Enhanced selective removal of Pb(II) by modification low-cost bio-sorbent: Experiment and theoretical calculations

Removal of Pb(II) from water is an important issue for improving water quality. However, the use of costeffective and more environmentally friendly adsorbents to achieve highly-efficient adsorption capacity is still a challenge. A novel bio-sorbent (PP-DBD) is developed by functionalizing pomelo peels to remove Pb(II) in water. PP-DBD achieves the enrichment of Pb(II) (adsorption amount of 443.51 mg/g and removal rate of 99.98%) after 2 h and exhibits good selectivity and reusability (6 cycles). Isothermal studies show that adsorption is an irreversible process with positive synergism of multiple sites, and a active site has the ability to adsorb 1.29 Pb(II). The kinetics indicates that adsorption is chemisorption and the rate-limiting step is surface diffusion. The thermodynamic study reveals that the adsorption of Pb(II) is enhanced at higher temperatures by a spontaneous process. This study also shows that hydroxyl sites have a better affinity and easier charge transfer capacity to Pb(II) than amino sites on PP-DBD by DFT and FMOs calculations. In conclusion, PP-DBD is a promising adsorbent for the removal of Pb(II) in aqueous solution.