Sustainable removal of N2O by mediated electrocatalytic reduction at ambient temperature electro-scrubbing using electrogenerated Ni(I) electron mediator

Direct catalysis is generally proposed for nitrous oxide (N2O) abatement but catalysis is expensive, requires high temperatures, and suffers from media fouling, which limits its lifetime. In the present study, an ambient temperature electroscrubbing method was developed, coupling wet-scrubbing with an electrogenerated Ni(I) ([Ni(I)(CN)4]3−) mediator, to enable N2O reduction in a single process stage. The initial studies of 10 ppm N2O absorption into 9 M KOH and an electrolyzed 9 M KOH solution showed no removal. However, 95% N2O removal was identified through the addition of Ni(I) to an electrolyzed 9 M KOH. A change in the oxidation/reduction potential from −850 mV to −650 mV occurred following a decrease in Ni(I) concentration from 4.6 mM to 4.0 mM, which confirmed that N2O removal was mediated by an electrocatalytic reduction (MER) pathway. Online analysis identified the reaction product to be ammonia (NH3). Increasing the feed N2O concentration increased NH3 formation, which suggests that a decrease in electrolyzed solution reactivity induced by the increased N2O load constrained the side reaction with the carrier gas. Importantly, this study outlines a new regenerable method for N2O removal to commodity product NH3 at ambient temperature that fosters process intensification, overcomes the limitations generally observed with catalysis, and permits product transformation to NH3

Continuous electro-scrubbers for the removal of perchloroethylene: Keys for selection

In this work, the removal of perchloroethylene (PCE) using continuous-operation electro-scrubbers is evaluated. Two types of electro-scrubbers were made by combining a jet mixer or a packed absorption column with a single flow-cell. The absorbent/electrolyte is recirculated between both devices, being electrolyzed in the cell and retaining the pollutant in the scrubber. In both scrubber’s system, an important amount of PCE was absorbed into the electrolyte and the application of electric current significantly improved the results, highlighting the efficiency of the integration of technologies. Tests in the absence of absorbent/electrolyte confirmed the reactivity of the PCE in the wet gas phase. The jet-mixer system turned out to be more efficient than the packed column, yielding better results both in absorption and electro-absorption modes, and reaching a PCE removal greater than 90%. Meanwhile, the addition of cobalt mediators did not improve the electro-scrubbing efficiency as initially expected: in the case of the packed column electro-scrubber there were no changes while in the case of the jet mixer surprisingly it is generated a negative effect

Proceedings of the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008

This volume contains full papers presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, between September 4th and 6th, 2008.FC