Sustainable Generation of a Homogeneous Ni(I) Catalyst in the Cathodic Compartment of a Divided Flow Electrolytic Cell for the Degradation of Gaseous Carbon Tetrachloride by Electroscrubbing

A mediated electrochemical reduction reaction using a divided electrolytic flow cell with a scrubber column in a closed loop process was successfully devised for the practical electrolytic degradation of gaseous chloro-organics. The authors describe the generation of a low valent homogeneous Ni(I) catalyst and its application for the degradation of gaseous carbon tetrachloride (CCl 4 ) at room temperature. The electrochemical generation of Ni(I) was identified using oxidation reduction potential (ORP) changes during electrolysis and its formation at KOH concentrations of >5 M demonstrated Ni(I) stabilization at higher KOH concentrations. Of the three different cathode materials (Ag, Cu, Ti) employed, Cu produced higher yield of Ni(I) (0.0042 M at 30 mA cm –2 ). An online FTIR analyzer showed almost 99% of gaseous CCl 4 fed continuously at 50 ppm was removed by the electrochemically generated Ni(I) catalyst. A reaction pathway is proposed based on the results of GC/MS analysis of reaction products formed in solution; this analysis also confirmed the complete removal of chlorine from gaseous CCl 4 . Three consecutive experimental runs showed that Ni(I) generation and CCl 4 removal rates were reproducible, which suggests the developed mediated electrochemical reduction (MER) process is sustainable and offers a promising means for treating chloro-organics in the gas phase.