Polyethersulfone mixed matrix membrane containing imprinted zeolite for cresol removal in hemodialysis application

Abstract

The adequacy of uremic toxins removal on hemodialysis treatment is essential to be achieved for kidney failure disease patient, as poor removal leads to heart failure, hypertension, and stroke. The combination of adsorption and diffusion process has become very advantageous for hemodialysis membrane. By this mechanism, the urea as water soluble uremic toxins (WSUT) and p-cresol as protein-bounded uremic toxins (PBUT) could be removed at one time. Therefore, this study aimed to develop the novel imprinted zeolite by p-cresol (IZC) then incorporated into polyethersulfone (PES) and poly(vinyl pyrollidone) (PVP) to produce hollow fiber mixed matrix membrane (HF-MMM). IZC was synthesized from sodium aluminate, NaOH, H2O and SiO2 through aging and hydrothermal process with an initial composition of 10SiO2:Al2O3:4Na2O:180H2O by using imprinting technology and p-cresol as a template. Based on the properties and performance achieved, IZC could increase the selectivity to adsorb p-cresol 4.30 times greater compared to synthesized Zeolite Y (ZeoY-S). Adsorption study proved that IZC could adsorb p-cresol 2.5 and 3.5 times higher than ZeoY-S and commercialized zeolite Y (ZeoY-C), respectively. This is because the pore size of IZC had been successfully printed to p-cresol. The Brunauer-Emmet-Teller and transmission electron microscopy characterization proved that imprinting process was successfully applied. The investigation by isotherm and kinetics models showed that IZC was sensitive to attract the adsorbate, classifying it as having a strong adsorption behavior. Accordingly, the IZC is very promising to be applied as adsorbent in hemodialysis treatment. In the second phase, IZC as p-cresol’s adsorbent was incorporated into PES-based polymeric membrane with small addition of PVP to produce HF-MMM by using dry/wet spinning process. The effect of air gap distance between spinneret and coagulant bath and percentage loading for PES, PVP, and IZC were studied and optimized to obtain the best performance of HF-MMM. The 40 cm of air gap distance, 16 wt.% of PES, 2 wt.% of PVP, and 1 wt.% of IZC loading were able to produce superior hemodialysis membrane. These optimized parameters showed sufficient uremic toxins removal i.e. 60.74% of urea, 52.35% of p-cresol in phosphate buffer saline solution and 66.29% of p-cresol in bovine serum albumin solution for 4 hours permeation by using dialysis system. These HF-MMMs also achieved pure water flux of 67.57 Lm-2h-1bar-1 and bovine serum albumin rejection of 95.05%. Therefore, this membrane has been proven to be able to clean up WSUT and PBUT through an one-step process. Moreover, as compared neat PES membrane, MMM was able to remove p-cresol 186.22 times higher. Then, capability of IZC to adsorb p-cresol decreased to around 69% by changing the form of adsorbent from powder to composite in the membrane. By leaching study, it was obtained that percentage of zeolite leaching was less than 1 mgL-1 and categorized safe. In the final phase of the study, the HF-MMM developed was evaluated in terms of biocompatibility test, that is hemocompatiblity by using protein adsorption, platetels adhesion, blood clotting time test, activated partial thromboplastin time, prothrombin time, and cytotoxicity evaluation by using 3-(4,5-dimethylthiazol-2yl)-5(3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTT assays). From the biocompatibility evaluation HF-MMM was observed to possess less protein adsorption, less activated state of the adhered platelets, non-toxic quality for red blood cells, and can prolong the clotting time and percentage of viability for more than 60%. These results proved that HF-MMM developed is safe for hemodialysis application.