GB571415A - Improvements relating to the preparation of cation-exchange materials - Google Patents

Abstract

A method of improving the cation exchange properties of a granular material substantially insoluble in water and prepared by the action of a concentrated liquid sulphonating agent on an organic carbonisable material such as wood, lignite, peat and bituminous coal, comprises further sulphonating the material, while containing less than 18 per cent moisture, with sulphur trioxide gas. The liquid sulphonating agents include concentrated or fuming sulphuric acid and chlorsulphonic acid. In this way the high capacities characteristic of the sulphur trioxide treatment are combined with the hardness characteristic of the liquid sulphonating treatment. The resultant products are useful in the softening of water and in other cation-exchange processes. The products of the invention may be prepared by adding the concentrated liquid sulphonating agent to the raw material which is preferably more or less granular in form, at a temperature in the range of 60 DEG to 100 DEG C. with agitation. Generally, from 0.85 parts to 4 parts by weight of sulphonating agent for each part of raw material should be used, the reaction time preferably lasting for several hours. The sulphonated material is then washed and dried or may first be converted to the sodium-exchanging condition by treatment with sodium carbonate solution. The gaseous sulphonation may be applied to the relatively dry product in the hydrogen- or sodium-exchanging condition or while the product is charged with calcium or other exchangeable cations. The simplest method is to pass the gas up through a column of the granular product using the gas pressure as a means of agitating the granules. The gas may be diluted with an inert gas such as air to avoid overheating; ratios of air to sulphur trioxide from 1 : 1 to 4 : 1 are satisfactory. The second sulphonation is complete when the swelling of the granules ceases. An example describes the treatment of granular bituminous coal with 20 per cent fuming sulphuric acid, giving a product which after washing and drying is treated with sulphur trioxide gas.