Scalable and renewable electromembrane contactors for freshwater recovery through membrane distillation

Abstract

Tube-shaped renewable carbon materials were developed from sugar cane harvest residues to work as membrane contactors for freshwater recovery from water solutions with elevated dissolved solid concentrations. The tubes have electrical properties and can be heated directly through the Joule effect by applying electric potential between the ends. Temperature increased more than linearly, which is consistent with a decrease of the tube's resistance. The Joule effect's experiments on the wet tubes showed that most of the loaded water was removed in less than 2 min for an applied voltage of 7.0 V. The tubes were tested as membrane contactors using ∼10 and ∼100 g/L NaCl solutions producing freshwater at a rate between ∼2.0 and ∼7.0 kg/m2 h with salt rejection values above 99.4%. The tested thermal conductivities of the membrane contactors were around 0.09 W/m·K, which are lower than many commercial membranes, thus making them promising in terms of the thermal efficiency of the process. These carbon tubes provide easy scalability and tolerance to corrosive and high-salinity waters, which is advantageous for water recovery from waste streams with high solute concentrations.