Coagulation behavior of humic acid in aqueous solutions containing Cs+ , Sr2+ and Eu3+ : DLS, EEM and MD simulations

Environmental Pollution
Liqiang TanXiangke Wang

Abstract

The coagulation behaviors of humic acid (HA) with Cs+ (10-500 mM), Sr2+ (0.8-10.0 mM) and Eu3+ (0.01-1.0 mM) at different pH values (2.8, 7.1 and 10.0) were acquired through a dynamic light scattering (DLS) technique combined with spectroscopic analysis and molecular dynamic (MD) simulations. The coagulation rate and the average hydrodynamic diameter (<Dh>) increased significantly as the concentration of nuclides increased. <Dh> could be scaled to time t as <Dh>∝ ta at higher Sr2+ concentrations, which shows that HA coagulation is consistent with the diffusion-limited colloid aggregation (DLCA) model. Trivalent Eu3+ induced HA coagulation at a much lower concentration than bivalent Sr2+ and monovalent Cs+. The coagulation value ratio of Sr2+ and Eu3+ to Cs+ is almost proportional to Z-6, indicating that the HA coagulation process is generally consistent with the Schulze-Hardy rule. Spectroscopic analysis indicated that the complexation between nuclides and carboxylic/phenolic groups of HA molecules played important roles in the coagulation of HA. MD modelling suggested that Sr2+ and Eu3+ ions increased the coagulation process through the formation of intra- or inter-molecular bridges between negatively charged HA molecules, whe...Continue Reading

Citations

Nov 28, 2020·Environmental Science and Pollution Research International·Hang YangShibin Xia
Sep 14, 2020·The Science of the Total Environment·Stefan DultzGeorg Guggenberger
Aug 29, 2019·ACS Omega·Azizul HakimMotoyoshi Kobayashi

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