Treatment of Chromium(III) in Tannery Wastewater Using LDH Incorporated With EDTA

Abstract

Removing of Chromium(III) from contaminated tannery wastewater by adsorption on Zn/Al layered double hydroxides incorporated with ethylenediamintetraacetic acid, referred to as Zn/Al-EDTA, has been investigated by batch experiments. The effects of different parameters on the percentage relative adsorption concentration were carried out. The adsorption capacity with the Zn/Al-EDTA, provided almost complete removal of chromium(III) which was accomplished within one hour, while the Zn/Al-EDTA particles were kept in suspension by shaking. The effect of pH on sorption in the range of 2-8 at an optimized temperature of 30⁰C   was studied having 95% removal efficiency. The kinetics of adsorption were evaluted and conformed well with the Langmuir isotherm The bound Cr(III) ions could be eluted successfully using 0.1?M HCl. The sorption–desorption studies employing that the Zn/Al-EDTA could be regenerated without any major loss in the adsorption capacity. The  Zn,Al layered double hydroxides (LDHs) host was intercalated by an anionic  ethylenediaminetetraacetate (EDTA) guest. It was prepared by coprecipitation of the EDTA anion with the precursor Zn,Al-NO₃ LDHs in a basic condition. Characterization of Zn/Al-EDTA was done using Powder X-ray diffraction (PXRD), elemental analysis and FTIR spectroscopy indicated that most of the interlayer nitrate anions were displaced by (EDTA) anions to form Zn/Al-EDTA which then used as sorption material for Cr(III) metal ion from tanning wastewater.

Keywords: tannery wastewater, layered double hydroxides, sorption, chromium(III), edta.