Development and evaluation of an antifouling coating for reverse osmosis membranes which can be applied in modules

Development and evaluation of an antifouling coating for reverse osmosis membranes which can be applied in modules


​​laghmaripng

 

Cooling water is used for process and product cooling in many industries; an example is steel production and processing with a water requirement of 2.3 billion m3/a for cooling circuits. The water cycles as well as the cooling water matrix are very complex due to process contamination and the addition of conditioning chemicals. Furthermore, salting appears to be a big problem because of the recirculation in the cooling circuits and the evaporation which requires up to 200 m3/h of blowdown water for a typical steel plant. Reverse osmosis (RO) provides a good alternative for processing water from cooling circuits. However, since RO membranes are able to retain all relevant substances including monovalent ions, they are particularly susceptible to all types of fouling. Thus, the required performance cannot be achieved without feed pre-treatment and/or the membranes should be made more resistant to fouling.

In this project desalination processes based on RO are developed by critically evaluating the separation performance of established membranes, by developing an in situ modification for RO flat-sheet membranes and transferring this to spiral-wound RO modules and by implementing such modules in a cooling circuit for the steel industry. As a first step, interactions between commercially proven membranes and critical components of the cooling water are investigated in dead-end batch mode with focus on membrane fouling. This provides the basis for the design of a novel antifouling hydrogel coating for flat-sheet membranes via concentration polarization-enhanced [1] cross-linking reaction of tailored polymeric building blocks [2]. Conditions which are suited for a protective polyzwitterionic hydrogel coating modification are identified in dead-end filtration experiments. Antifouling properties at minimized loss of initial membrane permeability can be obtained. In a second step, the novel antifouling coating is transferred to spiral-wound RO membrane modules. In the last step, a detailed investigation of the fouling behavior and long-term stability of hydrogel-coated modules which are implemented in a cooling circuit is done in pilot scale tests.

References

  1. R. Bernstein, S. Belfer, V. Freger, Langmuir 2010, 26, 3168
  2. P. May, Ph.D. project, in progress

Funding

This work is part of the cooperative project “WEISS” which is funded by the Bundesministerium für Bildung und Forschung (BMBF) within the funding initiative “WavE”; reference number: 02WAV1411.

Contact:
Soraya Laghmari

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