Study on the effect of Si and silicide on leaching Al_2O_3 from magnesium smelting reduction slag

摘要

The main phases of the reduction slag from magnesium production by vacuum aluminothermic reduction using dolomite and magnesite as materials and using Al-Si alloy as reductant are CaO·2Al_2O_3 and 2CaO·SiO_2. It also has amount of unreacted Si. The Al_2O_3 content of reduction slag is about 55% and SiO_2 is about 10%. When leaching Al_2O_3 with a mixture solution of sodium hydroxide and sodium carbonate, Si and SiO_2 would enter into leaching solution and has a negative effect on Al_2O_3 leaching. The effect of Si and silicide on leaching Al_2O_3 from magnesium smelting reduction slag was studied in laboratory. The results show that total Si and partial SiO_2 would enter into leaching solution and react with NaAl(OH)_4 to form (Na_2O·Al_2O_3·SiO_2)6·27H_2O which is present in leaching residue and makes a loss of Al_2O_3.