Multi-scale modeling of natural organic matter–heavy metal cations interactions: Aggregation and stabilization mechanisms

Molecular Dynamics Simulation of the Interaction within the Carboxymethyl Cellulose-Modified Montmorillonite Lamellae at Aggressive CuCl2 Concentrations

“…These observations further supported that the carboxyl groups of CMC served as effective oxygen-containing functional groups in the formation of cation bridges with adsorbed Cu 2+ on the MMT surface. Analogous divalent cation bridge phenomena have been reported in various systems, such as the adsorption of anionic per- and polyfluoroalkyl substances (PFAS), Magnafloc, methyloic soil organic matters (SOMs), natural organic matters (NOMs), as well as polycarboxylates by MMT laminae via Ca 2+ bridges. ,,,, Additionally, multivalent heavy metal cation bridges, involving Cd 2+ , Pb 2+ , Zn 2+ , and Eu 3+ , were substantiated to facilitate the NOMs’ aggregation through carboxyls …”

“…When CuCl 2 reached 800 mM, the peaks of the bimodal distribution became sharper with a value of 1.61 nm –3 compared to those of 400 mM. The increased sharpness could be attributed to the strong electrostatic screening and the formation of Cu 2+ cation bridges between the MMT basal surface and carboxyls of CMC chain. − …”

“…11,19,41,54,56 Additionally, multivalent heavy metal cation bridges, involving Cd 2+ , Pb 2+ , Zn 2+ , and Eu 3+ , were substantiated to facilitate the NOMs' aggregation through carboxyls. 47 Radial functional groups that was inferred, but not yet proved, to effectively bind with Cu 2+ and MMT, namely, carboxylic oxygen, alcoholic oxygen, carbinol oxygen, glucose oxygen, and bridging oxygen (connecting two glucose rings, Table S1). 57 The RDF and CN of Na + and Cu 2+ with the central atoms of these five types of oxygens (Figure 3) determined the most effective oxygen-containing functional groups for guiding future organoclay design.…”

Nanoscale Insights into the Interaction Mechanism Underlying the Adsorption and Retention of Heavy Metal Ions by Humic Acid

“…Typically, NOM has a complex molecular structure with a variety of functional groups, such as carboxyl, hydroxyl, phenol, and amine, which enable versatile intermolecular interactions with HMs. The HM−NOM interactions dictate the adsorption and retention of HMs by NOM, which further governs the reactivity, bioavailability, toxicity, and transport of HMs within a diverse range of geochemical and environmental systems 10 and plays a critical role in the fate of both organic and inorganic compounds associated with the global carbon cycle. 11 Therefore, it is of great environmental significance to understand the interaction mechanism between the NOM and different types of HMs.…”

“…10.1021/acs.est.3c08309. QCM-D measurement methods; HA-functionalization methods of AFM probes and substrates; elemental composition of the HA sample; typical molecular structure of HA; water contact angle test results; FTIR spectroscopy of HA before and after Cd(II)/Pb(II) adsorption; typical force−separation approach profiles between the HA-functionalized AFM tip and substrate; species distribution diagrams for 1 mM HMs; net atomic charge transfer of HMs before and after adsorption; and dehydration penalty for hydrated Cd 2+ /Pb 2+ (PDF) Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada; orcid.org/0000-0002-1432-5979; Email: hongbo.zeng@ualberta.ca…”