GB700731A - Improvements in or relating to the production of cation exchangers - Google Patents

Abstract

The ion-exchanging capacity by volume of cation-exchange material prepared from solid carbonaceous materials by the process of the parent Specification is increased by a subsequent treatment with an acid to bring about a decrease in volume of the material. The preferred acid is hydrochloric; sulphuric acid of a concentration greater than 50 per cent. by weight and nitric acid of all concentrations are unsuitable because of their water-adsorbing and oxidizing actions on the material. To avoid the use of large volumes of solution the pH value of the acid solution should be less than 2. The treatment is effected preferably at normal temperatures but the temperature should not exceed 60 to 70 DEG C. With material having a capacity of approximately 1,000 m.eq. CaO per litre the treatment may be effected with 100 ml. 38 per cent. HCl or 1 litre normal HCl, the resulting volume-decrease being about 25 per cent. of the original volume. The amount of acid required varies directly as the ion-exchanging capacity. Since the total-weight-capacity of the material is increased a little by the treatment the increase in volume-capacity amounts to from 30 to 35 per cent. The "breakthrough" capacity of the material in the H-ion-exchanging p form is less than that of the material in the neutral form. The material is therefore transformed, after the acid-treatment (which has converted it into the H-ion-exchanging form), into the salt form, by washing with a neutral or weakly-alkaline salt solution such as sodium carbonate or sodium acetate. Liquids exhibiting a more alkaline reaction should not be used since they cause a swelling of the material. Examples of the process are given in the Specification.ALSO:The ion-exchanging capacity by volume of cation-exchange material prepared from solid carbonaceous materials by the process of the parent Specification is increased by a subsequent treatment with an acid to bring about a decrease in volume of the material. The preferred acid is hydrochloric; sulphuric acid of a concentration greater than 50 per cent by weight and nitric acid of all concentrations are unsuitable because of their water-absorbing and oxidizing actions on the material. To avoid the use of large volumes of solution the pH value of the acid solution should be less than 2. The treatment is effected preferably at normal temperatures but the temperature should not be above 60 to 70 DEG C. With material having a capacity of approximately 1000 m.e.q. CaO per litre the treatment may be effected with 100 ml. 38 per cent HCl or 1 litre normal HCl, the resulting volume-decrease being about 25 per cent of the original volume. The amount of acid required varies directly as the ion-exchanging capacity. Since the total weight-capacity of the material is increased a little by the treatment the increase in volume-capacity amounts to from 30 to 35 per cent. The "break-through" capacity of the material in the H-ion-exchanging form is less than that of the material in the neutral form. The material is therefore transformed after the acid-treatment (which has converted it into the H-ion-exchanging form), into the salt form, by washing with a neutral or weakly-alkaline salt solution such as sodium carbonate or sodium acetate. Liquids exhibiting a more alkaline reaction should not be used since they cause a swelling of the material. Examples of the process are given in the Specification.