Innovative reductive remediation of carbon tetrafluoride at room temperature by using electrogenerated Co1+

Among the non-CO2 greenhouse gases, carbon tetrafluoride (CF4) is the most recalcitrant and should be eliminated from the atmosphere. In the present study, a non-combustion electroscrubbing method was used in an attempt to degrade CF4 with an electrogenerated Co1+ mediator in a highly alkaline medium. The initial absorption experiments revealed 165 mg L−1 CF4 gas dissolved in 10 M NaOH. Different mediator precursors, [Co(II)(CN)5]3−, [Ni(II)(CN)4]2−, [Cu(II)(OH)4]2−, and [Co(II)(OH)4]2−, were used and the electroscrubbing results showed that the electrogenerated Co1+ or [Co(II)(OH)4]2− precursor effectively degraded up to 99.25% of the CF4 gas. The variations in [Co(II)(OH)4]2− reduction efficiency and cyclic voltammetry revealed CF4 degradation followed by electrogenerated Co1+ mediated reduction. The increased zeta potential (+6 mV) of the electrogenerated Co1+ showed that the degradation reaction occurs preferably at the solution interface. Electroscrubbing for CF4 removal and the resulting products were controlled by the carrier gas. Air and H2 carrier gases lead to the formation of CHF3 and COF2. N2 as the carrier gas caused 99.25% degradation with ethanol as a product. An 80% CF4 degradation efficiency with CHF3 as the product was observed when a mixture of N2 and air was used as the carrier gas.