Abstract: A process for removing cations of a first alkaline earth metal species from an aqueous solution with an ion exchanger material that is a cation exchanger or contains one and subsequently regenerating the loaded or exhausted ion exchanger material. A cation exchanger that has been loaded in advance with cations of a second alkaline earth metal species is used to remove the cations of the first alkaline earth metal species. The cation exchanger that is loaded or exhausted with the first species to be removed is regenerated by bringing the loaded or exhausted cation exchanger into contact with an aqueous suspension of a slightly soluble carbonate and/or hydroxide of the second alkaline earth metal species, either alone or in a mixture with an anion exchanger, and introducing a CO.sub.2 -containing gas into the suspension.

Abstract: A process for removing heavy metal cations and/or alkali metal cations from aqueous solutions with an ion exchanger material that comprises a cation exchanger loaded with alkaline earth metal ions, and subsequently regenerating the loaded or exhausted ion exchanger material. The loaded or spent cation exchanger either alone or in a mixture with an anion exchanger is regenerated by bringing it into contact with an aqueous suspension of a slightly soluble carbonate and/or hydroxide of an alkaline earth metal ion and/or a completely or partially calcined, natural carbonate and introducing a CO.sub.2 -containing gas into the suspension.

Abstract: A method of purifying waste water with treated aluminum oxide. The method comprises contacting the waste water with Al.sub.2 O.sub.3 which has been treated with ions which when incorporated in the crystal lattice of the Al.sub.2 O.sub.3 are capable of delaying crystallization of the gamma phase of the Al.sub.2 O.sub.3 or with the salts of said ions.In one embodiment, the Al.sub.2 O.sub.3 is artificially synthesized and the treatment comprises incorporating the ions, which may be either anions or cations, in the course of the synthesis.Alternatively, the Al.sub.2 O.sub.3 may be treated by subjecting the Al.sub.2 O.sub.3 to a surface treatment with ions capable of delaying crystallization of the gamma phase or the salts thereof.In yet another embodiment, the Al.sub.2 O.sub.3 may be doped with CO.sub.2.

Abstract: Process for purifying phosphate containing waste waters in which aluminum oxide is used as the sorption material. The waste water is brought into contact with fine-grained aluminum oxide in a grain size range from 0.05 to 0.2 mm. Simultaneously, a gas is blown in, which is inert with respect to Al.sub.2 O.sub.3 and with respect to phosphate ions.