Removal of Co²⁺ Ions in Aqueous Solution via Capacitive Deionization Using a TiO₂ Nanoparticle-Based Electrode

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Cobalt contamination from industrial and radioactive sources presents significant environmental and health hazards.
• Conventional cobalt removal methods often generate secondary waste, incur high costs, and lack selectivity.

Purpose of the Study:

• To develop and evaluate a capacitive deionization (CDI) system employing TiO2 nanoparticle-based electrodes for effective cobalt ion (Co2+) removal.
• To enhance the adsorption capacity of CDI electrodes using anodized TiO2 nanoparticles.

Main Methods:

• Fabrication of a CDI system with anodized TiO2 nanoparticle-based electrodes.
• Optimization of CDI performance by varying applied voltage, pH, and initial Co2+ concentration.
• Analysis of removal mechanisms using isotherm, kinetic, surface chemical, and electrochemical analyses.
• Evaluation of system performance in the presence of competing ions and assessment of regeneration and cycling stability.

Main Results:

• The TiO2 nanoparticle-based CDI system achieved a maximum Co2+ removal efficiency of 99.1% under optimized conditions.
• The system demonstrated superior removal efficiency compared to commercial TiO2 and activated carbon electrodes.
• Effective removal (up to 80%) was observed even with coexisting Na+, Ni2+, and Zn2+ ions.
• High desorption rate (88%) using 1 M HCl and stable performance (89% removal) up to the third cycle were achieved.
• Isotherm and kinetic analyses indicated heterogeneous multilayer adsorption, with initial physical adsorption followed by chemical adsorption.

Conclusions:

• The developed TiO2 nanoparticle-based CDI system is a highly effective strategy for removing Co2+ from contaminated water.
• The system offers exceptional efficiency, selectivity, and regeneration capabilities, making it suitable for environmental remediation and radioactive wastewater treatment.