Mobility of Included Soda in Sodalite
Mobility of Included Soda in Sodalite
Mobility of Included Soda in Sodalite
1. Introduction From the discussion above, the extent to which included soda
is recoverable will be related to the distribution of anions in the
“Desilication Product” (DSP) is a collective term used to describe
sodalite as it is formed and the mobility of these ions during
several silica containing compounds that precipitate as a result of
the extraction process. Before any soda recovery process can
the dissolution of “reactive silica” from bauxite into Bayer liquor,
be considered it will be important to understand the relative
- mostly during the operations of pre-desilication and digestion.
leachability of anions from sodalite, particularly those typical of
Bayer sodalite is the main desilication product, consisting of a caged
refineries processing high reactive silica bauxites.
aluminosilicate structure (a feldspathoid) with charge balancing
sodium cations. Included in the cage structure are sodium salts of
the common anion impurity ions in Bayer liquor (Riley et al. 1999).
This distinguishes Bayer sodalite from the natural form of the
mineral which contains only chloride. The process of desilication
has positive and negative aspects. It scavenges significant
quantities of inorganic impurities from the liquor but also results
in the loss of caustic soda (NaOH) from the same liquor. Since
in almost all cases, DSP is discarded with the red mud residue,
the loss of this caustic (fixed soda) is a major cost for refineries
processing bauxites with high levels of reactive silica.
(a)
(a)
(b)
Figure 4. (a) Washing of sodalite formed caustic only solution (b) The re-
digestion of this sodalite in water and its subsequent washing.
6. Conclusions
The main conclusions of this work therefore are:
3 Caged zeolites have been used to sequester neutral CO2 from the gas phase for many
years. A recent study examines the stability of CO2 in faujasites, Plant et al. (2006).
References
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Plant, D.F., Maurin G., Deroche I., Gaberova L. and Llewellyn P.L., (2006) Chemical Physics Letters 426, pp387-392.
Riley G., Smith P., Binet D., and Pennifold R., (1999) Proceedings of the Alumina Quality Workshop (AQW 5, Bunbury), pp404-414.
Smith P., Lowe J.L., Rohl A.L., Pennifold R. and Parkinson G.M., (2002) Proceedings of the Alumina Quality Workshop (AQW 6, Brisbane), pp191-194.