KHCO3 activated biochar supporting MgO for Pb(II) and Cd(II) adsorption from water: Experimental study and DFT calculation analysis

Zhengyuan Feng; Nan Chen; Tong Liu; Chuanping Feng

doi:10.1016/j.jhazmat.2021.128059

KHCO₃ activated biochar supporting MgO for Pb(II) and Cd(II) adsorption from water: Experimental study and DFT calculation analysis

J Hazard Mater. 2022 Mar 15:426:128059. doi: 10.1016/j.jhazmat.2021.128059. Epub 2021 Dec 9.

Authors

Zhengyuan Feng¹, Nan Chen¹, Tong Liu¹, Chuanping Feng²

Affiliations

¹ School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China.
² School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, PR China. Electronic address: fengcp@cugb.edu.cn.

PMID: 34920220
DOI: 10.1016/j.jhazmat.2021.128059

Abstract

A new strategy that simultaneous use of KHCO₃ activated biochar and nano-MgO incorporation for Pb²⁺ and Cd²⁺ removal from water was raised. After activating by KHCO₃, the BC showed a higher surface area and could carry more MgO nanoparticles the BC owned. The synthesized MgO-K-BC had a large adsorption capacity for Pb²⁺ (1625.5 mg/g) and Cd²⁺ (480.8 mg/g). Multiple characterization and comparative test have been performed to demonstrate that ion-exchange, precipitation, and complexation are the main mechanisms for Pb²⁺ and Cd²⁺ removal by MgO-K-BC. In order to further explore the adsorption mechanism in-depth, the density functional theory (DFT) calculation combined with experimental results were performed. The O-top of MgO was the most stable adsorption site for Pb²⁺/Cd²⁺ adsorption compared with other adsorption sites (Mg-top, bridge, and hollow). In addition, the results of charge density maps and projected density of state (PDOS) showed that the overlap of electron cloud and orbits between MgO and Pb²⁺ were denser than Cd²⁺, indicating that MgO-K-BC had a stronger affinity for Pb²⁺ than Cd²⁺, so that, MgO-K-BC had a higher adsorption capacity for Pb²⁺ than Cd²⁺. This work provides a deep understand of the mechanism for heavy metals adsorption by metal oxide and a practical and theoretical guidance for adsorbent preparation with high adsorption ability for heavy metal.

Keywords: Biochar; Density functional theory; KHCO(3); MgO; Pb(2+) and Cd(2+).