Using structural adaptations in plants for desalination

Biologically-inspired abiotic systems are becoming a central pillar in how we respond to critical grand challenges that accompany exponential population growth, uncontrolled climate change and the reality that 96.5% of the water on the planet is saltwater. One fascinating biologic adaptation to saltwater is the growth of mangrove trees in brackish swamps and along the coasts. Through salt exclusion, the mangrove maintains a near freshwater flow from roots to leaves for survival. One abiotic approach to water desalination is capacitive deionization (CDI), which uses electrostatic force to adsorb ions from a feed stream to a pair of charged electrodes. In this work, we use one-step carbonization of mangrove roots with developed aerenchyma tissue to enable highly-permeable, freestanding flow-through (FT) CDI electrodes. We demonstrate the use of the intact carbonized mangrove roots as electrodes in a FT-CDI system. We also show that the structure of carbonized aerenchyma from mangrove roots reduces the resistance to water flow through the electrodes by 65-fold relative to carbonized plant structure lacking this biological adaptation (woody biomass). These findings have implications in a range of fields including desalination, bioinspired materials, and plant-structure functionality.