MAGNESIUM AND pH EFFECT ON ZINC SORPTION BY GOETHITE

Ankomah, A. B.

doi:10.1097/00010694-199209000-00004

Cited by 13 publications

(8 citation statements)

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“…Therefore, it was the amount of Zn added and not the number of charge sites that was limiting retention. The shapes of the sorption curves resembled those obtained for Zn sorption by hydrous oxides (Bruemmer et al, 1988;McBride, 1989;Ankomah, 1992), and indicated that, in the two soils, the maximum sorption would be expected with larger additions of Zn and higher pH values. Sorption was also observed at pHs below the PZC of the soils, when most of the surface sites are positively charged .…”

Section: Discussionsupporting

confidence: 62%

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Zinc sorption–desorption by two Andepts: effect of pH and support medium

Pardo¹,

Guadalix²

1996

European J Soil Science

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Laboratory experiments were carried out to evaluate the effect of pH, ionic strength and electrolyte composition on zinc sorption-desorption by two Andepts from the Canary Islands (Spain). At the natural soil pH, the soils exhibited little net negative surface charge and small Zn sorption capacities. More than 75% of the sorbed Zn was apparently strongly bonded. The pH greatly influenced the sorption-desorption reactions. Sorption increased with increasing pH, and retention increased abruptly at pH > 6.0. Sorption also occurred at pH values below the point of zero charge (PZC) of the soils, when most of the surface sites are positively charged. Desorption decreased continuously with rising pH and became a trace at pH > 6.0. An increase in the ionic strength of the background electrolyte decreased Zn sorption and enhanced the amount of sorbed metal that could be subsequently released. In the two soils, Zn sorption diminished somewhat in the K and Ca electrolytes as compared with the Na electrolyte. However, this did not happen at small Zn loadings. Desorption was not affected by the type of electrolyte and cation used. The results are consistent with chemisorption being responsible for most of the sorption. The results also suggested a strong affinity sorption or even precipitation at high pHs.

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Section: Discussionsupporting

confidence: 62%

“…Calcium has appeared to be the most effective cation in inhibiting sorption, followed by Mg, K and Na. The extent of the effect, however, was affected by the accompanying anion (Pulford, 1986), varied amongst soil types (Zhu & Alva, 1993) and also depended on metal loadings (Zasoski & Burau, 1988;Ankomah, 1992).…”

Section: Introductionmentioning

confidence: 99%

Zinc sorption–desorption by two Andepts: effect of pH and support medium

Pardo¹,

Guadalix²

1996

European J Soil Science

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“…These values can be compared with the specific adsorption capacity reported for amorphous iron oxide 7.78 mg g −1 ( Brummer et al . 1983 ), ferrihydrite 28.6 mg g −1 at pH ∼ 7 ( Kinniburgh, 1983), and goethite 25.5 mg g −1 at pH 8.5 ( Ankomah, 1992). Our calculated specific adsorption capacities were up to 7‐fold larger than those reported by Ankomah 1992) and Kinniburgh 1983) , which were measured under similar pH conditions.…”

Section: Resultsmentioning

confidence: 99%

Reactions of zinc with iron‐oxide coated calcite surfaces at alkaline pH

Uygur¹,

Rimmer

2000

European J Soil Science

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Summary Both iron oxides and carbonate minerals, such as calcite, can sorb zinc (Zn), and therefore are important in controlling the solution concentration and availability of Zn to plants growing in calcareous soil. When present together, interactions between these components affect their sorption behaviour. We investigated changes in the reactions of Zn with calcite at alkaline pH, as the calcite surface was progressively coated by iron oxide. Coated calcite surfaces were prepared that had from 0.05 to 1.45% iron oxide. The initial concentration of Zn and the amount of iron oxide on the calcite were the most critical factors affecting adsorption, precipitation of solid phases, and the desorbability of sorbed Zn. For pure calcite at small initial Zn concentrations (< 2.5 × 10−5 m) adsorption was dominant; with increasing concentration, precipitation of hydrozincite (ZHC) became more important. With increasing amounts of iron oxide the amount of Zn adsorbed increased, the desorbability of the Zn decreased, and precipitation became progressively less evident, and at 1.45% iron oxide content there was no evidence of any precipitation of ZHC. The calculated maximum adsorption attributable to the iron oxide coating was inversely proportional to the thickness of the oxides on the calcite, and greatly exceeded that of iron oxide as a separate phase. The common occurrence of iron‐coated carbonates in calcareous soils and their capacity to adsorb Zn contributes to the problems of Zn deficiency, for which these soils are noted.

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“…Because of the complexity of metal-particle interactions, two common features of this type of study are single metal-substrate experimental designs, and the use of syntheticallyderived goethite (a-FeOOH), a crystalline Fe oxide (e.g. Ankomah, 1992;Barrow et al, 1989). In natural sediments, however, other oxides such as ferrihydrite and lepidocrocite have been identified (Fortin et al, 1993, which are more amorphous than goethite and consequently may have quite different sorption characteristics (Schwertmann & Cornell, 1991).…”

Section: Introductionmentioning

confidence: 99%

Geochemical partitioning and bioavailability of copper to aquatic plants in an artificial oxide-organic sediment

1995

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This study investigated the effects of competition between binding substrates (organic matter and iron oxide) and between metals (cadmium and copper), on the partitioning of sedimentary copper and its subsequent bioavailability to an aquatic plant. Organic matter and a synthesized iron oxide, ferrihydrite, were added singly and in combination to a series of sand sediments, which were then dosed with environmentally realistic concentrations of cadmium and copper and planted with rice, O0'za sativa.Organic matter controlled copper partitioning and bioavailability, whereas the synthetic ferrihydrite bound negligible amounts of either metal, even in the absence of organic matter. As organic matter concentrations increased, operationally-defined leachable copper decreased, organic-associated copper increased and the survival of rice plants improved in an approximately linear fashion. At a nominal starting copper concentration of 5.8 F~g g dry wt -I , plant survival after four weeks averaged 0-8% in sediments without organic matter, 25% in a sediment containing 0.18% organic matter and 58% in a sediment containing 0.36% organic matter. These results suggest that organic-associated forms of copper are unavailable to plants, and that the operational definition of 'leachable' copper (extracted with dilute ammonium acetate) adequately represents the species of copper that is (are) available to plants. Our study using a well-characterized artificial sediment supports the copper fractionation patterns and correlations between copper partitioning and bioavailability reported from the heterogeneous, poorly characterized sediments of natural lake and river sediments.

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MAGNESIUM AND pH EFFECT ON ZINC SORPTION BY GOETHITE

Cited by 13 publications

References 0 publications

Zinc sorption–desorption by two Andepts: effect of pH and support medium

Zinc sorption–desorption by two Andepts: effect of pH and support medium

Reactions of zinc with iron‐oxide coated calcite surfaces at alkaline pH

Geochemical partitioning and bioavailability of copper to aquatic plants in an artificial oxide-organic sediment

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