| For the utilization of the zinc plant residues composed chiefly of ammoniojarosite and carphosiderite, the separation methods of iron oxide from the residues are studied. By thermal decompositions of the residues, gaseous ammonia and SO₃ were separated at the temperatures of 420° and 710℃ respectively and the remaining solids were iron oxide. When the mixtures of the residues and anhydrous Na₂CO₃ were heated, NH₃ was eliminated at much lower temperature (80°) and the remainders became iron oxide and water soluble Na₂SO₄ at 400℃. In the solutions of Na₂CO₃, the jarosite group compounds of the residues were converted to iron (III) hydroxide with SO²₄^- in solution, The conversion rate was increased and the amount of Na₂CO₃ required was decreased by increasing temperature of the solution. Among the methods studied, the conversion of the zinc plant residues to iron hydroxide in the solutions of Na₂CO₃ was considered the most economical for the recovery of iron oxide from the residues because of its low treatment temperature. |
|
