Separation performance of cationic and anionic dyes from water using polyvinylidene fluoride-based ultrafiltration membrane incorporating polyethylene glycol
Abdullah G. Saleem, Sama M. Al‐Jubouri
Abstract
Membrane separation shows high performance in the dye’s removal at nanofiltration conditions. Pinpointing the problems accompanying using high pressure in the nanofiltration process sparks increased interest among investigators to tackle this important point. This work tackles the problem of using the nanofiltration process to remove intermediate molecular weight dyes by decorating new functionalized membranes working at ultrafiltration conditions. Flat sheet ultrafiltration membranes were successfully prepared by the phase inversion technique from polymeric solutions containing 16, 18, and 20 wt% of polyvinylidene fluoride (PVDF) and N, N-dimethyl formamide as a solvent. The prepared membranes were tested using rhodamine B (RhB) dye as a model pollutant at different transmembrane pressures of 1, 2, 3, and 4 bar. Optimistic permeability, permeate flux, and dye removal were obtained using 18 wt% of PVDF. This membrane was developed with different polyethylene glycol (PEG) contents of 3, 6, and 9 wt% to improve the hydrophilicity and permeability of the membrane surface at low pressure. The morphology analysis, elemental composition, and surface functional groups of the pure and modified membranes were examined. The effect of dye concentration and pH of the feed solution on the permeate flux and RhB removal was studied using an 18 wt% PVDF membrane containing 6 wt% of PEG. The results showed that incorporating 6 wt% of PEG in the 18 wt% PVDF casting solution reduced the CA from 78.85° for pure PVDF to 62.08° and enhanced the permeability from 7.16 L/m2.h for pure PVDF to 74.72 L/m2.h at 1 bar and initial RhB concentration of 10 mg/L. While RhB dye removal slightly decreased from 93.08 % for pure PVDF to 91.26 %. The results showcased the potential efficiency of the (6 wt%)PEG/(18 wt%)PVDF membrane for dye separation from water. Also, molecular weight cut-off was evaluated using RhB as a cationic dye, acid orange 10, and congo red as anionic dyes and it was 478 Da.