One of the streamlets which drains the waste-rock dumps of the abandoned Pb-As mine of Baccu Locci (Sardinia, Italy) shows relatively low dissolved As content (tenths of μg/L) in spite of up to 10 wt. % of As in the <2 mm fraction of mine wastes. Sulphates of Zn-Cu-Al belonging to the hydrotalcite group precipitate copiously from streamlet waters; they always contain significant As amounts (up to 2 wt. %). The general structure of hydrotalcites (also called “anionic clays” or “layered double hydroxides”) is composed of a brucite-like octahedral sheet with an interstitial anionic layer. Laboratory experiments on synthetic sulphate-bearing hydrotalcites showed that (AsO4)3- is a strong competitor of (SO4)2- for the anion position within the interstitial layer, those phases thus acting as As removers from solution.
Ruolo delle idrotalciti nella rimozione dell’arsenico in acque di miniera
ARDAU, CARLA;FRAU, FRANCO
2008-01-01
Abstract
One of the streamlets which drains the waste-rock dumps of the abandoned Pb-As mine of Baccu Locci (Sardinia, Italy) shows relatively low dissolved As content (tenths of μg/L) in spite of up to 10 wt. % of As in the <2 mm fraction of mine wastes. Sulphates of Zn-Cu-Al belonging to the hydrotalcite group precipitate copiously from streamlet waters; they always contain significant As amounts (up to 2 wt. %). The general structure of hydrotalcites (also called “anionic clays” or “layered double hydroxides”) is composed of a brucite-like octahedral sheet with an interstitial anionic layer. Laboratory experiments on synthetic sulphate-bearing hydrotalcites showed that (AsO4)3- is a strong competitor of (SO4)2- for the anion position within the interstitial layer, those phases thus acting as As removers from solution.
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