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

Abstract

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 (

CO2 capture by calcium aluminate pellets in a small fluidized bed

“…The whole experiment was performed with a sample gas flow-rate of 100 cm 3 /min of N2. The TGA plot shows four characteristic steps of mass loss: the first step at 100 ºC related to loss of chemically unbound water; the second step is around 200 ºC and is likely to correspond to decomposition of calcium aluminium hydroxide hydrates (see, for example, Packter and Khaw [38]); the third step leading into 450 ºC relates to decomposition of any calcium hydroxide; and the fourth step leading into 900 ºC relates to calcination of any calcium carbonate.…”

Aluminum “Core-shell” microparticles with an oxide shell - fillers of spatially strengthened composites, facilitating material digitization

“…The liquid-phase oxidation method can also form hydroxide coatings of mixed elemental composition on the POSAP surface [17], which, in turn, can be transformed into oxide coatings of mixed composition upon heating. As an example of such a mixed oxide coating, one can cite POSAP, which are formed using a chemical activator [10] calcium oxide (CaO), also having the "Nanowalls" structure, the images of which are shown in Fig.…”