Remediation of copper and lead contaminated sediments using iron-based granule biochar: mechanisms and enzyme...

In recent years, there has been a growing concern about heavy metal contamination in sediments. In this study, iron-based granular biochar (MGB) is prepared to remediate Cu and Pb contaminated sediments. Characterizations via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that the rough surface of MGB with abundant pore structures and a large number of oxygen-containing functional groups that facilitate stabilization of Cu and Pb in sediments. Potential mobility and bioavailability of Cu and Pb are investigated using BCR sequential extraction in the 35 day remediation experiment. The XPS results indicate that FeOOH and C-OH play a crucial part in stabilizing heavy metals. Large affinity of FeOOH for Pb allows it to occupy a proportion in F₂ while C-OH is attractive to Cu. Changes of pH, organic matter (OM), and available phosphorus (AP) in sediments after adding MGB as well as the relationship between changes and the stable solidification of Cu and Pb are explored. The stable solidification of heavy metals effectively reduces the available phosphorus in sediments. Magnetic and particle properties of the material are used to reduce the impact of MGB aging on sediment environment and separate it from the remediated sediment. Finally, 3% of MGB significantly enhanced the sediment catalase activity in the biological enzyme activity experiment. All findings indicate that MGB is a green and environmentally friendly sediment remediation material with satisfactory potential in synergistically stabilizing heavy metals and phosphorus.Highlights The complexation of FeOOH with Pb on the surface of MGB fixes it to the reduced stateThe C-OH on the surface of MGB is more attractive to Cu than PbMGB effectively mitigates the release of bioavailable phosphorus from sediments to overlying water.