Abstract
Boric acid was adsorbed by ferric hydroxide precipitated by the reaction of ferric chloride with sodium hydroxide. The pH of the solution showed a remarkable effect upon the adsorption, and the optimum range of the pH was 7 to 9. The amount of the boron which was adsorbed by the precipitation showed an increase in proportion to the decrease in temperature and the increase in the amount of the precipitation.
Then, the adsorption of boron in artificial or natural bittern was investigated, and the following results were obtained.
(1) The optimum range of pH was 6 to 7. The amount and the rate of the boron adsorbed were less than those of the boric acid solution. When the mol ratio of the amount of ferric hydroxide to the amount of boron in bittern was approximately 13 at pH 6 and 20°C, the adsorption ratio of boron ranged from 55% to 65%. The relation between the amount of the adsorbed boron and the concentration of the boron agreed with Freundlich's adsorption isotherm.
(2) Some amount of elements contained in bittern was adsorbed or co-precipitated with ferric hydroxide. Magnesium and sulphate ions were somewhat strongly adsorbed and seemed to have formed some complex compounds with ferric hydroxide. Therefore, the bittern from which sulphate is removed can utilized for recovering boron.
The method of adsorption with the use of ferric hydroxide is applicable to the collection of boron from bittern.
