Efficient and selective Lead(II) removal within a wide concentration range through chemisorption and electrosorption coupling process via defective MoS₂ electrode

Developing method for efficient lead(II) removal from aqueous solutions over a wide concentration range is urgent but challenging. In this work, defective molybdenum disulfide (MoS2) was served as electrode coating to capture lead(II) over a wide range from aqueous solution via chemisorption and electrosorption coupling (CEC) process. The distinct adsorption behaviors of lead(II) on defective MoS2 electrode were theoretically and experimentally investigated. In a wide concentration range (1 similar to 100 mg/L), the removal efficiency of lead(II) from aqueous solutions can be close to similar to 100 %. Adsorption capacities for lead(II) removal at initial concentration of 8.37 and 18.71 mg/L were 64.99 and 159.98 mg/g, respectively. After applying voltage, adsorption capacity and removal efficiency were enhanced almost 8 folds due to strengthened migration of ions, electrostatic interaction and electric double layer. Besides, lead(II) was completely desorbed from defective MoS2 electrode within 60 min, and defective MoS2 electrode by CEC process maintained excellent regeneration ability even after 10 cycles. Defective MoS2 electrode has shown superior properties for lead(II) removal, such as (i) great specific capacitance and (ii) low charge transfer resistance toward the enhanced adsorption capacity and diffusion for lead(II) in the electrical double layer, compared with MoS2. Extensive computations and characterizations of defective MoS2-lead(II) interaction demonstrated that the active unsaturated S sites were indispensable for lead(II) adsorption, which was beneficial for chemisorption. Based on the strong interaction with lead(II), defective MoS2 electrode showed high-selectivity lead(II) adsorption with co-existence metal ions. Overall, defective MoS2 as electrode coating by CEC has a great potential for the practical application in removing heavy metal ions from aquatic environment.