Species formed on iron surface during removal of copper ions from aqueous solutions

The subject of the research covered in this paper is the removal of copper (Cu2+) cations from water at low pH (initial values of pH 3 and 6) by means of zero-valent iron. The chemical states and atomic concentrations of solids formed on the surface of zero-valent iron, and the type of deposited polycrystalline substances have been analyzed with the use of XPS and XRD. The type of process causing the copper removal from water at low pH, corresponding to the effect of acid mine drainage, has been identified by analyzing the changes of physicochemical parameters and specified chemicals content in water. Cu2+ was removed from water for the initial pH of 6 was much more effective than at lower pH. The formation of CuxFe3-xO4 , where x≤1, and to a lesser degree Cu2O, Cu0 and/or CuO and/or Cu2S, were the basic processes of the removal of copper at almost neutral pH of water (pH about 6), while the formation of copper in metallic form and Cu2O, as well as probably CuO, were the basic processes for lower pH (pH about 3). The adsorption of Cu2+ on the surface of shell covering square-shaped cold-rolled steel sheet cell was an additional process causing the removal of copper from water at almost neutral pH.