In Situ Electrochemical Dilatometry of Phosphate Anion Electrosorption

• DOI: 10.1021/acs.estlett.8b00542
• Publication Date: 2018-11-14T15:40:15Z
• Authors: Daniel Moreno; Yousuf Bootwala; Wan-Yu Tsai; Qiang Gao; Fengyu Shen; Nina Balke; Kelsey B. Hatzell; Marta C. Hatzell
• Keywords: 02 engineering and technology; 0210 nano-technology; 6. Clean water

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 HPO42–. Because the ionic radius of Na+ is smaller than that of HPO42–, 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 mono...