Remediation and resource utilization of petroleum-contaminated soil by pyrite-assisted pyrolysis as bifunctional materials to adsorb heavy metal and activate peroxymonosulfate oxidation

Abstract

Petroleum-contaminated soil (PCS) requires not only efficient remediation technology but also economically viable reuse strategy of remediated soil with vast volume. This study developed a pyrite-assisted pyrolysis to convert PCS into a bifunctional material for the adsorption of heavy metal and the activation of peroxymonosulfate (PMS) oxidation. Adsorption isotherm and kinetic model fitting by Langmuir and pseudo-second-order well clarified the adsorption capacity and behavior of carbonized soil (CS) loaded with sulfur and iron (FeS@CS) for heavy metals. The theoretic maximum adsorption capacities of Pb2+, Cu2+, Cd2+, and Zn2+ by Langmuir model were 415.40, 80.25, 61.55, and 30.90 mg/g, respectively. The main adsorption mechanism includes sulfide precipitation, co-precipitation and surface complexation by iron oxides, and complexation by oxygen-containing functional groups. When the dosage of FeS@CS and PMS were both 3 g/L, the removal rate of aniline reached 99.64 % in 6 h. After five cycles of reuse, the aniline degradation rate was still as high as 93.14 %. The non-free radical pathway dominated in CS/PMS and FeS@CS/PMS systems. The electron hole was the primary active species in the CS/PMS system, which promoted aniline degradation by accelerating direct electron transfer. In comparison with CS, the surface of FeS@CS contained more iron oxides, oxygen-containing functional groups, and oxygen vacancies, making 1O2 the primary active species in the FeS@CS/PMS system. This study proposed a new integrated strategy for the efficient remediation of PCS and value-added reutilization of remediated soil.