and softness characteristics of the surface, respectively. Their ratio gives information on the nature of bonding. Results suggest that covalent bonding modifies electrostatic interactions, which in turn affect selectivity, with an increasing influence of covalent bondings in the order: Pb < Cd < Zn < Cu.To balance the lack of representativity of the model for the small molar fraction (ARM), we propose to associate to the HSAB model an equation describing the variation of the Vanselow selectivity coefficient as a function of the molar fraction of metal on clay.

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Calcium-zinc and calcium-cadmium exchange in suspensions of various types of clays

Cited by 50 publications

References 6 publications

Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

Sorption of Heavy-Metal Cations by Al and Zr-Hydroxy-Intercalated and Pillared Bentonite

Sorptive capacity of montmorillonite for hydroxy-Cr polymers and the mode of Cr complexation

Hard and Soft Acid-Base Model Applied to Bivalent Cation Selectivity on a 2:1 Clay Mineral

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