On-demand delivery of nanoheaters under electromagnetic field for enhanced thermal desorption of soil organic contaminants

Herein, we present a transformative approach integrating thermosensitive poly(N-isopropylacrylamide)-functionalized nanoscale zero-valent iron (P-nZVI) with electromagnetic-field (EMF) activation. In naphthalene (Nap)-contaminated soil, 5 g P-nZVI heats soil from 25.0 to 41.5 °C and reduces Nap from 251.1 to 130.3 mg kg−1 within 120 min, whereas nanoscale zero-valent iron (nZVI) produces an 11.6 °C rise and 155.0 mg kg−1 residual Nap, corresponding to a 3.0-fold higher iron-normalized heating capacity for P-nZVI.

Even at comparable bulk temperatures, P-nZVI achieves greater desorption, consistent with thermo-responsive redistribution toward soil organic matter rich microdomains. Column experiments show that segment-specific EMF modulation, based on matrix-dependent deceleration or promotion of P-nZVI transport, enables migration through uncontaminated zones and retention in contaminated zones, increasing target-zone delivery to 44-45% and Nap desorption to 39-47% versus 5-16% for nZVI controls, while yielding a preliminary energy-use estimate of approximately one-third that of conductive heating under reference assumptions.</p>