Mn assisted electrochemical generation of two-dimensional Fe-Mn layered double hydroxides for efficient Sb(V) removal

In this work, MnSO4 was added into iron electrocoagulation (EC) system to enhance the removal efficiency of pentavalent antimony (Sb(V)) from wastewater. 99% of Sb(V) was removed after 10 min in the presence of 0.5 mM MnSO4, which was higher than that of without the addition of MnSO4 (72%). In addition, Mn2+ can be removed simultaneously and did not cause secondary pollution. The influencing factors such as MnSO4 concentration, initial pH and current density were investigated. It was found that high concentration of MnSO4, acid or neutral pH conditions and current density of 5-10 mA cm(-2) benefited the removal of Sb(V). The flocs generated in the EC process were analyzed by in-situ Raman, XRD and TEM. The results showed that 2-dimensional Fe-Mn layered double hydroxides (LDHs) were formed. Fe-Mn LDHs possess large internal surface areas with amphoteric surface hydroxyl groups, which are beneficial to the sorption of Sb(V). FT-IR and XPS results indicated that the removal of Sb(V) was mainly achieved through adsorption onto the surface of the Fe-Mn LDHs. The obtained results may provide meaningful insights into understanding the mechanisms of Fe coagulation and improving the efficiency of pollutants removal in Fe EC systems. (C) 2017 Published by Elsevier B.V.