| The formation of iron oxide in a synthetic picklic sulphuric acid studied at elevated temperature and pressures. Waste picklic sulphuric acid was neutralized by adding sodium hydroxide, resulting hydrous ferrous oxide. The hydrous ferrous oxide thus formed was digested under a pressure of 3 to 5 atmospher at 100℃ for two hours. The results obtained were as follows; 1) When Fe(OH)₂ and picklic acid of pH 7.9 were reacted, 74% of iron was recovered in the form of α-goethite. 2) When Fe(OH)₂ and ferric sulphate solution (spent solution) were reacted, the yield in magnetite was better than 90%. 3) When Fe(OH)₂ of pH 12 reacted alone, δ-goethite was formed and yield was higher than 90%. When magnetite and α-goethite obtained were calcined at 600℃ it had been shown that they both could be turned into α-ferric oxide of the pigment grade, a mixture of α-ferric oxide and magnetite was also formed, when σ-goethite was calcinated at 600℃. |
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