Abstract: The compaction degree is one of the main factors affecting the geo-environmental properties of arsenic (As) and antimony (Sb) co-contaminated soil stabilized by ferric salts. The effect of compaction degree on the geo-environmental properties of As and Sb co-contaminated soil stabilized by a ferric salt-based stabilizer (PFSC, polymerized ferrous sulfate-Ca(OH)2) was investigated, including unconfined compressive strength (UCS), leached concentrations of As and Sb, and hydraulic conductivity . The varied characteristics of the micro pores and the element valence in the stabilized soil with compaction degree were clarified by adopting industrial CT scanning and X-ray photoelectron spectroscopy (XPS) in the study. The leached concentration of As decreased first and then increased with the increase of compaction degree, and reached the lowest as the compaction degree was 93%. The leached concentration of Sb decreased with the increase of compaction degree, while remained constant until the compaction degree was larger than 85%. When the compaction degree increased from 75% to 96%, the UCS of the stabilized soil increased from 4.26 kPa to 43.78 kPa. As the compaction degree increased from 80% to 96%, the of the stabilized soil decreased from 1.33×10–7 m/s to 2.81×10–9 m/s. In addition, it can be observed from the industrial CT results that the porosity of stabilized soil decreased from 7.54% to 5.30% with the increase of compaction degree, hence leading to the more compactness structures of the soil. The XPS analysis of the As, Sb and Fe indicated that increasing the compaction degree of stabilized soil promoted the transformation of As(V), Sb(V), and Fe(III) to As(III), Sb(III), and Fe(II), respectively. The study mainly focused on revealing the effects of compaction degree on the geo-environmental properties of As and Sb co-contaminated soil stabilized by PFSC, which will provide a theoretical basis for the engineering application and the optimization for the operation parameters of PFSC-stabilized As and Sb co-contaminated soil.

Key words: compaction degree, arsenic and antimony co-contaminated soil, stabilization, unconfined compressive strength, leached concentration, hydraulic conductivity