Efficient removal of dyes by a novel magnetic Fe3O4/ZnCr-layered double hydroxide adsorbent from heavy metal wastewater

A novel magnetic Fe3O4/ZnCr-layered double hydroxide adsorbent was produced from electroplating wastewater and pickling waste liquor via a two-step microwave hydrothermal method. Adsorption of methyl orange (MO) from water was studied using this material. The effects of three variables have been investigated by a single-factor method. The response surface methodology (RSM) based on Box-Behnken design was successfully applied to the optimization of the preparation conditions. The maximum adsorption capacity of MO was found to be 240.16 mg/g, indicating that this material may be an effective adsorbent. It was shown that 99% of heavy metal ions (Fe2+, Fe3+, Cr3+, and Zn2+) can be effectively removed into precipitates and released far less in the adsorption process. In addition, this material with adsorbed dye can be easily separated by a magnetic field and recycled after catalytic regeneration with advanced oxidation technology. Meanwhile, kinetic models, FTIR spectra and X-ray diffraction pattern were applied to the experimental data to examine uptake mechanism. The boundary layer and intra-particle diffusion played important roles in the adsorption mechanisms. (C) 2012 Published by Elsevier B.V.