Biochars preparation from waste sludge and composts under different carbonization conditions and their Pb(II) adsorption behaviors

: This study prepared nine biochars from three biomass wastes (CompostA, CompostB and Sludge) through different carbonization conditions. The adsorption behaviors and mechanisms of these biochars for Pb(II) were tested by a series of adsorption experiments and properties analysis. Preliminary experiments showed biochars obtained from CompostA and Sludge had better Pb(II) adsorption performance than CompostB and the optimum carbonization temperature of CompostA was lower than that of Sludge. Adsorption experimental results demonstrated that CompostA600 (numbers represent carbonization temperatures) had the largest adsorption capacity of 57.34 mg/g for Pb(II) among samples, followed by Sludge800 of 50.00 mg/g. The kinetic adsorption of CompostA600 and Sludge800 were both described by the Nth-order model very well. Pb(II) adsorption of CompostA600 most appropriately followed the Langmuir-Freundlich model and the Redlich-Peterson model. Characterization analysis suggested diverse carbonization temperatures and precursors caused discrepant pore size distributions and element contents, which determined the deposition of lead compound crystals on materials. This study examined the effects of raw materials and carbonization temperatures on obtained biochars and provided an inexpensive and environmental-friendly way for biochar sorbent preparation and heavy metal wastewater treatment.