Insight Into the Role of Fiber Diameter on Electrospun Polysulfone Mats

Abstract

Fiber electrospun mats created using cylindrical collectors have been extensively studied as effective membranes for water treatment. However, the relationships between the properties of electrospun mats and the characteristics and performance of membranes are not well‐established. This research examined two samples with average fiber diameters of 1.8 ± 0.49 μm and 0.47 ± 0.26 μm, which were evaluated as supporting substrates for the separation of MgSO4 ions. The variation in fiber diameter resulted from consistent conditions of voltage, distance, and collector rotation speed, while the injection rates were different, set at 2 mL/h and 0.8 mL/h, respectively. The resulting thin‐film composite (TFC) membrane consists of three layers: the first layer is a mesh polyester that underlies a middle hydrophobic electrospun support layer made from a 20 wt.% polysulfone solution. The third layer is a polyamide layer created through interfacial polymerization, involving a reaction between piperazine (PIP) monomers at a concentration of 2% by weight and trimesoyl chloride (TMC) monomers at a concentration of 0.2% by weight. Due to its hydrophobic nature, PSU repels water monomers from its surface during polymerization. Consequently, surface modification using plasma treatment alters the surface characteristics from hydrophobic to hydrophilic, resulting in the formation of a superior polyamide layer. The results indicate that membranes with larger fiber diameters exhibit a rougher texture. Additionally, the increased void space between the fibers in these membranes leads to an increase in pure water flux that is 92% higher compared to membrane samples with smaller fiber diameters; this higher flux is due to larger pore size. Furthermore, membranes with smaller fiber diameters possess a finer pore structure, resulting in a polyamide layer with fewer defects than membranes with larger fibers. This improved structure achieved a separation efficiency of 68% ± 1.02% for MgSO4, while the membrane with an average fiber diameter of 1.80 ± 0.49 μm demonstrated a separation rate of 20% ± 2.26%. These findings provide a step forward in the development of a theoretical framework for engineering TFC membranes with electrospun mats as supports.