Development of Microwave Induced Membrane Distillation with Carbon Nanotube Immobilized Membranes: A Sustainable Solution for Solvent Recovery from Aqueous Wastes

Project Summary Our project aims to recover solvents from waste streams with low concentrations of solvents, such as chlorinated and aromatic solvents, DNAPL, MTBE, tetrahydro furan, and others. These waste streams are typically produced by Superfund sites, and our primary objective is to recover the solvents from them. These wastes are currently treated as hazardous waste for disposal, which is an expensive and wasteful approach. Our proposal offers a sustainable solution by concentrating dilute (1 to 10%) solvent waste to 60 or 70%, which can be sent to a distillation column or purified through membrane separations such as pervaporation and nanofiltration to generate pure solvents (95-99%). These recycled solvents can be resold in the market or repurposed for other applications. To achieve our goals, we propose the development of Microwave Induced Membrane Distillation (MIMD) with Carbon Nanotube Immobilized Membrane (CNIM) or MIMD-CNIM. Here, a hydrophobic porous membrane with immobilized carbon nanotubes separates a hot feed waste stream and a cold permeate. The membrane prevents the aqueous solution from entering the pores, while the solvent vapor passes through and is condensed on the permeate side of the membrane. The major advantage of CNIM is its ability to selectively transport solvents by increasing the partitioning on the nanotube surface. The waste stream is heated using a microwave heater, which enhances recovery via non-thermal effects such as localized superheating, breakdown of hydrogen-bonded structures in aqueous environments, and the creation of nanobubbles. We propose three specific aims, which include 1) membrane development; 2) testing of MIMD for different solvent streams and 3) testing with real-world wastes. By developing this technology, we hope to provide a sustainable solution for recovering solvents from aqueous solvent wastes, which can reduce the amount of hazardous waste generated by Superfund sites and other industries. Moreover, this approach can contribute to the circular economy by promoting the recycling and reuse of solvents.