Supermacroporous monoliths based on polyethyleneimine: Fabrication and sorption properties under static and dynamic conditions

Here we report fabrication of monolith sorbents (cryogels) based on polyethyleneimine (PEI) cross-linked with diglycidyl ethers of glycols and polyglycols at subzero temperature. Comparative analysis of cryogels swelling, morphology, rheological properties, permeability, and maximal sorption capacities under static and dynamic conditions showed that commercially available and affordable 1,4-butanediol diglycidyl ether yields materials most suitable for separation applications. Sorption performance of the supermacroporous monolith was investigated for small ions (Cu2+), anionic dye (Alizarin Red), and humic acid, which represent important classes of inorganic and organic pollutants. We have shown that adsorbate molecule size and the sorption mechanism (coordination or electrostatic attraction) had significant effect on the shape of the breakthrough curves and dynamic sorption capacities at different flow rates.. We have also demonstrated that the maximal dynamic sorption capacity can be higher than the apparent static sorption capacity of cryogel due to the more efficient mass transfer in monolith column than in batch mode for sorption on highly swollen beads of cryogel. Effective and overall dynamic sorption capacities of covalently cross-linked PEI monoliths at flow rate of 84 bed volumes/ h were 131 mg/g and 141 mg/g for Cu(II) at pH = 5, and 938 mg/g and 1899 mg/g for Alizarin Red at pH = 5.6, respectively.