压实度对铁盐稳定化砷、锑污染土特性的影响及机制研究

压实度是影响铁盐稳定化砷(As)、锑(Sb)污染土环境岩土工程特性的主要因素之一。通过测定不同压实度铁盐稳定剂(PFSC)稳定化As、Sb污染土无侧限抗压强度(UCS)、As和Sb浸出浓度、渗透系数kw,研究了压实度对PFSC稳定化As、Sb污染土环境岩土工程特性的影响规律。通过工业CT扫描、X射线光电子能谱(XPS)明确了稳定化土微观孔隙特征、元素价态随压实度的变化规律。As的浸出浓度随着压实度的提高先降低后略微上升,压实度为93%时,As的浸出浓度最低;Sb的浸出浓度随着压实度的提高而降低,压实度大于85%后趋于平稳。压实度由75%提高至96%,稳定化土UCS由4.26 kPa增大至43.78 kPa。压实度由80%提高至96%,稳定化土k_w由1.33×10^–7 m/s降低至2.81×10^–9 m/s。工业CT扫描结果表明,随着压实度的提高,土体逐渐紧实,土体孔隙度由7.54%降低至5.30%。As、Sb和Fe的XPS分析结果表明,压实度增高促使As(Ⅴ)、Sb(Ⅴ)和Fe(Ⅲ)分别向As(Ⅲ)、Sb(Ⅲ)和Fe(Ⅱ...

Mechanisms analysis of the effect of compaction degree on the properties of arsenic and antimony co-contaminated soil stabilized by ferric salts

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);) was investigated,including unconfined compressive strength(UCS), leached concentrations of As and Sb, and hydraulic conductivity k_w. 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 k;of the stabilized soil decreased from 1.33×10^-7m/s to 2.81×10^-9m/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.