GB450210A - Improvements in or relating to the recovery of iodine from seaweed - Google Patents

Abstract

Iodine or iodine compounds are recovered from seaweed by extraction of the seaweed to obtain an aqueous solution of soluble iodine salt which is then treated with a soluble copper salt, preferably sulphate, in the presence of an acid, e.g. sulphuric or hydrochloric acid, and of a metal, preferably copper, acting as an antioxidizing agent. The seaweed is extracted with a dilute solution of an alkaline earth salt, e.g. calcium or barium chlorides, which dissolves laminerine and iodine containing material, leaving the algulose and algin undissolved, preferably in the cold state. Subsequent washing with soft water removes the excess alkaline earth salt and the remaining iodine &c. Impurities are then removed from the extract by treatment with a 15 per cent aqueous solution of sodium carbonate. The precipitate of alkaline-earth carbonate carries down the impurities. The precipitate is washed thoroughly and the wash waters added to the mother liquor containing iodine. This liquor is then treated as above to obtain a precipitate of cuprous iodide. Copper is recovered from the liquor remaining after separation of the precipitate by treatment with iron, and the other salts present may be separated by fractional crystallization. Iodine may be recovered from the cuprous iodide by calcination with caustic soda or potash with the addition of a substantially equal weight of sodium nitrate at a temperature of 350 DEG --375 DEG C. followed, for example, by treatment with chlorine, or recovery of iodine by other known methods. Alternatively, barium iodide may be obtained by treating the cuprous iodide with baryta water at 90 DEG --100 DEG C., and metal iodides may be obtained therefrom by treatment with sulphates, e.g. sodium sulphate. Specification 450,358 is referred to.