Uranium speciation in coal bottom ash investigated via X-ray absorption fine structure and X-ray photoelectron spectra.

Similar to chromium contamination, the environmental contamination caused by uranium in radioactive coal bottom ash (CBA) is primarily dependent on the chemical speciation of uranium. However, the relationship between uranium speciation and environmental contamination has not been adequately studied. To determine the relationship between uranium speciation and environmental contamination, X-ray absorption fine structure (XAFS) and X-ray photoelectron spectra (XPS) analyses were performed to determine the uranium speciation in CBA exposed to different chemical environments and simulated natural environments.

Novel synthesis of cyano-functionalized mesoporous silica nanospheres (MSN) from coal fly ash for removal of toxic metals from wastewater.

Trace amounts of toxic metals are usually difficult to be purified by conventional chemical precipitation or physical adsorption in wastewater. In this study, in order to realize high-value utilization of coal fly ash for wastewater purification, a novel method was applied to prepare high-performance mesoporous silica materials from coal fly ash. In comparison with a commonly used method, characterizations revealed that the new method obtained mesoporous silica nanospheres with uniformly distributed cyano groups (denoted by MSN), while the common method only obtained irregular sponge-like microstructure (denoted by ISM).

Distribution and mode of occurrence of uranium in bottom ash derived from high-germanium coals.

The radioactivity of uranium in radioactive coal bottom ash (CBA) may be a potential danger to the ambient environment and human health. Concerning the limited research on the distribution and mode of occurrence of uranium in CBA, we herein report our investigations into this topic using a number of techniques including a five-step Tessier sequential extraction, hydrogen fluoride (HF) leaching, Siroquant (Rietveld) quantification, magnetic separation, and electron probe microanalysis (EPMA). The Tessier sequential extraction showed that the uranium in the residual and Fe-Mn oxide fractions was dominant (59.

Removal of uranium and gross radioactivity from coal bottom ash by CaCl2 roasting followed by HNO3 leaching.

A roast-leach method using CaCl2 and HNO3 to remove uranium and gross radioactivity in coal bottom ash was investigated. Heat treatment of the ash with 100% CaCl2 (900°C, 2h) significantly enhanced uranium leachability (>95%) compared with direct acid-leaching (22.6-25.