Adsorption/coprecipitation of trace elements from water with iron oxyhydroxide

Abstract

This study has examined the adsorptive/coprecipitation behavior of several inorganic cations and anions in systems containing freshly precipitated x-ray amorphous iron oxyhydroxide. The project examined experimentally several simple, well-characterized model systems to establish type behavior in sufficient detail to allow interpretation of subsequent experimental work on less well-characterized waste materials. A prominent feature of this project was evaluation of the feasibility of utilizing iron-bearing waste liquids as source materials for the precipitation of amorphous iron oxyhydroxide in trace element removal processes. The roles of complexing ligands and competing metals and ligands, and their significance in controlling the distribution of trace elements at the solution/oxide interface have been characterized. From this research a new semi-quantitative model of oxide surfaces has been proposed, as well as a model to describe adsorption of various metal-ligand complexes. Experimental results indicate the adsorption/coprecipitation process with amorphous iron oxyhydroxide is feasible for removing trace elements from a variety of power plant waste streams. In addition, the feasibility of using an acid-metal cleaning waste containing high concentrations of dissolved iron as the iron source for coprecipitation of trace elements has been confirmed. The adsorptive removal of trace elements from real waste streams in complex systems (real wastes)more » using either reagent iron sources or acid-metal cleaning waste can be interpreted in terms of the generalized behavior of model systems. Trace elements considered included Zn, Cd, and Cu, selenites, chromates, and arsenates.« less