Y. L. Wei

Role of Fe compounds in light aggregate formation from a reservoir sediment

A one-step thermal process at 1050 degrees C and 1150 degrees C including bloating and sintering reactions produced lightweight aggregates (LWAs) with an apparent particle density of 2.08 and 1.18gcm(-3), respectively, from pellets made of the sediment of a local reservoir. The roles of Fe compounds occurred in the sediment in bloating mechanism were determined with X-ray absorption spectroscopy (XAS) technique. About 59at% of the total Fe is in forms of Fe(2+) in the raw sediment; whereas most Fe was oxidized to Fe(3+) in all LWAs, except in core part of the LWA produced at 1150 degrees C. The bloating reactions occurred in the core of the 1150 degrees C LWA is suggested to be mainly associated with the decomposition of FeSO(4) into FeO with a concomitant release of SO(2), SO(3), and O(2); the valence state of Fe was not changed. The generally accepted mechanism - the chemical reduction of Fe(2)O(3) component to FeO with a release of O(2) is responsible for the bloating phenomenon - is not observed in present study.

Effect of potassium hydroxide on PAH formation during toluene incineration

A laboratory-scale liquid-injection incinerator was used to incinerate toluene at 750°C and PAH emission was analyzed. The results indicate that the emission of solid-phase PAHs considerably increased when potassium hydroxide was added into a fuel-lean toluene flame; more potassium hydroxide resulted in more solid-phase PAHs. But this phenomenon was not observed for the fuel-rich toluene flame. The enhanced PAH formation is proposed as by-product of the partial oxidation or incomplete burning of soot in the secondary flame zone of the fuel-lean flame. It is suggested that reducing soot formation via potassium hydroxide addition may increase PAHs.

The chemical transformation of copper in aluminium oxide during heating

Thermal treatment has recently been emerging as a promising environmental technology to stabilize heavy metal-containing industrial sludge. This study used x-ray absorption spectroscopy (XAS) to identify the species of copper contaminant contained in aluminium oxide that is one of the main compositions of sludge and soil. Results indicate that the originally loaded copper nitrate was transformed into Cu(OH)2 after its dissolution in the aluminium oxide slurry. Extended x-ray absorption fine structure (EXAFS) fitting indicates that the main copper species in the 105 °C dried Cu(NO3)2-loaded aluminium oxide is Cu(OH)2 which accounts for ca. 75% of the loaded copper. After thermal treatment at 500 °C for 1 h, both x-ray absorption near-edge structure (XANES) and EXAFS fitting results show that CuO became the prevailing copper species (about 85%); the rest of the copper consisted of Cu(OH)2 and a negligible amount of Cu(NO3)2. It was found that most Cu(OH)2 and Cu(NO3)2 decomposed into CuO at 500 °C. Further increase of the heating temperature from 500 to 900 °C resulted in more decomposition of Cu(OH)2 and Cu(NO3)2; therefore CuO remained as the main copper species. However, it was suggested that about 15% of the loaded copper formed CuAl2O4 through the chemical reaction between CuO and Al2O3 at 900 °C.