Controllable construction of an interpenetrating FeC2O4/amorphous SiO2 composite derived from copper smelting slag for efficient photocatalytic degradation of antibiotics

The construction of highly active photocatalysts featuring the merits of high quantum efficiency and superior stability from solid wastes for the photocatalytic degradation of organics remains a great challenge. Herein, an acid leaching and in situ self-assembly strategy was proposed to engineer a series of FeC2O4/SiO2 amorphous composites with a Si-O-Fe bridged interpenetrating structure, using copper smelting slag as the only source of Fe and Si. The loaded porous amorphous SiO2 creates new charge transfer states within the FeC2O4 crystal, and the formed Si-O-Fe bond acts as an electron conduction bridge, extensively promoting charge separation and utilization. The alpha-FeC2O4 with wider layer spacing was generated under high temperature, which can provide smoother channels for charge transfer. Thus, alpha-FeC2O4 with higher Si content (alpha-FOD/SiH) showed excellent photocatalytic activity, achieving a chlortetracycline hydrochloride removal rate of 91.9 % within 120 min, which is 16.7, 3.8 and 2.0 times faster than copper smelting slag, alpha-FOD and (3-FOD/SiH, respectively. The composite also exhibited remarkable structural stability, with the chlortetracycline hydrochloride removal rates remaining above 85.1 % after five consecutive cycles, ascribed to the interpenetrated SiO2 structure and the formation of soluble [Fe3+-(C2O4 2-)2] complexes, which greatly reduce iron ions release and prevent the formation of Fe(III) oxide/hydroxide passivation layers. This study provides a new idea for synthesizing highly active and stable FeC2O4 catalysts through a "treat the wastes with wastes" strategy.