Change of crystallinity and mineral composition of fly ash with mechanical and chemical activation for the improvement of phosphate uptake

Abstract

A detailed investigation of the development of the mineral composition and crystallinity of fly ash (FA) activated by an integrated process, as well as the relation between that development and phosphate uptake (PU) in solution, was conducted. This process, consisting of pretreatment (mechanical milling), alkali fusion (sodium hydroxide) at 550 °C and acid attack (3 mol L^—1 sulfuric acid), exhibited a remarkable activation effect. One-hour grinding could enhance PU from 0.67 to 1.66 mg PO₄ ^3—-P g^—1 FA, and then under the optimum chemical conditions with the ratio of NaOH to FA of 0.5 g g^—1 and that of H₂SO₄ to FA of 3 mL g^{— 1}, the PU was further improved to 7.14 mg g^{— 1}. Results also indicated that the PU performance was closely linked with the crystallinity and mineral composition of FA, that is, the treated material with the lowest crystallinity and least crystal phase could achieve the highest PU. For the purpose of destroying original minerals in raw FA farthest and avoiding the production of new crystals, therefore, control on the ratio of NaOH to FA and that of acid to FA was very important during the chemical treatment.

Keywords

Fly ash phosphate uptake activation crystallinity mineral composition

Get full access to this article

View all access options for this article.

References

Boldyrev, V.V. ( 2006) Mechanochemistry and mechanical activation of solids. Russian Chemical Reviews, 75, 177-189.

Cerqueira, D.A. , Filho, G.R. & Assuncao, R.M.N. ( 2006) A new value for the heat of fusion of a perfect crystal of cellulose acetate. Polymer Bulletin, 56, 475-484.

Chen, X.C. , Kong, H.N. , Zhang, D.L. , Wang, X.Z. & Zhang, A.P. ( 2006) Preparation of phosphorus removing agent by modified fly ash. Industrial Water & Wastewater, 37, 65-67. (in Chinese).

Cheung, K.C. & Venkitachalam, T.H. ( 2000) Improving phosphate removal of sand infiltration system using alkaline fly ash. Chemosphere, 41, 243-249.

Chindaprasirt, P. , Homwuttiwong, S. & Sirivivatnanon, V. ( 2004) Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar. Cement and Concrete Research, 34, 1087-1092.

El-Naggar, M.R. , El-Kamash, A.M. , El-Dessouky, M.I. & Ghonaim, A.K. ( 2008) Two-step method for preparation of NaA-X zeolite blend from fly ash for removal of cesium ions. Journal of Hazardous Materials, 154, 963-972.

Fernandez-Bertran, J.F. ( 1999) Mechanochemistry: an overview. Pure and Appllied Chemistry, 71, 581-586.

Fotovat, F. , Kazemian, H. & Kazemeini, M. (2009) Synthesis of Na-A and faujasitic zeolites from high silicon fly ash , Materials Research Bulletin, 44, 913-917.

Hillebrand, W.F. , Lundell, G.E.F. , Bright, H.A. & Hoffman, J.I. ( 1962). Applied Inorganic Analysis, 2nd edn. Wiley, New York, USA.

10.

Kumar, R. , Kumar, S. & Mehrotra, S.P. ( 2007) Towards sustainable solutions for fly ash through mechanical activation. Resources Conservation and Recycling, 52, 157-179.

11.

Liang, Z. & Ni, J.R. ( 2008) Improving the ammonium ion uptake on natural zeolite by using an integrated modification process. Journal of Hazardous Materials, doi:10.1016/j.jhazmat.2008.11.002

12.

Misran, H. , Singh, R. , Beguma, S. & Yarmo, M.A. ( 2007) Processing of mesoporous silica materials (MCM-41) from coal fly ash. Journal of Material Processing Technology, 186, 8-13.

13.

Molina, A. & Poole, C. ( 2004) A comparative study using two methods to produce zeolite from fly ash. Minerals Engineering, 17, 167-173.

14.

Pengthamkeerati, P. , Satapanajaru, T. & Chularuengoaksorn, P. ( 2008) Chemical modification of coal fly ash for the removal of phosphate from aqueous solution. Fuel, 87, 2469-2476.

15.

Ugurlu, A. & Salman, B. ( 1998) Phosphorus removal by fly ash. Environment International, 24, 911-918.

16.

Vassilev, S.V. & Vassileva, C.G. ( 2007) A new approach for the classification of coal fly ashes based on their origin, composition, properties, and behaviour. Fuel, 86, 1490-1512.

17.

Wang, S.B. & Wu, H.W. ( 2006) Environmental-benign utilisation of fly ash as low-cost adsorbents. Journal of Hazardous Materials, B136, 482-501.

18.

Yan, J.Y. , Kirk, D.W. , Jia, C.Q. & Liu, X.N. ( 2007) Sorption of aqueous phosphorus onto bituminous and lignitous coal ashes. Journal of Hazardous Materials, 148, 395-401.

19.

Yang, L.F. , Zhai, J.P. , Zhen, B. & Sheng, G.H. ( 2006) Experimental study on the removal of phosphate from wastewater with acid-modified fly ash. Fly Ash Comprehensive Utilization , 3, 18-20 (in Chinese).

20.

Yildiz, E. ( 2004) Phosphate removal from water by fly ash using crossflow microfiltration. Separation and Purification Technology, 35, 241-252.

21.

Zhang, B.H. , Wu, D.Y. , Wang, C. , He, S.B. , Zhang, Z.J. & Kong, H.N. ( 2007) Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment. Journal of Environmental Sciences, 19, 540-545.