Revolutionizing thorium capture: g-C3N4 electrodes for enhanced thorium electrosorption

Abstract This study investigates electrosorption as an innovative and effective technique for the removal of radioactive thorium ions from aqueous solutions, with potential applications from real residue samples. A positively polarized graphitic carbon nitride (g-C 3 N 4 ) electrode was employed in a batch mode configuration to evaluate the effects of applied voltage, operation time, and initial thorium concentration on the adsorption process. Under a 1.0 V applied voltage, thorium ions demonstrated a strong affinity for the charged g-C 3 N 4 surface, resulting in a substantial increase in adsorption capacity, from 40.98 mg. g −1 to 124.31 mg. g −1 . This substantial enhancement highlights the role of electrical stimulation in facilitating thorium removal. The adsorption process conforms to the Langmuir isotherm model and exhibits pseudo-second order (PSO) kinetics, indicating that the applied potential enhances not only electrostatic interactions but also promotes chemisorption through complexation of thorium ions with the carbon and nitrogen atoms present on the g-C 3 N 4 surface, as validated by XPS analyses. Additionally, the g-C 3 N 4 electrode exhibited excellent reusability, achieving ~ 80% removal efficiency after five regeneration cycles. Furthermore, the g-C 3 N 4 electrode demonstrated effective selective adsorption of Th from real wastewater residue containing other rare earth elements such as Ce, La, Nd and Pr.