| 摘要 |
1485067 Treating sulphuric acid effluent TIOXIDE GROUP Ltd 7 June 1976 [25 July 1975] 31187/75 Heading C1A Sulphuric acid containing dissolved iron is purified by (a) adding calcium carbonate to selectively precipitate calcium sulphate; (b) separating the precipitate from the mother liquor, (c) adding sufficient calcium carbonate to the mother liquor to give a pH of at least 4À5 (at 50‹ C.), (d) passing a free-oxygen containing gas simultaneously or subsequently to step (c), (e) adding calcium carbonate when necessary to maintain pH above 5À0, (f) separating the liquid from the insoluble solids. Step (a) is usually performed at 35-100‹ C. to give a pH of 1-4À5. The oxygenating gas is preferably air and step (d) may be performed in the presence of finely-divided inert particles. The calcium sulphate/metal oxide/hydroxide solids precipitate may be disposed of as landfill, preferably after drying and/or calcining. The calcium sulphate from step (b) may be used in the manufacture of plasterboard. |
