Adsorption of Heavy Metal Pb(II) in Dredged Sediment Using Different Biochar Materials

China generates a significant amount of dredged sediment annually, much of which is contaminated with heavy metals. This study investigates the adsorption of Pb(II) from water and dredged sediment using different biochar materials, including BC and HC. The results show that the maximum adsorption of Pb(II) by BC-350-2h and HC-350-1:2-0.5h was 9.90 mg/g and 9.95 mg/g, respectively, with adsorption efficiencies of 99.0% and 99.5% for a 50 mg/L Pb(II) solution at a dosing concentration of 5 g/L, under 10 min of adsorption. BC-350-2h effectively adsorbed Pb(II) from dredged sediment, with no detectable Pb(II) concentration in the liquid fraction of the dredged sediment after 20 days. However, when the adsorption time increased, a small portion of Pb migrated into an unstable form, probably due to its binding to dissolved organic carbon (DOC), which dissolves out of the biochar. Microbial activity may also contribute to the degradation of DOC into small-molecule dissolved organic carbon (SDOC), thereby reducing the binding strength of biochar to DOC, which adsorbs Pb(II). This study highlights the importance of considering the effects of DOC and the long-term stability of biochar when used to treat contaminated dredged sediment.