A study of different concentrations of bio-silver nanoparticles in polysulfone mixed matrix membranes in water separation performance

Abstract

Silver/silver oxide nanoparticles (AgNPs) is one of the most effective inorganic compounds that acts as an antibacterial agent against Escherichia coli (E. coli) bacteria. In this study, bio-silver or -silver oxide (bio-AgNPs) was synthesised from the seeds and peels of the Parkia speciosa (P. speciosa) plant, a green reducing agent. The seeds and peels were extracted separately via facile methods using a solution of silver nitrate (AgNO3). The seeds were soaked and peels mixed with the AgNO3 solution. The resulting bio-AgNPs were then incorporated into polysulfone (PSf) membranes at different weight percentages (0.1, 0.3, 0.5, and 1.0 wt%). The results showed that the PSf mixed matrix membrane (MMM) with 1.0 wt% of P. speciosa peel-derived bio-AgNPs (PP1.0) had the most optimum properties with a smaller crystallite size of 51.60 nm, an average diameter of finger-like cavities of 15.23 μm, the smallest mean pore size of 10.20 nm and the highest surface roughness of 39.90 nm. PP1.0 was also found to be highly hydrophilic since it had the lowest contact angle (63.30°) which was corroborated by the highest hydroxyl (−OH) peak (3454.21 cm−1) seen during Fourier-transform infrared (FTIR) spectroscopy analysis. PP1.0 also had the highest water permeation flux (327.73 L m−2 h−1), lowest rejection rate (67.21%), lowest bio-AgNP leaching after water filtration (1.56 μg/L) and the formation of a 16.34 mm2 antibacterial inhibition ring. This proved that PP1.0 had the potential to be applied as an antibacterial membrane for water separation.