Persulfates (PS) are a mainstream oxidant used for soil remediation contaminated by organic pollutants (petroleum hydrocarbons). Nano zero-valent iron (nZVI) is a well-known activator of persulfates, with the advantages of high catalytic reaction and long-term performance. However, nZVI readily undertakes agglomeration and oxidation processes in soils and thus displays poor stability and migration potential, both of which inhibit the activation potential of nZVI. In this study, we prepared PASP-S-nZVI composite materials by conducting combined modifications of nZVI with polyaspartic acid (PASP) and sodium hydrosulfite, and carried out quartz sand column experiments of PASP-S-nZVI and remediation experiments of petroleum-contaminated soils by PASP-S-nZVI/PS. Both SEM-SDS and XPS spectra of materials showed that the PASP-S-nZVI composite materials were characteristics of nZVI with both PASP coating layer and FeSx
layer on the surface. The combined modifications resulted in reduction of total iron contents in composite materials but a notable increase in the stability of materials, due to both increases in zeta potential and specific surface area of materials. Both column experimental results and T-E model simulations showed that PASP-S-nZVI had higher mobility in the subsurface than nZVI and S-nZVI, due to notable reductions of actual single-collector removal efficiency of the composite materials by 73.5% and 62%, respectively. It was because PASP-S-nZVI had extremely low attachment efficiency, due to the PASP coating layer. The mobility of PASP-S-nZVI was dependent of particle sizes of porous medium and water pH in the subsurface. Under the optimized conditions, PASP-S-nZVI/PS efficiently removed petroleum hydrocarbons (TPHs) in soils, and the removal rate of TPHs (3 d) was 77±2% in the laboratory experiments. The pilot experiment also yielded a high removal rate of TPHs (3 d) by 53±2%, further indicating the performance of PASP-S-nZVI/PS in soils. This study indicates that PASP-S-nZVI with both improved mobility and catalytic reactivity may find its applications in soil remediation.