Highly adsorptive pristine and magnetic biochars prepared from crayfish shell for removal of Cu(II) and Pb(II)

Background: Biochar has attracted considerable attention as a low-cost adsorbent comprised of carbon matrix and mineral for treatment of wastewater. The main purpose of this work was to manufacture CaCO3-rich biochars using crayfish shell as feedstock for removal of Cu(II) and Pb(II) from aqueous solution. Methods: Pristine and magnetic biochars were prepared via direct pyrolysis and K2FeO4-promoted pyrolysis, respectively, and characterized by element analysis, BET, FTIR, SEM-EDS, XRD and XPS. Moreover, their adsorption capabilities toward Cu(II) and Pb(II) were investigated in aqueous solution. Findings: A large amount of CaCO3 was assembled on the pristine biochar pyrolyzed at 600 degrees C, leading to 715.10 mg/g and 1682.87 mg/g adsorption capacities for Cu(II) and Pb(II), respectively. Whereas, CaCO3 and single phase Fe3O4 were simultaneously introduced into the magnetic biochar with K2FeO4-promoted pyrolysis at 600 degrees C using 1/1 (g/g) ratio of K2FeO4 to crayfish shell, where 417.05 mg/g and 974.10 mg/g maximum adsorption capabilities were obtained for Cu(II) and Pb(II) with 29.66 emu/g saturation magnetism, respectively. Cu(II) and Pb(II) were mainly adsorbed onto the biochars as carbonates and oxides by their interaction with CaCO3 and carbon matrix. (C) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Y