Application of Thermally Treated Crushed Concrete Granules for the Removal of Phosphate: A Cheap Adsorbent with High Adsorption Capacity
2017
Kang, Ku | Lee, Chang-Gu | Choi, Jae-Woo | Hong, Seong-Gu | Park, Seong-Jik
The aim of this study was to investigate phosphate removal using crushed concrete granules (CCGs). The CCGs were thermally treated at different temperatures (300, 500, 700, and 900 °C) for 3 h under anoxic conditions. The results showed that CCGs thermally treated at 700 °C (700TT-CCGs) were the most effective for the removal of phosphate. The equilibrium adsorption data fitted well the Langmuir isotherm model with a maximum phosphate adsorption capacity of 21.522 mg/g, higher than that of granular adsorbents in the literature. In pH experiments, phosphate adsorption by 700TT-CCGs decreased as initial pH increased from 3 to 5, but sharply increased above pH 5 (final pH 9.1), which was favorable for the formation of calcium phosphate precipitate. The effect of competing anions on phosphate adsorption follows the order: HCO₃⁻ > SO₄²⁻ > NO₃⁻, which is consistent with the reverse order of the shared charge. Column experiments showed no breakthrough of phosphate in the column packed with half 700TT-CCGs and half sand for over 300 h. This study demonstrates that CCGs can be used for phosphate removal from aqueous solution after thermal treatment, which is a simple and cheap way to improve the phosphate removal capacity of CCGs.
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