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 H-2 carrier gases lead to the formation of CHF3 and COF2. N-2 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 N-2 and air was used as the carrier gas. (C) 2016 Elsevier B.V. All rights reserved.