Result 5 · Figure 7
A mild acetic-acid extraction dissolves only the carbonate phase. Calcium and nickel come out together — the same nickel is also locked into the new calcite formed from the half-burned dolomite.
Nickel concentration plotted against calcium concentration in 10 carbonate-bound extracts from filter solids of the spray-aerated open filter (German: Fall-Verdüsungs-Filter) of Wasserwerk Breyell. The samples were leached with 1 M sodium-acetate / acetic-acid solution at pH 5 for 24 hours, following the Tessier et al. (1979) step 2 protocol for the carbonate-bound fraction, and analysed by ICP-MS; both axes are reported in mg/L of the extractant. The strong positive correlation (r² = 0.86) indicates that dissolved Ni²⁺ is incorporated into the calcite that precipitates as the half-burned dolomite (Magnodol, CaCO₃·MgO) dissolves and raises the pH. *