Advanced lignin-derived carbon aerogel for efficient uranium removal from complex mining wastewater: adsorption performance, mechanism, and thermodynamics

Uranium (U) is widely used as nuclear fuel and in military applications. The expansion of uranium mining has raised serious concerns about environmental contamination and human health, necessitating appropriate remediation measures. In this study, lignin carbon aerogel (LCA) was synthesized and evaluated for uranium removal from industrial wastewater generated by uranium mining activities. Comprehensive characterization demonstrated that LCA possesses abundant oxygen-containing functional groups and a suitable surface area, both of which are favorable for U uptake. Inductively coupled plasma optical emission spectroscopy (ICP-OES) proved the presence of multiple competing elements in the mining waste effluent, emphasizing the complexity of the treatment matrix. PFO and PSO models represented the adsorption kinetics, indicating fast initial uptake and equilibrium attained within 10 h. Equilibrium data were best fitted by the Langmuir model, yielding a maximum adsorption capacity ( qₘ ) of 26.3 mg g −1 at pH 3.5. Uranium speciation analysis confirmed that anionic uranyl species [UO 2 (SO 4 ) 2 ] 2− and [UO 2 (SO 4 ) 3 ] 4− predominates under the investigated pH conditions. The adsorption process was spontaneous and exothermic. The moderate enthalpy change suggests a physisorption-dominated mechanism involving electrostatic attraction, Cation–π interactions, hydrogen bonding, and partial ionic exchange effects at the solid–liquid interface. This work demonstrates the successful conversion of raw lignin (RL) into a high-performance lignin carbon aerogel, providing an efficient and low-cost adsorbent for uranium removal from complex mining wastewater systems.