Abstract:In order to remove or reduce the negative effect of MgO in calcium aluminate slags, the method of adding Na₂O into calcium aluminate slags was studied and its effect on leaching mechanism was also analyzed. The results show that the alumina leaching efficiency of the calcium aluminate slag increases from 68.73% to 80.86% with Na₂O content increasing from 0 to 4% when MgO content is 3%. The XRD results show that the quaternary compound C₂₀A₁₃M₃S₃ disappears when Na₂O content increases to 4%. The addition of Na₂O cannot remove the negative effect of MgO on leachability completely. XRD and EDS results indicate that Na₂O can come into the lattice of 12CaO·7Al₂O₃ and promote the formation of 12CaO·7Al₂O₃

Key words: calcium aluminate slag; Na₂O; MgO; phase transformation; alumina leaching