Nanoscale Insights into the Interaction Mechanism Underlying the Adsorption and Retention of Heavy Metal Ions by Humic Acid
ENVIRONMENTAL SCIENCE & TECHNOLOGY(2024)
Abstract
The mobility and distribution of heavy metal ions (HMs) in aquatic environments are significantly influenced by humic acid (HA), which is ubiquitous. A quantitative understanding of the interaction mechanism underlying the adsorption and retention of HMs by HA is of vital significance but remains elusive. Herein, the interaction mechanism between HA and different types of HMs (i.e., Cd(II), Pb(II), arsenate, and chromate) was quantitatively investigated at the nanoscale. Based on quartz crystal microbalance with dissipation tests, the adsorption capacities of Pb(II), Cd(II), As(V), and Cr(VI) ionic species on the HA surface were measured as similar to 0.40, similar to 0.25, similar to 0.12, and similar to 0.02 nmol cm(-2), respectively. Atomic force microscopy force results showed that the presence of Pb(II)/Cd(II) cations suppressed the electrostatic double-layer repulsion during the approach of two HA surfaces and the adhesion energy during separation was considerably enhanced from similar to 2.18 to similar to 5.05/similar to 4.18 mJ m(-2). Such strong adhesion stems from the synergistic metal-HA complexation and cation-pi interaction, as evidenced by spectroscopic analysis and theoretical simulation. In contrast, As(V)/Cr(VI) oxo-anions could form only weak hydrogen bonds with HA, resulting in similar adhesion energies for HA-HA (similar to 2.18 mJ m(-2)) and HA-As(V)/Cr(VI)-HA systems (similar to 2.26/similar to 1.96 mJ m(-2)). This work provides nanoscale insights into quantitative HM-HA interactions, improving the understanding of HMs biogeochemical cycling.
MoreTranslated text
Key words
heavy metal ions,humic acid,bindingenergy,atomic force microscope (AFM),QCM-D adsorption,DFT simulation
AI Read Science
Must-Reading Tree
Example
![](https://originalfileserver.aminer.cn/sys/aminer/pubs/mrt_preview.jpeg)
Generate MRT to find the research sequence of this paper
Chat Paper
Summary is being generated by the instructions you defined