Insights into removal efficiency and mechanism of microwave remediation of soils contaminated with polyaromatic hydrocarbons of low molecular weight assisted by bluecoke-based conditioner

Abstract

Microwave remediation of polyaromatic hydrocarbons-contaminated soils has garnered extensive attention owing to its cost effectiveness, time saving, homogeneous heating, and low energy consumption. The prepared bluecoke-based conditioner (KHCO₃@BC) was used in this study to enhance microwave remediation and improve the naphthalene (NA) removal efficiency and soil properties. We investigated the optimal conditions, including the heating time, microwave power, bluecoke-based conditioner, initial concentration of NA, and moisture content of the soils. We evaluated the removal efficiency of NA and compared the remediation products after the addition of bluecoke, KHCO₃, and KHCO₃@BC conditioners. The results showed that the removal efficiency of NA reached 96.46% under the following optimized conditions: heating time of 20 min, microwave power of 700 W, 2 g of KHCO₃@BC conditioner, initial NA concentration of 1 wt%, and soil moisture content of 4 wt%. The KHCO₃@BC conditioner improved the contents of total K and fast-acting K during microwave remediation, and the mechanical components of the remediation soils were also optimized significantly. We proposed a feasible mechanism and evaluated the main reasons for the removal of NA from the soils based on the mechanical components of remediation soil and the remediation products, namely, gas stripping, boiling vaporization of NA, and breakage of soil grains by thermal stress.

Keywords: Contaminated soils; Microwave remediation; Polyaromatic hydrocarbon; Remediation mechanism; Removal efficiency.