Magnetite nanoparticles for the remediation of soils co-contaminated with As and PAHs

Abstract Commercial magnetite nanoparticles (NPs) were used to immobilize As and organic pollutants, mainly PAHs, in a polluted soil. The composition, structure and morphology of the NPs were examined by means of electron microscopy, X-ray analysis, infrared spectroscopy, dynamic light scattering, thermogravimetric analysis, and magnetic property determination. To evaluate the immobilization of As and organic pollutants, soil subsamples were treated with the magnetite NPs at different doses (0.2%, 1%, 2% and 5%). The availability of As was then examined by the TCLP test and the Tessier sequential extraction procedure, whereas TPH and PAHs were measured by GC–MS. Notable results for As immobilization were achieved at a dose of 1% NPs (42.5% decrease in As, TCLP test), although the best result was obtained at the highest dose of 5% (92.3% decrease in As, TCLP test) without significant variations in As speciation. Regarding organic pollutants, a decrease in TPH and PAHs content was detected even at the lowest dose of NPs tested (49% and 89% respectively). The treatments had no negative effects on soil parameters such as soil pH and electrical conductivity. In turn, the increase in Fe availability after application of NPs was insignificant whereas soil phytotoxicity assessed by germination test was reduced. In conclusion, the use of magnetite NPs opens up new nanoremediation options to treat soils affected by both organic and metal(loid) pollution.