The observed lower capacity of kaolinite to adsorb P compared with that of gibbsite
(BARBIERI et al., 2009; BROGGI et al., 2010; CESSA et al., 2009; FONTES; WEED, 1996) has been related to the lower concentrations of OH sites on its surface (CELI et al., 2003).
A great deal of effort has been expended in intensifying gibbsite
precipitation from sodium aluminate liquor and progress has been achieved.
The considerable sensitivity of this method is evident from different chemical shifts of three Al minerals (Table 2, corundum, gibbsite
and kaolinite, see below).
As stated above, the mineral composition of residue sand is dominated by quartz, with lesser amounts of hematite, gibbsite
, goethite, and amorphous Fe and A1 oxides, and these materials exhibit a PZNC of ~3, 8.5, 9.8, 8.8, 8.0, and 9.3, respectively (Theng 1980; Goldberg et al.
For CAC, the solubility products for the hydrates Katoite and Gibbsite
At variance with these results, a previous [sup.31]P magic angle spinning NMR and surface complexation modelling study suggested that two outer-sphere ternary complexes can be formed on gibbsite
in the presence of both IHP and Cd(II), and the predominant one is dependent on the adsorbate concentration (Ruyter-Hooley et al.
The first weight loss of 12.51% from 25 to 139[degrees]C was ascribed to the physically adsorbed water; the second weight loss of 8.02% from 139 to 294[degrees]C may be due to gibbsite
and Fe hydroxide (formed in the homogeneous precipitation process during catalyst preparation) decomposing into [gamma]-[Al.sub.2][O.sub.3]  and hematite, respectively; the third weight loss of 6.36% in the temperature range from 294 to 800[degrees]C was attributed to decomposition of the remaining hydroxides.
Equatorial and tropical weathering of recent basalts from Camerroon: allophanes, halloysite, metahalloysite, kaolinite and gibbsite
At pH >5.6, naturally occurring aluminium compounds exist predominantly in an undissolved hydroxide form such as gibbsite
[Al[(OH).sub.3]] or as aluminosilicates.
This has resulted in the separation of the gibbsite
octahedral and silicon tetrahedral layers.
At the interface the minerals Apatite, Calcite and Gibbsite
were found, whereas in the bulk Gibbsite
and Katoite were present.
In some samples aluminium hydroxide (gibbsite
) was added to the initial ash.