Adsorption of aqueous uranium(VI) species on graphitic carbon nitride adsorbent (g-CNA): kinetic, isotherm and thermodynamic studies

A graphitic carbon nitride adsorbent (g-CNA) has been developed for the removal of uranium from water. Experiments revealed that g-CNA exhibited a U(VI) adsorption capacity of 312.5 mg g⁻¹, reaching equilibrium within 30 min at pH 6.0. The Langmuir isotherm fit confirmed the monolayer U(VI) adsorption. Pseudo-second-order kinetics indicated that U(VI) and g-CNA concentrations influenced the reaction rate, with electrostatic interactions involved in the adsorption mechanism. Thermodynamic studies indicated spontaneous exothermic adsorption of U(VI) on g-CNA. The adsorption efficiency of g-CNA remained stable with the electrolytes, and the adsorbed U(VI) was removed with HCl, confirming its potential for U(VI) remediation.