Investigation on membrane morphological and chemical properties changes at different reaction times and its effect on dye removal

Abstract

Abstract The thin film composite (TFC) membranes were prepared and examined under different reaction times between piperazine and trimesoyl chloride. The physical and chemical properties of the membranes produced were investigated and related to their performance in terms of flux and rejection of methylene blue. Morphological studies were performed with Atomic Force Microscope (AFM) to determine the membrane’s surface roughness, whereas chemical properties (bonding ratio of hydroxyl and carbonyl) of the membranes were evaluated based on Fourier Transform Infrared (FTIR). It was found that the interfacial polymerization (IP) process was almost instantaneous in which the dense film layer was developed within 10 s of reaction time. Longer reaction time (10–30 s) reduced the flux through film growth, whereas 50–70 s further reduced the flux due to polymer crosslinking. The AFM images showed that the membrane roughness increased steadily with the reaction time and formed supernodules on membrane surface. The formation of supernodules at elongated reaction time imposed higher diffusional resistance to the membrane with minimum improvement of rejection due to the poor packing density of nodules aggregate. On the other hand, at very short reaction time (5 s), the membrane produced had the highest flux. However, the membrane produced at 5 s exhibited poor rejection of methylene blue and poor reproducibility due to the uncontrolled instantaneous IP. Besides, the prepared polypiperazinamide membrane showed good fouling resistance towards cationic dye.