The goal of this study was to produce a fouling-resistant membrane by attaching a stimuli-responsive polymer on the membrane surface, which collapsed or expanded as a response to the stimulus. The phase change arises from the existence of a lower critical solution temperature (LCST) such that the polymer precipitates from solution as the temperature is increased. The polymers studied for this application were hydroxypropyl cellulose and N-isopropylacrylamide, which have LCSTs of 46 C and 32 C, respectively.
Roughness measurements, using a wet atomic force microscopy (AFM) cell, and filtration experiments (to monitor flux declines) were performed at cold temperatures (25oC), at hot temperatures (60oC) and with temperature oscillations. The unmodified membrane roughness values were unaffected by temperature changes, and it displayed flux declines under all temperature conditions. When the modified membranes were tested, both roughness values and filtration experiments supported temperature activation.
Developing a membrane with high flux and selectivity along with low fouling is one of the goals of membrane research. There are physical and chemical limitations, however, that cannot be disregarded. For microfiltration/ultrafiltration systems higher flux operation requires energy input, in the form of back flushes, air scouring, physical agitation, etc, to reduce fouling. The work presented here developed a membrane with desired inherent properties along with fouling control.