Speciation of Rubber Wood Bark Ash
Ahmad Tarmizi Abd. Karim, Mohd Idrus Mohd Masirin, Lee Yee Loon, Ab Aziz Abd Latiff, Mohd Raihan Taha

Abstract
Malaysia produces approximately 1.5 million cubic meters of rubber wood medium density fiberboards (MDF) annually. During the manufacture of the fiberboards, the floem (outer skin) of the rubber logs would be debarked and burnt. The ashes would usually be disposed in landfills. The chemical constituents of the ashes would leach and contaminate the groundwater. Therefore a sequential leaching procedure was conducted to investigate the speciation and extraction of five heavy metals (Cd, Cr, Cu, Pb and Zn) in rubber wood bark ash (RBA). The mobility and bioavailability of the metals was investigated through five fractions: (1) exchangeable, (2) bound to carbonate, (3) bound to Fe-Mn oxides, (4) bound to sulfide, and (5) residual fraction. The metal concentration of the leaching solutions was determined by inductively coupled plasma mass spectrometer (ICP-MS). In general Cd was the dominant metal in the exchangeable and carbonate fractions making up 70.2% while Cu was predominantly associated with the sulfide fraction (28.5%). Zn (11.7%) and Cd (9.2%) were also present mainly in the Fe-Mn oxide fraction while the residual fraction was dominated by Cr (40.0%) and Cu (34.0%). In addition the leachate derived through the TCLP tests indicated that the ashes may be disposed into landfills safely.

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