Polyelectrolyte complex composite cryogels with self-antibacterial properties and wide window for simultaneous removal of multiple contaminants

Abstract

Tricomponent polyelectrolyte complex (PEC) composite cryogels, with remarkable sorption capacity of multiple contaminants and self-antibacterial properties were fabricated from chitosan (CS) and aromatic ionene type polycations evenly dispersed in carboxymethyl cellulose (CMC) aqueous solution. Fast cryostructuration at −196 °C (5 min) and overnight at −18 °C conducted to pre-PECs which, after exposure to a source of H+ and freeze-drying, led to PEC composite sponges. The PECs were characterized by FTIR, SEM, EDX, streaming potential titrations, swelling kinetics, swelling at equilibrium as a function of pH, and compressive tests. These PECs were able to simultaneous adsorb oxyanions (HCrO4−, H2PO4−, HAsO42−), and heavy metal ions (HMIs) (Cu2+, Cd2+, Pb2+), and to kill ∼100 % of Gram+ (Staphylococcus aureus) bacteria. Only the tricomponent PECs were able to kill 100 % of Gram- (Escherichia coli) bacteria, while the bicomponent PECs (containing only CS and CMC) were less efficient in this case (only 70 % inhibition of bacteria). The pseudo-first-order kinetic model fitted the best the kinetic data, suggesting the sorption of pollutants by physisorption. In multicomponent systems, HCrO4− ions are preferred, the selectivity coefficients being higher in the case of tricomponent PECs than in the case of bicomponent PECs, while in the case HMIs, Pb2+ ions were preferentially selected. The sustainability of the PEC composite cryogels was demonstrated by their reuse up to five sorption/desorption cycles, with a decrease of the sorption capacity in the fifth cycle of 7 % for H2PO4−, 8.1 % for HCrO4−, and 6.9 % for HAsO42− when tricomponent PEC cryobeads were used as sorbents. All these abilities recommend the PEC composite cryogels as potential materials for filters suitable for point-of-use water purification.