Spectroscopic Investigations and Density Functional Theory Calculations Reveal Differences in Retention Mechanisms of Lead and Copper on Chemically-Modified Silicon-Rich Biochars
Journal
SSRN
ISSN
15565068
Date Issued
2022-02-24
Author(s)
Li, Jianhong
Zheng, Lirong
Chen, Dongliang
Wu, Zhipeng
Sun, Chenghua
Bolan, Nanthi
Zhao, Hongting
Peng, An-An
Fang, Zheng
Zhou, Rongfu
Liu, Guobin
Bhatnagar, Amit
Qiu, Yong
Wang, Hailong
Abstract
A better understanding of different retention mechanisms of potentially toxic elements (PTEs) by biochars during the remediation of contaminated sites is critically needed. In this study, several synchrotron-based spectroscopic techniques were used to investigate lead (Pb) and copper (Cu) retention mechanisms on silicon-rich coconut-fiber biochar (CFB) and ammonia, nitric acid and hydrogen peroxide modified CFB (i.e., ACFB, NCFB and HCFB). Results showed that binding-sites on ACFB and NCFB were more efficient compared to that on CFB and HCFB to bind Pb/Cu. The percentage of Pb species as Pb(C2H3O2)2 increased from 22.2% (Pb-loaded CFBs) to 47.4% and 41.9% on Pb-loaded NCFBs and HCFBs, while the percentage of Cu(OH)2 and Cu(C2H3O2)2 increased from 5.8% and 32.8% (Cu-loaded CFBs) to 41.5% and 43.4% (Cu-loaded NCFBs) and 27.1% and 35.1% (Cu-loaded HCFBs), respectively. Due to their similar atomic structures of Pb/Cu, Pb(C2H3O2)2/Pb-loaded montmorillonite and Cu(C2H3O2)2/Cu(OH)2 were identified as the predominant Pb/Cu species observed in Pb- and Cu-loaded MCFBs. Density functional theory calculations suggested that silicate and the synergistic effect of hydroxyl and carboxylic-groups on MCFBs were highly efficient in Pb retention, while azido-groups and/or carboxylic-groups played major roles in Cu retention. These results provide novel insights into the PTE retention mechanisms of MCFBs.
Subjects
Binding sites
Metal retention
Modified biochar
Potentially toxic elements
Synchrotron radiation
Publisher
SSRN
Type
preprint