Sr(Ⅱ) and Cs(Ⅰ) adsorbed by graphene synthesized from spent lithium-ion batteries anode materials via novelly electrochemical exfoliation

The discharge of nuclear wastewater into the sea may pose a significant environmental and health risk due to radionuclides such as ¹³⁷Cs and ⁹⁰Sr. Consequently, the efficient removal of these nuclides has emerged as a focal point in the field of radioactive wastewater treatment. Traditional restoration methods, which rely on physical and chemical interventions as well as bioremediation, are economically burdensome and unsuitable for large-scale restoration efforts. Waste graphite of spent lithium-ion batteries (LIBs) is also a challenge to repurpose, yet its resourceful utilization is crucial in the context of the dual-carbon goals. In this study, layered graphene materials were successfully synthesized from spent LIBs anode materials by electrochemical exfoliation. Adsorption experiments revealed that the removal efficiency of Sr(II) and Cs(I) by the graphene increases with increasing pH from 1.0 to 6.0, achieving a higher adsorption at pH 6.0. The adsorption kinetics show that the adsorption of Sr(II) and Cs(I) on the graphene fits the pseudo-second-order kinetic model. Calculated from the Sips model, the maximum adsorption capacity for Sr(II) and Cs(I) is determined to be 73 mg/g and 55 mg/g, respectively, at pH 6.0 and 298 K. Furthermore, the graphene exhibited excellent regenerability, maintaining over 90 % of its adsorption capacity after four cycles. The adsorption mechanism involved a synergistic effect of monolayer uniform adsorption and non-uniform adsorption, where Sr(II) and Cs(I) occupied the active sites of the graphene material. These findings suggest that electrochemical exfoliation is a novel and effective approach for graphene synthesis, while waste graphite of spent LIBs hold a great potential for nuclear wastewater treatment and electrochemical exfoliation.