STNF - Solvent Tolerant Nanofiltration and reverse osmosis membranes for the purification of industrial aqueous streams

Towards nanofiltration membranes for separation of solvent containing aqueous process streams


In a Dutch/Belgian project coordinated by the Institute for Sustainable Process Technology (ISPT), new solvent tolerant nanofiltration (STNF) membranes are being developed that enable purification of solvent containing industrial aqueous streams. When widely applied in the chemical and petrochemical industries, such membranes could potentially save 20 PJ/year in energy, and reduce CO2 discharges with 1.3 million ton/year in the Benelux.

Membranes to treat aqueous wastewater streams

Over the past decades, membrane technology has become a preferable option for the treatment of aqueous wastewater streams. Membrane-based processes such as nanofiltration or reverse osmosis provide an energy- and cost-saving alternative for traditional methods, in particular distillation. What’s more, membranes allow for mild separation conditions, they reduce the need for chemicals and enable the use of flexible and modular equipment in a fairly straightforward operation.

STNF - Water drop

Barriers to overcome

Thus, there is an urgent need for solvent tolerant nanofiltration (STNF) membranes able to purify industrial aqueous streams. ISPT is coordinating a project where significant steps are being made to develop such membranes and bring them to application. The project partners are the University of Twente, ECN part of TNO, KU Leuven, VITO, and membrane developer SolSep, who are among the front-runners on developing promising STNF technology. From industry, DOW Benelux, Shell, and Huntsman Holland contribute to the project. This participation is considered to be unique and valuable as it focusses on a major challenge within the bulk liquid stream treatments in the chemical and petrochemical industries. As such, it can potentially contribute to some 20 PJ/year in energy savings or a reduction in CO2 discharge of 1.3 million ton/year in the Benelux alone.

Solvent tolerant nanofiltration membranes as a solution

Regrettably, the advantages of membrane technology have remained out of reach for industrial aqueous process streams that consist of a mixture of solvents with water in different ratios and with different types of solutes. Such feeds cannot be treated by membranes developed for aqueous treatments, as the pollutants cause detrimental swelling and even degradation of the polymeric nanofiltration membranes. On the other hand, existing solvent tolerant membranes developed for solvent streams are hydrophobic, which hampers aqueous application.

Promising results

The STNF project is characterized by combined research of membrane development, application testing and modelling, which in an international perspective is rather unique. Currently halfway, it has already delivered some promising results. One is the development of a novel membrane by SolSep and the University of Twente, consisting of a support layer and a functional layer that are both based on epoxy chemistry. It has been produced and characterized in the laboratory and is now ready for further testing at the facilities of DOW Benelux and VITO.