Pb2+-imprinted thermosensitive antibacterial adsorbent derived from sodium alginate and PNIPAM for Pb2+ recovery

Two sodium alginate-based Pb 2+ -imprinted thermosensitive hydrogels (SPIT (without ɛ-PL) and SPPIT (with ɛ-PL)) were synthesized, with sodium alginate and ɛ-polylysine (ɛ-PL) as the matrix, N-isopropylacrylamide as the monomer. Characterization with differential scanning calorimeter, Fourier transform infrared spectroscopy , thermogravimetric analyzer, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy confirmed the aimed structure of the hydrogels. The adsorption capacity of SPIT and SPPIT for Pb 2+ was 98.64 mg/g and 153.49 mg/g, respectively. Washing the Pb 2+ -loaded adsorbent with 10 °C deionized water, SPIT and SPPIT achieved a desorption efficiency of 94.59 % and 97.51 %, respectively. After 10 cycles of adsorption-desorption process, the adsorption capacity and desorption efficiency remained at about 80–88 % of the original ones, expressing excellent reusability. In a mixture containing eight metal ions (Pb 2+ , Cu 2+ , Mg 2+ , Ca 2+ , Cd 2+ , Na + , K + , Fe 3+ ), the adsorption capacity of SPIT to Pb 2+ was 92.49 mg/g, and that of SPPIT was 102.49 mg/g, much higher than that to the other ions (1.50–11.38 mg/g on SPIT, 9.48–27.45 mg/g on SPPIT), showing excellent adsorption selectivity. The introduction of ɛ-PL enhanced the adsorption capacity, antibacterial ability and stability of the hydrogel, ensuring better application potential in real wastewater.