Ionic Crosslinking of Linear Polyethyleneimine Hydrogels with Tripolyphosphate

Area of Science:

• Materials Science
• Polymer Chemistry
• Environmental Engineering

Background:

• Linear polyethyleneimine (PEI) hydrogels chemically crosslinked with ethyleneglycoldiglycidyl ether (EGDE) exhibit limited mechanical strength.
• Ionic crosslinking offers a promising strategy to enhance hydrogel properties.

Purpose of the Study:

• To improve the mechanical properties of PEI-EGDE hydrogels.
• To investigate the use of sodium tripolyphosphate (TPP) as an ionic crosslinker.
• To evaluate the adsorption capacity of the modified hydrogels for emerging contaminants.

Main Methods:

• Quaternization of PEI nitrogen atoms to introduce permanent positive charges.
• Ionic co-crosslinking with sodium tripolyphosphate (TPP).
• Characterization using 1H high-resolution magic angle spinning (1H HRMAS) NMR, X-ray photoelectron spectroscopy (XPS), organic elemental analysis, ICP-MS, and low-field 1H NMR.
• Adsorption studies for penicillin V, methyl orange, and copper(II) ions at different pH values.

Main Results:

• TPP addition significantly increased deformation resistance of PEI-EGDE hydrogels from 320% to 1080%.
• Hydrogels maintained high adsorption capacities for emerging contaminants: 77 mg g-1 (penicillin V), 512 mg g-1 (methyl orange), and 55 mg g-1 (copper(II) ions) at pH 4.
• Adsorption capacity decreased at neutral and alkaline pH levels.

Conclusions:

• Ionic crosslinking with TPP effectively enhances the mechanical performance of PEI-EGDE hydrogels.
• The modified hydrogels demonstrate excellent potential for removing diverse emerging contaminants from aqueous solutions.
• The pH-dependent adsorption behavior highlights the importance of environmental conditions for contaminant removal efficacy.