Construction of ternary Bi2O3/biochar/g-C3N4 heterojunction to accelerate photoinduced carrier separation for enhanced tetracycline photodegradation

As an efficient means to facilitate separation of photoinduced charge carriers, Z-scheme heterojunction photocatalysts have been constructed recently for degradation of antibiotic residues. In this work, an innovative ternary Bi2O3/biochar/g-C3N4 Z-scheme heterojunction was prepared as a promising photocatalyst for efficient photodegradation of tetracycline, of which conductive biochar was introduced to boost the separation rate of photoinduced carriers. The as-prepared Bi2O3/biochar/g-C3N4 heterojunction delivered a high visible-light-driven photodegradation efficiency of tetracycline at 86.7% in 30 min with an apparent kinetic constant at circa 0.0610 min−1, which was larger by circa 6, 3, and 2 times, respectively, than those of pure g-C3N4 (0.0104 min−1), binary biochar/g-C3N4 (0.0223 min−1), and binary Bi2O3/g-C3N4 (0.0393 min−1). Such Bi2O3/biochar/g-C3N4 heterojunction was demonstrated excellent stability upon recycled usage. The free radical quenching testing and ESR results verified that superoxide (•O2–) and hydroxyl (•OH) radicals played a significant role in the photodegradation reaction of tetracycline, and the transfer process of photoinduced charge carrier was proposed as a Z-scheme mechanism. This research offers a potential way to construct high-performance Z-scheme heterojunction photocatalysts for practical wastewater treatment.