The reaction of aluminium with silicic acid in acidic solution: an important mechanism in controlling the biological availability of aluminium?
- Coordination Chemistry Reviews, 228(2), p.127-135, 2002 .
The reaction of aluminium (Al)with monomeric silicic acid (Si(OH)4)to form an hydroxyaluminosilicate (HAS)has been well documented over the past 40 or so years. The formation of an aluminium hydroxide template, upon which Si(OH)4 will condense in competition with Al, was demonstrated to be a prerequisite to HAS formation. This initial reaction results in the formation of a slowly aggregating HAS, with a Si:Al ratio of 0.5, in which silicon tetrahedra are bonded to Al octahedra through three Si---O---Al linkages. We have called this HASA. In solutions in which the concentration of Si(OH)4=Al HASA acts as a template for the incorporation of further silicon tetrahedra to give a rapidly precipitating HAS (that we have called HASB), with a Si:Al ratio of 1.0, in which up to 50