High Capacitive Removal of Pb<sup>2+</sup> from Wastewater and Mechanism Study over MoO<sub>2</sub>@N-Doped Hollow Carbon Sphere Anodes
Jinyun Luo, Jincheng Mu, Xinyong Li, Baojun Liu
Abstract
Lead pollution in the water has become a serious environmental problem with the development of metallurgy, chemical manufacturing, and mining, especially battery industries. Highly efficient removal of Pb 2+ is a big challenge to wastewater treatment. In this work, highly efficient removal of Pb 2+ from wastewater over MoO 2 @N-doped hollow carbon sphere (MoO 2 @NHCS) anodes was developed by a capacitive deionization (CDI) process. The adsorption capacity of Pb 2+ is as high as 202.14 mg/g in a 50 ppm Pb 2+ solution (pH = 6 and U = 1.2 V). In addition, MoO 2 @NHCS electrodes show high selectivity toward Pb 2+ under competition from Na + and other heavy metal ions. Meanwhile, the MoO 2 @NHCS electrodes maintain an excellent recycling ability after 20 cycles for a unique hollow structure. Moreover, the density functional theory calculations show that MoO 2 crystals adsorb Pb 2+ in a tetrahedral mode with the highest adsorption energy ( E ads = −1.61 eV). The selective removal of Pb 2+ is attributed to the octahedral MoO 2 transformed into tetrahedral [MoO 4 ] 2– and then could trap the Pb 2+ to form PbMoO 4 . Hence, this work provides an innovative thinking for the effective removal of Pb 2+ from wastewater.