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Several ions were studied for their effects on an innovative iron treatment process under controlled laboratory conditions. The iron treatment method stabilizes iron by adding sodium silicate and chlorine. Calcium greatly increased the silicate dosage necessary to maintain low turbidity and high iron filterability. Iron was stabilized for more than 10 days at a 12-mg/L silicate dosage as SiO2 without calcium, but precipitated after 3 days in the presence of 10 mg calcium as CaCO3/L. With 100 mg Ca/L, iron precipitated before one day. Sodium had approximately 100 times less effect than calcium. Equilibrium calculations and analysis of previous work show that calcium's action is not a simple complexation with silicate. Rather, the effect of calcium is hypothesized to be a divalent cation acting on a negatively charged colloid. Includes 21 references, tables, figures.

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Edition: Vol. 79 - No. 7 Published: 07/01/1987 Number of Pages: 10File Size: 1 file , 1.5 MB