Polyethyleneimine‐grafted membranes for simultaneously adsorbing heavy metal ions and rejecting suspended particles in wastewater

Heavy metal ions (HMIs) in wastewater can be removed by polyethyleneimine (PEI) adsorption, however, it is difficult to recycle PEI macromolecules from their mixture with suspended particles in wastewater. A novel HMIs adsorption technique with renewable PEI‐grafted porous membranes was developed. PEI molecules were dispersed with high specific area and structured morphology, which allowed HMIs and suspended particles to be retained separately at different locations of the membrane, with the former adsorbed in matrix and the latter rejected on surface. The membranes with the optimized PEI loading ratio of 30 k wt % behaved excellently with microsphere rejection and Co(II) adsorption reaching 98.5% and 51.0 mg/g, respectively. They successfully decreased Co(II) concentration from 3.0 mg/L to the allowable discharge standard (0.5 mg/L), even with an enhanced flux of 6200 L/m 2 /h at 0.12 MPa under the cyclic tests. Overall, PEI‐grafted membrane adsorption is highly efficient for removing HMIs and suspended particles simultaneously from wastewater. © 2017 American Institute of Chemical Engineers AIChE J , 63: 4541–4548, 2017