Ni-P-Pd catalysts from spent electroless nickel baths for peroxymonosulfate activation: Complete degradation of...

This study pioneers a waste-to-catalyst strategy by transforming spent electroless nickel baths (SENB) into a high-performance Ni-P-Pd@SiO₂ heterostructure for peroxymonosulfate (PMS) activation. Pd doping electronically modulates the NiP structure, achieving near-complete removal of nitrogenous pollutants (hydrazine hydrate: 97.2 %; COD_Cr: 96.7 %; NH₃-N: 97.0 %) from actual propellant gradient denitration wastewater at neutral pH. In situ radical trapping and DFT calculations demonstrate that PdNi synergy enhances PMS adsorption and reactive oxygen species (ROS) generation, with non-radical ¹O₂ identified as the dominant ROS, followed by •OH and SO₄•^-. The Ni-P-Pd@SiO₂ catalyst exhibits exceptional stability and reusability over multiple cycles. This dual-functional strategy simultaneously mitigates two industrial waste streams-SENB (Ni/P recovery) and toxic ammunition wastewater pollutant degradation- embodying green chemistry principles and providing a sustainable environmental remediation solution.