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Increasing production and disposal of coal fly ash (CFA) is a matter of serious environment concern. However, CFA contains various beneficial metals and mineral matters whose demand is increasing in the industrialized world, while natural supplies are diminishing. Therefore, recovery of these potential resources from CFA can be an alternative way to save mineral resources, as well as to reduce the environmental burden of CFA disposal. There are numerous methods developed for the recovery of beneficial products from CFA. Based on the US patents and journal literatures, the present review describes the recovery status and technologies of major elements such as Al, Si, Fe and Ti, and trace elements such as V, Ga, Ge, Se, Li, Mo, U, Au, Ag, Pt groups and rare earth elements (REEs) and other beneficial products such as magnetic materials, cenospheres, and unburned carbon from CFA. It also highlights the recovery efficiency and drawbacks for their extraction, and suggests future research to develop satisfactory results in terms of selective recovery and purification.

Epilithic biofilms, growing on submerged boulders, were collected upstream and downstream of sites of industrial discharge into the Brahmani River, Orissa State, India. Transmission electron microscopy (TEM) showed that the outer cell walls of attached bacteria in all samples were often encrusted with fine-grained (<1 µm) inorganic precipitates. The density of mineralization ranged from a few epicellular grains to complete encrustation by clayey materials. Energy-dispersive x-ray spectroscopy (EDS) and selected-area electron diffraction (SAED) indicated that the most abundant inorganic phase was a complex, poorly ordered, (Fe, Al)-silicate of variable composition, containing minor amounts of potassium. No trace metals were detected in the authigenic precipitates. Bacterial cells were also found to entrap or adsorb detrital minerals such as kaolin, mica, quartz, iron oxide, and gibbsite onto their outer surfaces. Because epilithic microbial biofilms have a very large and highly reactive surface area, binding of major solutes and/or suspended detrital sediment will influence the chemical composition of the substrate-water interface and, ultimately contribute to the makeup of the river bottom sediment.The chemical composition of waters at the sediment-water interface is influenced by (1) sedimentation, entrainment, and dissolution of metal-rich particulate material; (2) metal adsorption onto clays, metal oxides-hydroxides, or organic material in the bottom sediment; and (3) precipitation of metal compounds or coprecipitation of metals by hydrous Fe and Mn oxides, carbonates, and phosphates (Förstner 1982;Hart 1982). However, the role of microorganisms, in particular biofilms, has seldom been considered as an important

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