Mechanochemical Remediation of Lindane-Contaminated Soil Via a Planetary Ball Milling: Contribution of Cao

Abstract

In this study, lindane contaminated soil was remediated by using a planetary ball milling, and CaO additive was employed for the effective degradation of POPs (Persistent Organic Pollutants) during the mechanochemical process. A Hertzian theory based mathematics model was proposed to simulate the trajectory of milling ball in a planetary ball mill and the local energy transfer during a planetary operation at the disk rotation velocity of 150~250 rpm. Besides, the influence of different parameters on lindane removal in soil was investigated, whose results showed that disk rotation velocity and reagent-to-soil ratio present positive effect while soil moisture, initial concentration, and treated amount demonstrated negative influence. The mechanochemical method presents a high degradation performance under an initial concentration of 500 ppm and 3wt.% CaO addition when the disk rotation velocity of 250 rpm was used. Active species generated by ball collision at presence of CaO, in particular superoxide (·O2–) demonstrated an significant behavior to participate the lindane conversion. Combined with GCMS and XPS analysis, the proposed model could gain insight into the process of mechanochemical remediation from physical and chemical point of views, which indicated that the process mainly consists of 4 main steps, i.e., mixing, inducing, chemical reaction, and structure destruction.

Keywords: Lindane contaminated soil, Mechanochemical, Ball motion, Numerous model