(545d) Activation of Persulfates by Catalytic Nickel Nanoparticles Supported on N-doped Carbon Nanofibers for Degradation of Organic Pollutants in Water

Peroxydisulfate (PDS) and peroxymonosulfate (PMS) as the active superoxides have been extensively studied to generate highly reactive species for wastewater decontamination during the past decade. Since PDS is stable, soluble, cheap (<$2.65/kg for Na₂S₂O₈) and owns high redox potential (2.01 V), it is widely used as a source of radicals. A series of methods have been used to activate PDS, including UV irradiation, heat, ozone, quinone and transition metal catalysis. In this paper, an N-doped carbon nanofiber cloth (CC) with anchored nickel nanoparticles (Ni@N-CC) was synthesized from a facile pyrolysis process and employed as a catalyst to oxidize target contaminants using PDS as both radical precursors and electron acceptors. An effective strategy was developed to control the porous structures and catalytic performances by optimizing the precursor weights and pyrolysis temperatures for Ni@N-CC preparation. The optimal temperature is 700 °C, and the best dicyanodiamine mass is 1.0 g. Ni@N-CC was found to be superior for PDS activation to CC and nickel nanoparticles (NPs), ascribing to highly active sites, intimate connection between the nickel NPs and highly conductive N-doped CC, as well as the formed three-dimensional architecture. The oxidation rates were influenced by the oxidant loading (0.185–1.11mM), initial organics concentration (10–50mg/L), temperature (5–45°C), pH (2.65–10.47), and inorganic anions. Furthermore, mechanistic investigations using various probe reagents and spin trapping technique identified the generation of several active species for oxidation. The reaction was found to proceed via the electron transfer mediation from organics to PDS on N-doped CC and one electron reduction of PDS on Ni⁰ NPs. This study highlights the design of highly active and reusable heterogeneous carbon/metal hybrids for more efficient PDS activation in environmental remediation.