Abstract: In order to achieve efficient remediation of arsenic(As) contaminated soil, the suspension of iron nanoparticles (EL-nFe) was prepared by eucalyptus leaves extract. The sorption capacities of EL-nFe for As(III) and As(V) were investigated. Chemical methods were further used to study the immobilization effects of severe As-contaminated soil by EL-nFe. The results showed that the adsorption process of As(III) and As(V) by EL-nFe could be well described by the pseudo-first-order and Langmuir isothermal adsorption model. The maximum adsorption capacities of EL-nFe for As(III) and As(V) were 8.08 and 24.68 mg/g, respectively. The soil after application of EL-nFe significantly reduced the leachability and bioavailability of soil As. The extraction of As by SPLP and the extraction of bioavailable As by KH₂PO₄ decreased by 33.26%~52.42% and 6.57%~14.21%, respectively. At the same time, the result of soil sequential extraction showed that EL-nFe promoted the transformation of soil soluble As to the low bioavailability of residual As, which improved the degree of stabilization of As in the soil. Therefore, EL-nFe had a good immobilization effect on soil As and the cost was low, which can be used as a good passivation agent for severe As-contaminated soil.

Key words: green synthesis, iron nanoparticles, arsenic, in-situ immobilization