The enhanced thermolysis of heavy oil contaminated soil using CO₂ for soil remediation and energy recovery

The enhanced thermolysis of heavy oil contaminated soil using CO₂ as reaction medium for the simultaneous soil remediation and energy recovery was investigated. To avoid any complexities arising from the heterogeneous matrix of soil, heavy oil contaminated soil was artificially mimicked by means of homogenizing sand and bunker C (the mass ratio of sand to oil was adjusted as 10). The TGA (thermo-gravimetric analysis)/DTG (differential thermogram)/DSC (differential scanning calorimeter) tests of bunker C oil in N₂ and CO₂ revealed that all physical aspects ruling mass loss, thermal degradation rate, and energy input were not affected by reaction medium (CO₂). However, all pyrogenic products were noticeably modified in the thermal degradation of bunker C oil contaminated soil in the CO₂ environment under the ambient pressure. In detail, shifting carbon distribution from the liquid products to the gaseous products (syngas) in the presence of CO₂ was observed. Also, the thermal degradation of bunker C oil contaminated soil led to carbon fixation onto soil, but the surface morphologies of charring material was modified in the presence of CO₂. Considering that no leaching of any chemical species from charring material, pyrolysis of heavy oil could be a viable option to remediate and stabilize heavy oil contaminated soil while recovering energy. Employing CO₂ as reaction medium in the thermolysis of heavy oil contaminated soil could provide a strategic means for the soil remediation contaminated with organic pollutants by means of modifying all pyrogenic products without an additional energy input.