Towards Energy – Efficient Industrial Separations: Non-Aqueous Solvent Permeation Profiles in Ceramic Membranes

Vincent Morehead,1 Shamsuddin Ilias,1 and Geoffrey D. Bothun2,*

1Department of Mechanical and Chemical Engineering, North Carolina Agricultural & Technical State University, Greensboro, NC 27411

2Department of Chemical Engineering, University of Rhode Island, Kingston, RI 02881

*Corresponding Author: bothun@egr.uri.edu (e-mail); 401-874-9518 (Tel)

Separation processes are critical in the fields of chemical, pharmaceutical and material synthesis and are often performed using gravity, centrifugation, evaporation and adsorption in non-continuous, batch modes. However, the design and implementation of continuous separations can significantly reduce equipment demands, increase throughput, and eliminate downtime. Membranes are an extremely useful platform for continuous separations and contain no moving parts. Separation is achieved as membranes selectively retain molecules or particles larger than a desired size or with a low relative membrane affinity.

Given their chemical and thermal stability, ceramic membranes provide an inert and robust separation medium for organic solvents. Currently, little is known about how solvent interactions with a ceramic surface effect transmembrane flux. With the goal of investigating these interactions, we examine the permeation behavior of both hydrophilic and hydrophobic solvents through ceramic membranes of different pore sizes (nanoscale: 1 KD ? 50 KD) and separation layer materials (titania and zirconia). Results for hydrophilic solvents ? ethanol, butanol and acetone ? have indicated a transient permeation profile which is likely due to solvent physisorption and/or chemisorption at surface hydroxyl groups, and a subsequent reduction in the effective membrane pore size. In general, the degree of transient behavior was greater for membranes with smaller pores, demonstrating the increasing importance of solvent-membrane interactions with decreasing pore size. Pre- and post-water permeation experiments indicated that adsorption of these hydrophilic solvents may be reversed with drying at 473 K. Comparative results will be presented for hydrophobic solvents (toluene and hexane) to examine critical solvent properties in ceramic membrane transport. Understanding solvent permeation profiles in ceramics will help process design and scale-up of this energy-efficient separation. This work is supported by the NSF Science & Technology Center for Environmentally Responsible Solvents & Processes and the Experimental Program for Education through Research & Training (EXPERT) at NC A&T SU.