Hydrogen production and nutrient recovery from seawater by electrodialysis assisted with ion-exchange resins

This study introduces an innovative approach to enhance operational efficiency and reduce the energy consumption of seawater desalination through electrodialysis (ED) by expanding the beneficial outputs beyond desalinated water. In addition to hydrogen (H₂) gas production, the system is designed to generate nutrient-rich water for hydroponic farming by selectively recovering essential ions from seawater. The core innovation lies in integrating Monovalent Selective Membranes-Electrodialysis (MVS-ED) with ion-exchange resins (IEX-R). The new configuration allows for the selective removal of monovalent ions while preventing the leakage of multivalent ions such as magnesium and calcium, which are captured by the IEX-Rs. The ED cell simultaneously generates hydrogen gas at the cathode, with the separation of anolyte and catholyte solutions facilitating efficient gas collection. Several experiments are conducted using seawater under varying current densities and voltages, achieving a 96.23% removal of harmful ions (NaCl) from the seawater. The results reflect that the maximum H₂ gas generation rate achieved is 18 mmol/h while applying 15 mA/cm² of current density and 8 V of applied potential. The system's minimum net energy consumption was calculated as 6.43 kWh/m³ of desalinated seawater with the benefit of producing carbon-free H₂ gas. The specific energy consumption for ion removal was 0.521 kWh/g, with energy and exergy efficiencies of 20.73% and 29.57%, respectively. This integrated MVS-ED and IEX-R system represents a significant advancement in sustainable desalination technology, offering a dual benefit of clean energy production and nutrient recovery, paving the way for resource-efficient agricultural practices and a sustainable future.