Metal-organic frameworks (MIL-101) decorated biochar as a highly efficient bio-based composite for immobilization of polycyclic aromatic hydrocarbons and copper in real contaminated soil

Real-contaminated soils are a significant source of combined polycyclic aromatic hydrocarbons and potentially toxic elements, which call for special methods of immobilization. Herein, for the first time, Fe-based metal-organic frameworks (MIL-101(Fe)) were composited with biochar to use as an amendment to a real highly contaminated soil in dynamic column leaching experiments. In this regard, MIL-101(Fe) was successfully mounted on the surface of rice husk biochar (RBC) to create a composite (RBC-MIL). Response surface methodology was used to model Cu contents in the leachate by considering two independent parameters: sorbent to soil mass ratio and leaching time. The effectiveness of Cu immobilization was observed to be improved in the presence of 3% RBC-MIL and a leaching period of two days with a minimum concentration of 0.2 mg L-1. According to the Tessier's chemical fractionation findings, RBC-MIL remarkably eliminated the acid soluble fraction of Cu by deploying it in the residual fraction. The composite was more effective at polycyclic aromatic hydrocarbon retention by having a capacity of 15.70 μg g-1, as opposed to RBC, which had a capacity of 4.86 μg g-1. Overall, our results demonstrate that MIL-based biochar composite can be utilized as advanced amendments for remediating real contaminated soil.