Nanofiltration for extreme conditions

At present practically all nanofiltration (NF) membranes are suitable for treatment of aqueous streams at pH levels between 2 and 10. However, most potential applications in the chemical industry require separation processes at more extreme conditions (lower or higher pH, and operation in environments with more aggressive organic chemicals). The objective of the project is to develop robust (chemically stable) NF membranes for bulk liquid separation in the chemical industry. The NF membranes should be stable at high and low pH, stable in hydrocarbon containing environments, stable in oxidative environments and not prone to abrasion.

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Figure 1. Thin NF layer on a porous support (courtesy of Dr. Jumeng Zheng).

NF membranes currently are predominantly prepared by interfacial polymerization on a support, which is often an ultrafiltration membrane. The approach of this project is to modify the chemistry of the conventional polymeric toplayer material. Interfacial polymerization is a very delicate and yet flexible process, the membrane properties can be altered by many process parameters: choice of reactants or solvents, concentration, reaction time, use of catalyst or phase transfer catalyst, etc. This project involves the understanding of the relationship between material stability with the polymer chemical structure, in addition to process optimization for ultrathin polymer film formation.

Figure 2. Interfacial polymerization process [1]

The developed membrane materials will be tested on a high pressure NF setup to determine the permselectivity. Then, the structure of the membrane will be analyzed via a number of spectroscopy and microscopy techniques.

[1] Mayur Dalwani, Thin film composite nanofiltration membranes for extreme conditions, PhD thesis, University of Twente, 2011.