Iron ions reclaiming from sludge resulted from hot-dip galvanizing process, as Mg3 Fe-layered double hydroxide used in the degradation process of organic dyes

Abstract

Iron sludge resulted from the neutralization of waste waters resulted during hot-dip galvanizing process was reclaimed in order to obtain a Fe(III) precursor solution used for the synthesis of Mg3Fe-layered double hydroxide. The Fe(III) precursor solution was extracted from the sludge with three inorganic acids. The influence of the inorganic acid type, concentration, contact time and solid to liquid ratio upon the extraction efficiency of the iron ions was determined. Two types of Mg3Fe-layered double hydroxides (LDH) were synthesized as follows: the first one was obtained starting from reagents and the second one from the iron precursor extracted from sludge. Both were characterized via X-ray powder diffraction (XRD), FT-IR spectroscopy, BET, TEM and SEM-EDX analysis. The results showed that the LDH obtained from the iron solution extracted from the recycled sludge had similar characteristics with the synthesized LDH from reagents. The photocatalytic activity of the both samples, in the degradation process of Congo Red, was also evaluated and was observed that the LDH obtained from sludge has photocatalytic properties almost similar to that synthetized from analytical grade reagents. All the results show the possibility of replacing the LDH synthesized from reagents with a viable, cheaper and green route of obtaining this material.