Insight into the mechanisms of efficient selective removal of Pb2+ from wastewater by nano-flowered MoS2/NHCS electrodes

Abstract

The shortage of clean water resources has become a major challenge to global sustainable development, and lead (Pb) pollution in natural water has made the issue even more severe. Efficiently removal of Pb2+ is a severe challenge to Lead-containing sewage disposal. Here, efficiently selective removal of Pb2+ from wastewater was tested over hollow nano-flowered MoS2/N-doped hollow carbon spheres (MoS2/NHCS) cathodes by capacitive deionization (CDI) process. The MoS2/NHCS electrodes exhibited an excellent removal efficiency of 96.9 % in 20 ppm Pb(NO3)2 solution at U = 1.2 V, pH = 6, and 40 mL/min of flow rate. In addition, MoS2/NHCS electrodes showed excellent regeneration ability in 10 ppm Pb2+ solution and still could reach 97.7 % after 20 cycles, especially the good selective removal efficiency in the mixed solution. In situ Raman spectrum and DFT calculations indicate that efficient selective removal of Pb2+ was attributed to Pb2+ directly combined with partially negatively charged S2- to generate PbS, and some S ions transformed into S2-2 by received electrons, which further combines with Pb2+ to form PbS2. Hence, this work proposes an innovative adsorption mechanism for selective capacitive removal of Pb2+ and provides the potential practical application for treating Lead-containing wastewater.