Preparation, characterization, and fouling analysis of PVC/ND-PEG ultrafiltration membranes for whey separation

In this work, polyvinyl chloride (PVC) membranes were embedded with nanodiamond-Polyethylene glycol (ND-PEG) nanoparticles. Fabricated membranes were characterized by FTIR, FESEM, AFM, pore size distribution, contact angle, porosity, pure water flux (PWF), and tensile strength. Successful functionalization of ND nanoparticles by PEG was proved by the FTIR test. According to the FESEM and pore size distribution results, there was an increase in the quantity of surface pores, a shift toward smaller pores, and larger macro-voids in the porous substructure of the nanocomposite membranes as the ND-PEG content in the dope solution increased. The decrease water contact angle from 79.8° for neat PVC membrane to 59.5° for 2.00 wt% ND-PEG containing membrane along with the increase of porosity from 53.89 % to 80.80 % respectively showed that the hydrophilicity of the nanocomposite membranes was improved by increasing nanoparticles content, and this phenome along with surface roughness increment caused PWF improvement from 206.8 LMH to 266.4 LMH. In addition, due to the uniform dispersion of ND-PEG nanoparticles and the high mechanical strength of NDs, the tensile strength of nanocomposite membranes reached a maximum value of 2.91 Mpa for 1.5 wt% ND-PEG membrane. The performance results showed that PVC/ND-PEG nanocomposite membranes had acceptable whey rejection along with a significant increment in flux recovery ratio. Moreover, PVC/ND-PEG membranes with 2.00 wt% ND-PEG had lower flux reduction in long-term filtration, improved antifouling properties and more turbidity removal efficiency in comparison with neat PVC membranes. The analysis of the fouling mechanism based on Hermia's model revealed that the cake formation is the prevailing mechanism for all fabricated membranes.