Issue 5, 2000

Carbonate removal from concentrated hydroxide solutions

Abstract

Methods for routinely lowering the carbonate content of concentrated aqueous hydroxide solutions [MOH with M+ = Li+, Na+, K+, Cs+ and (CH3)4N+] to analytically negligible levels (⩽ 0.2% of the total alkalinity) are described. No single method was satisfactory for all MOH. Carbonate can be removed from highly concentrated (ca. 50% w/w) NaOH solutions by filtration since Na2CO3 is almost insoluble in this medium. However, for LiOH (ca. 4 M), (CH3)4NOH (ca. 4.5 M) and KOH (ca. 14 M) and less concentrated NaOH (<10 M), treatment with excess solid CaO followed by filtration gave the best results. For CsOH, which may be seriously contaminated with carbonate, the only satisfactory procedure was treatment of very concentrated solutions with excess solid Ba(OH)2. Residual calcium and barium concentrations in the decarbonated solutions were at trace levels.

Article information

Article type
Paper
Submitted
24 Dec 1999
Accepted
08 Mar 2000
First published
10 Apr 2000

Analyst, 2000,125, 955-958

Carbonate removal from concentrated hydroxide solutions

P. Sipos, P. M. May and G. T. Hefter, Analyst, 2000, 125, 955 DOI: 10.1039/A910335J

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