Preparation of Adsorbent with High Removal Ability for Phosphate Ion from Blast Furnace Slag using Alkali Fusion

Abstract

We attempted to convert blast furnace slag into an adsorbent for phosphate removal using the alkali fusion method. The slag was mixed with NaOH powder (NaOH/Slag=1.6), and the mixture was heated at 600°C for 6 h to prepare the precursor, which was then stirred at room temperature in various aqueous solutions: distilled water, 1 M NaOH, 1 M NaCl, 1 M NaNO₃, 1 M Na₂CO₃ and 1 M Na₂SO₄, to synthesize the adsorbent. Regardless of the reaction solution, products were synthesized, including hydrocalumite and calcite. Phosphate ions in solution were removed as calcium phosphate minerals using all obtained adsorbents. The PO₄^3- adsorption abilities of all products obtained and the solution pHs after removal were similar. The adsorbents could adsorb PO₄^3- selectively in the presence of F^-, Cl^-, Br^-, NO₃^- and SO₄^2-. We have prepared a new inorganic adsorbent with high affinity for phosphate from wastewater.