Acase Studyon Stabilizationand Reuse of Geopolymer-Encapsulated Brown Coalflyash

Acase Studyon Stabilizationand Reuse of Geopolymer-Encapsulated Brown Coalflyash

P. Bankowski L. Zou R. Hodges

School of Engineering and Technology, Deakin University, Geelong, Victoria, Australia.

School of Applied Science, Monash University, Churchill, Victoria, Australia.

Page: 
76-90
|
DOI: 
https://doi.org/10.2495/SDP-V1-N1-76-90
Received: 
N/A
|
Accepted: 
N/A
|
Published: 
3 March 2006
| Citation

OPEN ACCESS

Abstract: 

Fly ash disposal for coal power stations is an ongoing problem. This paper explores the use of a geopolymeric material to stabilize fly ash and reduce the leach rates of metals, and at the same time determine whether the stabilized material can be reused and recycled as value-added products. Fly ash from the LatrobeValley,Victoria, Australia, was collected and stabilized in a geopolymer with a molar silica to alumina ratio of 3. Fly ash was collected from electrostatic precipitators [precipitator fly ash (PFA)] and ash disposal ponds [leached fly ash (LFA)] so that a comparison in results between the two types could be made. In terms of stabilization of selected heavy metals, PFA showed better trends towards reduction in leach rates, although for this fly ash the initial concentration of heavy metals is low. LFAshowed better trends towards reduction in major elemental leach rates. Compressive strength tests were carried out to determine the potential of the material to be used as recycled products. A maximum compressive strength of 32 MPa was achieved with a PFA–geopolymer combination, which shows that these materials can be recycled and reused. However, more research is still required to achieve greater compressive strengths. Scanning electron microscopy linked the leaching behaviour and compressive strength values with images that showed the fly ash particle–geopolymer interaction. Materials cost estimation was conducted to determine the cost of materials required to stabilize and reuse fly ash geopolymers.

Keywords: 

fly ash, material costs, metal leaching, stabilization, waste management

  References

[1] Barber, E.G., Jones, G.T., Knight, P.G.K. & Miles, M.H., PFA Utilization, Central Electricity Generation Board, Gibbons: Wolverhampton, pp. 17–74, 1973.

[2] Black, C. et al., Utilisation of Latrobe Valley brown coal fly ash. Gippsland Basin Symposium, Melbourne, 1992.

[3] Iyer, R.S. & Scott, J.A., Power station fly ash—a review of value added utilization outside of the construction industry. Resources, Conservation and Recycling, 31(3), pp. 217–228, 2001.

[4] Davidovits, J., Geopolymers: inorganic polymeric new materials. Journal of Thermal Analysis, 37, pp. 1633–1656, 1991.

[5] Van Jaarsveld, J.G.S. & Van Deventer, J.S.J., The effect of metal contaminants on the formation and properties of waste-based geopolymers. Cement and Concrete Research, 29(8), pp. 1189– 1200, 1999.

[6] Barbosa, V.F.F., MacKenzie, K.J.D. & Thaumaturgo, C., Synthesis and characterisation of materials based on inorganic polymers of alumina and silica: sodium polysialate polymers. International Journal of Inorganic Materials, 2(4), pp. 309–317, 2000.

[7] Van Jaarsveld, J.G.S., Van Deventer, J.S.J. & Lorenzen, L., Factors affecting the immobilisation of metals in geopolymerised fly ash. Metallurgical and Materials Transaction B, 29, pp. 283– 291, 1998.

[8] Van Jaarsveld, J.G.S., Van Deventer, J.S.J. & Schwartzman, A., The potential use of geopolymeric materials to immobilise toxic metals: Part II. Materials and leaching characteristics. Minerals Engineering, 12(1), pp. 75–91, 1999.

[9] Alonso, S. & Palomo, A., Alkaline activation of metakaolin and calcium hydroxide mixtures: influence of temperature, activator concentration and solids ratio. Materials Letters, 47(1–2), pp. 55–62, 2001.

[10] Purdon,A.O., The action of alkalis on blast furnace slag. Journal of the Society of the Chemical Industry, 59, pp. 191–202, 1940.

[11] Xu, H. & Van Deventer, J.S.J., The geopolymerisation of alumino-silicate minerals. International Journal of Mineral Processing, 59(3), pp. 247–266, 2000.

[12] Van Jaarsveld, J.G.S., Van Deventer, J.S.J. & Lorenzen, L., The potential use of geopolymeric materials to immobilise toxic metals: Part I. Theory and applications. Minerals Engineering, 10(7), pp. 659–669, 1997.

[13] Khalil, M.Y. & Merz, E., Immobilisation of intermediate-level wastes in geopolymers. Journal of Nuclear Materials, 2(1), pp. 141–148, 1994.

[14] Palomo, A. & Lopez de la Fuente, J.I., Alkali-activated cementitious materials: alternative matrices for the immobilisation of hazardous wastes. Part 1. Stabilisation of boron. Cement and Concrete Research, 33(2), pp. 281–288, 2003.

[15] Palomo,A. & Palacios, M.,Alkali-activated cementitious materials: alternative matrices for the immobilisation of hazardous wastes. Part 2. Stabilisation of chromium and lead. Cement and Concrete Research, 33(2), pp. 289–295, 2003.

[16] USEPA, Toxicity Characteristic Leaching Procedure, Methods 1311, 1992.

[17] Standards Australia, Method of testing Portland, blended and masonry cements, Method 11: Compressive strength, pp. 1–9, 2001.

[18] Victorian EPA, Publication 448: Classification of Wastes, Victorian EPA: Melbourne, pp. 1–6, 1995.

[19] Davidovits, J., Davidovits, M. & Davidovits, N., Process for obtaining a geopolymeric aluminosilicate and the products thus obtained, US Pat. No. 5,342,595, 1994.

[20] Phair, J.W. & Van Deventer, J.S.J., Effect of the silicate activator pH on the microstructural characteristics of waste-based geopolymers. International Journal of Mineral Processing, 66(1–4), pp. 121–143, 2002.

[21] Lee,W.K.W.&VanDeventer,J.S.J.,Theeffectofioniccontaminantsontheearly-ageproperties of alkali activated fly ash-based cements. Cement and Concrete Research, 32(4), pp. 577–584, 2002.