Efficient Dechlorination of α-Halocarbonyl and α-Haloallyl Pollutants by Electroreduction on Bismuth

Abstract

The electrocatalytic activity of bismuth considered as a low cost and green electrode material was studied in reductive dechlorination processes. Cyclic voltammetry analyses showed that the Bi electrode exhibited a high catalytic activity to reduce alachlor, a chlorinated herbicide, in aqueous medium at different pH. Bulk electrolyses were performed at different potentials and pH. Alachlor was reduced in deschloroalachlor, its dechlorinated derivative, with a high selectivity (96%) and with a current efficiency of 48%. The reductive dechlorination of other chlorinated compounds with an activated carbon atom was then studied, showing that the bismuth electrode catalyzed the electroreduction of chloroacetamides, -halocarbonyl and haloallyl pollutants. Cyclic voltammetry experiments allowed us to propose a mechanism explaining the high catalytic activity of bismuth to reduce these families of compounds.

High activity of step sites on Pd nanocatalysts in electrocatalytic dechlorination

“…5. Based on that, the deschloroalachlor (compound B) was determined as the main product (Path 1), 27 and the alachlor degradation mechanism involves hydrogenation and the cleavage of C–Cl, C–N, and C–O bonds. A hydrogenated product compound C was identified as an intermediate of alachlor (Path 2).…”

Bismuth coated graphite felt modified by silver particles for selective electroreduction of CO2 into formate in a flow cell

“…than the reduction potential of oxides on Bi [33] and Ag. A synergistic effect due to electronic interactions between Bi and Ag is unlikely owing to the absence of a crystal growth of Ag on Bi and to the amorphous character of deposited Ag particles, although in situ investigations would be necessary to confirm it.…”

“…For these first experiments, this home-made cell was used instead of the classical flow cell with gas-diffusion electrodes [43] since it has previously shown good performances for pollution treatment and it is well-adapted to three-dimensional porous electrode materials [29,31,33]. Since the reduction of CO 2 on bismuth in aqueous medium is known to produce formate [13], the liquid phase was analyzed by ion chromatography (Fig.…”

“…In the pursuit of our investigations on the modification of graphite felts and their use in depollution processes [29][30][31], Bi coated graphite felts with high surface area and good stability [32] were prepared and their high catalytic activity toward the reductive dechlorination of chloroacetamides was highlighted [33]. Herein, Bi modified graphite felts were used in a flow system for CO 2 reduction.…”

“…The electrodes were pre-treated in the flow cell by electroreduction at -1.1 V SCE until the current was constant (for 1-2h) in 0.1 mol L -1 Na 2 SO 4 and then washed with ultrapure water. This pre-treatment was necessary to eliminate oxides formed at the surface of Bi electrode [33]. The 0.5 mol L -1 KHCO 3 solution was saturated with CO 2 for 30 min before to be pumped through the electrochemical cell.…”