Efficient and selective Pd(II) capture from simulated electronic waste leachate by pyrimidine-based cellulose

Efficient and selective recovery of palladium is essential for sustainable resource utilization. In this work, three pyrimidine-functionalized cellulose adsorbents (MCGC, MCGT and MCGU) were synthesized via radiation grafting with cytosine, thymine, and uracil, respectively. Their adsorption behaviors toward Pd(II) were systematically evaluated through batch and column experiments. The adsorbents demonstrated high Pd(II) selectivity in multi-ion systems, with adsorption capacities following the order MCGC > MCGU > MCGT. Among them, MCGC showed the most outstanding performance, exhibiting a maximum capacity of 94.0 mg/g at pH = 5 (Langmuir R² > 0.99) and maintaining over 80% efficiency even at molar ratio (C_Pd: C_{coexisting ions}) of 1:2000. Furthermore, MCGC retained stable adsorption-desorption performance over ten cycles. Comprehensive characterization verified successful functionalization and Pd-ligand interactions, while density functional theory (DFT) calculations revealed that cytosine-based groups provided the most favorable electrostatic potential distribution and binding energetics for PdN coordination. Overall, this study demonstrates that the potential of pyrimidine-functionalized cellulose, particularly cytosine-modified MCGC, as a sustainable and selective adsorbent for Pd(II) recovery.