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The coprecipitation of magnesium hydroxide aluminium hydroxide powders from aqueous solution with sodium hydroxide: Precipitate compositions and coprecipitation mechanisms
Author(s) -
Packter A.,
Panesar K. S.
Publication year - 1985
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.2170200608
Subject(s) - magnesium , coprecipitation , aluminium hydroxide , chemistry , inorganic chemistry , aluminium , sodium hydroxide , hydroxide , precipitation , aqueous solution , potentiometric titration , nuclear chemistry , ion , organic chemistry , physics , meteorology
Magnesium aluminium hydroxides were coprecipitated from different mixed metal cation solutions — at total C M = 0.1 M and Mg/Al 2 ratios from 1 to 6 — with sodium hydroxide solution at ambient temperature, with different pre‐ageing conditions for the aluminium hydroxide pre‐precipitate. The coprecipitations were monitored by potentiometric (pH) titration and the final precipitate compositions were examined by chemical analysis, infrared spectrophotometry and thermal analysis. Magnesium hydroxide was coprecipitated onto completely recrystallised aluminium hydroxide as a simple mixture. Generally, with no to three days pre‐ageing, microcrystalline aluminium hydroxide was first precipitated at pH about 4; this then partially redissolved on further addition of sodium hydroxide (to form hydroxoaluminate anion) and magnesium aluminium hydroxide coprecipitates were formed continuously at pHs from 8.0–8.7 to 12.0–12.5. Their compositions were similar to the magnesium hydroxoaluminate hydrates formed by direct precipitation from high pH sodium hydroxoaluminate solutions.