Construction of Fe and g-C3N4 codoped magnetic bamboo charcoal for enhanced catalytic degradation of tetracycline: Mechanism, degradation pathway, and ecological toxicity.

The well-designed bamboo charcoal (BC) composite Fe-g-C₃N₄/BC with multi-active sites of FeO_x, FeN_x, and g-C₃N₄, was fabricated in-situ by calcining Fe-melamine loaded bamboo charcoal (Fe-Me-BC) under nitrogen atmosphere. The as-synthesized Fe-g-C₃N₄/BC(550) exhibited a mesoporous structure with a large specific surface area of 108.23 m²/g. The adsorption of tetracycline (TCL) on Fe-g-C₃N₄/BC(550) was calculated following the Langmuir isotherm model, and showed a maximum adsorption capacity of 19.92 mg/g. Furthermore, the pseudo-second-order kinetic model showed a good fit for the TCL adsorption process on Fe-g-C₃N₄/BC(550). The Fe-g-C₃N₄/BC(550)/H₂O₂ system exhibited excellent photo-Fenton catalytic performance in degrading TCL with a degradation efficiency reaching up to 98.9% within 5 min under visible-light. The effects of initial pH value and coexisting anions on TCL degradation were determined. As narrow band gap semiconductors, g-C₃N₄, Fe₃O₄, and Fe₂O₃ in the Fe-g-C₃N₄/BC exhibited good visible-light-driven photocatalytic activity. Moreover, photogenerated electrons could further activate H₂O₂ to produce high concentrations of ∙OH radicals. This outstanding photo-Fenton catalytic performance can be ascribed to the synergistic effect of g-C₃N₄/Fe₃O₄-Fe₂O₃/Fe_xN multi-active sites as well as the excellent adsorption ability and conductivity provided by bamboo charcoal. This work presents a convenient approach for constructing economical catalysts for environmental remediation through g-C₃N₄ and Fe-N codoped BC.