Toward sustainable and cost-effective capacitive deionization: A comparative study of symmetric and hybrid asymmetric electrode systems

Global water scarcity, exacerbated by urbanization, industrialization, and climate change, demands sustainable, energy-efficient desalination technologies. Capacitive deionization (CDI) has emerged as a viable alternative to traditional methods, offering low energy consumption and ease of operation. This study examines the optimization of CDI by developing symmetric (CNT/CNT) and asymmetric (CNT/MnO₂) electrode designs to balance desalination efficiency and material cost-effectiveness. The efficacy of both systems was assessed utilizing saline water, campus water, and river water, with important metrics such as salt adsorption capacity (SAC), salt adsorption rate (SAR), and charge efficiency being measured. The results demonstrate that the symmetric arrangement attained enhanced performance, with average SAC, SAR, and charge efficiency values of 15.342 mg/g, 4.62 mg/g/min, and 2.73%, respectively, in saline water. The asymmetric design exhibited competitive efficacy (12.75 mg/g SAC, 3.984 mg/g/min SAR, 2.35% charge efficiency) while decreasing total electrode material expenses by 33.57%. Despite a slight performance compromise, the asymmetric system achieved equivalent end water purity across several water types, underscoring its suitability for scalable, cost-effective applications. The results confirm the viability of hybrid asymmetric CDI systems as a sustainable solution for brackish water treatment, with suggestions for further study that emphasize improved materials, hybrid system integration, long-term stability, and broader application areas. • Symmetric CDI achieved SAC 15.34 mg g −1 and SAR 4.62 mg g −1 min −1 . • Asymmetric CDI showed SAC 12.75 mg g −1 with SAR 3.98 mg g −1 min −1 . • Charge efficiency reached 2.73% for symmetric and 2.35% for asymmetric CDI. • Electrode material cost was reduced by 33.57% using asymmetric design. • Comparable effluent quality was achieved for saline, campus, and river water.