Pyrolysis as a Remediation Strategy for Weathered Oil-Contaminated Soil: The Role of Minerals and Native Organic Matter

Soil contaminated by weathered oil (WO) is the most challenging and toxic type of oily sludge (OS) to remediate. Its pyrolysis behavior is significantly affected by soil composition, including minerals and natural organic matter, yet the interaction mechanism remains unclear. This study systematically investigates the influence of natural minerals and organic matter on the pyrolysis behavior of WO-contaminated soil, with a particular focus on the mechanisms of key minerals (e.g., SiO2, CaO, MgO, Fe2O3, and Al2O3) and natural organic matter, represented by humic acid (HA). The findings reveal substantial differences in the catalytic performance of various minerals during pyrolysis. MgO and CaO exhibit exceptional catalytic cracking capabilities in the mid- to high-temperature range, significantly enhancing the quality of pyrolysis-derived oil and gas fuels. Fe2O3 demonstrates superior performance at elevated temperatures by promoting aromatic stability and hydrogen production. Moreover, HA, in synergy with minerals, optimizes pyrolysis pathways, improves hydrocarbon fuel yields, and refines the characteristics of the residual materials. This study further elucidates the distribution patterns of pyrolysis products and their intricate interactions with minerals and organic matter, providing critical insights for the efficient remediation of WO-contaminated soil. These findings offer a novel perspective on the restoration and resource utilization of WO-contaminated soil while delivering valuable guidance for advancing catalytic pyrolysis technologies.