Capacitive deionization of ground water using carbon aerogel based electrodes

Abstract

Energy-efficient desalination technologies are needed to address the growing requirements of potable water owing to population increase, industrial development, and increasing energy cost. Capacitive deionization (CDI) technique is receiving attention because it offers an energy-efficient method of removing dissolved salts by electro-adsorption. The technique has been explored for ground water with total dissolved solids (TDS) of 500–1,500 mg/l, typical of rural areas in India. We have therefore undertaken development of a test cell and report its use for electro-sorption of dissolved ions in groundwater. The active material used is mesoporous carbon aerogel having surface area ~2,000 m²/g, developed in house. The carbon aerogel-based electrodes have shown high salt adsorption capacity of 8.4 mg/g with NaCl electrolyte. CDI cell modules of 500 ml capacity with eight-electrode stack have been used in single and multiple stages, depending on the ground water TDS. Water having salt concentration of 1,500 mg/l was treated to achieve output of ~238 mg/l with power consumption ~0.5 kWh/m³. The low power requirement, chemical free regeneration, and applicability for the ground water make this system of potential interest for addressing the issue of potable water in rural and remote areas.

Keywords:

• Carbon aerogel
• Desalination
• Capacitive deionization
• Specific capacitance
• Adsorption capacity

Acknowledgment

We would like to thank Shri Gopal Mohod for his help in the experiments and TDS analysis of samples.

Notes

Presented at Trombay Symposium on Desalination and Water Reuse, Mumbai, India, 22–23 January 2015