Abstract
This paper assesses the feasibility of further desalination of seawater reverse osmosis (SWRO) brine by direct contact membrane distillation (DCMD) process using novel blended polyvinylidene fluoride (PVDF) membranes. Blends of PVDF homopolymer (HP; Solef (R) 6020, Solvay), as a core polymer, with PVDF copolymer (CP; Solef (R) 21510, Solvay) and N-methyl-2-pyrrolidone (NMP) as a solvent were used at two PVDF concentrations and various CP/HP ratios to prepare flat sheet membranes using the non-solvent induced phase -separation (NIPS) method. The average porosity of membranes was found 42% and 46% when the PVDF concentration of the dope solution was 20 and 25 wt%, respectively. At lower values of CP/HP ratio, no clear trend of porosity changes was observed; however, the higher values of CP/HP ratio improve the porosity of the membranes. With distilled water as a feed, the permeate water flux of prepared membranes decreased from 2.9 to 1.6 kg/m(2). h when the PVDF concentration increased from 20 to 25 wt%, respectively. For the commercial PVDF membrane, the permeate water flux achieved was 17.5 kg/m(2). h at cross flow velocity of 0.25 m/s and was almost doubled when the cross flow - velocity increased to 0.75 m/s. The water flux was almost reduced by half when SWRO brine was used as feed instead of pure water for both the prepared and commercial membranes. The flux performance efficiency of the MD system was evaluated and was found to be an appropriate indicator of the - temperature polarization.