Effect of ZnO nanoparticles loading in double‐layer polyvinylidene fluoride membrane for desalination via direct contact membrane distillation

Abstract

In this study, double‐layer flat sheet membranes consist of nanocomposite polyvinylidene fluoride (PVDF)–ZnO layer on the top, whereas pristine polymeric PVDF on the bottom was fabricated via the double‐casting phase inversion (DCPI) method. The nanocomposite layer was prepared by loading 0.5%, 1.0%, 1.5% and 2.0% of ZnO nanoparticles. The morphology of the membranes changed as ZnO nanoparticles were introduced in the top layer, where the structure is more rigid and porous than the bottom layer. The increment concentration of nanoparticles in the top layer of the double‐layer membrane gives an effect in increasing of water contact angle slightly, which is from 136° to 140°. Furthermore, the liquid entry pressure of water (LEPw) decreases gradually from 0.69 to 0.4 bar with a high concentration of ZnO due to the presence of large pores. The increment concentration of ZnO nanoparticles also resulted in high porosity and reduced pore size, which reduce the resistance of water vapour to pass through the pores as well as enhancing the performance of membrane distillation (MD). Direct contact membrane distillation (DCMD) experiments were carried out to evaluate the efficiency of the fabricated double‐layer membrane in the desalination of seawater from fish farm water for 6‐h operation. The optimal double‐layer membrane with 0.5% ZnO nanoparticles loading maintained a stable flux of 9.42 L/m2h with 99.9% salt rejection and has antifouling properties. The results indicated that the fabricated double‐layer membrane via the DCPI method fulfils the required properties for MD application with excellent salt rejection.

Double layer PVDF blends PVDF‐HFP membrane with modified ZnO nanoparticles for direct contact membrane distillation (DCMD)

“…10,11,22 Besides, this agrees with another study, where the hydrophobic macromolecules can move to the air/polymer solution interface during the membrane casting and changes their chemical and physical properties. 11 Further analysis of the porosity of the membrane shows there was does not have significant changes when PVDF-HFP was blended in the top layer membrane, where 87% AE 0.02 and 88% AE 0.04, for membrane DB and D1 (from the previous study), 9 respectively. The blending ratio of PVDF-HFP in the membrane was suitable as compared to other studies reported by Wu et al, 11 where the blending of high PVDF-HFP content resulted in the less porous membrane.…”

“…The membrane was fabricated following a modified double casting phase inversion (DCPI) method from the previous study as shown in Figure 2. 9 In this method, solution A was cast with a thickness of 350 μm, and solution B was cast with a gap clearance of 50 μm. The membrane was cast twice continuously, where a glass plate with cast solution A was not removed from the casting machine.…”

“…The schematic diagram in Figure 4 shows the DCMD setup used in examining the performance of the fabricated membranes. 9 Salt solution (35 g/L) was used as the feed solution, while deionized water was used as distillate. The feed temperature was set to 60 C, while the distillate temperature was set to 20 C and operated with a…”

“…Researches were producing double or tri-layer membranes via phase inversion. [2][3][4][5][6][7][8][9] Researchers believed the double layer (DL) membrane is possible to use in the MD process due to its capability in increasing the surface hydrophobicity, surface roughness, flux performance, and strengthen the mechanical properties of the membrane. 3,5,10,11 It was reported the DL membrane causes the minimum production process, save time, reproducibility, minimum materials cost, and the properties of each layer secured.…”

“…4,12 The intention of producing the DL membrane was to produce a defect-free membrane and to modify the surface membrane. 2,4,8,9 Recent studies on producing DL membrane were by double casting, co-casting, double pass casting, electrospinning, and electrospraying. 3,4,8,9,12 There was a unique double-casting method by Mahlangu et al, 4 named the double casting phase inversion (DCPI) method, whereas two casting solutions were prepared and then cast twice before immersing in the coagulation bath.…”