MACROPOROUS POLYETHYLENIMINE GEL-COATED ON ACRYLONITRILE-DIVINYLBENZENE COPOLYMER: A GRANULAR SORBENT OF HIGH CAPACITY AND FAST KINETICS

Abstract

Gel coating of polyethylenimine (PEI) resin was performed on macroporous polyacrylonitrile (PAN) granules by a Cu(II)-mediated chemical process, which can be easily extended to any type of PAN substrate, including fibers, fabrics, and films. The process, named CR Process of Gel Coating, has been modified in the present work for imparting a high degree of macroporosity to the gel coat to enhance the sorption kinetics and to improve resistance to organic fouling. The process produces a thin, firm coating of PEI that is cross-linked with glutaraldehyde and rendered macroporous by acid decomposition of pre-deposited CaCO₃ on a PAN substrate that has been chemically modified a priori by limited hydrolysis with NaO-HH₂O₂. Designated as HYPAN(Na⁺). [PEI.XG], the gel-coated granular, macroporous sorbent affords nearly full attainment of the theoretical proton capacity of the coated resin and exhibits significantly faster attainment of equilibrium sorption than does the conventional bead-form ion exchanger. p-Toluenesulfonic acid (PTSA) and CuSO₄ were used as test sorbates for comparing the performance of the gel-coated sorbent with Reillex 425, a commercial poly(4-vinylpyridine) (PVP) resin. In sorbate solutions of relatively low concentration (<2 mmol/L), the gel-coated sorbent had 2 to 3 times higher sorption of PTSA and Cu(II) than did the PVP resin beads. Large differences were also observed in sorption rates of gel-coated beads and conventional whole-resin beads. Thus, under similar conditions, the initial rate of attainment of equilibrium sorption on HYPAN(Na⁺).[PEI.XG] was nearly twice that on PVP in both PTSA and CuSO₄ solutions. Application of the shell-core model equation to the initial sorption rate data yields for the gel-coated particles diffusivity values that are 2 to 3 times higher than those obtained for PVP resin beads.

^*On leave from Indian Institute of Science, Bangalore, India.

ACKNOWLEDGMENT

The financial support of research from the Natural Sciences and Engineering Research Council of Canada is gratefully acknowledged.

Notes

^*On leave from Indian Institute of Science, Bangalore, India.