Abstract

Oil contamination poses environmental risks due to its persistence, toxicity, and tendency to migrate through porous media. In peatlands, oil-saturated peat moss can act as a secondary pollution source through gradual hydrocarbon leaching, highlighting the need for stabilization approaches that reduce contaminant mobility. This study evaluates NaOH-modified biochar (MBC) as a sustainable amendment for stabilizing oil-contaminated peat moss under variable environmental conditions. MBC and other carbonaceous sorbents were applied at different treatment conditions to assess their influence on petroleum hydrocarbon immobilization. Material characterization was conducted to identify key differences in properties relevant to sorption. Toxicity Characteristic Leaching Procedure tests were performed to evaluate hydrocarbon mobility and resulting leachate quality. Results showed that increasing sorbent dosage substantially reduced oil release, with MBC exhibiting higher efficiency than unmodified commercial biochar at comparable levels. pH had only a minor effect, while moderately increasing temperature resulted in a modest improvement in removal. Statistical modelling demonstrated good agreement with experimental data and identified sorbent dosage as the most influential factor controlling oil reduction in the leachate. Optimization analysis indicated that high removal efficiency could be achieved within a practical application range, with mildly alkaline conditions and moderate temperatures identified as optimal. Overall, the findings suggest that modified biochar can help stabilize oiled peat moss, offering practical value in settings where intrusive remediation approaches are limited.