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, XRD 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(III) 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.