Environmental fate mapping of lead-free piezoelectrics: Synergistic stress-induced leaching kinetics and multi-trophic dose-response in BFO/rGO hybrids.

Sustainable implementation of smart civil infrastructure requires replacing hazardous lead-based piezoelectrics with eco-benign alternatives. However, the environmental fate of lead-free substitutes like Bismuth Ferrite (BFO) under synergistic operational and environmental stressors remains poorly understood. This study investigates the leaching kinetics and multi-trophic ecotoxicity of BFO/rGO-epoxy nanocomposites. We implemented a safe-by-design interfacial engineering strategy using (3-aminopropyl)triethoxysilane (APTES) covalent anchoring and bio-inspired polydopamine (PDA) conformal wrapping. Composites were subjected to a 720-h Worst-Case Simultaneous Stress (WCSS) protocol involving cyclic piezo-transduction, UV photo-aging, and acidic hydrothermal weathering. Results demonstrate that unmodified composites (G2) suffer severe structural degradation, retaining less than 35% of multiferroic constituents. Conversely, the dual-modified G5 architecture maintained high morphological retention, retaining over 96% of Bi and Fe. Mathematical modeling revealed a shift in leaching kinetics from matrix-degradation-driven wash-off (n ≈ 1.0) to restricted Fickian diffusion (n < 0.45). Multi-trophic bioassays across microbial, producer, consumer, and vertebrate models confirmed that interfacial engineering effectively mitigated acute toxicity and teratogenic risks, yielding a statistically significant Synergy Factor of +18.4% (p < 0.01). This research provides a predictive framework for developing structurally stable and environmentally benign multifunctional materials, supporting the transition toward zero-pollution smart cities.