ISSN:
1365-2389
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Citrate forms strong complexes with A1 ions and may thus influence the stability and formation of Clay-A1 hydroxide polymer systems (CAIHO). We studied the adsorption of citrate to CAIHO and the influence of citrate on the stability and formation of CAIHO at different A1:clay and A1:citrate ratios and pH values and at a total salt concentration of 0·01 M monovalent anions. The amount of citrate sorbed to the aged CAIHO was independent of the A1 fixed to the clay as A1 hydroxide polymers (AIHO) at 5 〈 pH 〈 6·6. The added citrate seemed not to sorb to the AIHO but only to the edges of the clay. As the citrate: Al ratio increased from 15–1:l at pH 6, more of the AIHO of the aged CAMO systems dissolved. The change in the CEC of the clay indicated that the nature of the remaining AIHO is independent of the amount of A1 dissolved. Citrate influenced the formation of CAIHO systems as measured at pH 6·6, to an extent which depended on the citrate: Al ratio. At a small ratio (1:5), AIHO formed and all citrate was incorporated in the AIHO, probably leading to a coprecipitate. The amount of citrate incorporated depended linearly on the amount of AIHO present. Co-precipitation of AIHO and citrate probably led to the formation of a separate phase, which was only weakly bound to the clay particles. At a large citrate: Al ratio (1:1) soluble Al-citrate complexes became dominant, and only a small part of the added A1 was present as AIHO.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2389.1997.tb00212.x
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