[Intensified Electrosorption of Pb²⁺ by 2,6-diaminoanthraquinone/Graphene Composite Electrode]

The key to efficient removal of heavy metal ions from water by electrosorption is to develop electrode materials with excellent performance. In this study, 2,6-diaminoanthraquinone (DA)-modified reduced graphene oxide (rGO) was used to prepare a DA@rGO composite electrode using the solvothermal method. The electrochemical properties, electrosorption of Pb²⁺, adsorption kinetics, and cycle regeneration performance of the composite electrode were investigated. Cyclic voltammetry showed that the composite electrode had excellent electrochemical properties, and the specific capacitance reached 304.4 F·g^-1 at a current density of 1 A·g^-1. The DA modification significantly increased the pseudocapacitance of the composite electrode. The electrosorption Pb²⁺ test showed that optimal electrosorption was achieved with -1.2 V of the applied voltage, and the removal rate of the Pb²⁺ reached 94.8% after 60 min. The electrosorption process is in accord with the first-order kinetic equation. The saturated adsorption capacity of Pb²⁺ obtained by the Langmuir model was 356.66 mg·g^-1, which is significantly higher than that of rGO electrode, at 319.40 mg·g^-1. The increase in Pb²⁺ adsorption amount of the composite electrode can be attributed to the increase in capacitance caused by DA modification. Treatment with 0.5 mol·L^-1 nitric acid can desorb the Pb²⁺ within 5 min to achieve regeneration of the composite electrode. After 10 adsorption-desorption cycles, the adsorption removal rate of Pb²⁺ by the composite electrode was kept at 88%, indicating robust stability.