The effects of pristine and silanized nanodiamond on the performance of polysulfone membranes for wastewater treatment by MBR system

In this study, silanized nanodiamond (SND) was synthesized and used as a nano additive to develop the polysulfone (PSf) nanocomposite membrane in order to investigate the effects of the functionalization of nanodiamond (ND) nanoparticles on the structure and performance of PSf membranes for wastewater treatment process. ND was functionalized by silanization method using vinyltrimethoxysilane (VTS) and the results of Fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of silane groups on the surface of NDs. Afterward, neat and nanocomposite PSf membranes containing 1.0 wt.% ND and 1.0 wt.% SND were prepared via phase inversion method. Prepared membranes were then characterized by field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDX), pure water flux (PWF), contact angle and mechanical strength analyses. FESEM images showed that the number of pores on the surface of membranes increased at the presence of ND and SND nanoparticles but the average pore size decreased. PSf/SND nanocomposite membrane had the maximum PWF of 112 Lm(-2) h(-1) and the lowest contact angle value of 76.44 degrees. However, the presence of ND and SND nanoparticles had no significant effect on mechanical strength of the membranes. Moreover, the EDX analysis showed that the SNDs were dispersed uniformly throughout the PSf matrix. After determination of critical flux, the performance of prepared membranes was investigated in a membrane bioreactor (MBR) system with pharmaceutical wastewater feed for 360 min operation. The obtained results revealed that PSf/SND nanocomposite membrane had the lowest irreversible fouling ratio (IFR) and the highest flux recovery ratio (FRR).