Energy-Optimized Degradation of 2,4,6-Trinitrotoluene in Water via Sono-Photo-Fenton-like Process and nZVI

This work optimizes the energetic performance of 2,4,6-trinitrotoluene (TNT) abatement in water using a sono-photo-Fenton-like (SPF) process coupled with nano zero-valent iron (nZVI). A response–surface methodology (RSM) with a five-level central composite design (CCD) was applied to concurrently minimize specific energy consumption (SEC) from ultrasound (US) and UV irradiation while maximizing TNT removal. The optimal conditions were US power 80 W for 2 min and UV power 10 W for 6 min, yielding 73.95% TNT removal with SEC = 101.19 kWh kg−1 TNT removed. The analysis of variance (ANOVA) test revealed that US power had the greatest effect on removal efficiency, whereas UV and US exposure times predominantly influenced SEC. Relative to the other Fenton-like configurations examined, the optimized SPF achieved superior removal at lower SEC and enabled enhanced iron recovery compared with photo-Fenton process using Fe2+. When applied to actual “yellow” wastewater, the optimized SPF again outperformed the photo-Fenton process using Fe2+, reducing SEC from 380.77 to 252.60 kWh kg−1 and increasing treatment efficiency. The high-power/short-duration US paired with a low-power/short-duration UV regime provides a favorable efficacy–energy trade-off and supports pilot-scale deployment.