Preparation and characterization of Co(II) ion-imprinted composite membrane based on a novel functional monomer

In this paper, a novel functional monomer, N-(pyrrolidin-2-ylmethyl) methacrylamide (PMMA), was synthesized. Using Co(II) ions as the template, 2,2-azoisobutyronitrile (AIBN) as the initiator, ethylene glycol dimethacrylate (EDGMA) as the crosslinking agent, twenty-seven Co(II) ion-imprinted composite membranes (Co(II)-PMMA-IICM1∼27) and their corresponding non-imprinted composite membranes (PMMA-NICM1∼27) were prepared. Additionally, the related parameters of the imprinting system were systematically optimized. Co(II) ion-imprinted composite membranes (Co(II)-PMMA-IICM16) were prepared using Nylon-6 as the supporting membrane, which was soaked in a pre-polymerized solution of N,N-dimethylformamide and water (DMF: H2O (v/v) = 1: 1) for 180 s, using a molar ratio of template, monomer, and crosslinker of 1: 4: 50. The obtained material had a higher adsorption capacity (Qe = 428.24 mg g−1) and imprinting factor (IF = 2.36). The surface and internal porosity of Co(II)-PMMA-IICM16 were characterized by scanning electron microscopy and a nitrogen adsorption apparatus. In addition, it was found that the adsorption process of Co(II)-PMMA-IICM16 prepared under optimal conditions was better described by a Langmuir isotherm adsorption model, which verified that the adsorption involved monolayer adsorption. The kinetics data was more closely fit by a pseudo-second-order kinetics model, indicating that this adsorption process proceeded via chemisorption. The permeation experiments indicated that a “delayed” permeation mass transfer mechanism also occurred (β(Co(II)/Cd(II)) = 2.11 and β(Co(II)/Cu(II)) = 1.55). The Co(II) ion-imprinted composite membrane prepared in this paper demonstrated a relatively better imprinting effect, a specific recognition ability for template ions, and good selective permeability. These results validated that the design of this novel functional monomer was reasonable, and that it has potential applications in various fields where adsorption is necessary.