Highlights
- Higher salinity and applied voltage accelerated acidification kinetics.
- Buffer capacity (HCO3−) negatively impacted acidification kinetics.
- Non-ideal membrane permselectivity allowed considerable transport of co-ions.
- Natural waters of low conductivity showed lower SEC during acidification.
Abstract
Anthropogenic CO2 emissions have reached unprecedented levels, where approximately 30% is absorbed by aquatic systems. This study investigated the acidification of natural waters using bipolar membrane electrodialysis (BPMED), a crucial step in the extraction of CO2 from water, i.e., key Carbon Dioxide Removal (CDR) technology. Natural waters of different salinity and bicarbonate concentration were selected: seawater (51.2 mS/cm, 140 mg/L HCO3−), brackish groundwater (5.4 mS/cm, 290 mg/L HCO3−), and surface freshwater (0.4 mS/cm, 162 mg/L HCO3−), where BPMED shifted the carbonate equilibrium toward H2CO3/CO2(aq), which could be subsequently extracted, thus making the current approach sustainable. The influence of applied voltage, the acidified:basified volume ratio, and hydrochemical composition on acidification kinetics, energy consumption, and ion transport was analyzed. Results showed that higher salinity and applied voltage accelerated acidification kinetics, whereas buffer capacity (HCO3−) slowed down the acidification process. In addition, waters with lower salinity required lower specific energy (1.02 vs 1.86 kWh/kg CO2 for freshwater and seawater, respectively) to achieve acidification (final pH 4), while increasing the acidified:basified volume ratio led to higher energy consumption. Acidified water exhibited increased Na+ and Cl− concentrations, while K+ and HCO3− decreased across all water sources. These findings contribute to the scientific understanding of electrochemically-based water acidification processes and provide insights into sustainable approaches for managing dissolved CO2 in natural waters.
Verdezoto-Intriago S., Mendez-Ruiz J. I., Franco-González K., Cobos J. K., Cornelissen E. R., Valverde-Armas P. E. & Gutiérrez L. A., 2026. Acidification of brackish, fresh, and seawater by bipolar membrane electrodialysis: impact of composition on kinetics and energy consumption. Sustainable Materials and Technologies 48: e02053. doi: 10.1016/j.susmat.2026.e02053. Article (subscription required).
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