| 摘要 |
Thermostable, and resistant cation exchangers are prepd. by (i) pptg. water-soluble salts of Gp. IV metal oxides in the presence of complexing salts and/or acids (opt. cooled) with solns. of anions which can form insoluble pptes. with the salified oxides so that the retarded pptn. is converted to an insoluble gel, (ii) stabilising the gel by extraction, and (iii) drying. The dried gel may be heated with extraction of the complexants or heated at high temp. without extraction of complexants which are thus carbonised or dehydrated inside the gels and deposited in the form of more or less active carbon. A structure of large surface area and high mechanical and chemical strength is obtd. The selectivity of the cation exchanger can also be adjusted by varying the complexants to give gels. |
