A porous carbon fiber material that promises to enhance the energy efficiency and yield of capacitive Schematic of a capacitive desalination cell. Source: Tianyu Liu et al.desalination operations has been engineered at Virginia Tech.

The material is composed of long, fibrous strands of carbon derived from poly(methyl methacrylate)-block-polyacrylonitrile (PMMA-b-PAN) with uniform mesopores of approximately 10 nm. Its application in capacitive desalination can reduce process energy consumption relative to reverse osmosis systems. After porous carbon fibers are immersed into a saline solution, voltage is applied through the fibers to generate an electrostatic force that naturally attracts the salt ions out of the water.

Yield improvements are attributed to the large effective desalination surface area imparted by uniform mesopores and interconnected micropores. The structure ensures the rapid electron transport and fast ion diffusion essential for high-rate desalination.

Tests with solutions containing 500 mg salt/liter demonstrated a high desalination capacity of 30.mg sodium chloride/g of porous carbon fiber, surpassing conventional carbon fiber, activated carbon and other state-of-the-art carbon materials. The 38 mg/g/minute desalination rate displayed by the porous carbon fiber was about 40 times faster than most carbon materials.

As reported in Science Advances, the material also adsorbs potassium, magnesium and calcium ions commonly found in saltwater.