Three dimensional (3-D) printing was utilized to manufacture micromixers directly on membrane swatches. To enhance performance, a two dimensional computational fluid dynamic model was used to select the optimal geometry and pattern of 3-D printed micromixers. The optimal geometry selected created unhindered flow between 0.2 m/s and 0.3 m/s, using an inlet flow velocity of 0.104 m/s, across 40% of the membrane surface.  Laboratory experiments were conducted to evaluate the performance of micromixers and compared to unmodified membranes with a standard 20 mil (0.508 mm) mesh feed spacer. Pure water flux and salt rejection were found to be similar to standard membranes, indicating the 3-D printing process did not damage intrinsic membrane properties. Calcium sulfate scaling experiments were conducted. Scale initially began to form within 2 hours of treatment resulting in a flux decline of approximately 10% for both modified and unmodified membranes. Over 14 hours, an average flux decrease of 24% was observed for modified membranes compared to an average flux decrease of 78% for the unmodified membranes. This demonstrated the improved resistance to fouling created by the open channel design with optimal flow conditions. Based on the open-channel flow paths created using 3-D printed micromixers, improved scale removal by reverse flow cleaning procedures was evaluated.  The modified membranes showed more removal for calcium sulfate compared to the unmodified membrane utilizing a 20 mil (0.508 mm) mesh feed spacer.  Following cleaning, all three unmodified membranes and feed spacers had significant remaining scale, while all three modified membranes showed minimal scale. Micromixers printed directly to the membrane surface offers the ability to optimize feed channel hydrodynamics, reduce scale formation, minimize flux decline, and allow for reverse flow cleaning of fouled membranes, representing a significant advancement in membrane technology.

Micromixers with bi-directional flow enhancing features to minimize scaling effects on reverse osmosis membranes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.