Efficient degradation of thiocyanate by persulfate activation of a novel SA@Fe-Ni-C composite: Properties, mechanisms and DFT calculations

The existing microelectrolytic materials are hindered in applying advanced oxidation processes due to their poor stability and easy bonding. Therefore, ternary iron-carbon microelectrolytic microspheres (SA@Fe-Ni-C) have been prepared by a simple embedding process and used to activate persulfate (PDS) to degrade thiocyanate (SCN-). The doping of Ni not only accelerates the electron transport and promotes the effective reduction of Fe3+ but also forms the cycle system of Fe2+/Fe3+ and Ni2+/Ni3+, which ensures the high catalytic activity of the catalyst. It was found that both free radicals (SO4•-, •OH and O2•-) and non-free radicals (1O2 and electron transfer) contributed to the removal of SCN-. The DFT results showed that Fe was the leading activation site of PDS, and Ni could also promote the activation of PDS. Finally, the high stability of SA@Fe-Ni-C and its anti-interference ability were verified by 5-cycle and coexistence ion experiments. This study provides some guidance for the synthesis of new micro-electrolytic materials and the treatment of industrial wastewater by an advanced oxidation process.