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 165mgL^-1 CF₄ gas dissolved in 10M 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 (+6mV) 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.