SAN-including PVDF membranes with improved permeability for hypersaline water desalination using DCMD process

Abstract

Styrene-acrylonitrile (SAN) was added to polyvinylidene fluoride (PVDF)/N-methyl-2 pyrrolidone (NMP) system to fabricate SAN-modified PVDF membranes using non-solvent induced phase separation (NIPS). By increasing the SAN concentration in casting solution, number of microbeads started to grow. However, by further increasing the amount of SAN, size of microbeads was also increased. Surface hydrophobicity of neat ethanol-induced composite membrane was increased from 139.2 ± 1 to 148.7° ±1, since SAN polymer incorporation bestowed another texture to whole structure. Different salty feed solutions, i.e., 35 and 105 g/L, were used as feed by direct contact membrane distillation (DCMD) process. Permeate flux and salt rejection were high enough with stable permeation using 35 g/L feed solution. Neat and well-modified PVDF/SAN membranes were then applied for hypersaline DCMD test. During 38 h desalination test using SAN-modified membrane, permeate flux and salt rejection of 29.74 ± 1 kg/m2 h and >99.9 % were achieved, respectively. Also, due to multi-textured structure, permeate flux enhancement and better scaling resistance were observed using SAN/PVDF membrane. A sufficient way was proposed to improve desalination performance using a straightforward fabrication process.