Synthesis and properties of inorganic polymers (geopolymers) derived from Bayer process residue (red mud) and bauxite
- 695 Downloads
Well-reacted geopolymers with good compressive strengths (44–58 MPa) were formed from highly alkaline residue from red mud (the residue remaining after extraction of alumina from bauxite by the Bayer Process) without the addition of strength-promoting components, such as fly ash or ground slag, by adjusting the composition to an optimal SiO2/Al2O3 ratio of about 3 with silica fume. The formation of these geopolymers is extremely energy-efficient since thermal dehydroxylation of the red mud is not required. The environment of the Si and Al in the geopolymers was shown by 27Al and 29Si NMR spectroscopy to be consistent with reasonably well-reacted aluminosilicate materials, suggesting that the red mud forms geopolymers by reaction of aluminate and silicate species in a process not dissimilar to that of alkali-activated kaolin. The presence of high concentrations of iron in the red mud principally in the form of hematite did not interfere with geopolymer formation, since it was shown by XRD and Mössbauer spectroscopy to remain largely unaltered and not participate in the reaction. Analogous experiments with bauxite from which red mud is derived by alkali treatment, produce geopolymers of significantly lower strength (up to 28 MPa), suggesting that the action of the alkali during bauxite processing facilitates the formation of the geopolymer binder, possibly by increasing the reactivity of the red mud, as occurs in alkali-treated kaolinite.
KeywordsCompressive Strength Geopolymer Silica Fume Boehmite Gibbsite
SNMH acknowledges the tenure of a Malaysian Government (MARA) Scholarship, and JJR acknowledges the tenure of a PhD Scholarship from the Victoria University of Wellington. We are indebted to Jeanette See, Rio Tinto Alcan for kindly supplying the red mud and to Ray L. Frost, Queensland University of Technology, for the Weipa bauxite.
- 5.Zhang G, He J, Gambrell RP (2010) Synthesis, characterization, and mechanical properties of red mud-based geopolymers. J Transport Res 2167:1–9Google Scholar
- 6.Mucsi G, Lakatos J, Molnar Z, Szabo R (2014) Development of geopolymer using industrial waste materials. In: Proceedings of 9th International Conference on Environmental Engineering, Vilnius, Lithuania, pp. 1–8Google Scholar
- 10.Vukcevic M, Turovic D, Krgovic M, Boscovic I, Ivanovic M, Zejak R (2013) Utilization of geopolymerization for obtaining construction materials based on red mud. Mater Technol 47:99–104Google Scholar
- 12.Komnitsas K, Zaharaki D (2009) Utilisation of low-calcium slags to improve the strength and durability of geopolymers. In: Provis JL, van Deventer JSJ (eds) Geopolymers: structures, processing, properties and industrial applications. Woodhead, Cambridge, p 353Google Scholar
- 14.Bošković I, Vukčević M, Krgović M, Ivanović M, Zejak R (2013) The influence of raw mixture and activators characteristics on red-mud based geopolymers. Res J Chem Environ 17:34–40Google Scholar
- 19.Bell JL, Kriven WM (2010) Formation of an iron-based inorganic polymer (geopolymer). In: Sing D, Kriven WM (eds) Mechanical properties and performance of engineering ceramics and composites. Wiley, Hoboken, pp 301–312Google Scholar
- 24.MacKenzie KJD, Smith ME (2002) Multinuclear solid state NMR of inorganic materials. Pergamon-Elsevier, OxfordGoogle Scholar