Value-added resource utilization of petroleum-contaminated soil as heavy metal adsorbent by ball milling with iron oxide and pyrolysis

This research developed an innovative strategy to concurrently achieve efficient remediation of PCS and high-value resource utilization of the remediated soil.

The combined treatment method of Fe₃O₄-assisted ball milling pretreatment and oxygen-limited pyrolysis was used to treat PCS and convert it into Fe-loaded carbonized soil (Fe-CS) to adsorb heavy metals in wastewater. The thermodynamic and kinetic models were used to fit the adsorption capacity and behavior of Fe-CS. The adsorption mechanism of heavy metals was analyzed and the contribution of each material component to heavy metal adsorption was quantified.

The obtained Fe-CS has a high and rapid adsorption capacity for heavy metals and shows good magnetic properties. Both residual total petroleum hydrocarbon (TPH) and dissolved organic matter in the Fe-CS were removed with high efficiency. The maximal adsorption capacities of lead, copper, zinc, and cadmium ions are 888.79, 69.33, 77.52, and 47.37 mg/g, respectively. The heavy metals adsorbed in Fe-CS are mostly bound to carbonates, followed by bound to iron-manganese oxides and organic matters. The adsorption mechanism of Me²⁺ by Fe-CS mainly includes carbonate binding, complexation by metal oxides and oxygen-containing functional groups, and π coordination of unsaturated bond.

The Fe₃O₄-assisted ball milling pretreatment significantly improves the heavy metal adsorption performance of carbonized soil derived from PCS treated by pyrolysis, which significantly improves the resource utilization value of the remediated soil, and has good application potential in PCS treatment.