PROCESS FOR PREPARING SODIUM SULFATE

1292530 Sodium sulphate SOC ITALIANA RESINE SpA 7 Dec 1970 [23 Dec 1969] 58105/70 Heading C1A Sodium sulphate is prepared from ferrous sulphate by feeding the latter together with sodium hydroxide solution and a stream of molecular oxygen or a gas containing it to an agitated vessel, whereby ferric hydroxide is precipitated; separating the precipitate by filtration in a second vessel; adding additional sodium hydroxide to the residual solution so as to cause precipitation of part of the sodium sulphate; recovering this precipitated sodium sulphate, e.g. by means of a centrifuge, and recycling back the residual solution comprising sodium hydroxide and sodium sulphate to the initial reaction vessel. The ferrous sulphate is preferably that obtained as a waste product in the manufacture of titanium dioxide from ilmenite and sulphuric acid.