A new MOFs/polymer hybrid membrane: MIL-68(Al)/PVDF, fabrication and application in high-efficient removal of p-nitrophenol and methylene blue

MOFs/polymer hybrid membranes combine the special surface activity of MOFs and the excellent carries nature of porous polymer and thus exhibit unexpected adsorption/separation performances in the solid-phase extraction. In this paper, a new kind of MOFs/polymer composite membrane, MIL-68(Al)/PVDF have been fabricated for the first time through blending the MIL-68(Al) nanoparticles and polyvinylidene fluoride (PVDF) casting solution and following the lyotropic phase transition. Some means such as SEM, MID and FT-IR are used to character the structure of these hybrid membranes. The membrane performances including the hydrophilic/ hydrophobic properties, membrane porosity and membrane water flux are also measured. The effects of doping amount of MIL-68(Al) on the structure and performances of MIL-68(Al)/PVDF hybrid membranes are discussed. Two persistent organic pollutants: p-nitrophenol (PNP) and methylene blue (MB) are chosen as main adsorption objects to evaluate the adsorption activity of MIL-68(Al)/PVDF hybrid membranes. The influences of various conditions on the adsorption activities are investigated in detail and the optimum adsorption conditions are determined. All the MIL-68(Al)/PVDF hybrid membranes exhibit enhanced adsorption capacity compared to pristine PVDF, and the adsorption activities of hybrid membranes are promoted continually with the increasing doping contents of MIL-68(Al). The adsorption thermodynamics analysis indicates that the adsorption process is mainly characterized by Langmuir monolayer adsorption and chemical adsorption. The coordination bonding formed between -NO2 of PNP and Al(III) of MIL-68(Al), and the acid-base interaction between the sulfur of MB and Al(HI) of MIL-68(Al) may be responsible to the highest removal efficiency of PNP and MB. The good dynamics adsorption and regeneration performances indicate the prospect applications of these MOFs/PVDF hybrid membranes in the separation of organic contaminants from industrial waste water.