Facile Processing of Polyelectrolyte Complexes for Immobilization of Heavy Metal Ions in Wastewater

Practical application of polyelectrolyte complexes (PECs) has been limited due to inadequate techniques to overcome processing challenges. This study aimed to explore seamless PEC processing techniques to fabricate adsorbents for wastewater treatment. The phase transition associated with poly(diallyldimethylammonium) and poly(styrenesulfonate) complexes in an aqueous solvent was studied as a function of polymer concentration, charge stoichiometry, and ionic strength. The complex-to-coacervate and coacervate-to-solution phase transitions were observed as the ionic strength increases for all the charge stoichiometries studied. We demonstrate that spherical PEC resins were prepared by injecting the liquid-like coacervates into pure water in a controlled manner. Also, the wastewater treatment experiment revealed that the PEC resins show outstanding performance for heavy metal adsorption with significant uptakes and easy separation. The maximum Pb(II) uptake was measured as 690 ± 0.2 mg/g by the Sips model, and the equilibrium adsorption rate was achieved within ∼2 h. This study thus lays down a protocol for the facile processing of PECs and the fabrication of PEC-based adsorbents for wastewater treatment and related applications.