Copper(II) was considerably enriched in the residual ash via thermal treatment of copper-sorbed rice husk at 700-1100 degrees C for 2 h, and the copper speciation was quantitatively determined with X-ray absorption spectroscopy. After the thermal process, the resulting ash only represents by weight 18.7-26.4% of the pre-heated samples. Copper content in the ashes is >7% which is far above the required minimum copper content in copper ores for the copper smelting sector, 0.5%. Crystalline SiO2 is observed only in the ash generated at 1100 degrees C, with more copper in this ash being available for leaching in acidic solution. It is suggested that this is due to the considerable dissimilarity in crystalline structure between copper compounds and crystalline SiO2. No chemical reaction between copper and SiO2 is observed in any ash. In fact, we suggest that the SiO2 crystalline phase repels copper during the thermal process: this would make it easy to extract copper from the ashes. For copper speciation in the ashes, CuO merely represents 0-12% of the total copper, while Cu2O and Cu(0) represent 34-42% and 46-63%, respectively. The lower copper oxidation state would be beneficial for the copper smelting process due to less usage of coke. (C) 2010 Elsevier B.V. All rights reserved.