| 摘要 |
An inexpensive cation exchanger useful in purifying waste water is produced by treating comminuted bark in separate steps with an alkali hydroxide solution of at least 5% by weight, preferably 20-40% by weight, and with 30-75% by weight sulphuric acid, preferably 50-65% by weight. After each step washing with water is performed until the pH-value after the alkali hydroxide treatment goes below 9 and after the sulphuric acid treatment goes above 3. Preferably, the treatment with alkali hydroxide precedes the treatment with sulphuric acid. The treatment with alkali hydroxide is carried out for 0.5-20 hours, preferably 3-10 hours, and the treatment with sulphuric acid is carried out from 0.5-8 hours, preferably from 1-6 hours. The cation exchanger can be regenerated with alkali hydroxide solution, particularly sodium hydroxide solution. |
