Fe/Fe₃C@CNTs anchored on carbonized wood as both self-standing anode and cathode for synergistic electro-Fenton oxidation and sequestration of As(III)

Considering the hypertoxicity and poor affinity of arsenite toward sorbent materials, development and construction of effective purification technologies are of vital importance for efficient conversion of As(III) to As(V) and concomitant capture of As(V). Herein, an electrochemical integrated system for As(III) removal is developed using 3D hierarchically porous hybrid monolith electrodes, constructed by Fe/Fe₃C nanoparticles (NPs) and clusters encapsulated in N,O-codoped carbon nanotubes (CNTs) anchored on carbonized wood (CW) framework (denoted as Fe/Fe₃C@CNTs/CW). Remarkably, the heterogeneous electro-Fenton reaction on the cathode promotes the oxidation of As(III) into As(V); while the electro-sorption on the anode is conducive to the subsequent arsenic immobilization. Under the optimized conditions, trace As(III) species (1 ppm) can be efficiently removed within 90 min, in which the residual arsenic concentration is below the threshold value (10 ppb) in the drinking water recommended by the World Health Organization (WHO). Significantly, the saturation electro-sorption capacity of the anode materials is approximately 10 times higher than that of physicochemical adsorption. The developed Fe/Fe₃C@CNTs/CW electrode exhibits not only superior structural stability due to the protective action from the carbon chainmail but also satisfactory recycling capability with negligible decay in removal efficiency after five cycles, signifying its huge potential in the future sustainable remediation application.