Dissolution behaviour of valuable elements from the CaO–SiO ₂ –Fe ₂ O ₃ glassy phase modified with Na ₂ O and Al ₂ O ₃ in an acidic solution

Dephosphorisation slag generally consists of a 2CaO·SiO 2 –3CaO·P 2 O 5 (C 2 S–C 3 P) solid solution, CaO–SiO 2 –FeO x glassy phase, and RO phase (FeO x , MgO and MnO). Its components, such as CaO, FeO x , MnO, and MgO, can be used as a soil conditioner in agriculture to improve acidic soil and supply nutrient elements. To promote its dissolution, CaO–SiO 2 –Fe 2 O 3 glassy phases with different Al 2 O 3 and Na 2 O contents were synthesised, and their dissolution behaviour and mechanism were investigated. The addition of Al 2 O 3 significantly inhibited the dissolution of the glassy phase because it increased the degree of polymerisation of the silicate network, and the glassy phase structure became more stable as the Al 2 O 3 content increased. When 3% Na 2 O was added, the dissolution ratios of elements from the glassy phase were the highest, with the dissolution ratio of Si reaching 21.0% and the dissolution ratios of Ca and Fe reaching 21.6% and 17.7% at pH 5. The substitution of CaO with Na 2 O significantly reduced the dissolution ratios of all elements. As the Na 2 O content increased, Na 2 O had a bigger influence on the silicate structure. Na 2 O addition enhanced the proportion of Q Si 2 units and formed additional bonds by interacting with non-bridging oxygens in the silicate tetrahedra, strengthening the stability of the glass network. Lowering pH increased the dissolution ratios of elements.