Surfactant structural effects on mediated electrocatalytic dechlorination: Links between the micellar enhancement of dechlorination reactions and micellar properties

Abstract

Electrocatalytic dechlorination mediated by micelle-solubilized electrocatalysts has attracted considerable current interest for pollutant degradation. Aggregation in micellar assemblies and their interactions with the additives in solution are affected by the surfactant structure. By choosing appropriate surfactant molecules, the system properties may be altered to achieve enhanced dechlorination efficiency. Cetyltrimethylammonium bromide-based surfactants with different hydrocarbon lengths and headgroup structures were studied for their structural effects on [Co(I)(bipyridine)3]+-mediated dechlorination reactions. A widely used pollutants allyl chloride derivatives were studied as the substrates. The performance of the surfactants towards various dechlorination reactions was evaluated by cyclic voltammetry (CV) based on the catalytic efficiency. Key micellar parameters were determined by CV and rotating disc electrode using [Co(II)(bipyridine)3]2+ as the micelle-solubilized redox probe. The surfactants affected the dechlorination reaction to different extents, correlating well with their structure. The catalytic efficiency was explained by the interactions of the Co(II)/Co(I) with the surfactant hydrophobic tail and headgroup. This is the first report quantitatively linking the performance of the surfactants in dechlorination reactions with their molecular structure, showing that is possible to use variant surfactant structures to tune the micellar properties for their application towards the enhanced dechlorination of organic pollutants. Substrate structure-susceptibility to reduction relationships were also discussed.