Investigation of fouling properties and fouling control of graphene modified polysulfone composite membranes

In this study, graphene-doped, polysulfone-based composite membranes with improved electrical properties were prepared, they were structurally and morphologically characterized, their performance and fouling properties were examined and by using the electrically connected cross-flow filtration cell prepared within the scope of the study, in-situ fouling control studies were carried out using electrical potential against various pollutant structures. Cross-sectional SEM images of the prepared membranes showed that the membrane became more finger-like porous in proportion to the increasing amount of graphene additive. Membrane surface contact angle measurements showed that the hydrophobicity of the membrane surface decreased with the addition of high amounts of additives due to the hydrophobic property of the graphene additive. Graphene additive in filtration processes had a increasing effect on membrane permeability. Conductivity measurement results showed that graphene additive had an increasing effect on the conductivity of PSf membranes and that the conductivity of PSf membrane could be increased 40 times by using 5% graphene additive. The BSA rejection performance for all membranes prepared through rejection studies was determined to be over 90%, and the results showed that the MWCO values of the membranes were approximately ~60,000 Da. Using filtration and a simple hydraulic cleaning process, flux recovery rates of 70%, 91%, and 93% were achieved for BSA, HA, and Cd2+ contaminants, respectively. The total fouling rates of the membranes for BSA, humic acid and Cd2+ pollutants are on average in the range of 35-45%, 20-30% and 18-20%, respectively. In addition, the irreversible fouling rates are higher for all pollutants, especially due to the charged structure of Cd2+ it has been determined that it tends to cause irreversible pollution at a high rate. Electrical fouling control studies have shown that the method with 15V continuous potential application works with optimum efficiency. In in-situ fouling control studies with the electrical potential effect performed with 5% graphene containing PSf membrane, 39%, 17% and 33% lower flux decline was obtained for BSA, humic acid, and Cd2+ pollutants, respectively.