Selective capacitive removal of Pb2+ ion contaminants from drinking water via nickel foam/Mn2CoO4@tannic acid-Fe3+ electrodes

Abstract

The health hazards caused by low concentrations of Pb²⁺ ions in drinking water systems are of significant concern. In order to remove Pb²⁺ ions and retain Na⁺, K⁺, Ca²⁺ and Mg²⁺ as harmless competitive ions without simultaneous removal, nickel foam (NF)/Mn₂CoO₄@tannic acid (TA)-Fe³⁺ electrodes were prepared by a hydrothermal method and a coating method and an asymmetric capacitive deionization (CDI) system is established using the prepared electrodes and a graphite paper positive electrode. The designed asymmetric CDI system exhibited a high Pb²⁺ adsorption capacity of 375 mg g⁻¹ with high removal efficiency and significant regeneration behavior at 1.4 V at neutral pH. When the asymmetric CDI system is used to enrich a hydrous solution of mixed Na⁺, K⁺, Ca²⁺, Mg²⁺ and Pb²⁺ ions each with a concentration of 10 ppm and 100 ppm by electrosorption at a 1.4 V operating voltage, the removal rate of Pb²⁺ is as high as 100% and 70.8% respectively, and the relative selectivity coefficients are 4.51–43.22. According to the different adsorption mechanisms of lead ions and coexisting ions, the separation and recovery of ions can be realized by a two-step desorption process, thereby providing a new method for removing Pb²⁺ ions from drinking water with excellent application potential.