Here we investigate the competitive electrosorption of mono- and divalent phosphate anions through electrochemical desalination- and dilatometry-based experiments. Through in situ dilatometry, we monitor the strain at the electrode surface as anions and cations are electrosorbed. Strain measurements show that the presence of divalent ions promotes a greater than anticipated electrode expansion during cation (Na+) electrosorption. The expansion observed with Na+ equaled the expansion observed with HPO4 2-. Because the ionic radius of Na+ is smaller than that of HPO4 2-, the symmetric expansion suggests that divalent anions do not completely desorb during electrode regeneration, causing the adverse interactions with the cation during co-ion expulsion. This results in a decrease in desalination performance, indicated by a decreased salt adsorption capacity. Conversely, an expected asymmetric expansion during anion and cation electrosorption occurs with monovalent phosphate anions (H2PO4 -), indicating that monovalent ions can be effectively replaced by the cation at the electrode surface.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry
- Water Science and Technology
- Waste Management and Disposal
- Health, Toxicology and Mutagenesis