Sulfonated polyethersulfone and functionalized multiwall carbon nanotubes/polyvinylpyrrolidone nanocomposite based hemodialysis membrane

Chemical modification of polymer and blending of suitable additives are the common methods used to improve the properties of polyethersulfone (PES) based hemodialysis membranes. In this research work, both methods are adopted and novel nanocomposite based additives were synthesized and blended with PES alone; and then with chemically modified PES (sulfonated PES (S-PES)). The whole research work was divided into three phases. In the first phase, the nanocomposites (NCs) were formed by mixing together the acid functionalized multiwall carbon nanotubes (f-MWCNT) and two different grades of polyvinylpyrrolidone (PVP-k90 and PVP-k30) in dimethylformamide and subsequently blended with PES. The f-MWCNT contained some hydrophilic functional groups (–COOH, and –OH) and heredity hydrophobic carbon part, which made it dual nature. On one side, it carbon part created sites for attachment for the hydrophobic polymer (PES) by hydrophobic–hydrophobic interaction and p–p stacking, whereas on the other side, its hydrophilic acid and hydroxyl groups attracted the hydrophilic sides of PVP by hydrogen bonding, dipole–dipole interaction and dispersion forces. Thus, f-MWCNT acted as the anchoring material between the PVP and PES in the membrane that also greatly reduced the leaching process of the additives and stabilize the membrane composition as shown by elution ratio test. The Fourier transform infrared spectroscopy spectra of fabricated membranes revealed that both types of NCs were physically bonded with PES by hydrogen bonding and the addition of NCs to PES, improved the internal capillary system of membranes as confirmed by field emission scanning electron microscope analysis. The results showed that f-MWCNT/PVP-k90 based membranes exhibited better performance than f-MWCNT/PVP-k30 based membranes in terms of flux rate, rejection rate and biocompatibility. The results from dialysis of uremic solutes unveiled that membrane formed by PVP-k90 based NCs demonstrated superior performance with 56.30%, 55.08% and 27.90% clearance ratio of urea, creatinine and lysozyme solutes, respectively. In the second phase, two best performance membranes of f-MWCNT/PVP-k90 NCs based were selected and then blended with variable ratio of S-PES. The outcome indicated that the blending of S-PES polymer, further enhanced the membrane biocompatibility and reduced the protein adsorption (bovine serum albumin, 55% and lysozyme, 65%), hemolysis process (74.80%) and illustrated longer clotting times than pristine and non-sulfonated membranes. The clearance ratio of uremic solutes was also improved and reached up to 57.3%, 57.1% and 32.4% of urea, creatinine and lysozyme, respectively. Thus, the blending of S-PES and NCs in the PES membrane greatly improved the biocompatibility and removal ability of uremic solutes. In the third and final phase, the hollow fiber (HF) membranes were spun using S-PES and PVPk90/f-MWCNT based NCs and the HF membrane characteristics and dialysis performances were evaluated. The results showed that HF membrane had a good flux rate (29.8l/h.m2.bar), low molecular weight cut off (29-34 kDa) than pristine PES membranes. The dialysis tests confirmed that the HF membranes illustrated 72.7%, 75.1% and 35.4% clearance ratio of urea, creatinine and lysozyme solutes, especially. Thus, the blending of S-PES and NCs in the PES membrane highly improved the biocompatibility and removal ability of uremic solutes and it can be used in commercial grade dialyzers.