Silica is a nutrient for diatom, which is a phytoplankton in oceans. We thus study the possibility of generating silica from steelmaking slag. Silicic acid present in steelmaking slag comprising of sodium chloride was examined. When non-carbonated slag and carbonated slag sample in solutions consisting of 0.5 mol dm
–3 sodium chloride were shaken for a week, a slightly higher pH for carbonated slag solution was observed. The concentration of extracted silicic acid from carbonated slag was higher than that from non-carbonated slag. Both solutions contained high concentrations of calcium ions.
Silicic acids show several chemical forms in solutions. The silicic acids contained in both non-carbonated and carbonated slag solutions were identified with FAB-MS (fast atom bombardment mass spectrometry): [Si(OH)
2O
2Na]
–, [Si(OH)O
3Ca]
–, [Si
2(OH)
5O
2]
– ([dimer]
–), [Si
2(OH)
4O
3Na]
–, [Si
4(OH)
7O
5]
– ([cyclic tetramer]
–), [Si
4(OH)
6O
6Na]
–, [Si
4(OH)
9O
4]
– ([linear tetramer]
–), and [Si
4(OH)
8O
5Na]
–. Among all these complexes the diatom uptakes [dimer]
–, and [linear tetramer]
–. The silicic acids in both solutions also showed almost the same peak intensity ratios of [Si(OH)
2O
2Na]
–, [Si(OH)O
3Ca]
–, [dimer]
–, and [linear tetramer]
– against [cyclic tetramer]. As a result, we consider carbonated slag to be a better supplier of silica to seawater than non-carbonated slag.
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