Optimizing biochar via microwave irradiation for phyto-stabilization of heavy metals through chili plants: a novel approach for sustainable bioremediation

Heavy metal pollution from industrial wastewater poses significant threats to agricultural productivity and human health, with global cropland contamination affecting 14–17% of areas. This study evaluated microwave-irradiated sugarcane biochar (BC) for enhancing Phyto stabilization in Capsicum annuum L. exposed to synthetic wastewater (WW) containing chromium (Cr), lead (Pb), and copper (Cu). Biochar prepared at 700 °C (0, 2, 5, 10 g) subjected to microwave irradiations for 0, 30, 60 and 90 s for 1 and 2 h’ adsorption batch experiments. The highest adsorption was achieved at 60s with irradiated BC 10 g in 2 h’ experiment where more than 80% Pb, Cu and Cr was removed. This Optimized BC (60s) doses (0, 1, 5 g/kg soil) were integrated into pot experiment with wastewater concentrations (0, 25, 50, 100%). Results indicated 75.5% reduction in leaf dry biomass at 100% wastewater without BC, mitigated by 73.1% increase with 5 g/kg BC; metal uptake decreased 18.4–25.0%; photosynthetic pigments rose 24.4–66.4%; oxidative stress markers (MDA, H2O2) declined 57.8–60.6%; antioxidants surged 631.2–686.9% under stress but balanced with amendment. PCA and correlations confirmed BC’s role in decoupling stress-growth tradeoffs, offering a sustainable, low-cost remediation strategy for contaminated agroecosystems.