FeNi₃ foam as cathode catalyst in electrocatalytic peroxydisulfate system for enhanced Hg⁰ removal from simulated flue gas

The feasibility of elemental mercury (Hg-0) removal from simulated flue gas in electrocatalytic peroxydisulfate (PDS) system employing FeNi3 foam as cathode catalyst was studied for the first time. The electrocatalytic (EC) performance of FeNi3 foam activating PDS process was evaluated to remove Hg-0 using Pt anode, FeNi3 cathode, and Na2SO4 electrolyte at room temperature. The results showed that the FeNi3 foam/PDS/EC system was superior to the other removal processes. According to the influence of experimental parameters, it was found that about 94% of Hg-0 was removed within 20 min under the conditions of voltage = 2 V, PDS = 1 mM, Na2SO4 = 0.05 M. Theoretical calculations showed that the Ni atom of the FeNi3 cluster would improve its reactivity. The chemical adsorption and hybridization between PDS and FeNi3 had contributed to an efficient production of SO4 center dot- free radical. The high removal efficiency of Hg-0 was due to the following assistances: (i) the O-2 gas adsorbed on the FeNi3 foam cathode surface was able to generate radicals O-center dot(2)- and (OH)-O-center dot by single electron reduction reaction, (ii) FeNi3 foam catalyst could afford ---Fe(II) and ---Ni(II) ions via two electron transfer, activating PDS to produce SO4 center dot-, and (iii) the copresence of Fe and Ni was useful to accelerate the ion cycles of Fe (III)/Fe(II) and Ni(II)/Ni(I), which played a crucial role in FeNi3 foam/PDS/EC system. The novel proposed FeNi3 foam cathode electro-catalyzing PDS system provided a promising prospect in the pollutant control field of Hg-0 removal.