Intensified cleaning of organic-fouled reverse osmosis membranes by thermo-responsive polymer (TRP)

The role of thermo-responsive polymer (TRP) in the cleaning of organic-fouled polyamide-based reverse osmosis membranes was systematically investigated in this study. Fouling and cleaning experiments were performed employing a laboratory-scale cross-flow test unit. Following accelerated organic fouling runs with bovine serum albumin (BSA), cleaning experiments were conducted using de-ionized water and de-ionized water containing TRP with low critical solution temperature under various conditions, respectively. The separation performances of the fresh, fouled and cleaned membranes were characterized through permeation tests. It was found that the phase transition of the TRP that had diffused into the fouling layer would facilitate the removal of foulants located on membrane surface, and thereby improve the cleaning efficiency. The efficiency of the intensified cleaning with TRP solution was largely affected by the type and concentration of TRP, as well as the soaking time of TRP solution. The efficiency of the intensified cleaning could be enhanced by increasing the concentration and/or prolonging the soaking time of TRP solution. Moreover, membrane surface characterization via scanning electron microscopy, attenuated total reflectance infrared and surface contact angle measurements also confirmed the beneficial effect of TRP on the removal of the deposited foulants from the membrane surface.