Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Silicon containing
Patent
1991-10-28
1992-12-08
Dees, Carl F.
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Silicon containing
502235, 423237, 210903, B01J 2010, B01J 2030
Patent
active
051698250
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an adsorbent which is capable of selectively adsorbing ammonium ions and ammonia (hereinafter referred to as "ammonium ions" unless required to be otherwise indicated), and a process for preparing the same.
The term "rate of ammonium ion adsorption" used herein refers to a rate given by the following equation: ##EQU1##
BACKGROUND ART
In recent years, there has arisen a question of how to purify water for use in keeping aquarium fishes and living fishes or in transporting living fishes. If the ammonia derived from decomposed excretion of aquarium fishes or feed leftovers is present in water at a concentration exceeding 10 ppm, it would exert a detrimental action on the central nerve system of fishes, resulting in increase of their mortality.
Silicone-coated zeolites have been used as ammonium-ion adsorbents in an attempt to obviate the above problem (Japanese Examined Patent Publication Sho 54-39279). However, such adsorbents act to adsorb about 7% of calcium ions and magnesium ions and are therefore unsuitable for use with seawater as a medium.
Na-type zeolites have been used as ammoniacal nitrogen adsorbents (Japanese Unexamined Patent Publications Sho 53-27387 and Sho 53-131291). These adsorbents are intended to utilize the selectivity of cation ion exchange. Yet due to the selectivity of K.sup.+ .apprxeq.C.sup.2+, Mg.sup.2+ >NH.sub.4.sup.+ >Na.sup.+, the adsorbents used in seawater rich in alkaline earth metal ions are unnegligibly inhibited from adsorbing ammonium ions by calcium ions and magnesium ions.
Conventional adsorbents have various problems to be resolved as described above. Especially there is a strong demand for the development of adsorbents which are capable of selectively and efficiently removing ammonium ions from seawater without likelihood of adversely affecting other seawater components and fishes.
It is an object of the invention to provide an adsorbent capable of selectively adsorbing ammonium ions which is free from the loss due to its dissolution when adsorbing and removing ammonium ions and ammoniacal nitrogen from not only fresh water but seawater, and which is capable of selectively adsorbing only ammonium ions without adsorption of calcium ions, magnesium ions and other mineral components in seawater, is capable of keeping the pH value of seawater varied in an extremely narrow range, and is inexpensive and highly safe, and a process for preparing the same.
DISCLOSURE OF THE INVENTION
The above object of the invention can be achieved as described below.
According to the invention, there are provided: SiO.sub.2 and Al.sub.2 O.sub.3 in a molar ratio of between 2.5/1 and 25/1, and which contains 0.05 to 3 moles of alkali metal ions capable of ion exchange per mole of Al.sub.2 O.sub.3, the adsorbent as defined above in item (1) at a temperature of 150.degree. to 400.degree. C., ammonium ion-selective adsorbent as defined above in item (1) or (2), adsorbent, comprising the steps of: adding dropwise to water an aluminum salt or an aluminate and a silicate provided in SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio of between 2/1 and 20/1 in an alkalinity pH range of 8 to 12; and adjusting the pH of the reaction mixture to 4 to 9 with an acid solution, and adsorbent, comprising calcining the adsorbent prepared by the process of item (4) at a temperature of 150.degree. to 400.degree. C.
A silica-alumina composite oxide is used as the starting material for the adsorbent of the invention. In the invention, the silica can effectively increase the specific surface area, and the aluminum can effectively enlarge the adsorption volume for ammonium ions. The p orbitals of aluminum element include empty orbitals capable of accepting electrons which can accommodate lone pairs of electrons in nitrogen atoms of ammonium ions. Namely the aluminum atoms function as an acceptor for lone pairs of electrons in nitrogen atoms of ammonium ions. The adsorbent of the invention is composed of a composite oxide so that the silica-alumina ratio in th
REFERENCES:
patent: 3056657 (1962-10-01), Nowak
patent: 3453077 (1969-07-01), Hyde
patent: 4290895 (1981-09-01), Iwamoto
Hayashi Hironobu
Kamewa Toshihiro
Miyawaki Keiko
Okubo Akira
Dees Carl F.
Tomita Pharmaceutical Co., Ltd.
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