Sorption of chloride-ion, sulfate-ion and phosphate-ion in calcium silicate hydrates

Abstract

This study discusses the capacity of sorption of various ions in calcium silicate hydrates. Chlorideion, sulfate-ion and phosphate-ion were sorbed in synthesized calcium silicate hydrates (C-S-H). The amount of sorbed chloride-ion, sulfate-ion and phosphate-ion in C-S-H were 172 mg/g, 54 mg/g and 667 mg/g, respectively. In the case of sorption of phosphate-ion, phosphate-ion and C-S-H reacted to produce hydroxyapatite. In the leaching test, 15% of chloride-ion, 18% of sulfate-ion and 34% of phosphate-ion were dissolved from C-S-H sorbing respective anions. On the other hand, 65% of fixed chloride-ion in Friedel's salt was dissolved in the leaching test. Therefore, the fixing ability of chloride-ion in C-S-H is higher than that in Friedel's salt.