Interfacial engineering of a 2D/3D Bi2MoO6-ZnIn2S4 Z-scheme heterojunction for tetracycline degradation: Performance, toxicity evaluation, and sustainability insights via material flow analysis

The practical implementation of photocatalytic antibiotic treatment remains limited by insufficient integration of degradation performance, toxicity, and material sustainability evaluation. Herein, we constructed a 2D/3D Bi 2 MoO 6 -ZnIn 2 S 4 heterojunction (BMZS) via in situ anchoring of Bi 2 MoO 6 nanoplates onto ZnIn 2 S 4 microflowers to enhance interfacial charge separation under visible light. The optimised BMZS-3 achieved 94.5% tetracycline degradation (20 mg L −1 ) within 120 min at pH 7, using a catalyst loading of 0.625 g L −1 , and maintained structural stability over repeated cycles, significantly outperforming pristine Bi 2 MoO 6 (37.4%) and ZnIn 2 S 4 (48%). The Z -scheme interface promoted efficient utilisation of multiple reactive oxygen species, facilitating the transformation of TCH into lower-molecular-weight intermediates, as confirmed by scavenger studies and LC-MS analysis. To evaluate environmental safety, QSAR modelling predicted the toxicity evolution of the degradation intermediates, while microbial ( Escherichia coli ) and phytotoxicity (fenugreek) assays indicated reduced residual toxicity after treatment. Material flow analysis showed that the final BMZS product retained less than 3% of the total input mass, while purification generated 37.323 MT of wastewater and lost 4.945 MT of ethylene glycol, identifying solvent consumption as the primary sustainability hotspot. These findings highlight opportunities for process intensification and improved material efficiency, supporting the development of environmentally responsible photocatalytic systems for sustainable antibiotic wastewater treatment.