Insights into the adsorption mechanism of tannic acid by a green synthesized nano-hydroxyapatite and its effect on aqueous Cu(II) removal

Wei Wei; Junsuo Li; Xuan Han; Yijun Yao; Wei Zhao; Ruiming Han; Shiyin Li; Yong Zhang; Chunmiao Zheng

doi:10.1016/j.scitotenv.2021.146189

Insights into the adsorption mechanism of tannic acid by a green synthesized nano-hydroxyapatite and its effect on aqueous Cu(II) removal

Sci Total Environ. 2021 Jul 15:778:146189. doi: 10.1016/j.scitotenv.2021.146189. Epub 2021 Mar 3.

Authors

Wei Wei¹, Junsuo Li², Xuan Han², Yijun Yao³, Wei Zhao⁴, Ruiming Han², Shiyin Li², Yong Zhang⁵, Chunmiao Zheng⁶

Affiliations

¹ School of Environment, Nanjing Normal University, Nanjing 210023, China; Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China; Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, Shenzhen 518055, China.
² School of Environment, Nanjing Normal University, Nanjing 210023, China.
³ Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
⁴ School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian, China.
⁵ Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487, USA. Electronic address: yzhang264@ua.edu.
⁶ Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, Shenzhen 518055, China; State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science & Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China. Electronic address: zhengcm@sustech.edu.cn.

PMID: 33714103
DOI: 10.1016/j.scitotenv.2021.146189

Abstract

The polyphenolic tannic acid (TA) has been widely used in the stabilization and surface modification of nanomaterials. The interaction mechanism of TA with the biogenic nano-hydroxyapatite (nHAP) and its environmental importance, however, are poorly understood. This study explored the adsorption of TA using the green synthesized, eggshell-derived nHAP and implications of this process for the removal of aqueous Cu(II) via batch adsorption experiments, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) investigations. TA adsorption by nHAP was a complex pH-dependent process and significantly correlated with TA molecule speciation and amphoteric properties of nHAP via multiple adsorption modes including surface complexation, electrostatic attraction, and hydrogen bond. The maximum TA adsorption amount was found to be 94.8 mg/g for less crystalline nHAP with lower calcination temperature. In the ternary Cu-TA-nHAP systems, TA promoted Cu(II) adsorption at pH < 5 and reduced Cu(II) uptake at pH > 5. Further studies of the effects of ionic strength and addition sequences, as well as Raman, FTIR, and XPS analyses revealed Cu(II) adsorption on nHAP was mainly dominated by inner-sphere surface complexation. These results can shed light on not only the utility of biogenic nHAP for TA and Cu(II) adsorption but also the evaluation of the effect of TA on the environmental behavior of heavy metals.

Keywords: Adsorption; Cu(II); Nano-hydroxyapatite; Surface complexation; Tannic acid.