Sains Malaysiana 36(1): 45-52 (2007)

Characterisation of The Leaching Behaviour of Coal Fly

Ash with Tank Leaching Test Method

(Pencirian Sifat Larut Resap Abu Terbang Arang Batu dengan

Kaedah Ujian Larut Resap Tangki)

Khoo Kok Siong & Lim Ai Ling

Pusat Pengajian Fizik Gunaan, Fakulti Sains & Teknologi

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

Sukiman Sarmani

Pusat Pengajian Sains Kimia & Teknologi Makanan

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia

ABSTRACT

Characterisation of the leaching behaviour of coal fly ash from Tenaga Nasional Berhad (TNB) by using tank leaching test method has been reported. The leachability of the constituents such as major elements and toxic metals in the coal fly ash was studied. Eight renewed leachant solutions after 6 hours, 1, 2, 5, 8, 21, 36 and 64 days were investigated after filtration. The parameters namely pH, cumulative release regarding the major elements and toxic metals to duration were presented. The results showed that the pH solutions increased from pH 4 to neutral and remained stable during the test. It might have resulted from the large buffering capacity of the coal fly ashes. Five major elements namely Al, Ca, K, Mg and Na were detected with Ca concentration in the leachant solutions was the highest for all samples. Toxic metals such as As, Ba, Co, Cr, Mn, Ni, Pb, Se and Zn were found and the test showed consistent results on the As, Ba, Mn, Se and Zn in leachant solutions. The findings also showed that some of the toxic metal concentrations namely As, Ba, Cr, Pb and Se exceeded the maximum allowance of the guideline of drinking water quality in Malaysia and WHO. Obviously, proper waste management has to be applied in this scenario.

Keywords: Coal fly ash; tank leaching test; major elements; toxic metals

ABSTRAK

Pencirian bagi sifat larut resap abu terbang arang batu dari Tenaga Nasional Berhad (TNB) dengan kaedah ujian larut resap tangki telah dilaporkan. Kebolehan larut resap juzuk misalnya unsur-unsur major dan logam toksik dalam abu terbang arang batu telah dikaji. Lapan larutan luluh larut yang diperolehi selepas 6 jam, 1, 2, 5, 8, 21, 36 dan 64 hari telah dianalisis setelah penapisan. Parameter-parameter seperti pH, pembebasan kumulatif unsur major serta logam toksik terhadap tempoh masa telah dipersembahkan. Keputusan menunjukkan bahawa larutan pH meningkat dari pH 4 ke neutral dan kemudian berada dalam keadaan stabil sepanjang ujian. Hal ini mungkin hasil daripada kapasiti penampan yang beasr bagi abu terbang arang batu. Lima unsur major seperti Al, Ca, K, Mg dan Na telah dikesan dalam larutan luluh larut dengan kepekatan Ca adalah tertinggi bagi semua sampel. Logam toksik seperti As, Ba, Co, Cr, Mn, Ni, Pb, Se dan Zn juga dikesan dan ujian ini menunjukkan bahawa As, Ba, Mn, Se dan Zn dalam larutan adalah konsisten. Kajian juga menunjukkan bahawa sebahagian daripada kepekatan logam toksik seperti As, Ba, Cr, Pb dan Se telah melampaui had maksimum kualiti air minum yang digariskan oleh Malaysia dan WHO. Jelas sekali, pengurusan sisa yang sesuai perlu digunakan dalam senario ini.

Kata kunci: Abu terbang arang batu; ujian larut resap tangki; unsur major; logam toksik

RUJUKAN/REFERENCES

Andac, M. & Glasser, F.P. 1999. Long-term leaching mechanisms of Portland cement-stabilized municipal solid waste fly ash in carbonated water. Cement and Concrete Research. 29: 179-186.

Balzamo, S. & Marchetti, A. 1996. A new standardized leaching test on stabilized wastes. Microchimica Acta. 123: 145-150.

Barna, R., Sanchez, F., Moszkowicz, P. & Menu, J. 1997. Leaching behavior of pollutants in stabilized/solidified wastes. Journal of Hazardous Materials. 52: 287-310.

Benito, Y., Ruiz, M., Cosmen, P. & Merino, J.L. 2001. Study of leachates obtained from the disposal of fly ash from PFBC and AFBC processes. Chemical Engineering Journal. 84: 167-171.

Catalan, L.J.J., Merliere, E. & Chezick, C. 2002. Study of the physical and chemical mechanisms influencing the long-term environmental stability of natrojarosite waste treated by stabilization/solidification. Journal of Hazardous Materials. B94: 63-88.

Garrabrants, A.C. & Kosson, D.S. 2000. Use of a chelating agent to determine the metal availability for leaching from soils and wastes. Waste Management. 20: 155-165.

Hohberg, I., Groot, G.J.de., Van der Veen, A.M.H. & Wassing, W. 2000. Development of a leaching protocol for concrete. Waste Management. 20: 177-184.

Khoo, K.S. 2006. Multi-element analysis for environmental impact assessment of solid wastes generated by incineration plants. Ph.D Thesis. National University of Malaysia (UKM).

Lim, T.T., Tay, J.H., Tan, L.C., Choa, V. & Teh, C.I. 2004. Changes in mobility and speciation of heavy metals in clay-amended incinerator fly ash. Environmental Geology. 47: 1-10.

Mehu, J., Moskowicz, P., Barna, R. & Sanchez, F. 1997. Waste stabilized/solidified with hydraulic binders. In: Van der Sloot, H.A., Heasman, L. & Quevauviller, Ph. (eds.). Studies in environmental science. Harmonization of leaching/extraction tests. Vol. 70. Amsterdam: Elsevier Science.

Poon C.S., Chen Z.Q. & Wai O.W.H. 2001. The effect of flow-through leaching on the diffusivity of heavy metals in stabilized/solidified wastes. Journal of Hazardous Materials. B81: 179-192.

Quevauviller, Ph., Van der Sloot, H.A., Ure, A., Muntau, H., Gomez, A. & Rauret, G. 1996. Harmonization of leaching/extraction tests for environmental risk assessment. The Science of the Total Environment. 178: 133-139.

Rauret, G., Lopez-Sanchez, J.F., Sahuquillo, A., Rubio, R., Davison, C.M., Ure, A.M. & Quevauviller, Ph. 1999. Improvement of the BCR three step sequential extraction procedure prior to the certificationof new sediment and soil reference materials. Journal of Environmental Monitoring. 1: 57-61.

Schreurs, J.P.G.M., Van der Sloot, H.A. & Hendriks, Ch. 2000. Verification of laboratory–field leaching behavior of coal fly ash and MSWI bottom ash as a road base material. Waste Management. 20: 193-201.

Tiruta-Barna, L., Imyim, A. & Barna, R. 2004. Long-term prediction of the leaching behavior of pollutants from solidified wastes. Advances in Environmental Research. 8: 697-711.

Ugurlu, A. 2004. Leaching characteristics of fly ash. Environmental Geology. 46: 890-895.

Van der Sloot, H.A. 1995. Environmental efficiency of immobilization techniques for wastes in relation to utilization and disposal. In: Cases, J.M. & Thomas, F. (eds.). Proceedings of the International Congress on Waste Solification-Stabilisation Processes. Nancy, France, 28 November-1 December.

Van der Sloot, H.A., Heasman, L. & Quevauviller, P. (eds.). 1997. Studies in environmental science. Harmonization of leaching/extraction tests. Vol. 70. Amsterdam: Elsevier Science.

Van der Sloot, H.A. 2000. Comparison of the characterization leaching behaviour of cement using standard (EN 196-1) cement mortar and assessment of their long-term environmental behaviour in construction products during their service life and recycling. Cement and Concrete Research. 30(7): 1079-1096.

Van der Sloot, H.A. 2002. Characterization of the leaching behaviour of concrete mortars and of cement-stabilized wastes with different waste loading for long term environmental assessment. Waste Management. 22: 181-186.

Van der Sloot, H.A., Seignette, P., Comans, R.N.J., Van Zomeren, A., Dijkstra, J.J., Meeussen, H., Kosson, D.S. & Hjelmar, O. 2003. Evaluation of environmental aspects of alternative materials using an integrated approach assisted by a database/expert system. Evaluation of Waste Materials, Advances in Waste Management and Recycling. Dundee.

Van der Sloot, H.A. & Dijkstra, J.J. 2004. Development of horizontally standardized leaching tests for construction materials: A material based or release based approach? Identical leaching mechanisms for different materials. ECN report: ECN-C—04-060. (Online) http://www.leaching.net/leaching/downloads/ (02 June 2005