Pre-embedded strategy for anti-NOM poisoning performance of palladium nanoparticles in electrocatalytic dechlorination

Abstract

Electrocatalytic hydrodechlorination (EHDC) represents a sustainable approach to detoxifying the chlorinated organic pollutants (COPs). However, electrodes often suffer from fouling due to the ubiquitous natural organic matters (NOM) in surface water bodies. Herein we demonstrated that pre-mixing humic acid (HA) with palladium nanoparticles (Pd NPs) is an ingenious approach to address this issue. The introduction of HA improved dispersion of Pd NPs, enhanced surface hydrophilicity to promote H* generation, and increased electrostatic repulsion and steric-hinerance against NOM in solution. As a result, the as-synthesized HA_0.2-Pd electrode exhibits significantly improved EHDC performance and anti-NOM poisoning ability. In the batch experiment, the HA_0.2-Pd NPs achieved removal efficiencies of 91.3 and 80.8 % respectively, for treating 50.0 mg L⁻¹ of 2,4-dichlorophenol (2,4-DCP, a probe COP) from contaminated water in the absence or presence of 20 mg L⁻¹ HA (representative of NOM) at -0.85 V vs. Ag/AgCl. Compared to that, the pure Pd/C electrode experienced a marked efficacy decline from 82.9 to 56.5 % in the presence of HA. Moreover, the HA_0.2-Pd/C electrode maintained a steady efficiency above 92.0 % over 12 h EHDC in a continuous-flow cell, while only 60.0 % for the Pd/C electrode. When subjected to contaminated natural water, the HA_0.2-Pd/C electrode afforded an EHDC efficiency of 75.4 %, significantly surpassing the 39.4 % efficiency of Pd/C electrode.