Desorption of calcium-rich crayfish shell biochar for the removal of lead from aqueous solutions

In this study, crayfish shell was pyrolyzed at 600 °C to obtain a calcium-rich biochar (CS600). The biochar was saturated with Pb2+ in batch adsorption experiment. Six desorption reagents including HCl, HNO3, H2SO4, NaOH, EDTA and EDTA-2NaCa were then used to desorb Pb2+ from the post-adsorption CS600 to determine the desorption mechanism. Lead adsorption experiments were performed to determine the adsorption capacity of the regenerated CS600. HCl, HNO3, EDTA and EDTA-2NaCa presented good desorption effect with desorption rates all over 80%. Most of the regenerated biochars lost their lead adsorption ability due to the destruction of CaCO3 mineral on their surface. Only the one desorbed by EDTA-2NaCa retained a preferable lead adsorption capacity. EDTA-2NaCa thus is a promising desorption reagent of CS600 for the removal of lead from aqueous solutions.