Selective removal of Pb²⁺ from seawater using Nano-ZnO-Loaded graphene oxide electrodes synthesized via catalytic pyrolysis of Petroleum tar

Petroleum tar (PT), a petroleum refining by-product, poses environmental challenges due to its high viscosity and toxic catalyst residues. In this study, zinc-based metal–organic frameworks and nickel foam were employed as synergistic catalysts for the catalytic pyrolysis of PT into binder-free nano-ZnO-loaded graphene oxide electrodes. Pyrolysis analysis revealed that GT/Z8 exhibited the highest H₂ production (975.30 mL) and CH₄ yield (41.93 mL) at 500–700 °C, owing to the superior thermal stability and catalytic effect of ZIF-8. The optimized electrode material, GT/M5, demonstrated excellent selective adsorption capacity for Pb²⁺ from seawater (5.60 mg/g) during membrane capacitive deionization, achieving a remarkable selectivity efficiency of up to 594.75 %. Furthermore, GT/M5 achieved a specific capacitance of 89.83F/g, maintaining about 77.90 % of its capacity after 3000 cycles. Density functional theory simulations confirmed strong Pb²⁺ binding (−5.02 eV) at ZnO–graphene oxide interfaces. This work provides an innovative route for efficient PT valorization, delivering promising electrode materials for energy storage and selective heavy-metal remediation.