The precipitation of calcium hydroxoaluminate hydrate powders from sodium hydroxoaluminate solutions: Precipitate phases and precipitation mechanisms

Barium hydroxoaluminate hydrates were precipitated from different sodium hydroxoaluminate solutions at 20 "C; CAI varied from 0.1 t o 0.5 M and initial Ba/Al, ratios (= excess OH/AI ratios) varied from 1 t o 7 . Precipitate compositions were determined by chemical analysis, infra-red spectrophotometry and thermal analysis. The compound BaO . A1,0, . 7 H,O was precipitated at initial Ba/Al, ratios of one to well above two while the compound 2 BaO . A1,0, . 5 H,O was only precipitated over a narrow range of concentrations. The compound Ba(OH), . 8 H,O was precipitated from solutions of high hydroxide and barium ion concentrations. The ionic equilibria and precipitation mechanisms in different solutions are discussed.

The precipitation of barium hydroxoaluminate hydrate powders from sodium hydroxoaluminate solutions: Precipitate phases and precipitation mechanisms

Packter¹

1983

The precipitation of magnesium hydroxoaluminate hydrate powders from sodium hydroxoaluminate solutions: Precipitate phases and precipitation mechanisms

Packter¹,

Slaughter²

1984

Magnesium hytlroxoalnminate hydrates were prwipitated from different sodium hyrlroxoaluminate and hydroxoaluminate-hydroxide solutions at arnhient temperature, at C A~ = 0.1 M, OH/AI ratios = 4 -9 arid XS OH/AI ratios = 1-6. T h e precipitations were monitored hy potentio~netric (pH) measiiremerits while t h e final precipitate compositions were examined by chetnical analysis, infra-red spectrophotometry and thermal analysis.

The coprecipitation of calcium aluminium hydroxide (calcium hydroxoaluminate hydrate) powders from aqueous solution with sodium hydroxide: Precipitate compositions and percipitation mechanisms

Packter¹,

Khaw²

1985

Calcium aluiiiiliiurii liydroxitlos were coprccipitatcd from cliffcrciit, iliixod metal cation solutioiis -at total C , = 0. I M arid Ca/AI, ratios from I to 4 -with sodium hydroxide solution at ambient temperature. The coprecipitations were monitored by potentiomotric (pH) titration arid the final coprecipitate compositions were examined by chemical analysis, infra-red spectrophotometry and thermal analysis Generally, microcrystalline aluminium hydroxide was first precipitated a t p H about 4; this then redissolved on further addition of sodium hydroxide to form hydroxoalumiiiate anion and polyaniori and ca1ciu.m aluminium hydroxide coprecipitates were formed continuously at p k l s from about 9 to above 12. Their compositions were similar to the calciiirn hydroxoalirrninato Iiydrates formed by direct precipitation from high p H sodium hydroxoaluminato soliitioiis.-A t Ca/AI, ratio-= 1, tho rnain phase was-probably Ca(H,O)h (AI (