(20e) Functionalized Nanoporous Ceramic Membranes Towards Low-Cost Electrodialysis

Authors: 
Newbloom, G., Membrion
Kingsbury, R., University of North Carolina at Chapel Hill
Malone, R., Membrion
The State of California has experienced annual snow pack depletion and persistent drought that is impacting agriculture, industry and day-to-day life. They are not alone as many parts of the world face a fresh water crisis. Interestingly, California, for example, has 38 times more brackish water than fresh water. Electrodialysis is known to be one of the most efficient technologies for purification of brackish water and yet it is often not considered as a leading solution to the fresh water crisis. This is in part due to the cost and performance of the ion exchange membranes (IEM). IEMs suffer from high cost, high resistance, poor durability and other problems. In this presentation, we discuss the design and scale-up of novel, functionalized ceramic IEMs that are ion selective, experience near-zero swelling and are inexpensive at 30% of the production cost of current IEMs.

In this work, we investigate the use of a surface-modified inorganic membrane created using sol-gel processing of siloxanes without calcination or sintering. Silica is an advantageous material for membranes because of its excellent durability, extremely low cost and lack of swelling in water. Membrane performance can be tuned by size exclusion (i.e., sub-5nm nanometer pores) and surface functionalization (i.e., silane chemistry) to achieve promising anion and cation-selective performance. Permselectivity and water permeance of these membranes are shown to be superior to an industry standard Neosepta, while area specific resistance has room for improvement. Area-normalized ion exchange capacities and accelerated degradation tests show nearly identical performance between the functionalized ceramic and Neosepta membranes. Design strategies for continued optimization will also be discussed. These promising preliminary results highlight the commercial potential for a new, inexpensive IEM with the potential to elevate the status of electrodialysis as a leading solution to the fresh water crisis.