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 10min in the presence of 0.5mM 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 5-10mAcm^-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.