Enhanced hydrodechlorination of p-chloronitrobenzene by a GAC-Fe-Cu ternary micro-electrolysis system: Synergistic effects and removal mechanism

A ternary micro-electrolysis system composed of a granular activated carbon (GAC) supported Fe0 and Cu0 nanocomposite (GAC-Fe-Cu) was synthesized for the removal of p-chloronitrobenzene (p-CNB). GAC-Fe-Cu exhibited excellent reusability and stability based on the stably anchored nanoparticles and the inner tailored Fe0 with persistent activity. A two-stage reaction revealed the simultaneous adsorption and degradation in the process of p-CNB removal, and the iron corrosion reaction mainly dominated the latter. A stepwise reduction of p-CNB was observed, where the main intermediates, such as p-chloroaniline (p-CAN) and aniline (AN), were formed in sequence. Furthermore, the mechanism of p-CNB removal could be explained by the synergistic effects of GAC-Fe-Cu. p-CNB could be rapidly adsorbed onto the surface of the system for in situ reduction. The conductive GAC cathode pre-accepted the released electrons from the Fe0 anode, and transferred them to the Cu0 cathode. Then, the electron-rich Cu0 cathode could intensively release electrons to form the “point discharge” phenomenon, which possessed strong reducing power to dramatically increase the hydrodechlorination rate of p-CAN. Additionally, the –C–OH and –COOH on the GAC surface could absorb p-CAN through electrostatic interactions with the amine group (–NH2), facilitating the selectivity of p-CAN dechlorination.