Capacitive deionization helps to remove tetracycline and water hardness ions simultaneously

Tetracycline (TC) is one of the most common broad-spectrum antibiotics. However, typically less than 30% of the antibiotic dose was absorbed by human and animal, while the remainder released into the environment through urine. The coexistence of TC and water hardness ions (Ca2+ and Mg2+) in natural water is a widespread pollution phenomenon. Especially, TC and water hardness ions could easily form TC-metal complex pollution in the environment.

In a recent study published in Journal of Cleaner Production, the researchers at Institute of Solid State Physics, Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences used capacitive deionization (CDI) technology to simultaneously remove TC and water hardness ions (Ca²⁺ and Mg²⁺) from water based on unique innate advantages of CDI technology. The method is efficient and eco-friendly with low-cost.

The researchers derived hierarchical porous carbon material from kelp and used it as symmetric electrodes. A maximum capacity of 925.3 mg g^-1 for TC removal was achieved, which is much higher than those of other materials reported. The removal efficiency can achieve over 90% even after five CDI adsorption-desorption cycles.

Besides, the metal ions with opposite charges were adsorbed on the counter electrode with a preferential ion electrosorption performances, proving the effective CDI technology for water purification.

This study has paved a way to synchronously eliminate multiple organic and inorganic contaminants from water by using CDI technology.